ABSTRACT
The incidence of sudden death in children with congenital aortic stenosis (CAS) varies between 4 and 20%. In several syndromes sudden death is associated with a long QT interval in the electrocardiogram (ECG). The aim of the study was to evaluate the cardiac repolarization in CAS during stress. We included 40 children and young persons, 20 with CAS and 20 healthy controls. All underwent echocardiographic study and treadmill stress test. The QT and relative RR intervals were measured in leads II and V6 at rest and during exercise at preselected heart rates. Mean values of QT were compared by analysis of variance, Student's t-test, and linear regression method. No statistically significant differences in the resting ECG were found between the two groups, whereas during exercise the mean QT of the CAS group was significantly longer than in the controls (p < 0.05), except at a heart rate of 140 +/- 5. Our study demonstrates that patients with CAS have transiently altered cardiac repolarization when there are sudden variations in heart rate. Such a defect could predispose patients with CAS to fatal arrhythmias and sudden death.
Subject(s)
Aortic Valve Stenosis/congenital , Death, Sudden, Cardiac/etiology , Electrocardiography , Exercise/physiology , Heart Conduction System/physiopathology , Myocardial Contraction/physiology , Aortic Valve Stenosis/mortality , Aortic Valve Stenosis/physiopathology , Child , Death, Sudden, Cardiac/epidemiology , Echocardiography , Exercise Test , Heart Rate/physiology , Humans , Incidence , Regression AnalysisABSTRACT
Our study was designed to assess potential cardiovascular adverse effects in clinically stable asthmatic children due either to oral sustained-release theophylline or theophylline in combination with an inhaled beta-2 adrenergic agonist. Twenty-five asthmatic children were evaluated while receiving no drugs, theophylline alone, and theophylline with an inhaled beta-2 adrenergic agonist. In each phase all patients underwent 24- to 48-hour Holter monitoring and a maximal treadmill exercise test. The results show that neither theophylline alone nor combined therapy was associated with any relevant cardiovascular adverse effect, including ectopic cardiac activity. A nonsignificant increase in mean heart rate was observed between each period of study. The data suggest that the use of theophylline either alone or in combination with a beta-2 adrenergic agonist in clinically stable asthmatic children is not associated with any serious cardiovascular effect.
