Mitral valve prolapse with mid-late systolic mitral regurgitation: pitfalls of evaluation and clinical outcome compared with holosystolic regurgitation.

Background: Mitral regurgitation (MR) of mitral valve prolapse predominates in late systole but may be holosystolic or purely mid-late systolic, but the impact of MR timing on MR left ventricular and left atrial consequences and outcome is unknown. Whether effective regurgitant orifice (ERO) by the flow convergence method is similarly linked to outcome in mid-late systolic MR and holosystolic MR is uncertain.

Methods And Results: We comprehensively and prospectively quantified MR in 111 patients with mitral valve prolapse and mid-late systolic MR and matched them to 90 patients with mitral valve prolapse and holosystolic MR for age, gender, atrial fibrillation, ejection fraction, and ERO (flow convergence). Mid-late systolic MR versus holosystolic MR groups were well matched, including for comorbidity, blood pressure, and heart rate (all P>0.10). Mid-late systolic MR versus holosystolic MR caused similar color jet area, midsystolic regurgitant flow, and peak velocity (P>0.40). Despite identical ERO (0.25±0.15 versus 0.25±0.15 cm(2); P=0.53), the shorter duration of mid-late systolic MR (233±56 versus 426±50 ms; P<0.0001) yielded lower regurgitant volume (24.8±13.4 versus 48.6±25.6 mL; P<0.0001). MR consequences, systolic pulmonary pressure, and left ventricular and left atrial volume index (all P<0.001) were more benign in mid-late systolic MR versus holosystolic MR. Under medical management, fewer cardiac events (5 years: 15.8±4.6% versus 40.4±6.1%; P<0.0001) occurred in mid-late systolic MR versus holosystolic MR, requiring less mitral surgery. Multivariable analysis confirmed the independent association of mid-late systolic MR with benign consequences and outcomes (all P<0.01). Absolute ERO was not linked to outcome, in contrast to regurgitant volume.

Conclusions: MR of mitral valve prolapse that is purely mid-late systolic causes more benign consequences and outcomes than holosystolic MR. Assessment may be misleading because jet area and ERO by flow convergence appear similar to those of holosystolic MR. However, shorter MR yields lower regurgitant volume, consequences, and benign outcomes. Instantaneous ERO by flow convergence should be interpreted in context, and in mid-late systolic MR, regurgitant volume provides information more reflective of MR severity. Therefore, for clinical management and surgical referral, clinicians should carefully take into account the timing and consequences of MR.