Exercise-Induced Pulmonary Hypertension Is Associated with High Cardiovascular Risk in Patients with HIV.

Background and Aim: Pulmonary hypertension (PH) at rest can be preceded by the onset of exercise-induced PH (ExPH). We investigated its association with the cardiovascular (CV) risk score in patients with human immunodeficiency virus (HIV).
Methods: In 46 consecutive patients with HIV with low (n = 43) or intermediate (n = 3) probability of resting PH, we evaluated the CV risk score based on prognostic determinants of CV risk. Diagnosis of ExPH was made by cardiopulmonary exercise test (CPET) and exercise stress echocardiogram (ESE).
Results: Twenty-eight % (n = 13) of the enrolled patients had ExPH at both CPET and ESE, with good agreement between the two methods (Cohen's kappa = 0.678). ExPH correlated directly with a higher CV score (p < 0.001). Patients with a higher CV score also had lower CD4+ T-cell counts (p = 0.001), a faster progression to acquired immunodeficiency syndrome (p < 0.001), a poor immunological response to antiretroviral therapy (p = 0.035), higher pulmonary vascular resistance (p = 0.003) and a higher right atrial area (p = 0.006). Conclusions: Isolated ExPH is associated with a high CV risk score in patients with HIV. Assessment of ExPH may better stratify CV risk in patients with HIV.

1. Introduction

HIV infection represents a potential risk factor for pulmonary arterial hypertension (PAH) [1]. PAH is the main cause of mortality in patients with HIV [2]. Reduced pulmonary vascular reserve may be silent at rest, while it occurs with PH during exercise. The onset of exercise-induced pulmonary hypertension (ExPH), therefore, represents the first clinical sign of pulmonary vascular disease that can progress to PAH. Similar to other clinical PAH groups, a significant number of patients with HIV may have ExPH [3,4,5,6,7]. However, the prognostic value of ExPH in patients with HIV is poorly studied and Guidelines from the American College of Cardiology/American Heart Association recommend further investigation [8].

Isolated ExPH is also associated with cardiovascular (CV) events in patients with valvular or ischemic heart disease [9,10], while it is associated with clinical worsening in patients with scleroderma [11].

We have recently shown that the onset of ExPH, diagnosed by exercise stress echocardiogram (ESE), is associated with poor control of HIV infection and ExPH is associated with impaired functional capacity, as measured by the World Health Organization functional class (WHO-FC), suggesting that disease progression in the lung leads to a reduction in the vasodilatory reserve of pulmonary circulation and, consequently, PH triggered by exercise [12]. How ExPH correlates with CV risk in patients with HIV has never been previously studied. Here, we hypothesized that an increased CV risk in patients with HIV can be determined early through the work-out for ExPH by ESE and cardiopulmonary stress testing (CPET).

2. Methods

Study Design and Data Collection. We conducted a prospective, observational, cohort study of patients with HIV recruited from the Infectious Disease Clinic at Pisa University Hospital. The study complies with the Helsinki Declaration, and informed consent was obtained from all patients prior to any diagnostic test. Local investigators had full access to patient data and medical records.

All of the enrolled patients underwent evaluation of PH probability at rest by transthoracic echocardiography (TTE) [9,12], followed by ExPH assessment by transthoracic exercise stress echocardiogram (ESE) and cardiopulmonary exercise test (CPET), as detailed in the Supplementary Materials. Patients included had either a “low” PH probability at rest (n = 43) or an “intermediate” PH probability at rest (n = 3). We excluded patients with a “high” PH probability (n = 8). Patients were then classified as either with or without ExPH at ESE or CPET. We evaluated the CV risk score by assessing the presence/absence of the prognostic determinants of cardiovascular (CV) risk, according to the 2015 European Society of Cardiology (ESC)/European Respiratory Society (ERS) Guidelines [1] and, as detailed in the Supplementary Materials. We assigned a severity score of 1–3 to each prognostic determinant and derived an overall CV risk score [11]. We then evaluated the association of a higher CV score with the presence/absence of ExPH, and with several echocardiographic parameters [12] and immuno-virological parameters.

Mono and 2D Transthoracic Echocardiography was performed using a Philips iE33 echocardiograph (Philips iE33 xMATRIX echocardiography system, Andover, MA) [13]. The images were recorded in at least three cardiac cycles. Right atrial pressure (RAP) was assessed by evaluating the inferior vena cava (IVC) diameter and collapsibility during inspirium [13]. Systolic pulmonary arterial pressure (PAPs) was calculated by adding RAP to the maximum systolic pressure gradient from tricuspid regurgitation velocity (TRV). Left atrial volume index (LAVi) was calculated by Simpson’s algorithm in apical four-chamber and two-chamber view [13]. Mitral, aortic and tricuspidal regurgitations were assessed by measuring the vena contracta at apical four-chamber view.

Stress echocardiography. All patients underwent a semi-supine ESE performed with a 2.5-MHz duplex transducer and a Philips iE33 echocardiograph (Philips iE33 xMATRIX echocardiography system, Andover, MA, USA) on a semi-recumbent cycle ergometer (Ergoline, model 900 EL, Germany), according to the European Association of Echocardiography (EAE) Guidelines [13,14,15,16,17,18]. A detailed protocol of the echocardiographic procedures is reported in the Supplementary Materials.

Cardiopulmonary Exercise Test. We performed the CPET on an electronically-braked cycle ergometer, using Vmax 6200 Spectra Series software (SensorMedics, Hochberg, Germany), according to a graded, cycling workload increase protocol. The test was interrupted when one of the following symptoms or signs occurred: angina; electrocardiographic signs of myocardial ischemia or injury; an excessive blood pressure increase (systolic blood pressure ≥ 240 mmHg, diastolic blood pressure ≥ 120 mmHg); dyspnea or maximal predicted heart rate. A detailed protocol is reported in the Supplementary Materials [19,20,21].

Statistical Analyses

Categorical data were expressed by absolute and relative frequency, and continuous data by mean and standard deviation (SD). The Chi square test and the Student’s t-test for independent (two-tailed) samples were used to compare categorial and continuous variables with ExPH, respectively. Pearson’s correlation analysis was used to compare the CV score with continuous factors, while the Student’s t-test for independent samples (two-tailed) was used to compare the CV score with categorical factors. All analyses were performed with the SPSS v.26 statistical software, with statistical significance set at 0.05.

3. Results

We enrolled 54 patients from January 2020 to July 2021 in the outpatient clinic dedicated to the diagnosis and treatment of pulmonary hypertension, University Cardiology Division, University Hospital of Pisa.

All patients included in the study had no abnormalities on chest x-ray, lung function tests or electrocardiogram. We excluded eight patients with a high probability of PH on the resting echocardiogram. The remaining 46 were admitted to the study. Table A1 and Table A2 report the baseline characteristics, medical and drug histories of the entire study cohort with respect to the presence and absence of isolated ExPH at CPET and ESE, respectively. In our cohort, 72% (n = 33) of the enrolled population did not develop ExPH at ESE and 91% (n = 30) of these patients also did not develop ExPH at CPET, with a Cohen’s kappa = 0.678, indicating moderate agreement in the diagnosis of isolated ExPH between the two different methods (Figure 1). The mean age of the 46 participants included in the study was 53 ± 11. The age of those with ExPH diagnosed by CPET (Table A1) and ESE (Table A2) was 52 ± 14 years and 51 ± 13 years, respectively, while the age of those without ExPH at CPET and ESE was 54 ± 10 and 55 ± 10, respectively. We observed no statistically significant differences in patients with and without ExPH on CPET and ESE in terms of mean body surface index (BSA) age, sex, body mass index (BMI), heart rate, systolic and diastolic blood pressure, history of hypertension, comorbidities, CV risk factors and concomitant drug use, bio-humoral data and proinflammatory markers such as IL-6, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) and fibrinogen (Table A1 and Table A2). Patients diagnosed with ExPH, both on CPET (Table A1) and ESE (Table A2), had reduced functional capacity compared to patients without ExPH (p < 0.001), while they did not show significant differences in terms of morphology and function of the right or left ventricle (Table A3 and Table A4). Patients with ExPH had higher values of sPAP (p < 0.001), TRV (p = 0.048), right atrial area (p = 0.008) and pulmonary vascular resistance (velocity ratio Peak TR and VTIRVOT > 0.20, p <0.003), compared to patients without ExPH (Table A4). We did not observe any correlation between the diagnosis of ExPH at CPET and the echocardiographic parameters associated with the pulmonary circulation and the right chambers, with the exception of sPAP (Table A3).

Table A1

Demographics, medical history and medication use according to presence and absence of ExPH at CPET.

Clinical Parameter	ExPH at CPET	Mean	SD	p-Value
Age	no	54.21	9.76	0.615
	yes	52.38	13.86
BSA	no	1.91	0.20	0.475
	yes	1.86	0.24
SAP	no	126.36	12.20	0.652
	yes	124.62	10.50
DAP	no	74.24	7.08	0.745
	yes	75.00	7.07
		ExPH at CPET
		no	yes
Sex	F	11	5	0.742
	M	22	8
Smoke	no	16	3	0.264
	yes	16	9
Functional class FC-WHO	I	32	3	<0.001
	II	1	0
	III	0	10
Chronic liver disease	no	16	8	0.425
	yes	17	5
Kidney disease	no	29	12	0.664
	yes	4	1
Thyroid disease	no	29	11	0.767
	yes	4	2
Arterial hypertension	no	29	13	0.189
	yes	4	0
Dyslipidemia	no	10	6	0.309
	yes	23	7
Diabetes mellitus	no	29	11	0.767
	yes	4	2
Familiarity for CAD	no	26	10	0.891
	yes	7	3
Calcium channel blockers	no	29	12	0.206
	yes	4	0
Hypoglycemic drugs	no	10	6	0.309
	yes	23	7
Beta blockers	no	32	13	0.526
	yes	1	0
ACE inhibitors or sartanics	no	32	13	0.526
	yes	1	0
Thyroid hormones	no	29	11	0.767
	yes	4	2
Lipid lowering drugs	no	10	6	0.309
	yes	23	7

Abbreviations: ExPH, isolated exercise pulmonary hypertension; CPET, cardiopulmonary exercise test; BSA, body surface area; SAP, systolic arterial pressure; DAP, diastolic arterial pressure; CAD, coronary artery disease; F, female; M, male; ACE, angiotensin converting enzyme.

Table A2

Demographics, medical history and medication use according to presence and absence of ExPH at ESE.

Factor	ExPH at ESE	Mean	SD	p-Value
Age	no	54.58	9.94	0.391
	yes	51.46	13.33
BSA	no	1.90	0.20	0.932
	yes	1.89	0.25
Heart rate	no	69.03	6.30	0.839
	yes	68.62	5.98
	yes	126.92	9.47
DAP	no	73.79	7.18	0.308
	yes	76.15	6.50
		ExPH at ESE
Factor		no	yes	p-value
Sex	F	12	4	0.720
	M	21	9
Smoke	no	15	4	0.570
	ex	1	1
	yes	17	8
Functional class FC-WHO	I	31	4	<0.001
	II	1	0
	III	1	9
Chronic liver disease	no	15	9	0.146
	yes	18	4
Kidney disease	no	29	12	0.664
	yes	4	1
Thyroid disease	no	28	12	0.499
	yes	5	1
Arterial hypertension	no	30	12	0.880
	yes	3	1
Dyslipidemia	no	9	7	0.088
	yes	24	6
Diabetes mellitus	no	28	12	0.499
	yes	5	1
Familiarity for CAD	no	27	9	0.351
	yes	6	4
Calcium channel blockers	no	30	11	0.937
	yes	3	1
Hypoglycemic drugs	no	9	7	0.088
	yes	24	6
Beta blockers	no	33	12	0.107
	yes	0	1
ACE inhibitors or sartanics	no	32	13	0.526
	yes	1	0
Thyroid hormones	no	28	12	0.499
	yes	5	1
Lipid lowering drugs	no	9	7	0.088
	yes	24	6

Abbreviations: ExPH, isolated exercise pulmonary hypertension; ESE, exercise stress echocardiography; BSA, body surface area; F, female; M, male; CAD, coronary artery disease; ACE, angiotensin converting enzyme.

Figure 1

Concordance of exercise stress echocardiography and the cardiopulmonary exercise test in the diagnosis of isolated exercise pulmonary hypertension. Abbreviations: ESE, exercise stress echocardiogram; ExPH, exercise-induced pulmonary hypertension; CPET, cardiopulmonary exercise test.

Table A3

ExPH at CPET vs. continuous or categorical ultrasound parameters.

Continuous Ultrasound Parameters	ExPH at CPET	Mean	SD	p-Value
LVEDD	no	43.656	5.522	0.959
	yes	43.558	5.978
LVESD	no	26.656	6.439	0.442
	yes	24.917	7.090
LVEDV	no	103.875	31.270	0.299
	yes	93.000	28.451
iLVEDV	no	36.676	10.597	0.163
	yes	31.559	10.808
LVESV	no	38.219	14.041	0.314
	yes	33.167	16.219
iLVESV	no	13.416	4.944	0.384
	yes	11.923	5.184
LV	no	152.884	48.281	0.443
	yes	140.817	38.913
iLVmass	no	79.132	29.520	0.255
	yes	68.110	24.111
LAD	no	48.359	8.571	0.919
	yes	48.083	5.744
LAV	no	38.778	20.368	0.294
	yes	32.317	7.786
iLAV	no	13.683	7.657	0.468
	yes	12.000	3.149
LVEF	no	65.147	6.406	0.584
	yes	66.500	9.200
FwSV	no	72.366	22.197	0.268
	yes	63.750	24.000
iFwSV	no	25.367	7.810	0.195
	yes	21.745	8.944
MR	no	0.688	0.780	0.027
	yes	0.250	0.452
AO	no	0.250	0.672	1.000
	yes	0.250	0.622
E wave	no	69.769	17.989	0.993
	yes	69.817	14.658
A wave	no	71.397	30.384	0.783
	yes	74.167	26.889
Septal e wave	no	9.959	3.003	0.837
	yes	9.767	1.837
E/A	no	1.067	0.394	0.909
	yes	1.085	0.629
E/e	no	6.458	3.408	0.299
	yes	7.575	2.193
iRVESA	no	4.055	1.879	0.396
	yes	4.578	1.542
iRVEDA	no	6.955	2.143	0.991
	yes	6.947	2.343
iRVESV	no	7.161	4.907	0.908
	yes	7.338	2.902
iRVEDV	no	16.048	6.550	0.220
	yes	13.507	4.273
RD1	no	36.128	7.270	0.822
	yes	36.667	6.372
RD2	no	33.472	5.483	0.116
	yes	30.333	6.513
RD3	no	20.503	6.485	0.041
	yes	16.083	5.351
RVOT prox.	no	31.716	6.057	0.627
	yes	30.792	3.905
RVOT dist.	no	32.353	7.471	0.166
	yes	29.042	5.163
eccentricity index	no	0.941	0.110	0.475
	yes	0.914	0.103
RV/LV basal diameter ratio	no	0.864	0.162	0.317
	yes	0.808	0.162
TAPSE	no	21.913	7.104	0.707
	yes	22.842	7.665
FAC	no	45.053	9.607	0.210
	yes	49.083	8.554
RV E/A	no	4.338	13.318	0.389
	yes	0.963	0.408
RV E/e	no	3.673	1.829	0.683
	yes	3.938	1.891
RV S vel	no	10.993	4.485	0.630
	yes	11.767	5.301
RV S VTI	no	3.608	4.050	0.024
	yes	1.810	0.926
TR	no	1.219	0.491	0.862
	yes	1.250	0.622
sPAP	no	22.375	5.752	0.749
	yes	21.750	5.675
sPAP at exercise peak	no	32.847	10.602	0.028
	yes	40.767	9.452
mPAP	no	16.333	3.623	0.969
	yes	16.385	4.636
TRV	no	2.009	0.373	0.622
	yes	2.075	0.449
TRV at exercise peak	no	2.544	0.555	0.557
	yes	2.658	0.616
RV outflow AT	no	102.714	42.717	0.014
	yes	138.167	34.821
VCI diameter	no	15.016	3.777	0.571
	yes	14.158	5.896
RA area	no	14.709	3.227	0.295
	yes	15.875	3.294
iRAV	no	5.356	2.191	0.410
	yes	5.924	1.420
VTI at rvot	no	15.843	3.811	<0.001
	yes	11.167	2.916
VRT/VTI at rvot	no	0.156	0.142	0.414
	yes	0.191	0.051
TAPSE/PAPs	no	1.033	0.347	0.609
	yes	1.100	0.471
Categorical ultrasound parameters	ExPH at ESE	no	yes	p-value
Concentric remodeling	no	19	5	0.293
	yes	13	7
Normal geometry	no	18	7	0.901
	yes	14	5
Concentric hypertrophy	no	29	12	0.272
	yes	3	0
Eccentric hypertrophy	no	31	12	0.536
	yes	1	0

Abbreviations: ExPH, isolated exercise pulmonary hypertension; CPET, cardiopulmonary exercise test; LVEDD, left ventricle end-diastolic diameter; LVESD, left ventricle end-systolic diameter; LVEDV, left ventricle end-diastolic volume; LVESV, left ventricle end-systolic volume; iLVEDV, indexed LVEDV; iLVESV, indexed LVESV; LAD, left atrial diameter; LAV, left atrial volume; iLAV, indexed LAV; LVEF, left ventricle ejection fraction; FwSV, forward stroke volume; iFwSV, indexed FwSV; iRVESA, indexed right ventricle end-systolic area; iRVEDA, indexed right ventricle end-diastolic area; iRVESV, indexed right ventricle end-systolic volume; iRVEDV, indexed right ventricle end-diastolic volume; RD, right diameter; RVOT, right ventricle outflow; TAPSE, tricuspid annular plane excursion; FAC, fractional area change; VTI, velocity time integral; sPAP, systolic pulmonary arterial pressure; mPAP, mean PAP; TR, tricuspid regurgitation; IVC, inferior vena cava, iRAV, indexed right atrial volume; TRV, tricuspid regurgitation velocity; ESE, exercise stress echocardiogram.

Table A4

ExPH at ESE vs. continuous or categorical ultrasound parameters.

Continuous Ultrasound Parameters	ExPH at ESE	Mean	SD	p-Value
LVEDD	no	43.459	5.322	0.745
	yes	44.083	6.445
LVESD	no	26.625	6.460	0.472
	yes	25.000	7.058
LVEDV	no	100.938	31.460	0.992
	yes	100.833	29.489
iLVEDV	no	35.857	10.955	0.568
	yes	33.743	10.596
LVESV	no	36.406	14.555	0.752
	yes	38.000	15.486
iLVESV	no	12.992	5.205	0.971
	yes	13.054	4.604
LV	no	149.453	44.358	0.974
	yes	149.967	51.515
iLV mass	no	77.544	28.061	0.593
	yes	72.343	29.882
LAD	no	48.531	8.481	0.737
	yes	47.625	6.057
LAV	no	38.844	19.955	0.276
	yes	32.142	10.252
iLAV	no	13.895	7.507	0.290
	yes	11.452	3.692
LVEF	no	66.459	7.437	0.157
	yes	63.000	6.030
FwSV	no	73.022	24.849	0.155
	yes	62.000	13.671
iFwSV	no	25.663	8.952	0.090
	yes	20.957	4.347
MR	no	0.656	0.787	0.193
	yes	0.333	0.492
AO	no	0.313	0.738	0.304
	yes	0.083	0.289
E wave	no	68.084	18.606	0.284
	yes	74.308	10.979
A wave	no	71.400	30.367	0.784
	yes	74.158	26.943
Septal e wave	no	10.128	2.958	0.384
	yes	9.317	1.908
E/A	no	1.037	0.397	0.415
	yes	1.166	0.613
E/e	no	6.251	3.400	0.077
	yes	8.129	1.778
iRVESA	no	4.083	1.862	0.492
	yes	4.505	1.622
iRVEDA	no	7.029	2.113	0.708
	yes	6.749	2.405
iRVESV	no	7.183	4.886	0.950
	yes	7.278	3.001
iRVEDV	no	16.217	6.461	0.126
	yes	13.058	4.326
RD1	no	35.987	6.920	0.660
	yes	37.042	7.344
RD2	no	33.188	5.538	0.297
	yes	31.092	6.712
RD3	no	20.031	6.699	0.222
	yes	17.342	5.520
RVOT prox.	no	31.119	5.782	0.505
	yes	32.383	4.882
RVOT dist.	no	31.656	7.305	0.754
	yes	30.900	6.468
Eccentricity index	no	0.943	0.112	0.335
	yes	0.908	0.096
RV/LV basal diameter ratio	no	0.852	0.157	0.815
	yes	0.839	0.179
TAPSE	no	21.707	6.949	0.495
	yes	23.392	7.958
FAC	no	45.397	9.376	0.391
	yes	48.167	9.609
RV E/A	no	4.333	13.319	0.391
	yes	0.976	0.431
RV E/e	no	3.729	1.882	0.946
	yes	3.774	1.739
RV S vel	no	10.950	4.497	0.561
	yes	11.883	5.251
RV S VTI	no	3.174	3.328	0.867
	yes	2.968	4.289
TR	no	1.313	0.471	0.077
	yes	1.000	0.603
sPAP	no	22.344	6.003	0.794
	yes	21.833	4.896
sPAP at exercise peak	no	30.909	8.846	<0.001
	yes	45.933	7.504
mPAP	no	16.351	3.802	0.991
	yes	16.337	4.212
TRV	no	2.009	0.389	0.622
	yes	2.075	0.409
TRV at exercise peak	no	2.472	0.502	0.048
	yes	2.850	0.659
RV outflow AT	no	105.027	43.990	0.065
	yes	132.000	36.352
VCI diameter	no	14.722	4.534	0.885
	yes	14.942	4.191
RA area	no	14.253	3.127	0.008
	yes	17.092	2.710
iRAV	no	5.266	2.186	0.189
	yes	6.166	1.300
VTI at rvot	no	16.065	3.552	<0.001
	yes	10.575	2.703
VRT/VTI at rvot	no	0.153	0.143	0.289
	yes	0.198	0.041
TAPSE/PAPs	no	1.024	0.321	0.448
	yes	1.123	0.516
Categorical ultrasound parameter	ExPH at ESE	no	yes	p-value
Concentric remodeling	no	19	5	0.293
	yes	13	7
Normal geometry	no	18	7	0.901
	yes	14	5
Concentric hypertrophy	no	29	12	0.272
	yes	3	0
Eccentric hypertrophy	no	31	12	0.536
	yes	1	0

Abbreviations: ExPH, isolated exercise pulmonary hypertension; ESE, exercise stress echocardiogram; LVEDD, left ventricle end-diastolic diameter; LVESD, left ventricle end-systolic diameter; LVEDV, left ventricle end-diastolic volume; LVESV, left ventricle end-systolic volume; iLVEDV, indexed LVEDV; iLVESV, indexed LVESV; LAD, left atrial diameter; LAV, left atrial volume; iLAV, indexed LAV; LVEF, left ventricle ejection fraction; FwSV, forward stroke volume; iFwSV, indexed FwSV; iRVESA, indexed right ventricle end-systolic area; iRVEDA, indexed right ventricle end-diastolic area; iRVESV, indexed right ventricle end-systolic volume; iRVEDV, indexed right ventricle end-diastolic volume; RD, right diameter; RVOT, right ventricle outflow; TAPSE, tricuspid annular plane excursion; FAC, fractional area change; VTI, velocity time integral; sPAP, systolic pulmonary arterial pressure; mPAP, mean PAP; TR, tricuspid regurgitation; IVC, inferior vena cava, iRAV, indexed right atrial volume; TRV, tricuspid regurgitation velocity.

We evaluated the CV risk score in all 46 patients. The population’s overall CV risk score ranged from 8 (low CV risk) to 14 (high CV risk), with an average of 10.2 ± 2.4. The isolated ExPH diagnosed by both CPET and ESE was directly correlated to a higher CV score (p < 0.001) (Table 1). Patients with a higher CV score also had lower CD4+ T-cell counts (p = 0.001), a higher proportion of clinical progression to AIDS (p < 0.001) and a poor immunological response to anti-retroviral therapy (ART) (p = 0.035) (Table 2) and a higher right atrial area (p = 0.006) at rest TTE compared to patients with a lower CV risk score (Table 3). Furthermore, the proportion of patients with PVRI (ratio of Peak TR velocity to VTIRVOT) > 0.20 and higher CV score was increased compared to patients with a lower CV score (p = 0.003), indicating higher total pulmonary vascular resistance in patients with higher CV risk (Table 3). No associations with time to HIV diagnosis, time to beginning ART, ART discontinuation, virological response to ART, current use of protease inhibitors and proinflammatory markers such as IL-6, ESR, CRP and fibrinogen were found (Table 2).

Table 1

Comparison between score and ExPH.

	CV Score	p-Value
ExPH at CPET		<0.001
no	8.8 (0.7)
yes	12.9 (2.1)
ExPH at ESE		<0.001
no	8.9 (1.1)
yes	12.5 (2.4)

CV score values are shown as mean (SD). Abbreviations: ExPH, isolated exercise pulmonary hypertension; CPET, cardiopulmonary exercise test; ESE, exercise stress echocardiogram.

Table 2

Comparison between score and virological and immunological factors.

	Statistics	p-Value
Time to HIV diagnosis (y)	−0.155	0.309
CD4+ T-cell count at diagnosis (cell/mmc)	−0.402	0.012
CD4+ T-cell count at diagnosis (%)	−0.380	0.020
CD4+ T-cell count last determination (cell/mmc)	−0.386	0.009
CD4+ T-cell count last determination (%)	−0.480	0.001
Clinical progression to AIDS		<0.001
no	8.8 (1.1)
yes	12.9 (2)
Development of resistance to ART		0.451
no	9.8 (2.1)
yes	10.4 (2.7)
HIV-RNA levels at diagnosis (cp/mL)	−0.116	0.502
HIV-RNA levels last determination (cp/mL)	0.010	0.949
HIV-RNA levels last determination (cp/mL)		0.949
<20 cp/mL	9.9 (2.3)
>20 cp/mL	10 (2.3)
Time to beginning of ART	−0.182	0.226
Current use of protease inhibitors		0.101
no	9.8 (2.2)
yes	11.5 (2.7)
Combination of ART with booster (ritonavir or cobicistat)		0.827
no	10.1 (2.4)
yes	9.9 (2.4)
Virologic response to ART		0.690
<20 copies/mL	9.7 (2.2)
20–50 copies/mL	10.1 (2.3)
50–200 copies/mL	11.5 (3.5)
>200 copies/mL	10.7 (2.9)
Immunologic response to ART		0.035 *
optimal	9.3 (1.8)
acceptable	10.6 (2.6)
not acceptable	12.3 (2.9)
ART discontinuation		0.536
no	10.2 (2.4)
yes	9.7 (2.3)
IL-6	0.289	0.152
PCR	−0.247	0.224
VES	0.194	0.354
FBG	−0.053	0.789

Statistics: Pearson’s r or mean (SD). Abbreviations: HIV, Human immunodeficiency virus; ART, antiretroviral therapy; IL-6, interleukin-6; PCR, reactive C protein; VES, Erythrocyte sedimentation rate; FBG, fibrinogen. * only the comparison between “optimal” and “not acceptable” was statistically significant with a p = 0.040, by Dunnett correction using “not acceptable” as the reference category.

Table 3

Comparison between score and ultrasound parameters.

Parameter	Statistics	p-Value
Concentric remodeling		0.557
no	9.9 (2.2)
yes	10.3 (2.6)
Normal geometry		0.755
no	10.1 (2.4)
yes	9.9 (2.3)
Concentric hypertrophy		0.014
no	10.2 (2.4)
yes	8.7 (0.6)
Eccentric hypertrophy		0.383
no	10 (2.3)
yes	11.5 (3.5)
LAD	−0.055	0.718
LAV	−0.076	0.620
iLAV	−0.067	0.667
LVEF	−0.164	0.281
FwSV	−0.097	0.527
iFwSV	−0.112	0.465
MR	−0.102	0.503
AO	−0.146	0.339
MS	−0.069	0.651
AS	−0.069	0.651
E wave	0.116	0.448
A wave	0.153	0.315
Septal e wave	0.025	0.871
E/A	−0.107	0.485
E/e	0.178	0.242
iRVESA	0.133	0.385
iRVEDA	0.069	0.652
iRVESV	0.124	0.419
iRVEDV	−0.133	0.385
RD1	0.075	0.626
RD2	−0.215	0.157
RD3	−0.275	0.068
RVOT prox.	−0.081	0.596
RVOT dist.	0.071	0.644
Eccentricity index	−0.207	0.171
RV/LV basal diameter ratio	−0.192	0.205
TAPSE	0.088	0.564
FAC	0.179	0.240
RV E/A	−0.140	0.358
RV E/e	−0.026	0.869
RV S vel	0.151	0.322
RV S VTI	−0.245	0.104
TR	−0.127	0.407
sPAP	−0.018	0.906
aPAP at exercise peak	0.269	0.074
mPAP	0.036	0.814
TRV	0.115	0.454
TRV at exercise peak	0.032	0.834
RV outflow AT	0.207	0.173
VCI diameter	−0.048	0.753
RA area	0.401	0.006
iRAV	0.273	0.070
VTI at rvot	−0.583	0.000
VRT/VTI at rvot	0.197	0.196
TAPSE/PAPs	0.101	0.508
PVRI		0.003
<0.20	8.88 (1.23)
>0.20	12.10 (2.55)

Statistics: Pearson’s r or mean (SD). Abbreviations: LVEDD, left ventricle end-diastolic diameter; LVESD, left ventricle end-systolic diameter; LVEDV, left ventricle end-diastolic volume; LVESV, left ventricle end-systolic volume; iLVEDV, indexed LVEDV; iLVESV, indexed LVESV; LAD, left atrial diameter; LAV, left atrial volume; iLAV, indexed LAV; LVEF, left ventricle ejection fraction; FwSV, forward stroke volume; iFwSV, indexed FwSV; iRVESA, indexed right ventricle end-systolic area; iRVEDA, indexed right ventricle end-diastolic area; iRVESV, indexed right ventricle end-systolic volume; iRVEDV, indexed right ventricle end-diastolic volume; RD, right diameter; RVOT, right ventricle outflow; TAPSE, tricuspid annular plane excursion; FAC, fractional area change; VTI, velocity time integral; sPAP, systolic pulmonary arterial pressure; mPAP, mean PAP; TR, tricuspid regurgitation; IVC, inferior vena cava; iRAV, indexed right atrial volume; TRV, tricuspid regurgitation velocity; PVRI, Pulmonary Vascular Resistance Index.

4. Discussion

We investigated whether isolated ExPH is associated with a higher CV risk score in patients with HIV without a high probability of PH at resting echocardiogram. We have found that patients who develop ExPH have a higher CV risk score, as assessed by the ESC/ERS Guidelines [1]. We have found that isolated ExPH is associated with worse WHO-FC, shorter walk distance at the 6MWT and a lower VO2 peak, indicating worse functional capacity. The worst CV risk score was actually clustered into the isolated ExPH group, suggesting the usefulness of ExPH in assessing CV risk of patients with HIV. This is supported by the fact that patients with a worse CV risk score who also had isolated ExPH showed worse echo parameters related to PH and its consequences on the right cardiac chambers, as these patients had a higher total pulmonary vascular resistance and a higher right atrial area at rest TTE. Our results suggest that the work-out of ExPH using the combined ESE and CPET approach allows for the identification of those patients with HIV who develop ExPH due to reduced pulmonary vasodilatory reserve and who have a worse CV risk profile.

Unlike the previous study, where we only used the echocardiographic approach in diagnosing ExPH [12], here we used a combined CPET-ESE approach to non-invasively assess cardiovascular and pulmonary responses to exercise. Several studies have shown that in different clinical settings, CPET is more sensitive and specific than ESE in identifying pulmonary vascular abnormalities precipitated by exercise [22]. In our cohort we could not evaluate the differential performance of CPET and ESE in detecting ExPH as we did not perform right stress cardiac catheterization, which is the reference gold standard [1]. However, we have shown that there is good agreement in diagnosis between the two different methods, as demonstrated by the high Cohen’s kappa index. However, the benefit of performing a combined CPET-ESE is the identification of concomitant left heart disease as the cause of exertional dyspnea and ExPH. Increased left ventricle filling pressure is known to lead to pulmonary venous congestion and post-capillary pulmonary hypertension, regardless of LVEF [23,24]. In our cohort, TEE at rest and ESE ruled out the existence of left heart disease as a possible cause of ExPH, regardless of the method used for diagnosis.

We have recently shown that the onset of ExPH, as diagnosed by ESE, is associated with poor immunological control of HIV infection [11]. Here we have found that those patients who have worse immunological control of the disease also have a higher CV risk score. Finally, patients with a higher CV risk score also had greater clinical progression to AIDS and poorer immunological response to ART. This confirms previous studies demonstrating the role of a weakened or dysfunctional immune system in determining CV risk and prognosis of HIV-related PAH [2,25,26]. Thus, isolated ExPH can identify patients with HIV at higher CV risk as a consequence of poorer immune control of the disease. PAH often complicates HIV infection and this leads to the increased mortality of these patients. We are now demonstrating that the development of isolated ExPH in such patients without a high PH probability at rest can be considered an early marker of a worsening outcome.

HIV proteins can trigger an inflammatory response, leading to PAH [27]. Patients with HIV have elevated levels of interleukin 6 (IL-6), tumor necrosis factor α (TNFα) and nitric oxide synthase (NO) inhibitors [28,29]. The inflammation theory of PAH is biologically and clinically plausible, as PAH continues to manifest significantly in patients with HIV as an expression of the persistence of this inflammatory component, despite a good response to ART [30]. However, so far there are no clinical studies that correlate high levels of these proinflammatory mediators with the development of PAH in patients with HIV. An exploratory Phase 1 clinical study, the first of its kind to our knowledge, is still ongoing to test the effects of a combination of the HIV protease inhibitors saquinavir and ritonavir on proinflammatory mediators and pulmonary hemodynamics in patients with idiopathic PAH (ClinicalTrials.gov identifier: NCT02023450). Therefore, the blood levels of these mediators may currently be useful biomarkers in the stratification of patients with HIV with a higher atherosclerotic CV risk, but not those who have a propensity to develop HIV-related PAH. On the other hand, these biomarkers are not included in any of the validated risk scores in patients with PAH group 1, including patients with HIV. In our cohort, we did not observe any significant association between levels of IL-6 or other proinflammatory markers and ExPH or a worse CV risk score. However, only a few patients had such biomarkers evaluated. Further investigation with more patients is needed to establish the role of proinflammatory biomarkers in the development of PAH and a worse CV risk score.

Study Limitations

This study has several limitations: (1) the small sample size, for which our report should be intended as a pilot study on the role of ExPH in risk stratification of patients with HIV; (2) patients with ExPH at ESE and CPET did not undergo cardiac catheterization, which is, however, not indicated, and therefore unethical in such patients with low and intermediate probability of PH [1]. Finally, adequate follow-up could allow us to verify if patients with ExPH develop PH at rest, and if this is associated with a worsening of CV risk over time. Our research group is carrying out a long-term follow-up, which will help to clarify the prognostic significance of ExPH in the HIV population.

In conclusion: Isolated ExPH associates with a higher CV risk score in patients with HIV. Assessment of ExPH by CPET or ESE can contribute to the risk stratification of patients with HIV.