Exercise Induced Worsening of Mechanical Heterogeneity and Diastolic Impairment in Long QT Syndrome.

Dafni Charisopoulou,Annika Rydberg,Michael Y Henein,Lucy F Law,George Koulaouzidis

doi:10.3390/jcm10010037

Abstract

Background: Electromechanical heterogeneities due to marked dispersion of ventricular repolarisation and mechanical function have been associated with symptoms in long QT syndrome (LQTS) patients; Aim: To examine the exercise response of longitudinal LV systolic and diastolic myocardial function and synchronicity in LQTS patients and its relationship with symptoms; Methods: Forty seven (age 45 ± 15 yrs, 25 female, 20 symptomatic) LQTS patients and 35 healthy individuals underwent an exercise test (Bruce protocol). ECG and echo parameters were recorded at rest, peak exercise (p.e.), and recovery; Results: LQTS patients had prolonged and markedly dispersed myocardial contraction, delayed early relaxation phase, and significantly decreased filling time at all exercise phases. Unlike controls, these electromechanical disturbances deteriorated further with exercise, during which additional decrease of the LV diastolic myocardial function and attenuated LV stroke volume were noted. Such abnormal responses to exercise were seen to a greater degree in symptomatic patients and in the LQT1 subgroup and improved with B-blocker therapy. Worsening myocardial contraction dispersion at p.e. was the strongest discriminator for previous clinical events, and its discriminating power excelled further by adding early relaxation delay; Conclusions: Electromechanical disturbances were shown to worsen during exercise in LQTS patients and were more pronounced in those with previous arrhythmic events.

Highlights

One of the greatest challenges in cardiology practice remains the prompt identification of long QT syndrome (LQTS) mutation carriers who are at highest risk of developing adverse cardiac events such as arrhythmias, syncope, or sudden cardiac death [1]
The study group consisted of 47 LQTS mutation carriers (36 LQT1 and 11 LQT2) who were compared with 35 healthy controls, matched for age (45 ± 15 vs. 47 ± 13 years, p = 0.2) and gender (53 vs. 54% females, p = 0.3)
Among the LQTS subjects, 20 (43%) were symptomatic based on documented history of syncope, cardiac arrest, or arrhythmia; three had an implantable cardioverter-defibrillator (ICD) inserted

Summary

Introduction

One of the greatest challenges in cardiology practice remains the prompt identification of long QT syndrome (LQTS) mutation carriers who are at highest risk of developing adverse cardiac events such as arrhythmias, syncope, or sudden cardiac death [1] This has been difficult in cases where the patients have a normal QTc interval or no previous symptoms [2]. Inherited LQTS was initially thought to be solely an electrical phenomenon with prolonged action potential and exaggerated dispersion of spatiotemporal repolarisation [3] Such electric abnormalities have been shown to correspond to mechanical ones, referred to as electromechanical (EM) disturbances [4,5].

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