SIGNIFICANCE AND PREVALENCE OF INDUCIBLE ATRIAL TACHYARRHYTHMIAS IN PATIENTS UNDERGOING ELECTROPHYSIOLOGIC STUDY FOR PRESYNCOPE OR SYNCOPE

The purpose of the study was to report the prevalence of inducible sup raventricular tachyarrhythmias (SVTA) in 827 consecutive patients aged 17 to 90 years who did not have spontaneous documented SVTA and who h ad unexplained presyncope and/or syncope. The electrophysiologic study (EPS) included programmed atrial and ventricular stimulation up to tw o extrastimuli at three cycle lengths, and the study of sino-atrial an d AV conduction. The results were as follows. EPS was normal in 386 pa tients. Inducible junctional tachycardia or atrial flutter and fibrill ation was the only finding in 187 patients (23%). In the remaining pat ients we found ventricular tachycardia in 103 (12%), heart block in 67 (8%), sick sinus syndrome in 56 (7%) and increased vagal tone in 28 ( 3%). The presence of an underlying heart disease (47%) and salves of a trial premature beats on Holter monitoring (39%) were significantly co rrelated with the induction of SVTA. However, the comparison with simi lar groups without syncope indicates that only the induction of SVTA i n patients with hypertrophic cardiomyopathy and mitral valve prolapse was significantly correlated with the history of syncope. In patients without heart disease or with prior myocardial infarction or decreased left ventricular function, the induction of SVTA, which is not associ ated with hypotension in the supine position, could require an inducti on after head-up tilting, because of the lack of specificity of progra mmed stimulation in these patients. Programmed atrial stimulation shou ld be systematically performed in patients with unexplained syncope, i n particular in those with hypertrophic cardiomyopathy and mitral valv e prolapse, who require a specific treatment, if a SVTA is induced. In other patients the results of programmed atrial stimulation should be interpreted cautiously.