[Syncope caused by paroxysmal atrial fibrillation and flutter: diagnostic usefulness of electrophysiological studies in the erect and supine positions].

In this study, we verified if the induction of atrial fibrillation/flutter, during the electrophysiological study, could be useful for the evaluation of syncope of unknown origin. Of 292 patients who underwent an electrophysiological study for unexplained symptoms, we selected 15 patients (5.1%) affected by syncope and pre-syncope. In these, the induction of atrial fibrillation (14 patients) or flutter (1 patient) just at the onset caused, the reproduction of the spontaneous symptoms. No other cause could be identified. These patients were affected by: 1) syncope or pre-syncope without electrocardiographic documentation of paroxysmal atrial fibrillation/flutter 2) syncope or presyncope and documented asymptomatic episodes of paroxysmal atrial fibrillation/flutter. Palpitations closely preceded or followed the syncope in 11/15 patients. Symptom reproduction was obtained in the supine position in 3 patients (heart rate 180 +/- 82 beat/min, systolic blood pressure 53 +/- 6 mmHg) and in the upright position in 12 patients (heart rate 177 +/- 24, systolic blood pressure 65 +/- 18 mmHg). The arrhythmia was induced by incremental atrial pacing or premature atrial beats in 3 cases, ramp in 3 cases and burst--mean rate 339 +/- 48 beat/min--in 9 cases. The arrhythmia lasted for a period of time ranging from a minimum of 1 mm to a maximum of 24 hours (median 1 hour). During sinus rhythm, an abnormal vasodepressor reflex (with a systolic blood pressure fall greater than or equal to 50 mmHg) could be induced in 7/9 patients by carotid sinus massage or 60 degrees tilt test.(ABSTRACT TRUNCATED AT 250 WORDS)