Abstract 14614: Sub Clinical Cardiomyopathic Abnormalities in Patients with Long QT Syndrome

Abstract

Objectives:Long QT syndrome (LQTS) is a cardiac channelopathy predisposing to syncope and sudden death secondary to LQT-triggered ventricular arrhythmias. Echocardiographic reports have shown that patients with LQTS have contraction abnormalities which are associated with cardiac arrhythmias. We here present the frequency of cardiac structural alterations in a large cohort of patients with LQTS.

Methods: Two-dimensional and Doppler echocardiographic studies performed during medical evaluation in Mayo’s LQTS Clinic were reviewed for 216 LQTS patients. Echocardiograms were evaluated for morphologic abnormalities and atrial and ventricular size and function. Left atrial volume was indexed by body mass (LAVI). Arrhythmic events were defined as a history of aborted cardiac arrest, documented VT or VF, and syncope.

Results: While 75% of patients had normal echocardiograms, 54 patients (25%) had ≥ 1 abnormal echocardiographic finding. Most common were sub-clinical changes that may be cardiomyopathic, including increased LAVI (n=25, 12%), left or right ventricular enlargement (n=7, 3%), and grade I-II LV diastolic dysfunction (n=7, 3%). LAVI was higher in LQTS patients with arrhythmic events compared to those without (24.4±5.5 ml/m² vs. 22.3±6.1 ml/m², p=0.02). QTc and LAVI correlated significantly albeit weakly (r²=0.04, p<0.01, Figure).

Conclusions: Sub-clinical cardiomyopathic changes were found in nearly 20% of patients with LQTS. Left atrial enlargement was the most common finding and was associated with prolonged QTc and arrhythmic events. These changes may stem from underlying contraction abnormalities caused by ion channel dysfunction.