Effect of a Systemic Right Ventricle With a Biventricular Circulation on Cardiorespiratory Fitness

Abstract

Background

Adults with transposition of the great arteries and a systemic right ventricle (sRV) generally have lower cardiorespiratory fitness (CRF) than healthy adults with a systemic left ventricle (sLV). However, studies to date have not accounted for systolic function of the systemic ventricle. The objective was to assess and compare CRF in adults with an sRV vs sLV matched for clinical characteristics and systemic ventricular function.

Methods

A retrospective cross-sectional analysis was conducted on 24 adults with an sRV and 24 adults with an sLV matched for sex (20 males), age, body mass index, ejection fraction of the systemic ventricle (dysfunction in 23 pairs), New York Heart Association functional class (class II-III in 18 pairs), and doses of diuretics. Peak oxygen consumption ($\dot{\mathrm{V}}{\mathrm{O}}_{2_{\text{peak}}}$) was compared with a Wilcoxon signed-rank test. The percentage of predicted $\dot{\mathrm{V}}{\mathrm{O}}_{2_{\text{peak}}}$ (% $\dot{\mathrm{V}}{\mathrm{O}}_{2_{\text{peak}}}$) and ventilation/carbon dioxide production slope (${\dot{\mathrm{V}}}_{\mathrm{E}}/{\dot{\mathrm{V}}}_{{\text{CO}}_2}$ slope) were presented as secondary outcomes. Statistical significance was set at P < 0.05.

Results

The population is characterized by high previous heart failure–related hospitalizations (22% in sRV and 58% in sLV) and diagnoses of pulmonary hypertension (61% in sRV and 60% in sLV). $\dot{\mathrm{V}}{\mathrm{O}}_{2_{\text{peak}}}$ did not differ between groups, with a mean difference (sRV – sLV) of 0.17 mL/kg/min (95% confidence interval [CI]: –2.74, 2.39; P = 0.770). The mean difference between groups for $\%\dot{\mathrm{V}}{\mathrm{O}}_{2_{\text{peak}}}$ was 5% (95% CI: –13, 2), and for ${\dot{\mathrm{V}}}_E/{\dot{\mathrm{V}}}_{{\text{CO}}_2}$ slope it was 0.92 (95% CI: –3.98, 2.14).

Conclusion

No differences in CRF were observed between adults with an sRV and an sLV when matched for clinical characteristics and systemic ventricular function.

Patients with a dextro-transposition of the great arteries (DTGA) with atrial switch repair, as well as those with congenitally corrected transposition of the great arteries (ccTGA), have a systemic right ventricle with biventricular circulation (sRV). Studies have reported that the population with an sRV has lower cardiorespiratory fitness (CRF), as measured by peak oxygen consumption ($\dot{\mathrm{V}}{\mathrm{O}}_{2_{\text{peak}}}$), from childhood to older age than the general healthy population with a systemic left ventricle (sLV). This difference persists even when the sRV has a normal ejection fraction and patients have normal functional status.1, 2, 3, 4 During adulthood, the percentage of predicted $\dot{\mathrm{V}}{\mathrm{O}}_{2_{\text{peak}}}$ ($\%\dot{\mathrm{V}}{\mathrm{O}}_{2_{\text{peak}}}$) is approximately 66% in patients with DTGA and 63% in patients with ccTGA compared with the normal values observed in healthy individuals with the same height, weight, sex, and age.³

The prevalence of heart failure is high in patients with an sRV (approximately 60% at 40 years of age).⁵ Cardiopulmonary exercise tests are routinely performed to measure CRF and assess the prognosis of patients with heart failure to guide treatment.⁶ However, current CRF-derived prognostic thresholds are based on values obtained from patients with sLV dysfunction.^6,7 No prognostic value has been reported to date for the population with an sRV in a heart failure state, and it is currently unknown whether prognostic values derived from patients with an sLV are applicable to those with an sRV as $\dot{\mathrm{V}}{\mathrm{O}}_{2_{\text{peak}}}$ is already reduced in asymptomatic patients with an sRV compared with the population with an sLV.² Previous studies mostly compared patients with an sRV with healthy individuals by only matching for sex and age. Furthermore, studies did not account for key clinical characteristics (eg, New York Heart Association [NYHA] functional class symptoms, medication, and systemic ventricular function) known to affect CRF.2, 3, 4^,8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18 To date, no studies have determined whether patients with an sRV have lower CRF than patients with an sLV when matched for systemic ventricular dysfunction and NYHA symptoms.

The objective of this study was to assess and compare CRF in adults with an sRV vs those with an sLV after matching for demographic and clinical characteristics, and systemic ventricular function.

Methods

Study design

A retrospective cross-sectional analysis of cardiopulmonary exercise tests carried out at the Montreal Heart Institute between 2013 and 2023 was performed. Demographic and clinical data, including type of cardiomyopathy (eg, ischemic, dilated, and toxic) for sLV, type of TGA for sRV, NYHA functional class, ejection fraction of the systemic ventricle (measured by transthoracic echocardiogram), and medication therapy, were collected at the time of the cardiopulmonary exercise test. Data on prior heart failure and electrophysiological complications before the cardiopulmonary exercise test were also collected (Fig. 1). The study was approved by the Research Ethics and New Technology Development Committee of the Montreal Heart Institute.

Figure 1.

Peak oxygen consumption difference between systemic right ventricle (sRV) and systemic left ventricle (sLV) population in biventricular physiology. The figure first illustrates the selection and matching process for the study population pairs, followed by the presentation of the results for the primary outcome: the peak oxygen consumption. BMI, body mass index; CI, confidence interval; MET, metabolic equivalent of task; MRA, mineralocorticoid receptor antagonists; NYHA, New York Heart Association; sVF, systemic ventricular function; TTE, transthoracic echocardiogram.

Inclusion/exclusion criteria

The results of cardiopulmonary exercise tests performed with direct gas exchange measurements were obtained from patients 18 years or older at the time of testing, who were diagnosed with DTGA with atrial switch or ccTGA. Exclusion criteria for patients with an sRV consisted of an arterial switch operation, cardiac transplantation, open-heart surgery in the previous 4 weeks, or pregnancy at the time of the cardiopulmonary exercise test. Patients with an sLV were excluded if the demographic data, the clinical data, or the cardiopulmonary exercise test results were not available or incomplete, or if the patient had a history of hypertrophic cardiomyopathy or significant aortic stenosis, open-heart surgery in the previous 4 weeks, or pregnancy at the time of the cardiopulmonary exercise test.

Pairing

Patients with an sRV were matched at a ratio of 1:1 to patients with an sLV. A combination of exact matching and coarse exact matching was used.¹⁹ Exact matching was used for biological sex (male/female) and NYHA functional class symptoms (class I, II, II, and IV). Coarse matching was used for age (±10 years), body mass index (±5 kg/m²), daily dose of furosemide (≤80 mg or >80 mg), and daily dose of spironolactone (≤25 mg or >25 mg). The transthoracic echocardiography evaluation of systemic ventricular ejection fraction, performed at the time of the cardiopulmonary exercise test, was used to match for qualitative function of the systemic ventricle. For patients with an sLV, the ventricular function was based on the quantitative analysis of the ejection fraction according to the American Society of Echocardiography/American Heart Association guidelines (normal: men 52%-72%/women 54%-74%; mild dysfunction: men 41%-51%/women 41%-53%; moderate dysfunction: 30%-40%; severe dysfunction: <30%).²⁰ For patients with an sRV, the ventricular function was reported as normal, mild, moderate, or severe dysfunction according to an in-house algorithm that combines measurements of tricuspid annular plane systolic excursion, tricuspid annular peak systolic velocity on tissue Doppler imaging, right ventricular fractional area change, and right ventricular free wall and septal systolic strain.²¹

Cardiopulmonary exercise testing

A ramp protocol on a treadmill with direct gas exchange measurements was used to determine CRF. The tests were individualized to each patient to attain maximal effort within approximately 10-12 minutes. After a 2-minute rest period in a seated position, patients stepped onto the treadmill, and speed and slope increased progressively and interchangeably every 15 seconds. Speed was increased by increments of 0.1 mph. The slope was increased by increments of 0.5%. On termination of exercise, patients recovered in a seated position for 3 minutes. Continuous gas exchange analysis was performed on a breath-by-breath basis with a metabolic cart (Omnia, Rome, Italy). Heart rate was derived from a 12-lead electrocardiogram and oxygen saturation from a pulse oximeter. Blood pressure was measured every 2 minutes by manual auscultation of the brachial artery. The rating of perceived exertion was measured with a Borg analog scale ranging from 6 (ie, no effort) to 20 (ie, maximal effort). Use of the handlebars was permitted only to keep balance. The test was considered maximal when the respiratory exchange ratio was ≥1.0.²²

Data analysis

Gas exchange measurements were averaged every 15 seconds. The highest 15-second average during the last minute of the cardiopulmonary exercise test was used to define $\dot{\mathrm{V}}{\mathrm{O}}_{2_{\text{peak}}}$.²³ The ${\dot{\mathrm{V}}}_{\mathrm{E}}/{\dot{\mathrm{V}}}_{{\text{CO}}_2}$ slope was calculated by linear regression from the start of the test to the ventilatory compensation point. The $\%\dot{\mathrm{V}}{\mathrm{O}}_{2_{\text{peak}}}$ was calculated according to the FRIENDS registry equations.²⁴ The data were inspected visually and with a Shapiro-Wilks test to determine the normality of distribution, and the homogeneity of variance was checked with the Fisher test. The primary outcome was $\dot{\mathrm{V}}{\mathrm{O}}_{2_{\text{peak}}}$ and was analyzed between the groups with 1-sided Wilcoxon signed-rank test and presented as the mean difference (sRV – sLV) with 95% confidence interval (CI). Statistical significance was set at P < 0.05. We considered that the minimal clinically significant difference between the groups for $\dot{\mathrm{V}}{\mathrm{O}}_{2_{\text{peak}}}$ was 3.5 mL/kg/min (ie, 1 metabolic equivalent of task) to account for measurement errors²⁵ and based on its association with heart failure incidence.²⁶ Secondary outcomes were $\%\dot{\mathrm{V}}{\mathrm{O}}_{2_{\text{peak}}}$ and ${\dot{\mathrm{V}}}_{\mathrm{E}}/{\dot{\mathrm{V}}}_{{\text{CO}}_2}$ slope and are presented as the mean difference with 95% CI. An exploratory analysis dichotomized patients based on the Weber prognostic criterion for patients with a heart failure phenotype, specifically according to a $\dot{\mathrm{V}}{\mathrm{O}}_{2_{\text{peak}}}$ of patients with an sLV of >20 mL/kg/min or ≤20 mL/kg/min.^2,6,7,27 Descriptive results in the text are presented as mean ± standard deviation or ratio (percentage). R (version 2023.03.0; R Foundation for Statistical Computing, Vienna, Austria) was used for statistical analysis.

Results

Pairing

A total of 256 cardiopulmonary exercise test reports from patients with an sRV and 959 cardiopulmonary exercise test reports from patients with an sLV were retrieved and considered for matching. Among these reports, 24 matches were identified (21 TGA/3 ccTGA) (Fig. 1 and Table 1). There was no significant age difference between patients with an sLV and those with an sRV (P = 0.809). On average, patients with ccTGA were 8 years older than patients with TGA and had a 1.6-unit higher ${\dot{\mathrm{V}}}_{\mathrm{E}}/{\dot{\mathrm{V}}}_{{\text{CO}}_2}$ slope than patients with TGA. Otherwise, $\dot{\mathrm{V}}{\mathrm{O}}_{2_{\text{peak}}}$ , $\%\dot{\mathrm{V}}{\mathrm{O}}_{2_{\text{peak}}}$, and other matching criteria showed little to no difference when compared with the rest of the study sample. The 24 paired patients represent a cohort with a high incidence of heart failure and cardiac complications, affecting both the sLV and sRV groups. Among the 24 pairs, 18 (75%) were classified as NYHA functional class II-III and 23 (96%) presented with systemic ventricular dysfunction. In patients with an sRV, 61% were diagnosed with pulmonary hypertension and 22% were previously hospitalized for heart failure. All 24 patients with an sLV were diagnosed with cardiomyopathy, with 19 classified as having heart failure with reduced ejection fraction (<40%) and 5 as having heart failure with preserved ejection fraction (>41%). The study sample presented a high proportion of past heart failure–related hospitalization (58%), pulmonary hypertension diagnosis (60%), a high mean N-terminal pro–B-type natriuretic peptide level (1484 ± 1504 pg/mL), and a high prevalence of heart failure medication.

Table 1.

Patient characteristics

Characteristics	sLV (n = 24)	sRV (n = 24)
Demographics
Male/female, n	20/4	20/4
Age (y)	48 (40-54)	47 (43-52)
BMI (kg/m2)	27 (25-30)	28 (25-31)
Congenital heart disease
DTGA with atrial switch	n/a	21 (87)
ccTGA	n/a	3 (12)
Cardiomyopathy
Dilated	12 (50)	n/a
Ischemic	5 (22)	n/a
Toxic	1 (4)	n/a
Valvular	2 (8)	n/a
Sarcoidosis	2 (8)	n/a
Myocarditis	1 (4)	n/a
Arrhythmogenic	1 (4)	n/a
Systemic ventricular function
Normal	1 (4)	1 (4)
Mild dysfunction	4 (17)	4 (17)
Moderate dysfunction	12 (50)	12 (50)
Severe dysfunction	7 (29)	7 (29)
NYHA class
I	6 (25)	6 (25)
II	17 (71)	17 (71)
III	1 (4)	1 (4)
Medications
MRA	18 (75)	8 (33)
Furosemide	11 (46)	5 (21)
β-Blockers	24 (100)	21 (88)
ACE/ARB/ARNi	24 (100)	17 (71)
iSGTL2	3 (12)	0 (0)
Others
Diabetes	8 (33)	4 (17)
Dyslipidemia	8 (33)	6 (25)
Arterial hypertension	10 (41)	6 (25)
Pulmonary hypertension∗	9 (60)	11 (61)
Heart failure–related hospitalization	14 (58)	5 (22)
Pacemaker	1 (4)	9 (37)
Defibrillator	16 (67)	9 (37)
Primary prevention	13 (54)	7 (29)
Secondary prevention	3 (12)	2 (8)
CRT	7 (29)	3 (12)
NT-proBNP (pg/mL)	792 (373-1889) (n = 23)	970 (431-1923) (n = 17)

Values are presented as median (interquartile range) or n (%).

ACE, angiotensin-converting enzyme; ARB, angiotensin receptor blockers; ARNi, angiotensin receptor/neprilysin inhibitor; BMI, body mass index; ccTGA, congenitally corrected transposition of the great arteries; CRT, cardiac resynchronization therapy; D-TGA, dextro-transposition of the great arteries; iSGTL2, sodium-glucose cotransporter 2 inhibitors; MRA, mineralocorticoid receptor antagonists; n/a, not applicable; NT-proBNP, N-terminal pro–B-type natriuretic peptide; NYHA, New York Heart Association functional class; sLV, systemic left ventricle in biventricular circulation; sRV, systemic right ventricle in biventricular circulation.

^∗Defined by a mean pulmonary artery pressure >20 mm Hg measured by cardiac catheterization (a cardiac catheterization was performed before the cardiopulmonary exercise test in 15 patients in the sLV group and 18 patients in the sRV group).

Primary outcome

The exercise stress test results are presented in Table 2 and Figure 2. $\dot{\mathrm{V}}{\mathrm{O}}_{2_{\text{peak}}}$ did not differ between the groups, with a mean difference of 0.17 mL/kg/min (95% CI: –2.74, 2.39, P = 0.770).

Table 2.

Exercise stress test results

Variables	sLV (n = 24)	sRV (n = 24)
$\dot{\mathrm{V}}{\mathrm{O}}_{2_{\text{rest}}}$, (mL/kg/min)	4.5 (4.0-5.5)	4.4 (4.1-4.9)
$\dot{\mathrm{V}}{\mathrm{O}}_{2_{\text{peak}}}$ (mL/kg/min)	19 (16.9-22.0)	20.3 (16.7-23.5)
Percent predicted $\dot{\mathrm{V}}{\mathrm{O}}_{2_{\text{peak}}}$, (%)	74 (54-80)	63 (51-72)
${\dot{\mathrm{V}}}_{\mathit{E}}/{\dot{\mathrm{V}}}_{{\text{CO}}_2}$ slope	30 (25-35)	29 (25-32)
Resting HR (bpm)	71 (35-79)	68 (61-77)
Peak HR (bpm)	119 (106-140)	125 (109-136)
Resting blood pressure (mm Hg)	100 (93-110)/64 (60-70) (n = 23)	108 (100-120)/69 (62-70)
Peak blood pressure (mm Hg)	122 (106-139)/70 (63-75) (n = 23)	131 (108-145)/71 (64-80)

Values are presented as median (interquartile range).

HR, heart rate; sLV, systemic left ventricle; sRV, systemic right ventricle; ${\dot{\mathrm{V}}}_{\mathrm{E}}/{\dot{\mathrm{V}}}_{{\text{CO}}_2}$, ventilation/carbon dioxide production slope; $\dot{\mathrm{V}}{\mathrm{O}}_2$, oxygen consumption.

Figure 2.

Peak values achieved during the exercise stress test. Peak oxygen consumption ($\dot{\mathrm{V}}{\mathrm{O}}_{2_{\text{peak}}})$, (A), percentage of age- and sex-predicted $\dot{\mathrm{V}}{\mathrm{O}}_{2_{\text{peak}}}$ ($\%\dot{\mathrm{V}}{\mathrm{O}}_{2_{\text{peak}}})$, (B), and the ventilatory/carbon dioxide production slope (${\dot{\mathrm{V}}}_E/{\dot{\mathrm{V}}}_{{\text{CO}}_2})$ (C) of patients with a systemic right (sRV, n = 24) or left ventricle in biventricular circulation (sLV, n = 24) during a maximal treadmill exercise stress test. The values are presented as mean with standard deviation (bars) and for each matched pair of patients (lines).

Secondary outcomes

The mean difference between the groups for $\%\dot{\mathrm{V}}{\mathrm{O}}_{2_{\text{peak}}}$ was 5% (95% CI: –13, 2), and for the ${\dot{\mathrm{V}}}_{\mathrm{E}}/{\dot{\mathrm{V}}}_{{\text{CO}}_2}$ slope, it was 0.92 (95% CI: –3.98, 2.14).

Exploratory analysis

Characteristics for each subgroup dichotomized according to the Weber criterion for optimal CRF are presented in Supplemental Table S1, and the stress test results are presented in Supplemental Figure S2. For the subgroup matched according to an sLV, $\dot{\mathrm{V}}{\mathrm{O}}_{2_{\text{peak}}}$ >20 mL/kg/min, the mean difference for $\dot{\mathrm{V}}{\mathrm{O}}_{2_{\text{peak}}}$ was –5.0 mL/kg/min (95% CI: –8.9, –1.2), for $\%\dot{\mathrm{V}}{\mathrm{O}}_{2_{\text{peak}}}\text{,}$ it was –18% (95% CI: –29, –6), and for the ${\dot{\mathrm{V}}}_{\mathrm{E}}/{\dot{\mathrm{V}}}_{{\text{CO}}_2}$ slope, it was 1.14 (95% CI: –3.43, 5.71). For the subgroup matched according to an sLV, $\dot{\mathrm{V}}{\mathrm{O}}_{2_{\text{peak}}}$ ≤ 20 mL/kg/min, the mean difference for $\dot{\mathrm{V}}{\mathrm{O}}_{2_{\text{peak}}}$ was 3 mL/kg/min (95% CI: 0.12, 5.34), for $\%\dot{\mathrm{V}}{\mathrm{O}}_{2_{\text{peak}}}\text{,}$ it was 2% (95% CI: –7, 11), and for the ${\dot{\mathrm{V}}}_{\mathrm{E}}/{\dot{\mathrm{V}}}_{{\text{CO}}_2}$ slope, it was 2.16 (95% CI: –6.51, 2.2).

Discussion

This cross-sectional analysis demonstrates that patients with an sRV have a reduction in CRF that is comparable to patients with an sLV with cardiomyopathy matched for demographic characteristics, clinical characteristics, and systemic ventricular function.

The primary finding of this analysis challenges previous literature that has systematically observed a lower CRF within the population with an sRV.1, 2, 3, 4^,8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18^,28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43 However, the majority of previous studies compared patients with an sRV with a healthy population with a normal sLV and only matched for sex and age.1, 2, 3, 4^,8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18^,28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43 The current analyses were performed on a cohort of 24 pairs of patients who presented with a high prevalence of heart failure–related hospitalizations, pulmonary hypertension, and heart failure therapy. The clinical trajectories also differed: 58% of patients with an sLV had been hospitalized for heart failure compared with 22% of those with an sRV. Patients with an sRV are typically managed chronically in congenital heart disease clinics, often as outpatients, whereas left-sided heart failure commonly presents acutely, requiring hospitalization. At this stage, a cardiopulmonary exercise test is more important to determine the prognosis of patients and to adapt heart failure treatment. In this context, patients with an sRV did not display lower CRF compared with patients with an sLV with cardiomyopathy. This result is consistent with the study by Diller et al.,² which compared CRF between 40 patients with an sRV (24 DTGA/16 ccTGA) and patients with an sLV with chronic heart failure who were dichotomized for NYHA functional class. In that study, no difference in $\dot{\mathrm{V}}{\mathrm{O}}_{2\text{peak}}$ was observed between adults with congenital heart disease and patients with an sLV and heart failure. The patients with an sLV and chronic heart failure displayed a decreased left ventricular ejection fraction, but the authors did not control for ejection fraction nor age (approximately 26 years of age difference) across groups due to the heterogeneity of congenital heart diseases.

The exploratory analyses suggest that CRF is lower in patients with an sRV when compared with patients with an sLV who have an optimal CRF ($\dot{\mathrm{V}}{\mathrm{O}}_{2_{\text{peak}}}$ >20 mL/kg/min). This observation is consistent with previous literature that compared patients with an sRV with asymptomatic healthy populations without cardiac disease, even in case of normal functional status (NYHA I) and normal ejection fraction of the sRV. This decrease in CRF is mostly attributed to a lower stroke volume response during exercise^28,44, 45, 46, which is not compensated by a greater rise in heart rate, resulting in a smaller increase in cardiac output from rest to peak exercise in patients with an sRV.⁴⁴ In contrast, the subgroup analysis comparing patients with an sRV with patients with an sLV and suboptimal CRF ($\dot{\mathrm{V}}{\mathrm{O}}_{2_{\text{peak}}}$ ≤20 mL/kg/min) suggests that, at a more advanced stage of heart failure, CRF is equally diminished in both sRV and sLV patients. These differences may highlight specific physiological adaptations of sRV relative to sLV, leading to an earlier decrease in CRF in patients with an sRV, but that remains stable causing the difference in CRF to diminish and become comparable to a population with an sLV that more progressively develops symptoms of heart failure. Whether such temporal differences in CRF decrements occur, and any potential mechanisms involved, remains speculative and should be investigated in future studies. Nonetheless, it remains to be determined whether heart failure therapies for the sRV could beneficially alter temporal patterns.

Although this analysis was not designed to determine CRF thresholds in the population with an sRV, the absence of a difference in CRF parameters between the groups suggests that the current threshold derived from adults with dysfunction of the sLV might be applicable to guide prognostic of patients with an sRV.⁶ Future studies should consider specifically investigating whether differential CRF thresholds are needed for the population with an sRV.

Limitations

The retrospective nature of this study explains why medication was not optimized according to the most recent guidelines for heart failure treatment, resulting in the low prevalence of sodium-glucose cotransporter 2 inhibitors for patients with an sLV.^47,48 Moreover, there are no clear guidelines to optimize heart failure treatment in patients with DTGA and ccTGA. In clinical practice, sacubitril/valsartan is often prescribed in case of sRV dysfunction and NYHA functional class II symptoms.^49,50 Given the varying degrees of heart failure severity in our population and the lack of clear guidelines for sRV, it was not feasible to match patients for medications other than diuretics. The retrospective nature of the study explains the unavailability of 3-dimensional echocardiographic data, as it is not part of the standard clinical protocol. In addition, the decision not to use magnetic resonance imaging to quantify sRV function was influenced by the high prevalence of implantable cardiac pacemakers and defibrillators, which limit magnetic resonance imaging accessibility. Furthermore, the subjective nature of the NYHA classification may have contributed to challenges in accurately categorizing patients. The matching approach used likely resulted in selection basis that may affect the interpretation of the results. However, this approach was deemed essential to ensure that both groups of patients were matched as closely as possible for key clinical characteristics known to affect CRF.

Conclusion

This retrospective cross-sectional analysis of cardiopulmonary exercise test results shows that patients with an sRV do not exhibit a reduced CRF when compared with patients with a cardiomyopathy and an sLV in biventricular physiology after matching for demographic characteristics, clinical characteristics, and systemic ventricular function.