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Heart 1998;79:256-261; doi:10.1136/hrt.79.3.256
Copyright © 1998 BMJ Publishing Group Ltd & British Cardiovascular Society

Heart 1998;79:256-261 ( March )

Prediction of the effectiveness of long term beta  blocker treatment for dilated cardiomyopathy by signal averaged electrocardiography

T Yamada,a M Fukunami,a T Shimonagata,a K Kumagai,a J Kim,a S Sanada,a H Ogita,a M Hori,b N Hokia

a Division of Cardiology, Osaka Prefectural Hospital, Osaka, Japan, b 1st Internal Medicine, Osaka University Medical School, Osaka, Japan

Correspondence to: Dr T Yamada, Division of Cardiology, Osaka Prefectural Hospital, 3-1-56, Mandai-Higashi, Sumiyoshi-ku, Osaka 558, Japan.

Accepted for publication 13 November 1997

Objective---To determine whether the effectiveness of long term beta  blocker treatment for idiopathic dilated cardiomyopathy can be predicted by signal averaged electrocardiography (ECG).
Patients---31 patients with dilated cardiomyopathy and without bundle branch block were included in a retrospective study and 16 in a prospective study.
Methods---A signal averaged ECG was recorded before beta  blocker treatment, and three variables were measured from the vector magnitude: QRS duration, root mean square voltage for the last 40 ms (RMS40), and duration of the terminal low amplitude signals (< 40 µV) (LAS40). In the retrospective study, these variables were compared among good responders (showing >=  0.10 increase in ejection fraction 12 months after start of beta  blocker treatment) and poor responders without such improvement. The validity of the signal averaged ECG criteria for prediction of the response to beta  blocker treatment was examined in the prospective study.
Results---In the retrospective study, good responders (n = 16) had a shorter QRS duration (mean (SD): 122.9 (11) v 138 (14.4) ms, p < 0.005) and LAS40 (33.1 (8.9) v 42.5 (7.8) ms, p < 0.005), and a higher RMS40 (31.6 (16.3) v 19.0 (10.3) µV, p < 0.02) than poor responders (n = 15). Signal averaged ECG criteria for good response were defined as two or more of the following: QRS duration < 130 ms, RMS40 > 20 µV, LAS40 < 40 ms (sensitivity 81%, specificity 73%). In the prospective study, six of seven patients who met these criteria showed a good response to the beta  blocker treatment, while eight of nine who did not showed a poor response (chi 2 = 6.1, p < 0.02). The signal averaged ECG criteria gave a sensitivity of 86% and a specificity of 89% for predicting the effectiveness of beta  blocker treatment.
Conclusions---A signal averaged ECG might be useful in predicting the effectiveness of beta  blocker treatment for dilated cardiomyopathy.

Keywords: signal averaged ECG;  beta blockers;  dilated cardiomyopathy

© 1998 by Heart
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