Effect of Cardiac Resynchronization Therapy on Exercise-Induced Pulmonary Hypertension and Right Ventricular-Arterial Coupling.

Background Acute and chronic effects of cardiac resynchronization therapy (CRT) on pulmonary pressures, right ventricular function, and ventricular-vascular coupling during exercise are insufficiently understood. Yet, these factors are strongly associated with functional status and outcome. Methods and Results Heart failure patients with reduced ejection fraction indicated for CRT were prospectively included to undergo exercise echocardiography simultaneously with cardiopulmonary exercise testing before (pre_CRT), 1 day after (post_CRT), and 6 months (post6_CRT) after CRT implant. Right ventricular-arterial coupling was assessed by the tricuspid annular plane systolic excursion (TAPSE)/systolic pulmonary artery pressure (SPAP) ratio. A total of 31 heart failure patients with reduced ejection fraction (age=66±13 years) were prospectively included. CRT resulted in an immediate reduction in rest SPAP (pre_CRT=32±16 versus post_CRT=23±16 mm Hg; P=0.006) and rest effective regurgitant orifice (pre_CRT=0.32±0.1 versus post_CRT=0.18±0.2; P=0.001) without changes in exercise mitral regurgitation or exercise SPAP indexed for cardiac output. Six months after CRT, in parallel with left ventricular reverse remodeling and a reduction in exercise mitral regurgitation and exercise E/e' ratio, the exercise SPAP/cardiac output significantly improved (post_CRT=5.6±3.1 versus post6_CRT=4.3±2.9 mm Hg·L-1·min-1; P=0.039), which was also illustrated by a reduced slope of ΔSPAP/Δcardiac output (post_CRT=5.2±3.7 versus post6_CRT=2.9±2.7 mm Hg·L-1·min-1; P=0.002). CRT did not result in an acute or chronic effect on TAPSE or TAPSE/SPAP ratio at rest. However, exercise revealed the presence of right ventricular-arterial uncoupling which was not affected by an acute CRT effect ( P=0.396) but only improved by a chronic CRT effect ( P<0.001; TAPSE/SPAP ratio: pre_CRT= 0.39±0.6 mm/mm Hg; post_CRT=0.42±0.5 mm/mm Hg; post6_CRT =0.84±0.12 mm/mm Hg). Of all exercise echocardiography variables, the TAPSE/SPAP ratio demonstrated the strongest correlation with Vo2 peak ( r=0.475), VE/Vco2 ( r=-0.585), and workload ( r=0.476) during cardiopulmonary exercise testing ( P<0.05 all). Multivariate predictors affecting exercise ventricular-arterial coupling after CRT included metrics of residual exercise mitral regurgitation and systolic and diastolic left ventricular function. Conclusions Chronic CRT beneficially influences pulmonary pressures and right ventricular-arterial coupling during exercise, which strongly relates to functional status. These findings are mechanistically linked to reverse remodeling with improved interventricular dependence and reduction in exercise mitral regurgitation.