Left ventricular mechanical dispersion predicts arrhythmic risk in mitral valve prolapse

Abstract

Objective: Bileaflet mitral valve prolapse (MVP) with either focal or diffuse myocardial fibrosis has been linked to ventricular arrhythmia and/or sudden cardiac arrest. Left ventricular (LV) mechanical dispersion by speckle-tracking echocardiography (STE) is a measure of heterogeneity of ventricular contraction previously associated with myocardial fibrosis. The aim of this study is to determine whether mechanical dispersion can identify MVP at higher arrhythmic risk.

Methods: We identified 32 consecutive arrhythmic MVPs (A-MVP) with a history of complex ventricular ectopy on Holter/event monitor (n=23) or defibrillator placement (n=9) along with 27 MVPs without arrhythmic complications (NA-MVP) and 39 controls. STE was performed to calculate global longitudinal strain (GLS) as the average peak longitudinal strain from an 18-segment LV model and mechanical dispersion as the SD of the time to peak strain of each segment.

Results: MVPs had significantly higher mechanical dispersion compared with controls (52 vs 42 ms, p=0.005) despite similar LV ejection fraction (62% vs 63%, p=0.42) and GLS (-19.7 vs -21, p=0.045). A-MVP and NA-MVP had similar demographics, LV ejection fraction and GLS (all p>0.05). A-MVP had more bileaflet prolapse (69% vs 44%, p=0.031) with a similar degree of mitral regurgitation (mostly trace or mild in both groups) (p>0.05). A-MVP exhibited greater mechanical dispersion when compared with NA-MVP (59 vs 43 ms, p=0.0002). Mechanical dispersion was the only significant predictor of arrhythmic risk on multivariate analysis (OR 1.1, 95% CI 1.02 to 1.11, p=0.006).

Conclusions: STE-derived mechanical dispersion may help identify MVP patients at higher arrhythmic risk.

Keywords: cardiac arrest; echocardiography; mitral regurgitation; valvular heart disease; ventricular tachycardia.

Figure 1

Examples of Tomtec Image Arena measurements of global longitudinal strain (GLS) and time to peak strain (TTP) in arrhythmic mitral valve prolapse (A-MVP) patients (top panel) and non-arrhythmic mitral valve prolapse patients (NA-MVP) (bottom panel). Greater variability in the TTP of each left ventricular (LV) wall segment is seen in the A-MVP patients compared with the NA-MVP patients reflecting increased mechanical dispersion. GLS is defined as the average peak systolic strain for all 18 LV segments. Mechanical dispersion is defined as the SD of the time to peak strain in all 18 LV segments.

Figure 2

Comparison of mechanical dispersion between controls, all mitral valve prolapse patients (MVP total), arrhythmic MVP patients (A-MVP) and non-arrhythmic MVP patients (NA-MVP). A-MVP patients had significantly higher mechanical dispersion compared with controls (mean 59 vs 42 ms, p<0.001) and NA-MVP patients (mean 59 vs 43 ms, p<0.001). There was no difference in mechanical dispersion between the control and the NA-MVP groups (p=0.78).

Figure 3

Comparison of mechanical dispersion between arrhythmic mitral valve prolapse patients (A-MVP) treated with an implantable-cardioverter defibrillator (ICD) and A-MVP with complex ventricular ectopy on monitor (ComVE). Mechanical dispersion was higher in A-MVP treated with an ICD compared with A-MVP with ComVE (mean 67 vs 56 ms, p=0.078).