Comparison of active standing test, head-up tilt test and 24-h ambulatory heart rate and blood pressure monitoring in diagnosing postural tachycardia.

Protocols for the assessment of postural tachycardia differ in both type of orthostatic challenge and test duration. We therefore compared heart rate (HR) and blood pressure responses during an active standing test (AST) and a head-up tilt test (HUT) in 34 patients with orthostatic intolerance and 31 asymptomatic subjects. A subset also performed 24-h ambulatory blood pressure monitoring (ABPM). HR responses were similar between AST and HUT both in asymptomatic and in orthostatic intolerant subjects. Specificity of HR increase ≥30 bpm for orthostatic intolerance was high (above 0.85) with both AST and HUT and was similar at 3 minutes and at 9 minutes. HR changes recorded during self-performed AST (in the context of 24-h ABPM) and circadian HR difference corresponded well to changes recorded during AST in the autonomic laboratory. We conclude that AST and HUT are comparable methods for the assessment of postural tachycardia, that 3-min and 9-min tests are appropriate, and that ABPM is a useful ancillary test in the assessment of orthostatic responses.