The electromechanical window in arrhythmogenic mitral-valve prolapse: a new tool for patient risk stratification

Abstract Background Mitral valve prolapse (MVP) is a common and mostly benign valvular heart disease. However, a subset of patients is at higher risk for developing malignant ventricular arrhythmias (AMVP). Risk stratification in (A)MVP is challenging, and novel risk stratification parameters incorporating electromechanical reciprocity are needed. Purpose Evaluation of the echocardiography-derived electromechanical window (EMW) as a potential marker of arrhythmia risk in MVP. Methods Controls, MVP patients without ventricular arrhythmia (MVP/-VA), with non-sustained ventricular arrhythmia (AMVP/nsVA), and patients with sustained ventricular arrhythmia (AMVP/VA) were retrospectively included from three referral centers. The EMW was calculated from apical Doppler echocardiography by subtracting the QT time from the aortic-valve closure time (QAoC). The assessment was blinded. Data are shown as mean±SD or median (25th to 75th percentile). Results 91 patients (52% female, 49±20 years old) were included: n=25 controls and n=66 MVP patients (n=33 MVP/-VA, n=19 AMVP/nsVA, and n=14 AMVP/VA). At the echo time point, 22% of the patients were treated with beta-blockers. Controls had a mean EMW of 30 (10 to 35) ms, while mean EMW was negative in the total MVP cohort (-15 (-46 to 8) ms, p0.0001). Whereas the rate-corrected (Bazett) QAoCc was similar in controls and the total MVP cohort (418±26 vs. 407±44 ms, p=0.27), QTc was longer in the MVP cohort (426 (400 to 450) vs. 396 (389 to 407) ms, p0.0001). When the subgroups of MVP were analyzed separately, only in patients with MVP/-VA (-10 (-28 to 6) ms, p=0.002) and AMVP/VA (-71 (-183 to -30) ms, p0.0001) a significantly lower EMW was found in comparison to controls, not in AMVP/nsVA (0 (-28 to 40) ms, p=0.25, Fig. 1). In AMVP/VA patients, pronounced EMW negativity was driven by both a shorter QAoCc (373±44 ms, p=0.001) and a longer QTc (445 (418 to 538) ms, p0.0001) compared to controls. The EMW in AMVP/VA patients was variable over time: EMW was -21±74 ms at a time point before VA, rendered more negative 1 (0 to 8) days after VA (-95±81 ms, p=0.02), and recovered during follow-up (-39±74 ms, p=0.06). This variability was particularly driven by a foreshortened QAoCc close to VA when compared to the time point before VA (373±44 vs. 426±32 ms, p=0.02). Within the MVP-cohort, receiver-operator characteristic analysis revealed an area under the curve for AMVP/VA patient identification of 0.86 (95% confidence interval 0.74-0.96) for the EMW (Fig. 2). An EMW of -29 ms had a sensitivity of 0.86 and specificity of 0.79 for AMVP/VA patient identification within the MVP cohort. Conclusion The EMW is rendered negative in MVP patients, particularly in those with sustained VA, indicating that AMVP/VA is associated with an altered electromechanical sequence, especially within days of VA. Therefore, the EMW may be an interesting parameter to aid arrhythmia risk prediction in the group of MVP patients.Figure 1 Figure 2