Left sided Wall Stress Causing Arrhythmia | 205 2). Presence of MVP was defined as displacement of >2 mm of one or both leaflets beyond the annular hinge points at end-systole, measured perpendicular to the annular plane in the 3-chamber view (Figure 2).24 Presence of the curling sign, defined as an unusual systolic motion of the inferior mitral annulus on the adjacent ventricular wall, was identified by visual assessment (online video A).8,25 Figure 2. Measurements of longitudinal MAD and MVP distance on CMR imaging All images are obtained at end-systole. The blue line connects the annular hinge points of the mitral valve, the white arrows are longitudinal MAD measurements, the orange arrow is the MVP measurement. Abbreviations: CMR = cardiac magnetic resonance, LA = left atrium, LV = left ventricle, MAD = mitral annulus disjunction, MVP = mitral valve prolapse. Clinical characteristics Clinical data was derived from the IVF registry. Enrolled patients all underwent detailed investigation of the medical history, physical examination, 12-lead ECG, laboratory testing, echocardiography, coronary angiography (or CT angiography) and CMR. All patients underwent echocardiographic imaging according to the standard clinical protocol.26,27 Additional investigations such as exercise ECG, sodium channel blocker provocation, endomyocardial biopsy and genetic testing were performed at the treating physician’s discretion.2,18 T-wave abnormalities were defined as inverted or biphasic T-waves. Genetic testing consisted of single targeted gene testing or next generation sequencing of a larger panel of genes, depending on the center where the genetic testing was performed. In line with previous studies, we also included patients with the DPP6 haplotype, a genetic variant associated with short-coupled Torsade de Pointes/IVF.1,28 Although we previously proposed that Ito overexpression particularly in Purkinje plays an essential role in these patients29, the underlying pathophysiological mechanism for VF remains uncertain. Follow-up data was retrospectively collected from all patients. All electrocardiographic data on ECGs, cardiac telemetry during admission, exercise ECG and Holter monitoring was analyzed for the occurrence of PVCs. A high PVC burden was defined as more than 1000 PVCs per 24 hours on Holter monitoring. In patients without Holter monitoring, a high PVC burden was defined as more than 20 PVCs during an exercise test or bigeminy or trigeminy on ECG or cardiac telemetry. Non sustained ventricular tachycardia was defined as three or more ventricular beats with a maximum duration of 30 seconds.30 Appropriate ICD therapy was defined as antitachycardia pacing or shock during a ventricular tachycardia or ventricular fibrillation. 10
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