Fifty patients with anteroapical left ventricular aneurysm secondary to prior myocardial infarction underwent aneurysmectomy, at which time endocardial sinus rhythm mapping was performed. Forty patients had a history of recurrent sustained monomorphic ventricular tachycardia, and 10 had an aneurysm but no history of spontaneous sustained tachycardia. A comparison of the clinical, angiographic and sinus rhythm endocardial electrographic characteristics of these two groups revealed that the patients without spontaneous ventricular tachycardia had more severe coronary artery disease (2.6 +/- 0.5 versus 1.9 +/- 0.8 coronary arteries having greater than 70% stenosis; p less than 0.03), underwent surgery earlier after infarction (3 +/- 2 versus 46 +/- 53 months; p less than 0.03) and had less extensive wall motion abnormalities on contrast ventriculography (0 of 8 versus 13 of 35 patients assessed had an abnormally contracting ventriculographic segment length greater than 60%; p less than 0.04). During intraoperative programmed electrical stimulation, all 40 patients with and 4 of 10 without a history of spontaneous ventricular tachycardia had inducible tachycardia. The patients with inducible tachycardia had a larger area of endocardium from which abnormal electrograms (duration greater than 70 ms or amplitude less than 0.7 mV) were recorded (62 +/- 17 versus 45 +/- 20% of electrograms; p less than 0.03) as well as fractionated (duration greater than 90 ms, amplitude less than 0.3 mV) electrograms (20 +/- 14 versus 9 +/- 7% of electrograms; p less than 0.04) than did patients without inducible tachycardia, but there were no angiographic differences between groups.(ABSTRACT TRUNCATED AT 250 WORDS)