Evaluation of exercise-induced T wave changes in patients with idiopathic dilated cardiomyopathy before and after beta-blocker therapy.
BACKGROUND
Ventricular repolarization abnormalities are thought to contribute to lethal ventricular arrhythmias in patients with idiopathic dilated cardiomyopathy (DCM). The purpose of this study was to evaluate exercise-induced T wave changes in DCM patients before and after beta-blocker therapy to investigate repolarization abnormalities.


RESULTS
Treadmill exercise testing was performed in 20 DCM patients and 50 normal subjects. T wave amplitude (TA: baseline to T wave apex; mV) and recovery time (RT: QRS onset to the maximum dV/dt point of the T wave; msec) were measured before and 1 minute after peak exercise. TA was averaged in the right and left precordial leads (TA(V1-3), TA(V4-6)). RT was normalized to the maximum QT interval in the 12-lead ECG and expressed as the %RT (%RT). %RT was also averaged in the precordial leads (%RT(V1-3), %RT(V4-6)). After exercise, TA increased and %RT decreased in both groups. In DCM patients, TA(V1-3) was greater and TA(V4-6) was less than in normal subjects before and after exercise. There was no difference in %RT(V1-3) between the groups, but %RT(V4-6) was greater in DCM patients both before and after exercise. DCM patients repeated the same evaluation after 6 months of oral beta-blocker therapy. Compared with measurements before beta-blocker therapy, TA(V1-3) and %RT(V1-3) did not change. However, TA(V4-6) increased and %RT(V4-6) decreased significantly both before and after exercise.


CONCLUSIONS
DCM patients showed small TA and large %RT in the left precordial leads at rest as well as after exercise. Chronic beta-blocker therapy in DCM patients normalized these ventricular repolarization abnormalities.
Hara
Hideyuki
H
Department of Internal Medicine/Cardiology, School of Medicine, Kitasato University, Kitasato, Sagamihara City, Kanagawa, Japan. hideyuki@med.kitasato-u.ac.jp
Niwano
Shinichi
S
Hirasawa
Shoji
S
Sasaki
Takeshi
T
Ikeda
Noriaki
N
Izumi
Tohru
T
D000319:Adrenergic beta-Antagonists / Q000627:therapeutic use*; D000328:Adult; D000368:Aged; D002311:Cardiomyopathy, Dilated / Q000188:drug therapy / Q000503:physiopathology*; D004562:Electrocardiography; D005080:Exercise Test; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged
D000319:Adrenergic beta-Antagonists