Exercise-Induced Cardiac Mechanics in Asymptomatic Primary Mitral Regurgitation: Insights from Stress Echocardiography and Cardiopulmonary Exercise Testing.

BACKGROUND

Stress echocardiography is recommended for evaluating asymptomatic primary mitral regurgitation (MR), but exercise-induced changes in myocardial mechanics and right ventricular-pulmonary artery (RV-PA) coupling remain incompletely characterized.

METHODS

63 patients with moderate-to-severe or severe primary degenerative MR (NYHA I) and 20 age-matched healthy controls prospectively underwent comprehensive transthoracic and supine bicycle stress echocardiography. Left ventricular global longitudinal strain (GLS), left atrial (LA) strain (reservoir, conduit and contraction), right ventricular (RV) strain, and RV-PA coupling (TAPSE/PASP) were assessed at rest and peak exercise. Cardiopulmonary exercise testing (CPET) was additionally performed in a subgroup.

RESULTS

Compared with controls, MR patients demonstrated significantly lower exercise capacity, achieving shorter exercise duration (8.26 ± 2.32 vs. 10.32 ± 1.34 minutes, p<0.001) and lower maximal workload (78.0 ± 21.2 vs. 101.3 ± 9.9 W, p<0.001). At rest, LV GLS and RV strain were comparable between groups, whereas LA conduit and contraction strain were already altered in MR patients. Exercise unmasked lower peak GLS and impaired RV-PA coupling in the MR group, while peak LA contraction strain remained significantly different between groups. Seven patients developed exercise-induced MR deterioration, exhibiting loss of LA functional reserve with deterioration of all LA strain components, unlike patients without MR deterioration. Peak VO2 was lower in MR patients and correlated with exercise RV-PA coupling, but not with LA strain.

CONCLUSIONS

Exercise echocardiography combined with myocardial deformation imaging identifies chamber-specific functional abnormalities not evident at rest, providing complementary physiological insight into cardiac adaptation in asymptomatic primary MR.