Absence of tachycardia during tilt test predicts failure of β-blocker therapy in patients with neurocardiogenic syncope

Not all patients with neurocardiogenic syncope respond to β-blockers. To determine whether differences in heart rate response to head-up tilt test with and without isoproterenol may predict drug efficacy, we evaluated 32 consecutive patients with a history of syncope, who were treated with β-blockers after a positive tilt test. During the tilt test 21 patients (group A) with a baseline heart rate of 72 ± 15 beats/min had tachycardia (mean 131 ± 15) during tilt, before syncope, whereas 11 patients (group B) with a baseline heart rate of 68 ± 13 beats/min did not (mean 86 ± 13; p < 0.001). There were no significant differences between groups with regard to demographic and clinical characteristics or mean heart rate and mean arterial pressure in the supine position and during syncope. However, the proportion of patients requiring isoproterenol for provocation of syncope was significantly higher in group A compared with group B (15 of 21 vs 1 of 11; p< 0.001). All patients were treated with β-blockers (propranolol or metoprolol). During a follow-up period of 18 ± 6 months only one patient in group A had syncope and a positive tilt test compared with six patients in group B (9% vs 54%; p < 0.01). Development of tachycardia was a better predictor of drug efficacy than an isoproterenol-induced positive tilt test. The six nonresponders from group B were subsequently treated with disopyramide. During a mean follow-up period of 9 ± 3 months, only one patient had syncope and another had a positive response to tilt test. In conclusion, in patients with a history of syncope, absence of tachycardia before syncope during the tilt test predicts failure of therapy with β-blockers. These patients may benefit from treatment with disopyramide.