Primary Atriopathy in Mitral Valve Prolapse: Echocardiographic Evidence and Clinical Implications

Abstract

Background: Prominent multi-scallop systolic leaflet displacement toward the left atrium (atrialization) is typically observed in bileaflet mitral valve prolapse (MVP) with mitral annular disjunction. We hypothesized that mitral leaflet atrialization is associated with an underlying left atrial (LA) myopathy characterized by progressive structural and functional abnormalities, irrespective of mitral regurgitation (MR) severity.

Methods: We identified 334 consecutive patients with MVP, no prior atrial fibrillation, and comprehensive clinical and echocardiographic data. LA function was assessed by LA reservoir strain, LA function index, and LA emptying fraction. We also classified the stage of LA remodeling based on LA enlargement and LA reservoir strain (stage 1: no remodeling; stage 2: mild remodeling; stage 3: moderate remodeling; and stage 4: severe remodeling). The primary end point was the composite risk of sudden arrhythmic death, heart failure hospitalization, or the new onset of atrial fibrillation.

Results: Bileaflet MVP with no or mild MR had a lower LA reservoir strain (P=0.04) and LA function index (P<0.001) compared with other MVP subtypes. In multivariable linear regression adjusted for cardiovascular risk factors and MR ≥moderate, bileaflet MVP remained significantly associated with lower LA function parameters (all P<0.05). There was a significant increase in the risk of events as the LA reservoir strain and LA remodeling stage increased (P<0.001). In multivariable analysis, stage 4 of LA remodeling remained significantly associated with a higher risk of events compared with stage 1 (hazard ratio, 6.09 [95% CI, 1.69-21.9]; P=0.006).

Conclusions: In a large MVP registry, bileaflet involvement is associated with reduced LA function regardless of MR severity, suggesting a primary atriopathy in this MVP subtype. Abnormal LA function, particularly when assessed through a multiparametric approach, is linked to a higher risk of cardiovascular events and may improve risk stratification in MVP, even in those without significant MR.

Keywords: atrial fibrillation; cardiovascular diseases; echocardiography; mitral valve prolapse.

Figure 1.

Study flow chart. AF indicates atrial fibrillation; LA, left atrial; MVP, mitral valve prolapse; and UCSF, University of California San Francisco.

Figure 2.

Distribution of LA function parameters according to MVP subtypes and MR severity. Comparison of LASr, LAFI, and LAEF according to MVP subtypes in no or mild (A, C, E) and moderate or severe (B, D, F) MR subgroups. The dot plot shows the median value (red line), and the error bars (dotted black line) represent the interquartile range (IQR). Numbers on top of the plot indicate the median with IQR between brackets. Numbers between brackets below the graph are number of patients. LA indicates left atrium; LAEF, left atrial emptying fraction; LAFI, left atrial function index; LASr, left atrial reservoir strain; MR, mitral regurgitation; and MVP, mitral valve prolapse.

Figure 3.

Risk of clinical events according to LA function. Survival curves with risk of cardiac death, heart failure hospitalization, or new onset of atrial fibrillation according to tertiles of LASr (A), LAFI (B), and the stage of LA remodeling (C). Patients were classified as follows: stage 1 (no remodeling); stage 2 (mild remodeling); stage 3 (moderate remodeling); and stage 4 (severe remodeling). Next to each curve is the percentage of patients with increased risk of events at 8 years of follow-up. Bottom numbers refer to patients at risk at each time interval. CV indicates cardiovascular; LA, left atrium; LAEF, left atrial emptying fraction; LAFI, left atrial function index; and LASr, left atrial reservoir strain.