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

Abstract

Objective To determine whether the effectiveness of long term β 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 β 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 β blocker treatment) and poor responders without such improvement. The validity of the signal averaged ECG criteria for prediction of the response to β 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 β blocker treatment, while eight of nine who did not showed a poor response (χ² = 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 β blocker treatment.

Conclusions A signal averaged ECG might be useful in predicting the effectiveness of β blocker treatment for dilated cardiomyopathy.