Left Ventricular Functional Remodeling after Primary Percutaneous Coronary Intervention.

Background: Improvement in left ventricular (LV) function after revascularization is an important determinant of long-term prognosis in a patient with acute myocardial infarction (AMI). However, data on the changes of LV function after revascularization are scarce in our population. Hence, this study was conducted to evaluate the changes in LV function and dimensions by echocardiography at 3 and 6 months after primary percutaneous coronary intervention (PCI). Materials and
Methods: A total of 188 patients were recruited in this study who had undergone primary PCI. Patients with preexistent LV dysfunction, prior PCI, or with congenital heart disease were excluded. Echocardiography was performed at baseline (within 24 h of intervention), 3 months, and 6 months of intervention. Remodeling in terms of change in LV ejection fraction (LVEF), LV end-diastolic dimension (LVEDD), LV end-systolic dimension, and wall motion score index (WMSI) was evaluated.
Results: Out of the 188 patients, 90.4% were male, and mean age was 53.94 ± 9.12 years. Baseline mean LVEF was 39.79 ± 6.2% with mean improvement of 5.11 ± 3.87 (P < 0.001) at 3 months and 6.38 ± 4.29 (P < 0.001) at 6 months. Baseline LVEDD was 46.23 ± 3.86 mm which improved to 44.68 ± 2.81 mm at 6 months. Basal WMSI decreased by -0.09 ± 0.08 and -0.13 ± 0.09 at 3 and 6 months, respectively, after revascularization. Conclusions: Primary PCI is the recommended mode of reperfusion in patients with AMI. It reduces infarct size, maintains microvascular integrity and preserves LV systolic function hence improving LV function. Copyright:

INTRODUCTION

The presence of coronary artery disease carries poor prognosis. One presentation of coronary artery disease is acute ST-elevation myocardial infarction (STEMI). If not treated promptly, STEMI leads to grave patient outcomes because of left ventricular (LV) dysfunction. Early restoration of patency of infarct-related artery either by thrombolysis or primary angioplasty with a balloon or stent placement improves patient's survival by decreasing infarct size, preserving LV function, and decreasing the rate of complications.[12] Primary percutaneous coronary intervention (PCI) is the recommended standard of care for treating acute STEMI patients at present.[3] The primary objective of reperfusion is not only to restore patency of the infarct-related artery but also to preserve myocyte integrity, hence improving LV function.

In survivors of acute myocardial infarction (AMI), the most important predictor of long-term prognosis is an improvement in LV function, either systolic or diastolic. However, LV function may alter during the ensuing months of myocardial infarction, by process of remodeling and gradual relief of stunning.[4] Establishing the predictors of alterations in LV function may offer important acumen into the process of the changes in LV function and may have significant implications for therapeutic strategies.[4] Various studies used different modalities for assessment of myocardial recovery after revascularization, such as longitudinal strain imaging,[5] layer-specific speckle tracking,[67] cardiac MRI,[78] radionuclide imaging,[4] all of which are highly cumbersome, costly and not readily available everywhere. In comparison, echocardiography is low cost, easy to perform, and readily available everywhere with nearly the same predictive value. Second, parameterization of LV functional remodeling (such as LV ejection fraction [LVEF], LV end-diastolic dimension (LVEDD), LV end-systolic dimension (LVEDS), and wall motion score index (WMSI)) is also variable. Hence, the aim of this study was to assess the changes in LVEF, LVEDD, LVEDS, and WMSI as a comprehensive assessment of LV functional remodeling after the 6th month of primary PCI using transthoracic echocardiography (TTE) as a cost effective and easy to perform modality.

MATERIALS AND METHODS

This prospective observational study was conducted between August 2018 and July 2020. Patients with AMI who underwent primary PCI at a tertiary care cardiac center in Karachi, Pakistan were recruited. Patients with preexistent LV dysfunction, history of past PCI, and congenital heart disease were excluded from the study. After approval from the ethical review committee of the institution, the required number of patients who fulfilled the inclusion criteria were enrolled. Informed consent was obtained from all the participating patients. Patient's preprocedural demographic characteristics, angiographic details, and echocardiographic parameters were obtained. TTE was performed for all recruited patients at baseline (within 24 h of intervention), 3 months and 6 months, to assess LV functional remodeling by experienced echocardiographers on Vivid 7 machine. In order to minimize the inter-observer variations, all TTE were reported by the two independent cardiologists blinded to the patients' clinical status and one another's assessments. The final measurements were taken as mean of the two assessments. Cases with more than 5% variation in any of the parameter measurements were not included in the final analysis. However, intra-observer variation could not be assessed due to single reading reporting by the each cardiologist.

Echocardiographic parameters of interest were LVEF, LVEDD, LVEDS, and WMSI. LVEF was obtained using modified Simpson method; cardiac chambers were quantified using two chamber, four chamber and short axis views.

WMSI was calculated using TTE, which has been reported to have a strong correlation with cardiac MRI. Each of 16 myocardial segments was assigned a score of 1, 2 or 3: 1-normal, 2-hypokinesis, and 3–-akinesis. Sum of the scores of all segments was divided by the total number of segments to obtain WMSI. All collected data were recorded on a preapproved, designated and structured pro forma.

The collected data were entered into IBM SPSS Version 21.0. (IBM Corp., Armonk, NY, US). After quality assessment, descriptive summary of data such as frequency (%) and mean ± standard deviation were computed for the categorical and continuous variables, respectively. Changes in echocardiographic parameters (LVEF, LVEDD, LVEDS, and WMSI) at 3 and 6 months were assessed by computing mean differences and by performing paired-sample t-test for quantitative comparison and Chi-square test for qualitative (categorical) comparison. A two-sided P ≤ 0.05 was taken as criteria for statistical significance.

RESULTS

A total of 188 patients were included, 90.4% of them were male, with a mean age of 53.94 ± 9.12 years. Traditional risk factors of coronary artery disease were present in the frequency of 24.5%, 40.4%, and 39.4% for diabetes, hypertension, and smoking, respectively. The mean symptom onset to device activation time was 5.27 ± 2.69 h. Anterior wall myocardial infarction was the most common type of infarction presented in 59.6% of individuals, followed by inferior wall myocardial infarction and lateral wall myocardial infarction. Thrombolysis in myocardial infarction flow grade 0 was noted in 47.9% preprocedure. Baseline demographic and angiographic characteristics are summarized in Table 1.

Table 1

Baseline demographic and angiographic characteristics

Characteristics	Total, n (%)
Total (n)	188
Gender
Male	170 (90.4)
Female	18 (9.6)
Age (years)	53.94±9.12
≤40	16 (8.5)
41-60	134 (71.3)
≥60	38 (20.2)
Risk profile
Diabetes	46 (24.5)
Hypertension	76 (40.4)
Smoker	74 (39.4)
Family history of CAD	30 (16)
Hyperlipidemia	10 (5.3)
CKD	4 (2.1)
Symptom to device activation time (h)	5.27±2.69
≤3	48 (25.5)
4–6	76 (40.4)
≥6	64 (34)
Type of MI
AWMI	112 (59.6)
IWMI	66 (35.1)
LWMI	10 (5.3)
Number of diseased vessels
SVD	90 (47.9)
2VD	60 (31.9)
3VD	38 (20.2)
Culprit coronary artery
LM	2 (1.1)
LAD	116 (61.7)
RCA	48 (25.5)
LCX	22 (11.7)
Locations of occlusion
Proximal	68 (36.2)
Mid	108 (57.4)
Distal	12 (6.4)
Preprocedural TIMI
TIMI – 0	90 (47.9)
TIMI – I	44 (23.4)
TIMI – II	32 (17)
TIMI – III	22 (11.7)
Myocardial blush grade
I	20 (10.6)
II	80 (42.6)
III	88 (46.8)

CAD=Coronary artery diseases, CKD=Chronic kidney disease, MI=Myocardial infarction, AWMI=Anterior wall MI, IWMI=Inferior wall MI, LWMI=Lateral wall MI, SVD=Single vessel disease, 2VD=Two vessel disease, 3VD=Three vessel disease, LM=Left main, LAD=Left anterior descending, RCA=Right coronary artery, LCX=Left circumflex, TIMI=Thrombolysis in myocardial infarction

Echocardiography performed at baseline (within 24 h of intervention) in all recruited patients, showed LVEF of 39.79 ± 6.2%, LVEDD, 46.23 ± 3.86 mm, LVEDS, 35.96 ± 4.42 mm, and WMSI, 1.61 ± 0.25. Echocardiographic parameters within 24 h of intervention are presented in Table 2.

Table 2

Echocardiographic parameters within 24 h of intervention

Characteristics	Total
Total (n)	188
LVEF (%)	39.79±6.2
LVEDD (mm)	46.23±3.86
LVEDS (mm)	35.96±4.42
WMSI	1.61±0.25

LVEF=Left ventricular ejection fraction, LVEDD=Left ventricular end diastolic dimension, LVEDS=Left ventricular end systolic dimension, WMSI=Wall motion score index

Mean improvement in LVEF (%) was found to be 5.11 ± 3.87 at 3 months (P < 0.001) and 6.38 ± 4.29 (P < 0.001) at 6 months. LVEF improved in 75.5% and remain the same in the remaining 24.5% of the patients (P < 0.001) at 6 months of intervention. Improvements were also noted in in LVEDS and LVEDD on follow-up. Segmental wall motion abnormalities, calculated and presented in the form of WMSI, also showed improvement when compared to baseline score. Difference from baseline at 6 months was -0.13 ± 0.09. Follow-up echocardiographic parameters are presented in Table 3 and schematized in Figure 1.

Table 3

Echocardiographic assessment of patients after 3 and 6 months of intervention

Characteristics	At 3 months	At 6 months
Total (n)	188	188
LVEF
Mean±SD	44.89±6.42	46.17±6.18
Difference from baseline	5.11±3.87	6.38±4.29
P	<0.001	<0.001
No change, n (%)	54 (28.7)	46 (24.5)
Increased, n (%)	134 (71.3)	142 (75.5)
Declined, n (%)	0	0
LVEDD
Mean±SD	46.34±3.1	44.68±2.81
Difference from baseline	0.11±1.87	−1.55±2.19
P	0.436	<0.001
No change, n (%)	34 (18.1)	30 (16)
Increased, n (%)	78 (41.5)	24 (12.8)
Declined, n (%)	76 (40.4)	134 (71.3)
LVEDS
Mean±SD	35.44±4.13	34.18±3.94
Difference from baseline	−0.52±1.65	−1.78±1.92
P	<0.001	<0.001
No change, n (%)	62 (33)	36 (19.1)
Increased, n (%)	38 (20.2)	8 (4.3)
Declined, n (%)	88 (46.8)	144 (76.6)
WMSI
Mean±SD	1.53±0.22	1.49±0.2
Difference from baseline	−0.09±0.08	−0.13±0.09
P	<0.001	<0.001
No change, n (%)	16 (8.5)	12 (6.4)
Increased, n (%)	8 (4.3)	6 (3.2)
Declined, n (%)	164 (87.2)	170 (90.4)

LVEF=Left ventricular ejection fraction, LVEDD=Left ventricular end diastolic dimension, LVEDS=Left ventricular end systolic dimension, WMSI=Wall motion score index, SD=Standard deviation

Figure 1

Comparison of echocardiographic parameters at baseline, after 3 months, and 6 months of the procedure. LVEF = left ventricular ejection fraction, LVEDD = left ventricular end-diastolic dimension, LVEDS = left ventricular end-systolic dimension

DISCUSSION

This study demonstrated a significant difference in the recovery of LV function in patients with AMI who underwent primary percutaneous intervention. The mean LVEF at baseline was 39.79 ± 6.2% which improved to 46.17 ± 6.18% at 6 months with mean improvement of 6.38 ± 4.29% (P < 0.001). Along with LVEF, we observed changes in other echocardiographic parameters such as LVEDD, LVEDS, and WMSI. Improvement in such parameters has great clinical relevance.

A study conducted by Ottervanger et al.[4] recruited patients with AMI who underwent primary percutaneous therapy. The study showed mean improvement in LVEF of 6% from 43.7 ± 11.3% at baseline to 46.3 ± 11.5% at 6 months, using radionuclide ventriculography in survivors at 6th month postintervention. These results are almost consistent with our study results, which is purely TTE based. Another study conducted by Baks et al.[3] reported an increase in ejection fraction from 48 ± 11% to 55 ± 9% (P ≤ 0.01), after 5 months of successful placement of a drug-eluting stent in twenty-two patients. This study also showed improvement in the WMS index from 1.86 (0.23) to 0.32 (0.34), with a P < 0.001 in the 6th month. However, the sample size of the study was far smaller than ours. Similarly, another study conducted by Wang et al.[6] reported increased LVEF from 59.35 ± 10.16% preoperatively, to 65.86 ± 9.83% after 6 months of indexed AMI.

Sharif et al.[9] concluded that LV WMS index improves with early restoration of blood flow through coronary arteries. We also studied WMSI, which showed similar consistent improvement of −0.09 ± 0.08 and −0.13 ± 0.09 at 3 and 6 months respectively.

Niccoli et al.[10] and other clinical trials[11121314] assesses the importance of micro vasculature on myocardial function recovery in patients with acute myocardial function showed the myocardial remodeling and stunning are the predictors of prognosis.

Reason behind quoting various studies is that they used different modalities which are highly cumbersome, costly, and not widely available for the assessment of myocardial recovery such as longitudinal strain imaging,[5] layer-specific speckle tracking,[7] cardiac MRI,[78] radionuclide imaging,[4] than echocardiographic parameters (LVEF, LVEDD, LVEDS, and WMSI) which are convenient and cost-effective with almost same results.

A key strength our study is that it is the first of its kind in our population, performed at a state of the art cardiac care facility of the country. However, despite very careful and extensive scrutiny our study has certain limitations. First, it is a single-center-based study. Second, baseline echocardiography was performed within 24 h of procedure and not at patient presentation. Hence, it is very difficult to predict the improvement of LV function from before to after the procedure. This is because as per the guidelines we do not routinely perform echocardiography before primary PCI to minimize delays from the onset of symptoms to device activation time.

CONCLUSIONS

This study demonstrated that primary PCI therapy not only reduces infarct size and preserves LV systolic function but also maintains microvascular integrity, thereby decreasing LV remodeling. LV functional remodeling has great impact on prognosis. Echocardiographic parameters (LVEF, LVEDD, LVEDS, and WMSI) can be used to detect LV functional remodeling in postprimary PCI patients rather than utilizing other cumbersome techniques as done in previous studies.

Ethical clearance

This study was approval by the ethical review committee of the National Institute of Cardiovascular Diseases (NICVD), Karachi (ERC-22/2018). Written informed consent was obtained from all the patients regarding their participation in the study and publication of data while maintaining confidentiality and anonymity.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.