New echocardiographic insights in short QT syndrome: More than a channelopathy?

BACKGROUND Short QT syndrome (SQTS) is a congenital ion channel disease characterized by an increased risk of sudden cardiac death. Little is known about the possibility that accelerated repolarization alters mechanical function in SQTS. OBJECTIVES The study investigated the presence of left ventricular dysfunction and mechanical dispersion, assessed by tissue Doppler imaging (TDI) and speckle tracking echocardiography (STE), and their correlation with QT interval duration and genetics. METHODS Fifteen SOTS patients (7 with HERG and 3 with KCNQ1 mutation) were studied. Electrocardiographic and echocardiographic parameters were compared with age- and sex-matched healthy controls. RESULTS When compared to the control group, SQTS patients showed reduced left ventricular contraction (global longitudinal strain: -16.0% +/- 3.4% vs -22.6% +/- 1.7%, P < .001; myocardial performance index 0.59 +/- 0.17 vs 0.34 +/- 0.08, P < .001) and a higher incidence of ejection fraction <55% (odds ratio 11, 95% confidence interval 1.045-374, P = .04). Mechanical dispersion assessed by TDI (P < .01) and STE (P < .001) was higher in the SQTS group than in controls; each parameter showed a significant inverse correlation with QT interval but not with QT dispersion. CONCLUSION This study showed that in SQTS systolic function may also be affected. SOTS patients presented a significant dispersion of myocardial contraction. TDI and STE could become part of the evaluation of this rare disease.