Altered cardiac repolarization during exercise in congenital aortic stenosis

Area of Science:

• Cardiology
• Pediatric Cardiology
• Clinical Electrophysiology

Background:

• Congenital aortic stenosis (CAS) is associated with a significant incidence of sudden death (4-20%) in children.
• Long QT interval on electrocardiograms (ECG) is linked to sudden death in certain pediatric syndromes.
• Evaluating cardiac repolarization during physiological stress in CAS is crucial for risk stratification.

Purpose of the Study:

• To assess cardiac repolarization abnormalities in children and young adults with CAS under stress conditions.
• To investigate the relationship between CAS, heart rate variability, and QT interval duration during exercise.
• To determine if altered repolarization during stress contributes to the risk of sudden cardiac events in CAS.

Main Methods:

• A study cohort of 40 participants (20 with CAS, 20 healthy controls) underwent echocardiography and treadmill stress testing.
• Electrocardiograms (ECG) were recorded at rest and during exercise, measuring QT and RR intervals in leads II and V6.
• Statistical analyses included ANOVA, Student's t-test, and linear regression to compare repolarization parameters between groups.

Main Results:

• No significant differences in resting ECG parameters were observed between the CAS and control groups.
• During exercise, the mean QT interval was significantly longer in the CAS group compared to controls (p < 0.05), except at a heart rate of 140 +/- 5 bpm.
• These findings indicate transiently altered cardiac repolarization in CAS patients with heart rate variations.

Conclusions:

• Patients with CAS exhibit transiently impaired cardiac repolarization during dynamic changes in heart rate.
• This repolarization defect during stress may predispose individuals with CAS to potentially fatal arrhythmias.
• The study highlights the importance of evaluating cardiac repolarization under stress in the management of pediatric CAS.