MAGNETIC-RESONANCE-IMAGING AND SIGNAL-AVERAGED ELECTROCARDIOGRAPHY INPATIENTS WITH REPETITIVE MONOMORPHIC VENTRICULAR-TACHYCARDIA AND OTHERWISE NORMAL ELECTROCARDIOGRAM

Early or localized forms of arrhythmogenic right ventricular dysplasia (ARVD) have been proposed as the arrhythmogenic substrate of repetiti ve monomorphic ventricular tachycardia (RMVT) originating in the right ventricular outflow tract in patients without any underlying cardiac abnormality on clinical examination and echocardiography. To further e xamine this hypothesis, magnetic resonance imaging (MRI) and signal-av eraged electrocardiography (SAECG) were performed on 23 patients with RMVT and normal 12-lead standard ECG of conducted sinus beats, MRI was performed using ECG-gated turbo spin-echo images of the heart in orde r to detect signs of early or localized forms of ARVD, such as localiz ed wall thickness reductions, signal intensity increase indicating adi pose tissue infiltrates, and regional bulgings or aneurysms. MRI was n ormal in 22 (96%) of 23 study patients. In the remaining patient (4%), MRI demonstrated signal intensity increase in the intraventricular se ptum but not in the right ventricular outflow tract. Time-domain analy sis of the SAECG was normal in 21 (91%) of 23 patients and revealed ve ntricular late potentials in 2 study patients (9%). Frequency-domain a nalysis of the SAECG was normal in 22 (96%) of 23 patients and reveale d ventricular late potentials in one study patient (4%). We conclude t hat normal MRI findings of the heart and absence of ventricular late p otentials in the SAECG in most patients with RMVT and otherwise normal ECG do not support the hypothesis that early of localized forms of AR VD create the arrhythmogenic substrate in the majority of these patien ts.