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In order to determine the role of tilt testing in the aetiological diagnosis of syncope unexplained by electrophysiological investigation, the authors retrospectively studied the results of this test in 275 patients with a mean age of 64 +/- 16 years. These 275 patients were divided into two groups: group I: 43 patients with a mean age of 50 +/- 19 years presenting with vagal syncopes, group II: 232 patients with unexplained syncope, probably vagal: group IIa (120 patients, mean age: 67 +/- 15 years), sudden syncope: group IIb (112 patients, mean age: 67 +/- 13 years). The electrophysiological investigation was inconclusive in every case. In group II, 50% of tilt tests were positive (19% under basal conditions, 31% after isoproterenol), with 61% of positive tests in group IIa, including 31% on the basal test, and 38% of positive tests in group IIb, including 11% on the basal test. In group I, 84% of tests were positive (33% on the basal test, 51% after isoproterenol), indicating a sensitivity of the test of 84%. In 96 patients with a doubtful electrophysiological investigation, the tilt test was positive in 70% of cases, allowing specific treatment or a pacemaker to be avoided in the majority of cases. 84% of vasovagal syncopes were therefore confirmed by tilt testing; 50% of syncopes unexplained by electrophysiological investigation were demonstrated to be of vasovagal origin. The author emphasize the value of tilt testing in certain discordant situations in which the clinical context is disturbing and/or electrophysiological investigation is not completely reassuring.

The authors report four observations: three are essentially clinical cases where sustained rate dependent left bundle branch block can induce syncope, where as there is no syncope when the same supraventricular tachycardia at the same frequency has narrow QRS complexes. The fourth case demonstrates the dramatic decrease of arterial electrophysiological slowly accelerated atrial pacing in a patient investigated for a loss of consciousness of unknown origin. The hemodynamic impairment due to intermittent left bundle branch block has been demonstrated even in patients with normal ventricular function. If there are critical hemodynamic events such as during fast supraventricular rhythms occurrence of a left bundle branch block may determinate a dramatic decrease of arterial pressure with syncope. Syncope of supraventricular tachycardias might be induced not only by very fast rate but also by functional left bundle branch block. It might have some interesting applications in the diagnosis of syncope when coexist electrophysiological data of supraventricular arrhythmia substrate and frequency dependent left bundle branch block.

The aim of this study was to compare the electrophysiologic properties of asymptomatic Wolff-Parkinson-White (WPW) syndromes with those of symptomatic WPW, and in particular the anterograde refractory period of the accessory tract and atrial vulnerability. This retrospective study involved 171 patients with WPW seen in their surface electrocardiogram, untreated, having undergone standard invasive electrophysiologic investigation. These patients were divided into two groups: group I consisting of 42 asymptomatic patients and group II consisting of 129 asymptomatic patients. 1) The mean anterograde refractory period (mean ARP) did not differ statistically between group I (330 +/- 97 msec) and group II (311 +/- 110 msec). The mean minimum interval between two preexcited complexes during atrial fibrillation (mean RR min) did not differ statistically between group I (313 +/- 80 msec) and II (300 +/- 105 msec). The mean retrograde refractory period (mean RRP) was significantly (p < 0.001) longer in group I (416 +/- 126 msec) than in group II (307 +/- 75 msec). 2) A reciprocal tachycardia was induced in 95% of cases in group II (122 patients) as compared with 9.5% of cases in group I (4 patients), with a very significant (p < 0.001) difference. Atrial fibrillation was induced in 24% of cases in group I (10 patients) and 34% of cases in group II (44 patients), the difference not being significant. 3) The incidence of potentially serious forms did not differ statistically between groups I and II. Nine patients in group I (21.4%) and 49 patients in group II (38%) had rapid anterograde conduction in the accessory tract (ARP or RR < or = 250 msec).(ABSTRACT TRUNCATED AT 250 WORDS)