Analysis of ventricular arrhythmias in patients with dilated cardiomyopathy--relationship between the effects of antiarrhythmic agents and severity of myocardial lesions.

In order to investigate the usefulness of antiarrhythmic drugs in patients with dilated cardiomyopathy (DCM), 42 patients with DCM were studied using 24 h ambulatory ECG monitoring, echocardiography and right ventricular endomyocardial biopsy. All 42 patients had ventricular arrhythmias with a Lown's classification of grade II or greater (grade IVb, 25; IVa, 7; III, 7; II, 3). The patients with grade IV arrhythmias tended to have greater dilating of the left ventricle and more pronounced interstitial myocardial fibrosis than patients with lower grades. Following procainamide and/or disopyramide treatment the severity of the ventricular arrhythmias improved in 12 (29%) of the 42 patients, did not change in 27 patients (64%), and deteriorated in 3 patients (7%). Treatment with aprindine or mexiletine was effective in 7 (50%) of the 14 patients who did not respond to procainamide and/or disopyramide. Although there were no significant differences in left ventricular dimension and contractility between patients in each group who did and did not respond to antiarrhythmic treatment, those who did respond had less interstitial myocardial fibrosis. Thus, in the procainamide and/or disopyramide treated group the percent interstitial fibrosis in responding vs nonresponding patients was 10.3 +/- 4.1% vs 18.7 +/- 8.3% (p less than 0.05) respectively, while in the group treated with aprindine or mexiletine these figures were 13.0 +/- 3.2% vs 26.1 +/- 7.9% (p less than 0.02), respectively. In conclusion, the effect of antiarrhythmic drugs in DCM was dependent on the severity of the pathological changes in the myocardium, and antiarrhythmic drugs should be appropriately used for the management of ventricular arrhythmias in DCM.