Impact of Exercise on Atrial Functional Mitral Regurgitation and its Ddeterminants. An Exercise Echocardiographic Study.

Atrial functional mitral regurgitation (AFMR) is a distinct form of MR in patients with atrial fibrillation and heart failure with preserved ejection fraction (HFpEF). Its pathophysiology remains elusive, and data on exercise-related AFMR are scarce. We sought to investigate the impact of acute exercise on AFMR severity and to identify its determinants. In total, 47 patients with HFpEF (n=39) and/or atrial fibrillation (n=22) were enrolled. We assessed AFMR severity, mitral annular dimensions, left atrial size, AFMR severity and parameters of systolic and diastolic function at rest and during maximal exercise by echocardiography. Increase in AFMR severity of ≥1 grade was observed in 20 patients (43%) during exercise, and was associated with impaired progression of peak mitral annulus systolic velocity (Med S') and increased systolic mitral annular diameter during exercise, while the systolic annular diameter decreased in patients without AFMR progression. Furthermore, patients with ≥moderate AFMR during exercise (n=19; 40%) had lower Med S', greater systolic mitral annular diameters, reduced tricuspid annular plane systolic excursion and more severe tricuspid regurgitation compared to patients with ≤mild MR during exercise. In conclusion, AFMR is a dynamic condition which may worsen during exercise. Deterioration of AFMR during exercise was associated with impaired longitudinal left ventricular contractile reserve and greater mitral annular dimensions. As impaired left ventricular longitudinal function may influence mitral annular dynamics, this attributes to the hypothesis that AFMR results from mitral annulus area/leaflet area imbalance caused by both annular dilation and impaired mitral annular dynamics.