Worsening of head-up tilt test response during chronic beta-blocker therapy in patients treated for neurally mediated syncope.

The prognosis of patients with neurally mediated syncope and asystolic response at tilt test is controversial and there is no consensus regarding their management. Many patients seem to benefit from beta-blockers and their effectiveness has been assessed with repeated tilt tests in asystolic patients as well. However, little is known about the long-term effects of beta-blockers. Preliminary data and isolated reports suggest that in some cases, these agents may actually worsen the clinical outcome or the tilt test response. Three patients are described who experienced worsening of tilt test response with prolonged asystole (19.9, 9 and 5.5 sec respectively) during chronic treatment with beta-blockers in the absence of spontaneous symptoms. At discharge, one patient received a dual-chamber pace-maker combined with metoprolol, another one continued to take metoprolol and enalapril. The third patient refused any further medication. During follow-up (8, 11, 13 months respectively), they were symptom-free. The clinical and prognostic significance of this response is not clear and needs further investigation.