Evaluation of right ventricular function during liver transplantation with transesophageal echocardiography.

BACKGROUND: The pathophysiology of advanced liver cirrhosis may induce alterations in the circulatory system that may be challenging for the anesthesiologist to manage intraoperatively, and perioperative cardiovascular events are associated with worse outcomes in cirrhotic patients undergoing liver transplantation. It remains controversial whether right ventricular function is impaired during this procedure. Studies using transesophageal echocardiography for quantitative analysis of the right ventricle remain scarce in this setting, yielding conflicting results. The aim of this study was to perform a quantitative assessment of right ventricular function with two parameters derived from transesophageal echocardiography during liver transplantation.
METHODS: Nineteen adult patients of both genders undergoing liver transplantation were evaluated in this observational study. The exclusion criteria were age under 18 or above 65 years old, fulminant hepatic failure, hepatopulmonary syndrome, portopulmonary hypertension, cardiopulmonary disease, and contraindications to the transesophageal echocardiogram. Right ventricular function was assessed at five stages during liver transplantation: baseline, hepatectomy, anhepatic, postreperfusion, and closure by measuring tricuspid annular plane systolic excursion and right ventricular fractional area change obtained with transesophageal echocardiography.
RESULTS: Right ventricular function was found to be normal throughout the procedure. The tricuspid annular plane systolic excursion showed a trend toward a decrease in the anhepatic phase compared to baseline (2.0 ± 0.9 cm vs. 2.4 ± 0.7 cm; P = 0.24) but with full recovery after reperfusion. Right ventricular fractional area change remained nearly constant during all stages studied (minimum: 50% ± 10 at baseline and anhepatic phase; maximum: 56% ± 12 at postreperfusion; P = 0.24).
CONCLUSIONS: Right ventricular function was preserved during liver transplantation at the time points evaluated by two quantitative parameters derived from transesophageal echocardiogram.

Introduction

Patients with end-stage liver disease may develop perioperative cardiovascular events associated with worse outcomes [1]. This is a significant concern, particularly as the recipients’ age has been increasing over the last years [2]. Thus, preoperative screening with 2D transthoracic echocardiography for all patients on the liver transplantation waiting list has been suggested by guidelines [3,4], including a dobutamine stress test in selected individuals to exclude significant myocardial ischemia. Cirrhotic cardiomyopathy is a distinct syndrome that may also be identified in preoperative screening. Typical findings include ventricular systolic or diastolic dysfunction and electrophysiological abnormalities, such as prolonged QT interval [5].

Other conditions suspected with preoperative echocardiography are hepatopulmonary syndrome and portopulmonary hypertension (PoPHTN). Regarding the latter, its pathophysiology shares some common features of primary pulmonary hypertension, including vascular remodeling [6]. It may affect 5 to 10% of patients who are candidates for a liver transplant and carries a poor prognosis if left untreated [6].

It should be noted that heart function impairment may lead to liver dysfunction, either acute or chronic. This reinforces the close physiological interplay between the heart and the liver [7]. For example, acute elevated pulmonary artery pressures may lead to right ventricular failure, which may impede liver venous outflow, leading to hepatic congestion and dysfunction. This scenario has been described after liver graft reperfusion in patients with PoPHTN undergoing orthotopic liver transplantation (OLT) [8]. In addition, major fluid shifts, bleeding, and inferior vena cava (IVC) manipulation by the surgeons often occur during the procedure, which may cause liver hypoperfusion and hemodynamic instability. These intraoperative events may overlap with the baseline hemodynamic alterations typical of cirrhotic patients, such as central hypovolemia, splanchnic hypervolemia, vasodilation, low systemic vascular resistance, and impaired vascular response to vasoconstrictors [9,10]. All of these factors are challenging for anesthesiologists to manage intraoperatively.

Although systemic hemodynamic alterations during OLT have been well reported [11], relatively few studies have focused on the right ventricular function (RVF) in this setting [12-15]. Most of these studies have used a modified pulmonary artery catheter (PAC), which measures the right ventricular ejection fraction (RVEF). More recently, the intraoperative use of transesophageal echocardiography (TEE) for cardiac function monitoring has been increasingly reported [16]. TEE has repeatedly demonstrated its usefulness during OLT, particularly in diagnosing intracardiac thromboembolism and cardiac dysfunction [17,18]. In this regard, most clinicians use TEE for subjective assessment only, whereas quantitative analysis by echocardiography is more accurate, mainly when RVF is to be evaluated [19,20].

To date, few studies have reported using TEE to evaluate RVF quantitatively during OLT, yielding conflicting results. One [21] used 3D TEE and showed normal RVF throughout the procedure, as assessed by RVEF. Another study [22] found that right ventricular dysfunction (RVD), diagnosed either by visual estimation or using a single quantitative index, might be quite common, particularly in the anhepatic and reperfusion stages. These findings could be explained at least in part by distinct methods used by the authors to quantify the RVF.

According to current guidelines, at least two quantitative indices should be used to properly evaluate the RVF [23,24]. The tricuspid annular plane systolic excursion (TAPSE) and right ventricular fractional area change (RVFAC) are commonly used parameters. TAPSE measurement is straightforward, relatively easy to perform, has excellent intra- and interreproducibility and is an independent predictor of mortality [25,26]. RVFAC is independent of geometric assumptions and correlates well with RVEF [23,24]. TAPSE and RVFAC values less than 1.7 cm and 35%, respectively, indicate decreased RVF [24].

To the best of our knowledge, no study using TEE for RVF assessment with two quantitative parameters during OLT has been reported. Therefore, the aim of this study was to evaluate the RVF by measuring TAPSE and RVFAC obtained with TEE at five time points during OLT: baseline, hepatectomy, anhepatic, postreperfusion, and closure phases.

Materials and methods

This study was approved by the Institutional Review Board of the Research Ethics Committee of the Clementino Fraga Filho University Hospital (HUCFF) from Faculty of Medicine of the Federal University of Rio de Janeiro (UFRJ), CAAE number 797638179.0000.5257, date of approval: 12/14/2017. The study protocol was registered at ClinicalTrials.gov as NCT03459924 (03/09/2018) and adheres to the applicable EQUATOR guidelines (STROBE checklist). Since this was a retrospective study, the Ethics Committee waived the requirement for informed consent.

We performed an observational, retrospective study and evaluated TEE data collected intraoperatively from nineteen adult patients of both genders who underwent OLT in our center. Our team has a strict protocol to save patient data and hemodynamic parameters on a database at well-defined time points throughout OLT. The principal researcher was responsible for all TEE measurements. The inclusion criteria comprised all adult patients who underwent OLT during the study period. All patients underwent a complete preoperative cardiovascular screening, including dobutamine stress echocardiography. Exclusion criteria for analysis were age under 18 or greater than 65 years old; past cardiac surgeries or cardiac disease (heart failure, arrhythmias, grade 2 or more diastolic dysfunction, left ventricular hypertrophy, significant aortic or mitral valve disease); any condition precluding the use of TEE (such as odynophagia or esophageal stricture); moderate or severe tricuspid regurgitation in the preoperative echocardiogram; fulminant liver failure; hepatopulmonary syndrome; PoPHTN, and the presence of esophageal varices with recent bleeding (< 6 months) or grade > 2.

Standard basic monitoring was initiated in the operating room with ECG leads DII and V5, noninvasive blood pressure, and a pulse oximeter (Datex AS/5 monitor, Datex GE®, Helsinki, Finland). After insertion of a peripheral intravenous line a rapid sequence induction of anesthesia was performed with fentanyl (1–3 μg kg-1), propofol (1–2 mg kg-1), and rocuronium (1 mg kg-1). The endotracheal tube position was confirmed with physical examination and capnography. A Foley catheter was inserted to monitor urine output. Neuromuscular transmission—train-of-four stimulus—was followed throughout the procedure, and the goal was to keep the train of four counts less than two. A nasopharyngeal temperature probe was carefully positioned, and air-forced warmed blankets were used to maintain normothermia (>36°C). An arterial cannula was inserted into the left radial artery for invasive blood pressure monitoring. Afterward, ultrasound-guided (M-Turbo machine–FUJIFILM SonoSite, Inc., Bothell, WA, USA) cannulation of the right internal jugular vein was performed. An 8 Fr double-lumen catheter and 8.5 Fr cordis were positioned (Arrows® International Inc., Reading, PA, USA). PAC was not used for any patient. A rapid infusion catheter (RIC 7 Fr, Arrows® International Inc., Reading, PA, USA) was inserted into the left antecubital or another large arm vein and then connected to an infusion system (Belmont®, Belmont Instrument Corporation, Boston, MA, USA). A cell saver device was used for all patients, and processed blood was returned through the rapid infusion system. Maintenance of anesthesia was performed with fentanyl (1–3 μg kg-1 h-1), cisatracurium (0.2–1 μg kg-1 min-1) and desflurane (0.75–1.3 MAC) in an O2:air mixture (FiO2 = 0.5–1.0).

A 3–8 MHz TEE probe (M-Turbo machine–FUJIFILM SonoSite, Inc., Bothell, WA, USA) was positioned. After a comprehensive examination [27], the probe was secured in the mid-esophageal position to obtain the four-chamber view throughout the procedure. A dedicated anesthesia team managed the cases clinically, while the principal researcher performed all TEE examinations and recordings.

If the patient developed significant hypotension (systolic blood pressure or mean arterial pressure (MAP) less than 90 and 65 mmHg, respectively), phenylephrine 50–100 μg was administered in bolus and then a 25–100 μg min-1 infusion. Norepinephrine 2.5–15 μg min-1 infusion was initiated in cases of nonresponsiveness to phenylephrine. Otherwise, if hypovolemia was suspected, as assessed by hemodynamic parameters or TEE findings, fluid resuscitation was performed with albumin 5% 5 ml kg-1 in bolus. A crystalloid infusion was kept minimal during the procedure. A fluid bolus of albumin 5% (30 ml kg-1) was routinely given within 30 minutes before the IVC clamp unless clear signs of hypervolemia were present. Packed red blood cells were given when hemoglobin decreased below 8 g dl-1 or if ongoing bleeding with hemodynamic instability developed. Fresh frozen plasma was administered for nonsurgical bleeding when coagulopathy was diagnosed (INR>2). Cryoprecipitate was given only in cases of severe fibrinogen deficiency (<80 mg dl-1). Platelets were transfused in selected patients with persistent bleeding and significant thrombocytopenia (<50.000 mm-3).

Only senior surgeons performed the surgical procedure. Most of them performed side clamping of the IVC, while some preferred a full IVC cross-clamp to make the venous anastomosis. No venovenous bypass was used in this study. If the patient developed significant hypotension after graft reperfusion (postreperfusion syndrome), epinephrine was administered (10 μg in bolus, maximum dose 50 μg), followed by vasopressin (0.2 IU in bolus) used as a rescue treatment.

RVF was assessed by two TEE-derived parameters, TAPSE and RVFAC, at five stages during the procedure: baseline (TB)—as soon as the patient developed hemodynamic stability after surgical incision; hepatectomy (TH)—approximately 10 minutes before the portal vein was clamped; anhepatic (TA)—approximately 10 minutes before the portal vein was unclamped; postreperfusion (TR) - 30 minutes after reperfusion of the graft; and closure (TC)—when abdominal wall aponeurosis closure was initiated. Other hemodynamic parameters were collected at the same stages: MAP, heart rate (HR), central venous pressure (CVP), and systolic pressure variation (SPV) (determined by using the cursor method directly on the monitor) [28].

TAPSE and RVFAC measurements were described as follows. The TEE probe was positioned in the mid-esophageal window to achieve the four-chamber view. With the right ventricle (RV) centered on the screen, the image was frozen and then captured in the end-diastole and end-systole frame using the cine loop function of the ultrasound machine. The distance (in cm) between the RV apex and the tricuspid valve annulus attached to the RV free wall was measured at end-diastole and end-systole [29]. The difference between the two values yielded the TAPSE (Fig 1). This measurement is sometimes referred to as modified TAPSE or m-TAPSE [30,31] compared to the more common method that uses the M-mode in the apical view obtained by transthoracic echocardiogram.

Fig 1

TAPSE measurement.

The image of the right ventricle in the mid-esophageal four-chamber view is captured at end-diastole (A) and end-systole (B). The distance between the right ventricular apex and the lateral tricuspid annulus was measured, as shown in (A) and (B) (yellow lines: 7.05 and 4.72, respectively). The difference yields the TAPSE, in this case, 2.3 cm. Source: principal researcher’s archive.

RVFAC was calculated by measuring the RV area with manual planimetry at end-diastole and end-systole. The following formula was then used to calculate RVFAC: (RVFAC: right ventricular fractional area change; RVEDA: right ventricular end-diastolic area; RVESA: right ventricular end-systolic area).

Left ventricular ejection fraction (LVEF) was calculated using the modified Simpson’s biplane method [32], as TAPSE may also depend on left ventricular function [33]. The principal researcher measured all TEE parameters three times, and the average (mean value) was recorded.

Statistical analysis

Continuous variables were assessed by Shapiro-Wilk test and summarized as mean values ± SD for normally distributed variables and median values [interquartile range; Q25 to Q75] for non-normally distributed variables. Frequencies and percentages were used for categorical variables. Hemodynamic and TEE data from the five stages (TB, TH, TA, TR, TC) were compared using one-way ANOVA for repeated measurements and Tukey’s test was applied for post hoc analysis in case of normal distribution. Otherwise, the Friedman test was employed, and Dunns’ test was applied for post hoc analysis. P < 0.05 was considered significant. The software used for statistical analysis was Prism 7 for Mac OS X, V7.0d (GraphPad Software, Inc., San Diego, CA, USA).

Results

After exclusion criteria were applied, nineteen (n = 19) adult patients who underwent OLT from April 2012 to April 2013 were included for analysis. Patient characteristics and intraoperative data are shown in Table 1.

Table 1

Patient characteristics and intraoperative data.

Gender (M/F)	(14/5)
Age (years)	52 ± 13
Weight (kg)	78 ± 14
Height (cm)	168 ± 9
MELD score	26 ± 10
Liver disease HCV Alcohol Biliary disease HBV Others	7 (37%)3 (16%)4 (21%)1 (5%)4 (21%)
Preoperative drugs Beta-blockers Diuretics	6 (31%)4 (21%)
Length of surgery (min)	450 ± 112
Intraoperative fluids Crystalloids (ml) 5% Albumin (ml)	1894 ± 7602115 ± 2062
Diuresis (ml)	300 [100 to 900]
Intraoperative vasopressor use Baseline Hepatectomy Anhepatic Postreperfusion Closure	9 (47%)16 (84%)18 (95%)17 (89%)14 (74%)
Packed red blood cells (units)	4 [1.5 to 9.5]
Fresh frozen plasma (units)	5 [0 to 11.5]
Platelets (units)	0 [0 to 1.5]
IVC clamp Full Partial (side-clamp)	7 (37%)12 (63%)
Postreperfusion syndrome	11 (58%)
Estimated blood loss (ml)	2800 [1600 to 8500]

Values are expressed as the absolute numbers when unspecified, means ± SD, medians [IQR 25 to 75] or n (%). Others included nonalcoholic steatohepatitis (n = 2), cryptogenic cirrhosis (n = 1) and hemangioma (n = 1). Abbreviations: M = male; F = female; MELD = Model for End Stage Liver Disease; HCV = Hepatitis C Virus; HBV = Hepatitis B Virus; IVC = Inferior vena cava.

The majority of participants were male (74%). The mean age and body mass index (BMI) were 52 ± 13 years old and 27 ± 6 kg m-2 respectively. Six patients (31%) were on low-dose beta-blocker therapy for esophageal variceal bleeding prophylaxis. The Model for End-Stage Liver Disease (MELD) score was relatively high (mean of 26), but exception points were given for six patients with hepatocellular carcinoma. Vasopressors were used in all patients at some point during the procedure. Phenylephrine infusion ranged from 25 to 80 μg min-1 while norepinephrine ranged from 2.5 to 10 μg min-1. Eleven (58%) patients developed postreperfusion syndrome and were successfully treated with adrenaline bolus. The median estimated blood loss was 2800 ml (IQR [1600 to 8500] ml). The total amount of fluid administered was 1894 ± 760 ml for crystalloids and 2115 ± 2062 ml for colloids (albumin 5%) (mean ± SD). The IVC was partially clamped in most patients (63%). No subjects died during the study period, and all patients were extubated in the operating room and admitted to the intensive care unit.

Hemodynamic and TEE parameters are shown in Table 2.

Table 2

Intraoperative hemodynamic and TEE data.

Variable	TB	TH	TA	TR	TC	P—value
MAP (mmHg)	76 [62 to 84]	85 [70 to 95]	73 [69 to 80]	70 [63 to 73]	70 [67 to 78]	0.15
HR (bpm)	73 ± 11	79 ± 15	81 ± 19	77 ± 16	78 ± 13	0.08
CVP (mmHg)	12 ± 7	8 ± 5	5 ± 6*	9 ± 4	9 ± 5	0.003
SPV (mmHg)	4 [3 to 6]	4 [3 to 8]	7 [4 to 15]	4 [3 to 7]	4 [2 to 10]	0.10
TAPSE (cm)	2.4 ± 0.7	2.4 ± 0.9	2.0 ± 0.9	2.5 ± 0.5	2.7 ± 0.9	0.24
RVFAC (%)	50 ± 10	55 ± 13	50 ± 11	56 ± 12	52 ± 12	0.24
LVEF (%)	66 ± 12	70 ± 14	68 ± 12	71 ± 12	70 ± 12	0.82

Data are expressed as the means ± SD or medians [IQR 25–75%] when appropriate. Abbreviations: TB: Baseline; TH: Hepatectomy stage; TA: Anhepatic stage; TR: Postreperfusion stage; TC: Closure stage; MAP: Mean systemic arterial pressure; HR: Heart rate; CVP: Central venous pressure; SPV: Systolic pressure variation; TAPSE: Tricuspid annular plane systolic excursion; RVFAC: Right ventricular fractional area change; LVEF: Left ventricular ejection fraction. Statistical comparisons were by repeated-measures ANOVA or Friedman’s test

*P < 0.05 from baseline.

Only CVP during the anhepatic period (TA) decreased significantly from baseline (P = 0.003).

TAPSE and RVFAC were within the normal limits throughout the procedure. TAPSE showed a trend toward a decrease in the anhepatic phase (TA) when compared to baseline (TB) (mean ± SD: 2.0 ± 0.9 cm vs. 2.4 ± 0.7 cm; P = 0.24) but fully recovered after reperfusion. RVFAC remained nearly constant during all phases studied (minimum: 50% ± 10 at TB and TA; maximum: 56% ± 12 at TR; P = 0.24).

Discussion

In this study, RVF was preserved during OLT, as revealed by TAPSE and RVFAC measurements obtained by TEE. Only TAPSE showed a mild trend toward a decrease in the anhepatic phase, with full recovery after reperfusion. This biphasic pattern of RVF has also been shown in previous studies using a modified PAC, which measures RVEF [12-15]. Indeed, TAPSE and RVEF correlate well when measured by cardiac magnetic resonance imaging [34], and our results reinforce this relationship.

The mean TAPSE and RVFAC found in our study at baseline were 2.4 cm and 50%, respectively, which should be considered normal. However, the normal range in this patient population is still unclear. One study reported similar values between cirrhotic and healthy individuals [35]. In contrast, two other studies [36,37] found that TAPSE was significantly higher among cirrhotic patients. If the latter data were considered, our patients’ TAPSE and RVFAC baseline values would be interpreted as decreased. However, the reproducibility of these findings remains to be determined. It is possible that in some patients with liver failure, the hyperdynamic circulation may help preserve TAPSE values in the normal range. Thus, more studies should be performed to identify a different baseline for hyperdynamic cirrhotic patients.

TAPSE is influenced by the loading conditions of the RV, particularly preload [38]. Of note, the mild alterations in CVP and SPV in the anhepatic phase found in our study suggest that the RV preload was not markedly reduced. This was likely due to the partial IVC clamp performed more frequently and the large fluid bolus of albumin routinely given before clamping. Furthermore, 95% of the patients were under vasopressors during this phase. All those factors might have contributed to the transient and slight TAPSE reduction found in this phase. This contrasts with the study of Shillcutt et al. [22], where a full IVC cross-clamp was routinely used for all patients. The incidence of RVD was 15% in the anhepatic phase, as assessed by TAPSE or visual estimation. However, the visual assessment of RVF is known to be inaccurate [23,24]. Therefore, RVD could have been overestimated. Indeed, those authors acknowledged the unusually high incidence of RVD compared to other studies [12-15,21]. Furthermore, fluid management data are lacking, and the authors did not clearly define the exact time point where measurements had been taken. Conversely, similar to our findings, Rosendal et al. [21] reported that RVEF was nearly unchanged in the anhepatic phase, as assessed by 3D-TEE. In their study, all patients received a partial IVC clamp, suggesting that RV preload may significantly influence RVF.

A decreased TAPSE may be secondary to left ventricular dysfunction or tachycardia [33], but neither LVEF nor HR showed significant alterations in our patients. In contrast to the normal LVEF values found in our study, cirrhotic patients may have a lower LVEF [5]. In our center, however, most of our patients had relatively stable liver disease, and preoperative left ventricular dysfunction was unusual. In addition, norepinephrine was frequently used intraoperatively, and its inotropic effects could have contributed. Changes in RV afterload were also unlikely to result in a decreased TAPSE, as previous studies have shown that pulmonary vascular resistance usually remains unchanged or slightly decreases in the anhepatic phase [14,15]. We do not know how the pulmonary pressure changed as we did not use PAC. The degree of tricuspid insufficiency may worsen in the face of an increase in pulmonary pressure or during intraoperative maneuvers, with consequent maintenance of TAPSE [39]. Finally, decreased RV contractility leading to a reduced TAPSE cannot be excluded, as it has been shown that myocardial depressant factors accumulate during OLT [40].

The RVFAC did not follow TAPSE trends in the anhepatic phase. Two possible reasons could explain this: first, RVFAC measurement is less reproducible than TAPSE, showing more significant variability among intra- or interobservers [29,41]. Second, preload changes may have a more considerable influence on TAPSE readings when compared to RVFAC [23]. The normal RVEF found in Rosendal et al. [21]’s study agrees with our results, as RVFAC may be considered a two-dimensional surrogate for RVEF [23,24].

Ellis et al. [42] used TEE during OLT and reported some cases of significant RVD within five minutes after reperfusion. Their results should be interpreted with caution, as a quantitative analysis was not performed. Moreover, surgical and anesthetic management for liver transplantation has dramatically evolved since their study. Shillcutt et al. [22] found a 22% incidence of RVD after reperfusion. However, the measurement timing was not standardized, and the authors neither quantified the degree of RV impairment nor reported the TAPSE values. Rosendal et al. [21] found a normal RVEF measured by 3D-TEE five minutes after reperfusion, suggesting that RVF was not impaired at this time. This agrees with the present study, as RVF assessment during this phase also showed normal values.

The timing of RVF assessment after reperfusion is of great relevance and influences the results. Unlike the authors above [21,22,42], who evaluated the RVF within five minutes, we assessed RVF thirty minutes postreperfusion. This time point was chosen for two reasons: first, the five minutes after reperfusion is a stressful and demanding time for the anesthesiologist. Even for experienced clinicians, performing quantitative and precise TEE measurements may be challenging during this time. Second, any RVD eventually found at this time point would be unrelated to the acute hemodynamic and metabolic events following five minutes of reperfusion. Accordingly, 58% of our patients received adrenaline bolus to overcome the postreperfusion syndrome, and this drug would influence RVF acutely.

Overall, our results are similar to those of Rosendal et al. [21]. However, in their study, only one parameter (RVEF) was measured as an index for RVF. At the same time, it has been recommended that at least two parameters be used to properly quantify the RVF [23,24]. Accordingly, both TAPSE and RVFAC were measured in our study, suggesting that RVF is well preserved throughout OLT when measured at specific time points during the procedure.

Further studies using more accurate indices of RVF, such as tissue Doppler and global strain of the RV, may be warranted to define whether clinically significant RVD occurs intraoperatively and whether it influences patient outcomes.

Study limitations

This was a retrospective study with a small number of patients enrolled. Thus, a type 2 statistical error cannot be excluded. The accuracy of echocardiographic measurements could have been improved if two or three physicians (blinded to each other) performed the exam. However, to accomplish this, those measurements should ideally have been done offline, but unfortunately, we did not have any specific software available to do so. Although we did not use PAC routinely, it could likely add more information about RVF, such as the pulmonary artery pulsatility index (pulmonary artery pulse pressure divided by the CVP) [43]. More accurate and less preload-dependent indices of RVF could have been measured, such as the global longitudinal strain and tissue Doppler [44]. Fluid therapy may influence RVF, and although we have reported the total amount of crystalloids and colloids during surgery, we lacked data on total fluid balance. Finally, we collected data from patients who underwent relatively uncomplicated liver transplants. Our results cannot be extrapolated to specific conditions, such as massive transfusion or profound vasoplegia, and patients with PoPHTN or hepatopulmonary syndrome who might behave differently.

Conclusions

In our study, RVF was preserved during OLT when evaluated by quantitative analysis with TAPSE and RVFAC derived from TEE, as assessed at five stages: baseline, hepatectomy, anhepatic, postreperfusion, and closure.

18 Jul 2022

A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.

A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.

An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: https://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols. Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols.

We look forward to receiving your revised manuscript.

Kind regards,

Vincenzo Lionetti, M.D., PhD

Academic Editor

PLOS ONE

Journal Requirements:

When submitting your revision, we need you to address these additional requirements.

1. Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. The PLOS ONE style templates can be found at

https://journals.plos.org/plosone/s/file?id=wjVg/PLOSOne_formatting_sample_main_body.pdf and

https://journals.plos.org/plosone/s/file?id=ba62/PLOSOne_formatting_sample_title_authors_affiliations.pdf

2. We note that you have stated that you will provide repository information for your data at acceptance. Should your manuscript be accepted for publication, we will hold it until you provide the relevant accession numbers or DOIs necessary to access your data. If you wish to make changes to your Data Availability statement, please describe these changes in your cover letter and we will update your Data Availability statement to reflect the information you provide.

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Partly

Reviewer #2: Yes

**********

2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: No

Reviewer #2: Yes

**********

3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: No

Reviewer #2: Yes

**********

4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

**********

5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: Cardiac complications in liver disease, especially in cirrhosis, are associated with increased mortality following liver transplant. Pre-transplant guidelines recommend risk stratification with 2D and dobutamine stress echocardiography, which may lead to coronary angiography or right heart catheterization. There is a paucity of data on the utility of RV hemodynamics during the perioperative period.

Cardiovascular events have a major impact on the outcomes of liver transplantation, especially since contemporary liver transplant patients are older than their predecessors and more likely to have cardiac comorbidities. Additionally, the pathophysiologic effects of advanced liver disease on the circulatory system pose challenges to perioperative management in liver transplant.

2012 American College of Cardiology and American Heart Association (ACC/AHA) guidelines for evaluation of cardiac disease in kidney and liver transplant patients note that it is reasonable for patients to undergo echocardiography to assess for pulmonary hypertension and intrapulmonary arteriovenous shunting, while 2014 guidelines from the American Association for the Study of Liver Diseases (AASLD) and American Society of Transplantation (AST) note that echo for this purpose should be done routinely. Portopulmonary hypertension is found in 5% to 10% of patients with chronic liver disease. Unless patients undergo liver transplant or start appropriate medical therapy, portopulmonary hypertension carries a very poor prognosis.

The pathophysiologic mechanisms specific to PoPHTN have been compared with other known forms of pulmonary hypertension, including primary pulmonary hypertension, and has been found to fall within a spectrum of disorders related to factors both due to intrinsic liver failure [with resultant portal hypertension and hepatopulmonary syndrome (HPS)] as well as pulmonary vascular remodeling.

The heart and the liver are in close relation to each other. Impairment of cardiac function may lead to hepatic dysfunction and vice versa. Liver hypoperfusion and hepatic congestion are the 2 central pathophysiological mechanisms, both in acute cardiogenic liver injury and hepatic congestion. Cirrhotic cardiomyopathy is a syndrome that includes systolic, diastolic, and electrophysiological abnormalities that develop in the setting of liver cirrhosis.

A significant number of patients presenting for liver transplant carry hemodynamic sequelae of end-stage liver disease, including generalized vasodilation, low systemic vascular resistance and an impaired vasoconstrictive response to endogenous and exogenous vasoconstrictors. These patients also have simultaneous central hypovolemia with splanchnic hypervolemia. The combination of acute blood loss, large fluid shifts and manipulation of the inferior vena cava during surgery can put significant stress on the cardiovascular system. Because of these factors, intraoperative hemodynamic instability is common during the dissection phase of liver transplant (due to blood loss) and the hepatic phase (due to obstruction of the inferior vena cava).

Mean normal TAPSE and PAPI in the literature are 2.0cm and 2.75, respectively, but in many studies mean TAPSE was 2.52cm and PAPI was 3.54. This is likely explained by the high cardiac output state in cirrhosis. In the RV failure group, TAPSE and PAPI were within the normal range suggesting the need to identify a different baseline for patients with a hyperdynamic state due to cirrhosis.

RV function was impaired in patients with cirrhosis and more commonly, in patients with ascites. However, values of RV-GLS did not distinguish the degree of severity of liver disease. In addition, the LVEF was low and LV-GLS was normal in patients with cirrhosis.

The manuscript contains many critical points. As stated by the authors, the number of enrolled patients is low and the "normal" haemodynamic conditions of the patients place this group as not representative of the average liver transplant population.

Other significant data is linked to the hyper dynamism of patients with hepatic insufficiency which can lead to a maintenance of TAPSE values in the normal range.

It would be more appropriate to study a GL strain of the RV.

The manuscript lacks data on fluid therapy (quantity and water balance) and pharmacological treatment (quantity of vasoconstrictor, if repeated boluses or continuous infusion).

We do not know if it was present and how the pulmonary pressure changed; the degree of tricuspid insufficiency present was mild and this situation may worsen during intraoperative maneuvers with consequent maintenance of TAPSE, in the face of an increase in pulmonary pressure.

The manuscript is interesting and I agree with extending intraoperative echocardiographic evaluation to most liver transplant candidates. I would also suggest to evaluate, in addition to the parameters reported in the study, also the tissue doppler and the global strain of the right ventricle.

Reviewer #2: The authors are to be commended for this study of RV function during liver transplantation. The study is well done, acknowledges prior studies on this subject appropriately, and adds to the body of evidence concerning monitoring of RV function throughout the operative period of liver transplantation.

The manuscript flows well, no significant grammatical errors (although authors should read the final version closely to eliminate any grammar problems), and is scientifically rigorous.

I wanted to state the method used for TAPSE is the m-TAPSE but this was noted in the methods section. One consideration is to explain this earlier (such as the introduction) but I don't think it's absolutely necessary.

The common surgical method for liver transplant anastomosis - partial caval clamp - was performed in the study which makes the findings of RV assessment that much more relevant to current practice of intraoperative monitoring.

**********

6. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

Reviewer #2: Yes: Antolin S. Flores MD

**********

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

29 Aug 2022

Reviewer #1

Cardiac complications in liver disease, especially in cirrhosis, are associated with increased mortality following liver transplant. Pre-transplant guidelines recommend risk stratification with 2D and dobutamine stress echocardiography, which may lead to coronary angiography or right heart catheterization.

We agree with your comments. All patients in our Liver Center undergo a complete cardiovascular screening, including dobutamine stress echocardiography (DSE) if indicated. In our cohort, all of them had a normal DSE. We included this information in the Methods. We also added this information in the first paragraph of the Introduction. References number 1 to 4 were added accordingly.

There is a paucity of data on the utility of RV hemodynamics during the perioperative period.

Indeed, this is one reason we have been focusing on RV monitoring in this setting. This has been written in the Introduction (4th paragraph).

Cardiovascular events have a major impact on the outcomes of liver transplantation, especially since contemporary liver transplant patients are older than their predecessors and more likely to have cardiac comorbidities. Additionally, the pathophysiologic effects of advanced liver disease on the circulatory system pose challenges to perioperative management in liver transplant.

2012 American College of Cardiology and American Heart Association (ACC/AHA) guidelines for evaluation of cardiac disease in kidney and liver transplant patients note that it is reasonable for patients to undergo echocardiography to assess for pulmonary hypertension and intrapulmonary arteriovenous shunting, while 2014 guidelines from the American Association for the Study of Liver Diseases (AASLD) and American Society of Transplantation (AST) note that echo for this purpose should be done routinely.

Our Liver Center also follows these guidelines. All patients on the waiting list undergo screening with echocardiography for portopulmonary hypertension (PoPHTN) and intrapulmonary shunting (particularly in patients with a history of hypoxemia). We added this information to the first and second paragraphs of the Introduction and referenced it accordingly (references number 3 and 4).

Portopulmonary hypertension is found in 5% to 10% of patients with chronic liver disease. Unless patients undergo liver transplant or start appropriate medical therapy, portopulmonary hypertension carries a very poor prognosis.

The pathophysiologic mechanisms specific to PoPHTN have been compared with other known forms of pulmonary hypertension, including primary pulmonary hypertension, and has been found to fall within a spectrum of disorders related to factors both due to intrinsic liver failure [with resultant portal hypertension and hepatopulmonary syndrome (HPS)] as well as pulmonary vascular remodeling.

We have excluded patients with PoPHTN in our study but fully agree with your comments. We believe these patients should be studied more precisely in multicenter research, as PoPHTN occurs less commonly. We highlighted information about patients with PoPHTN in the Introduction (second paragraph) and added reference number 6.

The heart and the liver are in close relation to each other. Impairment of cardiac function may lead to hepatic dysfunction and vice versa. Liver hypoperfusion and hepatic congestion are the 2 central pathophysiological mechanisms, both in acute cardiogenic liver injury and hepatic congestion.

We added this information in the third paragraph of the Introduction. References 7 and 8 were included.

Cirrhotic cardiomyopathy is a syndrome that includes systolic, diastolic, and electrophysiological abnormalities that develop in the setting of liver cirrhosis.

We agree that the role of cirrhotic cardiomyopathy cannot be overemphasized. We added this information in the Introduction (first paragraph) and reference number 5.

A significant number of patients presenting for liver transplant carry hemodynamic sequelae of end-stage liver disease, including generalized vasodilation, low systemic vascular resistance and an impaired vasoconstrictive response to endogenous and exogenous vasoconstrictors. These patients also have simultaneous central hypovolemia with splanchnic hypervolemia. The combination of acute blood loss, large fluid shifts and manipulation of the inferior vena cava during surgery can put significant stress on the cardiovascular system. Because of these factors, intraoperative hemodynamic instability is common during the dissection phase of liver transplant (due to blood loss) and the hepatic phase (due to obstruction of the inferior vena cava).

Hemodynamic data were collected during specific time points, such as hepatectomy (dissection phase), anhepatic, and post-reperfusion phases. Cardiovascular function (including RVF) could likely be compromised at these phases. The type of inferior vena cava clamp (partial versus full) was also described in our paper. All this critical information has been added in the Introduction (third paragraph) and referenced (numbers 9 and 10).

Mean normal TAPSE and PAPI in the literature are 2.0cm and 2.75, respectively, but in many studies mean TAPSE was 2.52cm and PAPI was 3.54. This is likely explained by the high cardiac output state in cirrhosis. In the RV failure group, TAPSE and PAPI were within the normal range suggesting the need to identify a different baseline for patients with a hyperdynamic state due to cirrhosis.

This information has been reinforced in the second paragraph of the Discussion section.

We highlighted that more studies should be done to define the normal range for cirrhotic patients.

Unfortunately, we did not measure the PAPI, calculated by pulmonary artery pulse pressure divided by the central venous pressure. This is a valuable RV function index that has been used in some recent studies. We added this in the Discussion (study limitations).

RV function was impaired in patients with cirrhosis and more commonly, in patients with ascites. However, values of RV-GLS did not distinguish the degree of severity of liver disease. In addition, the LVEF was low and LV-GLS was normal in patients with cirrhosis.

Unfortunately, we did not measure the degree of ascites in our patients. However, none had severe ascites as observed clinically or during surgery. This may be explained by our selective cohort of relatively stable patients.

The RV-GLS is a more accurate parameter to evaluate the right ventricular function, and less preload-dependent. We also included this in the study limitations. We look forward to measuring it in future studies.

In our results, LVEF was normal throughout the procedure. Most of our patients were under norepinephrine intraoperatively, and its inotropic effects could possibly explain a higher than expected LVEF. We added this comment in the Discussion section (4th paragraph).

The manuscript contains many critical points. As stated by the authors, the number of enrolled patients is low, and the "normal" haemodynamic conditions of the patients place this group as not representative of the average liver transplant population.

The authors agree and have pointed out these issues in the Discussion section (study limitations). Further studies with more severely affected patients should be done.

Other significant data is linked to the hyper dynamism of patients with hepatic insufficiency, which can lead to a maintenance of TAPSE values in the normal range.

This observation was inserted into the Discussion, second paragraph.

It would be more appropriate to study a GL strain of the RV.

We agree that more accurate parameters should be used to evaluate the RV. The GL strain of the RV is certainly one, and this issue has been added into the Discussion (last paragraph).

The manuscript lacks data on fluid therapy (quantity and water balance) and pharmacological treatment (quantity of vasoconstrictor, if repeated boluses or continuous infusion).

In our study, only the total amount of crystalloids (mean of 1894 ml) and albumin (mean of 2115 ml) throughout the procedure were reported (Table 1). We presented only generalized data about the use or not of vasopressors in different phases of the transplant (Table 1), highlighted as “Intraoperative vasopressor use .” The role of vasopressors influencing RVF is described in the Discussion.

We do not know if it was present and how the pulmonary pressure changed; the degree of tricuspid insufficiency was mild. This situation may worsen during intraoperative maneuvers with consequent maintenance of TAPSE in the face of an increase in pulmonary pressure.

Pulmonary artery catheter data would undoubtedly add more information to our paper, but unfortunately, we do not insert them on a routine basis anymore. We added this thoughtful observation in the Discussion section. Reference number 38 was added.

The manuscript is interesting and I agree with extending intraoperative echocardiographic evaluation to most liver transplant candidates. I would also suggest to evaluate, in addition to the parameters reported in the study, also the tissue doppler and the global strain of the right ventricle.

Thank you. Your suggestion is actually in our plans. We are willing to purchase an advanced echocardiogram

software package to extract recorded images during the procedure. This will allow us to measure various parameters to assess the RVF more accurately. The global strain and tissue Doppler will undoubtedly be part of it. We added this in the discussion (conclusions).

We included a new coauthor who revised the statistical analysis.

We thanked you so much for your thoughtful comments and added them accordingly to the paper.

Reviewer #2

The authors are to be commended for this study of RV function during liver transplantation. The study is well done, acknowledges prior studies on this subject appropriately, and adds to the body of evidence concerning monitoring of RV function throughout the operative period of liver transplantation.

We appreciate your comments; thank you.

The manuscript flows well, no significant grammatical errors (although authors should read the final version closely to eliminate any grammar problems), and is scientifically rigorous.

We are committed to reading the final version carefully to avoid any grammar issues.

I wanted to state the method used for TAPSE is the m-TAPSE but this was noted in the methods section. One consideration is to explain this earlier (such as the Introduction) but I don't think it's absolutely necessary.

We also thought to include m-TAPSE earlier in the text, but in the end, we decided to put it in the Methods, where a more detailed description of the echocardiogram measurements is given. We thought it could be a bit confusing to the reader if it had been written at the beginning of the text. Thus, we will keep the m-TAPSE description in the Methods when sending the revision. However, should the reviewer change his mind and think it would be better in the Introduction, we will change it accordingly.

The common surgical method for liver transplant anastomosis - partial caval clamp - was performed in the study which makes the findings of RV assessment that much more relevant to the current practice of intraoperative monitoring.

We agree with this point. Partial clamping of the inferior venous cava is performed much more commonly nowadays.

Thank you so much for your thoughtful comments, and we will keep following your suggestions in future revisions if you perform it again.

Submitted filename: Reponse to Reviewers.docx

Click here for additional data file.

13 Sep 2022

Evaluation of right ventricular function during liver transplantation with transesophageal echocardiography

PONE-D-22-12798R1

Dear Dr. Gouvêa,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

An invoice for payment will follow shortly after the formal acceptance. To ensure an efficient process, please log into Editorial Manager at http://www.editorialmanager.com/pone/, click the 'Update My Information' link at the top of the page, and double check that your user information is up-to-date. If you have any billing related questions, please contact our Author Billing department directly at authorbilling@plos.org.

If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org.

Kind regards,

Vincenzo Lionetti, M.D., PhD

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: All comments have been addressed

Reviewer #2: All comments have been addressed

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: Thank you very much for addressing every questions. In this revised version, the manuscript is clearer in understanding the cardiovascular issues in liver transplant patients. Some points deserve more elucidation, but in consideration of the understanding of the text, they would not produce substantial improvements.

Reviewer #2: Thank you for the revision of your manuscript. The discussion section is greatly improved and this study adds to the body of evidence regarding RV function and monitoring of it during liver transplantation. I didn't find any large grammar errors and the conclusion discusses all of the results appropriately. It flows well and doesn't make assumptions that aren't supported by data - it is scientifically rigorous.

I hope that the authors consider a larger study in the future or a multicenter study.

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: Yes: luigi tritapepe

Reviewer #2: No

**********

26 Sep 2022

PONE-D-22-12798R1

Evaluation of right ventricular function during liver transplantation with transesophageal echocardiography

Dear Dr. Gouvêa:

I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department.

If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org.

If we can help with anything else, please email us at plosone@plos.org.

Thank you for submitting your work to PLOS ONE and supporting open access.

Kind regards,

PLOS ONE Editorial Office Staff

on behalf of

Prof. Vincenzo Lionetti

Academic Editor

PLOS ONE