Variable late potentials in long-term ECG of the post-infarct patient at risk for ventricular fibrillation

Abstract

Ventricular late potentials are found more readily in post-infarction patients who had sustained ventricular tachycardia than in those who survived ventricular fibrillation. Hypothetically, a daytime variability of late potentials might be responsible for this finding. Therefore a conventional late potential analysis only performed once a day was compared to a late potential analysis in time and frequency domain repeatedly performed every hour in the Holter-ECG of 160 post-infarction patients (50 patients (= VT-group) with documented, sustained ventricular tachycardia (cycle-length > 230 ms), 50 patients (= VF-group) who survived, documented ventricular fibrillation and 60 patient, without ventricular arrhythmias (= O VT/VF-group)). The conventional analysis showed late potentials in time domain in 72% of the patients in the VT-group, in 40% of patients in the VF-group and in 20% of the patients in the O VT/VF-group. The Holter-ECG showed late potentials to be permanently present in frequency domain in 66% of the patients in the VT-group, in only 6% in the patients in the VF-group and in no patient in the O VT/VF-group. However, in at least one analysis we detected late potentials in 84% of patients of the VF-group, in 90% of patients in the VT-group and in 18% of patients in the O VT/VF-group. Transiently detectable late potentials in patients of the VF-group were predominantly seen at heart rate accelerations in the morning hours, ST-segment shifts or transitory decreased heart rate variability. Post-infarction patients with sustained ventricular tachycardia predominantly have constantly detectable late potentials over 24 hours. In these patients conventional late potential is successful for post-infarction risk stratification at any time of the day. However, in post-infarction patients who survived ventricular fibrillation, late potentials are found to be transitory and only detectable by Holter-ECG. Thus, late potential analysis performed in the Holter-ECG might improve post-infarction risk stratification in patients prone to sudden cardiac death.