Abstract 3554: Mechanism for Exacerbation of Functional Mitral Regurgitation During Exercise in Patients with Chronic Heart Failure
Background: Functional mitral regurgitation (MR) in patients with chronic heart failure can increase during exercise. Interrelationship between transmitral closing force mediated by left ventricular (LV) pressure and tethering of the mitral leaflets has been implicated as a mechanism of MR.
Methods: To investigate how and why MR changed, we performed exercise echocardiography in 20 patients with dilated cardiomyopathy (mean age 50±15 years, LV end-diastolic volume index 141±53 ml/m2, LVEF 23±8%, all sinus rhythm) who had at least mild MR. Instantaneous flow rate of MR was measured by the proximal flow convergence method. The tenting area (TA) was measured from apical 4-chamber view. Dynamic changes in MR and TA were evaluated by frame-by-frame analysis. The maximal rate of LV systolic pressure rise (LV+dP/dtmax) was estimated using continuous wave Doppler signal of MR.
Results: MR showed a biphasic pattern with a trough at mid-systole both at rest and during exercise. MR flow rate at early-systole significantly increased during exercise (peak flow rate: 39.6±34.2 vs. 68.0±46.0 ml/s, P<0.0001), whereas it did not change at mid- and late-systole. TA and its increase during exercise were largest at early-systole. The increase in peak flow rate of MR at early-systole correlated positively with that of corresponding TA (r=0.64, P<0.01) and negatively with that of LV+dP/dtmax (r=-0.53, P<0.05).
Conclusion: MR increased mainly at early-systole during exercise in patients with chronic heart failure. An insufficient rise in LV pressure at early-systole may be the main factor impeding effective mitral valve closure and producing large TA, leading to exacerbation of MR during exercise.