Significance of signal-averaged electrocardiography in relation to endomyocardial biopsy and ventricular stimulation studies in patients with ventricular tachycardia without clinically apparent heart disease

Signal-averaged electrocardiography (ECG) was performed in 38 patients (mean age 38 years, range 15 to 70) with ventricular tachycardia who had no clinical evidence of structural heart disease. Spontaneous ventricular tachycardia was nonsustained in 23 patients and sustained in 15. None of the patients had symptoms of heart failure or ischemic heart disease, and at cardiac catheterization none had significant coronary artery disease or left ventricular wall motion abnormalities. In addition, all patients underwent left and right ventricular endomyocardial biopsy and ventricular stimulation studies. Signal-averaged ECG was performed and late QRS potentials were defined with use of Simson's method. Late QRS potentials were detected in a minority (18%) of patients including 2 of 23 with nonsustained and 5 of 15 with sustained (p = NS) ventricular tachycardia. Fifteen patients (40%) had abnormal endomyocardial biopsy results and these findings were more common in patients with s sustained than in those with nonsustained ventricular tachycardia (9 of 15 versus 6 of 23, p < 0.05). Late potentials were associated with abnormal endomyocardial biopsy findings (6 of 15 versus 1 of 23, p < 0.01). An increase in fibrous tissue was the most frequent histopatho logic abnormality; this increase was quantified by morphometric methods and compared with biopsy findings in normal control subjects. In the control group the proportion of collagen in relation to myocytes was <10%. All patients with both late potentials and abnormal biopsy findings had a >15% ratio of collagen to myocytes in at least one specimen and the biopsies revealed marked interstitial fibrosis. At programmed electrical stimulation clinical tachycardia was more commonly induced in patients with sustained than in those with nonsustained ventricular tachycardia (12 of 15 versus 7 of 23, p < 0.01). The presence of late QRS potentials in patients with ventricular tachycardia without clinically apparent structural heart disease was not a sensitive marker for abnormal myocardial histologic findings (63%) or inducible ventricular arrhythmia (37%), but was very specific for these variables (84% and 100%, respectively). The majority of patients with normal findings on endomyocardial histologic study and signal-averaged ECG have a tachycardia with a left bundle branch block configuration and a right frontal plane axis.