Mitral valve area during exercise after restrictive mitral valve annuloplasty: importance of diastolic anterior leaflet tethering.

Abstract

BACKGROUND Restrictive mitral valve annuloplasty (RMA) for secondary mitral regurgitation might cause functional mitral stenosis, yet its clinical impact and underlying pathophysiological mechanisms remain debated. OBJECTIVES The purpose of our study was to assess the hemodynamic and clinical impact of effective orifice area (EOA) after RMA and its relationship with diastolic anterior leaflet (AL) tethering at rest and during exercise. METHODS Consecutive RMA patients (n ¼ 39) underwent a symptom-limited supine bicycle exercise test with Doppler echocardiography and respiratory gas analysis. EOA, transmitral flow rate, mean transmitral gradient, and systolic pulmonary arterial pressure were assessed at different stages of exercise. AL opening angles were measured at rest and peak exercise. Mortality and heart failure readmission data were collected for at least 20 months after surgery. RESULTS EOA and AL opening angle were 1.5 0.4 cm2 and 68 10, respectively, at rest (r ¼ 0.4; p ¼ 0.014). EOA increased significantly to 2.0 0.5 cm2 at peak exercise (p < 0.001), showing an improved correlation with AL opening angle (r ¼ 0.6; p < 0.001). Indexed EOA (EOAi) at peak exercise was an independent predictor of exercise capacity (maximal oxygen uptake, p ¼ 0.004) and was independently associated with freedom from all-cause mortality or hospital admission for heart failure (p ¼ 0.034). Patients with exercise EOAi <0.9 cm2/m2 (n ¼ 14) compared with $0.9 cm2/m2 (n ¼ 25) had a significantly worse outcome (p ¼ 0.048). In multivariate analysis, AL opening angle at peak exercise (p ¼ 0.037) was the strongest predictor of exercise EOAi. CONCLUSIONS In RMA patients, EOA increases during exercise despite fixed annular size. Diastolic AL tethering plays a key role in this dynamic process, with increasing AL opening during exercise being associated with higher exercise EOA. EOAi at peak exercise is a strong and independent predictor of exercise capacity and is associated with clinical outcome. Our findings stress the importance of maximizing AL opening by targeting the subvalvular apparatus in future repair algorithms for secondary mitral regurgitation. (J Am Coll Cardiol 2015;65:452–61).