Abstract 15398: Myocardial Function is Reduced in Patients With Long QT Syndrome Type 2 Compared to Type 1
Introduction: Long QT syndrome (LQTS) is an inherited cardiac ion channelopathy predisposing to ventricular arrhythmias. The most commonly affected ion channels are IKs (KCNQ1-gene/ LQT1) and IKr (KCNH2-gene/LQT2). Recent reports have indicated presence of subtle myocardial contraction abnormalities in LQTS patients by myocardial strain. We wanted to explore if myocardial function assessed by strain echocardiography shows genotype specific differences in LQT1 and LQT2 patients.
Methods: We included 153 mutation positive LQT1 and LQT2 subjects in addition to 26 age and sex matched healthy individuals. Exclusion criterion was cardiac disease of other origin. We performed echocardiography, including left ventricular (LV) ejection fraction (EF) and LV speckle tracking strain. LV global longitudinal strain was calculated as the average of maximal longitudinal shortening from 16 LV segments. QTc was measured from 12 lead ECG. LQTS symptoms were defined as cardiac syncope, documented ventricular arrhythmia or aborted cardiac arrest.
Results: Of the 153 LQTS subjects, 107 had LQT1 (mean age 37±15 yrs, 64% female, QTc 461±31 ms) and 46 had LQT2 (mean age 36±19 yrs, 54% female, QTc 463±30 ms). LQT2 subjects were more frequently symptomatic (21/46 (46%) vs. 30/107 (28%) p=0.03). Myocardial function by global strain was lower in individuals with LQT2 compared to LQT1 (-20.8±1.9%, vs. -21.7±2.1%, p=0,02) and lower compared to healthy individuals (-22.6±2.0%, p<0.01), while EF did not differ between LQT2, LQT1 and healthy (61±7% vs. 61±5% vs. 63±6%, p=0.08).
Conclusions: Myocardial function by LV global strain was subclinically lower in LQT2 subjects compared to both LQT1 mutation positive and healthy individuals. This result supports that mechanical alterations are present in LQTS, and are most pronounced in LQT2. Moreover, genotype specific differences may indicate that there is a link between specific ion channel dysfunction and mechanical alterations.
- © 2013 by American Heart Association, Inc.