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Evaluation of Exercise‐Induced T Wave Changes in Patients with Idiopathic Dilated Cardiomyopathy Before and After Beta‐Blocker Therapy
Author(s) -
HARA HIDEYUKI,
NIWANO SHINICHI,
HIRASAWA SHOJI,
SASAKI TAKESHI,
IKEDA NORIAKI,
IZUMI TOHRU
Publication year - 2006
Publication title -
journal of cardiovascular electrophysiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.193
H-Index - 138
eISSN - 1540-8167
pISSN - 1045-3873
DOI - 10.1111/j.1540-8167.2006.00521.x
Subject(s) - medicine , cardiology , dilated cardiomyopathy , qrs complex , repolarization , treadmill , qt interval , cardiomyopathy , electrocardiography , heart failure , electrophysiology
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. Methods and 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. Conclusion: 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.