Evidence for slow conduction areas during pacing in patients with sinus rhythm, and their relation to the site of VT origin.

UNLABELLED

In 52 patients with reentrant monomorphic sustained ventricular tachycardia (VT), the site of VT origin was determined by endocardial mapping and the interval from stimulus artifact to the onset of QRS complex (St-QRS) was measured during pace-mapping. Eleven patients had remote myocardial infarction (group 1), 25 patients had other underlying heart diseases (group 2), and 16 had idiopathic VT (group 3). At St-QRS interval of 40 msec or longer was defined as abnormal. (1) Long St-QRS interval: Thirteen sites with long St-QRS intervals were detected in 13 (25.0%) of 52 patients: 5 patients in group 1 (45.5%), 7 (28.0%) patients in group 2 and one (6.3%) in group 3. (2) Local electrogram: The local electrogram at sites with a long St-QRS interval was wide and 113 +/- 38 msec in duration during sinus rhythm which increased to 159 +/- 64 msec during VT (p < 0.05). In sinus rhythm, an abnormally prolonged local electrogram was observed in 11 of 13 sites with a long St-QRS interval, and mid-diastolic potential or continuous activity was observed in 3 sites during VT. (3) Relation to VT origin: At sites with a long St-QRS interval, concealed entrainment was observed in 3 patients, and the earliest activated local electrogram during VT in 5 patients.

CONCLUSION

Sites with a long ST-QRS interval were observed in 25% of the patients with VT, and their incidence tended to be higher in patients with ischemic heart disease. Such sites were associated with abnormal local electrograms and some of the sites were considered to be the active limb of the reentry circuit.