SYMPTOMATIC SINUS DYSFUNCTION - A NEW APP LICATION OF ELECTROPHYSIOLOGY

The authors undertook a prospective electrophysiological study of 950 patients : 53 subjects considered to be << controls >> since they were free of any history of syncope or faintness were identified, as well as 39 symptomatic subjects with a strong suspicion of sinus dysfunctio n, since no other detectable cause of fainting episodes was found by e xtracardiac investigation, 24 hour ECG nor electrophysiology. Followin g the creation of a computerised tool enabling not only the entry of i ndirect tests, processing, averaging of results, printing and memorisa tion, but also assistance in interpretation, several electrophysiologi cal parameters were used : heart rate and existence of sinus arrhythmi a, Strauss tests with adjusted data or not, effective nodal refractory period, Guize, Narula and Mandel tests, and an atropine (0.03 mg/kg) test which was performed only in the symptomatic group. These tests we re studied by single-variate and correlative analysis to define their normal ranges, their critical values and their dependence or independe nce. The performance of each test (i.e. its efficiency, and the specif icity and sensitivity of each critical value) was measured. Tests foun d to be most useful (specificity and efficiency > 90%) were as follows : Mandel test = CSRT greater-than-or-equal-to 534 ms, Narula test = TE CASA greater-than-or-equal-to 339 ms, heart rate less-than-or-equal-to 55/min, type II, III and chaotic Strauss curve associated with a path ological Guize test. The combination of these tests in this algorithm resulted in an increase in sensitivity to 84%, at the price of a very moderate fall in specificity to 87%. The use of this approach is justi fied by the need to adapt diagnostic methods in light of advances in p ermanent pacing.