FUNCTIONAL LATE POTENTIAL ANALYSIS FOR RI SK STRATIFICATION IN PATIENTS AFTER MYOCARDIAL-INFARCTION PRONE TO VENTRICULAR-TACHYCARDIA

Background. Electrophysiological abnormalities during ischaemia and in creased heart rate may influence the detection of ventricular late pot entials in the surface electrocardiogram. Whether the analysis of func tional changes adds information to the risk stratification of patients prone to ventricular tachycardia is unclear. Methods. We therefore re trospectively investigated 100 selected patients (25 with documented, sustained ventricular tachycardia (< 230/min) (= VT group), 25 resusci tated from ventricular fibrillation (VF group) and 50 without ventricu lar arrhythmias (empty set VT/VF group)) in the chronic phase after my ocardial infarction. Late potential analysis was performed at rest, du ring atrial pacing at a rate of 100/min and 120/min (n = 60), during a nd after occlusion of the coronary artery for coronary angioplasty (PT CA) (n = 70), and immediately after maximum exercise using selective s ignal averaging. Results. At rest in 72% of patients in the VT group, in 32% of the VF group, and in 6% of the empty set VT/VF group late po tentials could be found. During atrial pacing in 80% of patients in th e VT group, in 72% of the VF group, and in 10% of the patients in the empty set VT/VF group and during ischaemia because of occluded coronar y artery in 86% of patients in the VT group, 70% of the VF group, and in 20% of the patients of the empty set VT/VF group late potentials we re present. Immediately after maximum exercise which let to both ischa emia and increased heart rate, late potentials were detectable in 92% of patients in the VT group, 80% of the VF group, and in 14% of patien ts in the empty set VT/VF group. Similar results could be achieved by using the Holter-ECG after exact correction of recorder tape speed var iations. 62% of patients with only by ischaemia, increased heart rate or exercise provokable late potentials and all patients with preexiste nt not by PTCA extinguished late potentials developed recurrent ventri cular tachycardias during the one year follow-up period. Patients with out late potentials (n = 50) and patients with preexistent by PTCA ext inguished late potentials (n = 11) had no recurrent ventricular tachyc ardias. Cycle length of recurrent and clinical tachycardia in patients with preexistent not by PTCA extinguished late potentials (n = 18) we re significantly longer than in patients with only provokable late pot entials (n = 21). Conclusions. Analysis of functional changes of ventr icular late potentials with exercise or in Holter ECG recordings promi ses considerable improvement of postinfarction risk stratification esp ecially in patients prone to ventricular fibrillation.