Prolonged left ventricular contraction duration in apical segments as a marker of arrhythmic risk in patients with long QT syndrome

Abstract

Aims Long QT syndrome (LQTS) is an inherited cardiac ion channelopathy predisposing to life-threatening ventricular arrhythmias and sudden cardiac death. The aim of this study was to investigate left ventricular mechanical abnormalities in LQTS patients and establish a potential role of strain as a marker of arrhythmic risk. Methods and results We included 47 patients with genetically confirmed LQTS (22 LQT1, 20 LQT2, 3 LQT3, and 2 SCN3B) and 25 healthy controls. A history of cardiac events was present in 30 LQTS subjects. Tissue Doppler and speckle tracking echocardiography were performed and contraction duration was measured by radial and longitudinal strain. The radial strain characteristic was subdivided into two planes — the basal and the apical. Left ventricular ejection fraction and global longitudinal strain were normal in LQTS patients. Mean contraction duration was longer in LQTS patients compared with controls in regard to basal radial strain (491 ± 57 vs. 437 ± 55 ms, P < 0.001), apical radial strain (450 ± 53 vs. 407 ± 53 ms, P = 0.002), and longitudinal strain (445 ± 34 vs. 423 ± 43 ms, P = 0.02). Moreover, contraction duration obtained from apical radial strain analysis was longer in symptomatic compared with asymptomatic LQTS mutation carriers (462 ± 49 vs. 429 ± 55 ms, P = 0.024), as well as in subject with mutations other than LQT1 considered to be at higher risk (468 ± 50 vs. 429 ± 49 ms, P = 0.01). Conclusion Myocardial contraction duration is prolonged for both radial and longitudinal directions in LQTS patients. Regional left ventricular function analysis may contribute to risk stratification. Apical radial deformation seems to select subjects at higher risk of arrhythmic events.

Electromechanical reciprocity and arrhythmogenesis in long-QT syndrome and beyond

“…prolongation of radial strain in the LV apex was associated with increased arrhythmic risk in a cohort of 47 genotyped LQTS patients. 65 More extensively prolonged time-to-diastolic peak measured by tissue-phase mapping MRI, which indicates contraction–relaxation delays, and a more pronounced mechanical dispersion, was observed in transgenic LQT2 rabbits exhibiting ventricular arrhythmias than in those without arrhythmia; and proved to be a better risk discriminator than the ‘classical’ electrical QTc or APD. 90 …”

“… 27 Magnetic resonance imaging-based mechanical mapping techniques hold promise especially with regard to assessing the apical mechanical behaviour, a region often difficult to accurately assess by speckle-tracking echocardiography but with a proarrhythmic potential. 65 …”