RESPONSE TO BETA-BLOCKERS IN PATIENTS WITH NEUROCARDIOGENIC SYNCOPE -HOW TO PREDICT BENEFICIAL-EFFECTS

No definitive data are available about the possibility of predicting i mprovement in patients with neurocardiogenic syncope treated with beta blockers, Among 112 patients with syncope and a positive head-up tilt test (HUT), independent predictors for prevention of symptoms with be ta blockers were determined using the Cox proportional hazards model, Each patient underwent HUT at 70 degrees for 20 minutes both in the dr ug-free state and during isoproterenol infusion given to increase the heart rate by at least 25%. Fifty-nine patients had a positive HUT dur ing isoproterenol infusion and 53 in the drug-free state. All patients were then given esmolol infusion at 500 mu g/kg per minute for 3 minu tes followed by 300 mu g/kg per minute maintenance dose, HUT was then repeated as previously described with or without isoproterenol, depend ing upon the initial positive response. Regardless of the response dur ing esmolol, all patients were treated with metoprolol 50 to 100 mg tw ice daily, At follow-up, 36 patients experienced symptom relapse, Four of them had negative HUT on esmolol, whereas the remaining 32 did not respond to the acute infusion of esmolol, Only four patients with pos itive HUT on esmolol had a favorable response to metoprolol. Patients responding to metoprolol were older (55 +/- 12 years vs 42 +/- 15 year s, P < 0.05). Response to metoprolol was predicted by a negative test on esmolol (P < 0.0001) and a positive HUT on isoproterenol (P < 0.001 ). Age older than 42 years was also associated with a higher likelihoo d of metoprolol success (P < 0.02). Conclusion: Acute challenge with e smolol infusion appears to be an accurate predictor of response to chr onic beta blockers, together with age and a positive HUT during low-do se isoproterenol infusion.