RELEVANCE OF ASYSTOLE DURING HEAD-UP TILT TESTING

The prognosis of patients manifesting prolonged asystole during head-u p tilt testing is unclear. In 209 consecutive patients with a history of syncope and positive head-up tilt tests, 19 had asystole lasting >5 seconds (mean duration 15 +/- 10) (group 1a). When compared with pati ents without asystole (group 1b), group 1a patients were younger (32 /- 12 vs 47 +/- 21 years, p <0.005), but clinical manifestations were not any more dramatic (the number of episodes of syncope [7 +/- 5 vs 8 +/- 6 episodes, p = NS] and injury during syncope [2 vs 13 patients, p = NS] were similar). During follow-up (mean 2 +/- 1 year), with the patient taking pharmacologic therapy such as beta blockers, ephedrine, theophylline, or disopyramide, the recurrence rate was 11% and 8% in groups 1a and 1b (p = NS). No patient In the asystole group underwent pacemaker implantation. Additionally, of 75 normal volunteers (group 2 ) with no history of syncope undergoing tilt tests to define its speci ficity, 3 had asystole (mean duration 10 seconds). During >1 year of f ollow-up, despite no treatment, all 3 are symptom free. Thus, asystole during head-up tilt testing does not predict either (1 more malignant outcome or a poor response to pharmacologic therapy. Moreover, an asy stolic response does not enhance the specificity of the head-up tilt t est because it may be present in asymptomatic ''normal'' volunteers.