Diastolic Potentials Recorded by Surface Electrocardiographic Signal Averaging During Sustained Ventricular Tachycardia: Possible Origin From the Reentrant Circuit

ECG signal averaging can detect low amplitude diastolic potentials in sinus rhythm. We, therefore, recorded signal‐averaged ECGs during eight episodes of inducible uniform sustained VT with coincident atrial pacing to look for continuous diastolic electrical activity. Simultaneous AV pacing in seven patients served as controls. The number of QRS complexes averaged (187 ± 47 vs 183 ± 63), the noise level (1.26 ± 0,88 vs 1.39 ± 0.47) and cycle length (385 ± 52 vs 404 ± 40) did not differ between VT and paced recordings. In each lead the difference in onset between the unfiltered surface recording and the filtered data (40 Hz bidirectional) was significantly greater in VT than the paced recordings (25 ± 16 vs 11 ± 8 msec, P = 0.0012), These late diastolic (pre‐QRS) potentials were > 15 msec duration in 65% of the leads in VT versus 20% of paced recording (P = 0.021). The maximum value was > 20 msec in six VT (75%) versus one (14%) paced recording (P = 0.019), The earliest filtered onset in any lead preceeded the earliest surface activity by > 12 msec, in 6 VT versus one paced recording (P = 0.019). Early diastolic (post‐QRS) potentials were also longer in VT than pacing (49 ± 40 versus 5 ± 20. P = 0.001) and exceeded 38 msec in seven of the VTs but none of the paced recordings (P ‐ 0.001). While no VT recording showed continuous activity, total electrical activation was longer in VT than pacing (282 ± 49 versus 210 ± 39, P = 0.0079) and constituted 73%± 9% of the VT cycle versus 52%± 8% of the paced cycle (P = 0.0004). We conclude that both early and late diastolic potentials can be demonstrated in inducible sustained uniform VT by signal averaging. These potentials might arise from the reentrant pathway and constitute a marker for ventricular reentry.