To assess whether the level of risk of having significant electrophysiologic abnormalities can be determined, 29 clinical variables were analyzed in 104 patients with unexplained syncope who underwent electrophysiologic testing. A positive electrophysiologic study was defined as: 1) a sinus node recovery time ≥3 seconds; 2) HV interval ≥100 ms; 3) infranodal block during atrial pacing; 4) unimorphic ventricular tachycardia; and 5) supraventricular tachycardia associated with hypotension. Thirty-one patients had a positive study, with inducible ventricular tachycardia being the most common finding (71% of positive studies). A left ventricular ejection fraction ≤0.40 was the most powerful predictor of a positive electrophysiologic study (p < 0.00001), followed by the presence of bundle branch block (p < 0.00003), coronary artery disease (p < 0.00003), remote myocardial infarction (p < 0.00006), use of type 1 antiarrhythmic drugs (p < 0.0003), injury related to loss of consciousness (p < 0.01) and male sex (p < 0.01). A negative electrophysiologic study was associated with an ejection fraction >0.40 (p < 0.00001), the absence of structural heart disease (p < 0.00001), a normal electrocardiogram (ECG) (p < 0.0001) and normal ambulatory ECG monitoring (p < 0.0001). The probability of a negative study increased as the number and duration of syncopal episodes increased. The results of electrophysiologic testing could be predicted with a probability (p) value ≥0.99 in 51% of patients who had a negative study and with a probability value ≥0.95 in 52% of those who had a positive study. Therefore, on the basis of clinical variables, a majority of patients with unexplained syncope can be stratified into subgroups with high and low probability of having an electrophysiologic abnormality that is likely to be related to syncope. This allows for more cost-effective use of electrophysiologic studies. © 1987, American College of Cardiology Foundation. All rights reserved.
Krol, R. B., Morady, F., Flaker, G. C., DiCarlo, L. A., Baerman, J. M., Hewett, J., & de Buitleir, M. (1987). Electrophysiologic testing in patients with unexplained syncope: Clinical and noninvasive predictors of outcome. Journal of the American College of Cardiology, 10(2), 358–363. https://doi.org/10.1016/S0735-1097(87)80019-0