Right ventricular function and its coupling to pulmonary circulation predicts exercise tolerance in systolic heart failure.

AIMS: Right ventricular (RV) dysfunction, pulmonary hypertension, and exercise intolerance have prognostic values, but their interrelation is not fully understood. We investigated how RV function alone and its coupling with pulmonary circulation (RV-PA) predict cardio-respiratory fitness in patients with heart failure and reduced ejection fraction (HFrEF). METHODS AND RESULTS: The Evaluation of Resynchronization Therapy for Heart Failure (EARTH) study included 205 HFrEF patients with narrow (n = 85) and prolonged (n = 120) QRS duration undergoing implantable cardioverter defibrillator implantation. All patients underwent a comprehensive evaluation with exercise tolerance tests and echocardiography. We investigated the correlations at baseline between RV parameters {size, function [tricuspid annular plane systolic excursion (TAPSE), RV fractional area change (RV-FAC), and RV myocardial performance index (RV-MPI)], pulmonary artery systolic pressure (PASP), and tricuspid regurgitation}; left ventricular ejection fraction (LVEF), left ventricular end-diastolic volume index (LVEDVi), and left atrial volume index (LAVi); and cardiopulmonary exercise test (CPET) [peak VO2 , minute ventilation/carbon dioxide production (VE/VCO2 ), 6 min walk distance (6MWD), and submaximal exercise duration (SED)]. We also studied the relationship between RV-PA coupling (TAPSE/PASP ratio) and echocardiographic parameters in patients with both data available. Univariate and multivariate linear regression models were used. Patients enrolled in EARTH (overall population) were mostly male (73.2%), mean age 61.0 ± 9.8 years, New York Heart Association class II-III (87.8%), mean LVEF of 26.6 ± 7.7%, and reduced peak VO2 (15.1 ± 4.6 mL/kg/min). Of these, 100 had both TAPSE and PASP available (TAPSE/PASP population): they exhibited higher BNP, wider QRS duration, larger LVEDVi, with more having tricuspid regurgitation compared with the 105 patients for whom these values were not available (all P < 0.05). RV-FAC (ß = 7.5), LAVi (ß = -0.1), and sex (female, ß = -1.9) predicted peak VO2 in the overall population (all P = 0.01). When available, TAPSE/PASP ratio was the only echocardiographic parameter associated with peak VO2 (ß = 6.8; P < 0.01), a threshold ≤0.45 predicting a peak VO2  ≤ 14 mL/kg/min (0.39 for VO2  ≤ 12). RV-MPI was the only echocardiographic parameter associated with ventilatory inefficiency (VE/VCO2 ) and 6MWD (ß = 21.9 and ß = -69.3, respectively, both P ≤ 0.01) in the overall population. In presence of TAPSE/PASP, it became an important predictor for those two CPET (ß = -18.0 and ß = 72.4, respectively, both P < 0.01), together with RV-MPI (ß = 18.5, P < 0.01) for VE/VCO2 . Tricuspid regurgitation predicted SED (ß = -3.2, P = 0.03). CONCLUSIONS: Right ventricular function assessed by echocardiography (RV-MPI and RV-FAC) is closely associated with exercise tolerance in patients with HFrEF. When the TAPSE/PASP ratio is available, this marker of RV-PA coupling becomes the stronger echocardiographic predictor of exercise capacity in this population, highlighting its potential role as a screening tool to identify patients with reduced exercise capacity and potentially triage them to formal peak VO2 and/or evaluation for advanced HF therapies.

Impact of Left Ventricular vs Biventricular Pacing on Reverse Remodelling: Insights From the Evaluation of Resynchronization Therapy for Heart Failure (EARTH) Trial.

BACKGROUND: Studies comparing biventricular (BiV) cardiac resynchronization therapy (CRT) and left ventricular (LV) pacing alone have yielded conflicting results. We recently reported the results of the Greater Evaluation of Resynchronization Therapy for Heart Failure (GREATER-EARTH) trial demonstrating similar clinical benefits of BiV and LV-CRT on exercise tolerance. We report the prespecified secondary outcomes of the GREATER-EARTH trial, comparing the impact of BiV vs LV-CRT on structural and biochemical cardiac remodelling. METHODS: Patients with a LV ejection fraction (LVEF) ≤ 35% and a QRS duration ≥ 120 ms were randomized to BiV-CRT or LV-CRT for a 6-month period, followed by crossover. The primary end point was a change in LV end-systolic volume (LVESV). Secondary end points included changes in LVEF, right ventricular (RV) dimensions and function, mitral regurgitation (MR), indices of diastolic function, systolic pulmonary artery pressure (sPAP), and disease-specific biomarkers. RESULTS: One hundred twenty patients (60.9 ± 8.8 years; 75.0% men; LVEF, 24.4% ± 6.3%) were enrolled. A similar reduction in LVESV was observed, from a baseline of 162.4 ± 57.2 mL to 130.4 ± 63.4 mL with BiV pacing and 130.3 ± 59.9 mL with LV pacing (P = 0.679, BiV pacing vs LV pacing). Improvements in LVEF, RV remodelling, and N-terminal pro b-type natriuretic peptide were similar between groups. BiV pacing yielded superior outcomes with respect to LV diastolic function, indexed left atrial volume, degree of MR, and sPAP (all P < 0.05), together with decreased N-terminal propeptide of type III collagen with LV-CRT. CONCLUSIONS: In this randomized double-blind crossover trial, BiV and LV pacing resulted in similar improvements in the primary LV remodelling end point (LVESV). Analyses of secondary end points revealed advantages of BiV pacing over LV pacing on several other features of cardiac remodelling, providing mechanistic insights to support the main finding of the GREATER-EARTH trial.