PREDICTION OF THE EFFECTIVENESS OF LONG-TERM BETA-BLOCKER TREATMENT FOR DILATED CARDIOMYOPATHY BY SIGNAL-AVERAGED ELECTROCARDIOGRAPHY

Objective-To determine whether the effectiveness of long term beta blo cker treatment for idiopathic dilated cardiomyopathy can be predicted by signal averaged electrocardiography (EGG). Patients-31 patients wit h dilated cardiomyopathy and without bundle branch block were included in a retrospective study and 16 in a prospective study Methods-A sign al 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 te rminal low amplitude signals (< 40 mu V) (LAS40). In the retrospective study these variables were compared among good responders (showing gr eater than or equal to 0.10 increase in ejection fraction 12 months af ter start of beta blocker treatment) and poor responders without such improvement. The validity of the signal averaged ECG criteria for pred iction of the response to beta blocker treatment was examined in the p rospective 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), an d a higher RMS40 (31.6 (16.3) v 19.0 (10.3) mu V, p < 0.02) than poor responders (n = 15). Signal averaged ECG criteria for good response we re defined as two or more of the following: QRS duration < 130 ms, RMS 40 > 20 mu V, LAS40 < 40 ms (sensitivity 81%, specificity 73%). In the prospective study, six of seven patients who met these criteria showe d a good response to the beta blocker treatment, while eight of nine w ho 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. Conclu sions-A signal averaged ECG might be useful in predicting the effectiv eness of beta blocker treatment for dilated cardiomyopathy.