Functional changes of ventricular late potentials by provocation with increase of heart rate - Evaluation during atrial pacing

Background Standard methods fail to reveal late potentials in 20 to 30% of patients with ventricular arrhythmias after myocardial infarction. However, these patients may develop transient delayed ventricular activation during increases in heart rate. Methods and Results Atrial pacing was performed, at the rates of 100 min(-1 ) and 120 min(-1), in 50 patients after myocardial infarction. Twenty-six p atients had a history of documented, sustained ventricular tachycardia, 12 had a history of ventricular fibrillation and 12 no history of ventricular arrhythmias. The low-noise surface electrocardiogram was analysed before an d during atrial pacing in the time and frequency domains. Fifteen of 26 pat ients with ventricular tachycardia, four of 12 with ventricular fibrillatio n and three of 12 without ventricular arrhythmias experienced late potentia ls during sinus rhythm. Atrial pacing led to a shift of 26 +/- 15 ms of pre existent late potentials into the ST segment, this being greater in patient s with anterior infarctions and to an increase in magnitude in patients wit h inferior infarctions. In patients without late potentials during sinus rh ythm, atrial pacing provoked late potentials in eight of 11 patients with v entricular tachycardia, in four of eight patients with ventricular fibrilla tion and in one of nine patients without ventricular arrhythmias. Low ampli tude signals (LAS) were increased in patients after inferior and filtered Q RS in patients after anterior infarction. In 10 patients without cardiac di sease no late potentials were detectable in the time and frequency domain e ither at rest or during increased heart rate. Conclusions Increase in heart rare may unmask late potentials in patients p rone to malignant ventricular arrhythmias. Therefore, functional late poten tial analysis with non-invasive clinical stress tests, i.e. exercise tests, should be performed only with an adequate rate response. This might identi fy patients at risk of malignant ventricular arrhythmias otherwise not iden tified with conventional late potential analysis.