Identification of ventricular late potentials in the surface electrocardiogram during atrial, atrioventricular...

Sudden cardiac death occurs in up to 30% of patients with cardiac pacemakers, caused by ventricular arrhythmias, but in these patients noninvasive risk stratification with Holter, exercise, or standard signal-averaged electrocardiogram is limited. This study investigated whether late potential analysis during cardiac pacing is applicable. In 50 postinfarction patients with documented sustained ventricular tachycardia (VT) and in 50 patients without VT, late potential analysis during sinus rhythm was compared with the corresponding patient's analysis during temporary pacing. During sinus rhythm late potentials were seen in 48 of 50 patients with VT and in 2 of 50 patients without VT. No significant changes were observed during atrial pacing. Modified QRS alignment for signal averaging, QRS endpoint definition, and adjusted cutoff values for abnormality in time and frequency domain analysis allowed retrieval of all late potentials observed during sinus rhythm even in ventricular-paced beats and retrograde conduction. By application of an adjusted analysis to 100 selected patients with permanent pacemakers (50 patients with a history of VT, 50 patients without VT) late potentials were detectable in 44 of 50 patients with VT and in 4 of 50 without VT (sensitivity 88%, specificity 92%). Thus, considering that varying pacing modes, ventricular-paced beats, and retrograde conduction do require modifications of standard late potential analysis, this is an applicable mode for noninvasive risk stratification even in patients with cardiac pacemakers.