[Unexplained syncope. Likelihood of inducing sustained ventricular tachycardia with electrophysiologic examination].

In patients with unexplained syncope and documented nonsustained VT or complex premature ventricular beats indication for programmed ventricular stimulation (PVS) should be considered. However, the variables derived from noninvasive methods that predict diagnostic yield of PVS are incompletely defined. The purpose of this study was to elucidate the role of noninvasive testing variables in predicting inducible monomorphic sustained ventricular tachycardia (SVT) in 116 patients (pts) presenting with syncope. The study group consisted of 45 pts with remote Q wave myocardial infarction. 5 pts with non-Q wave myocardial infarction, 21 pts with another heart disease and 45 pts without organic heart disease. All pts underwent standard ECG, Holter monitoring, echocardiography, signal-averaged ECG and PVS with 1, 2 and 3 extrastimuli at three basic cycle lengths. Nonsustained VT, low ejection fraction, prolongation of QTc interval, abnormal Q waves in postinfarction pts (Q-MI) and late potentials (LP) indicate a greatly increased probability of inducible SVT. Inducible SVT was present in 15 of 45 (33%) pts with Q-MI. Although in the group of 71 pts without Q-MI, nonsustained VT on Holter monitoring was detected in 20 pts, LP in 16 pts, prolongation of QTc interval in 3 pts and low ejection fraction in 2 pts, the positive yield of PVS was documented in only one case (1%). The combination of Q-MI and LP best predicted inducible SVT showing a sensitivity of 75%, specificity of 93%, overall predictive accuracy of 91%, predictive value of positive response of 63% and negative response of 69% to identify pts who would have inducible SVT. Thus, the combination of Q-MI and LP variables was shown as the best predictor of inducible SVT in pts with unexplained syncope. In pts without Q-MI the noninvasive testing variables have considerably less value in selection of pts to PVS, because inducible SVT is very rare in this population.