Beat-to-beat variability of ventricular late potentials in the unaveraged high resolution electrocardiogram--effects of antiarrhythmic drugs.

Abstract

The aim of this study was to assess variability of ventricular late potentials (VLP) in patients with and without inducible ventricular tachycardia (VT), and the effects of antiarrhythmic drugs on VLP variability in the high-resolution electrocardiogram (HRECG). In 27 patients 90 s of unaveraged HRECGs were analysed before and 2 h after oral administration of 200 mg disopyramide, 400 mg mexiletine, 300 mg propafenone and 160 mg DL-sotalol. The duration of the QRS (QRSD) and the duration of the terminal low amplitude signal (LASD) was measured from each beat. Beat-to-beat variability was defined as standard deviation of the differences between consecutive beats. Patients with inducible sustained VT (n = 9) showed higher LASD variability than patients without inducible VT (12.3 vs 9.3 ms.beat-1, P < 0.01). Patients with VLP (n = 17), as defined by the signal averaged ECG, also had higher QRSD and LASD variability (11.8 vs 9.5 ms.beat-1, P < 0.05; 11.5 vs 8.2 ms.beat-1, P < 0.01, respectively) compared to those without VLP. All class I drugs lengthened QRSD and LASD in terms of the absolute values, but only propafenone increased QRSD and LASD variability (9.7 to 12.0 ms.beat-1, P < 0.01; 8.9 to 11.9 ms.beat-1, P < 0.01, respectively). In patients with inducible VT, sotalol decrease LASD variability from 14.3 to 9.3 ms.beat-1 (P < 0.05). We conclude that beat-to-beat VLP variability is increased in patients at a high risk of malignant arrhythmias.(ABSTRACT TRUNCATED AT 250 WORDS)