INTRAVENOUS CANNULATION ALTERS THE SPECIFICITY OF HEAD-UP TILT TESTING FOR VASOVAGAL SYNCOPE IN ELDERLY PATIENTS

Prolonged head-up tilt is increasingly used as a diagnostic test for v asovagal syncope. Its sensitivity is reported to increase with the con current administration of intravenous isoprenaline. False-positive res ponses are common in young controls particularly following intravascul ar instrumentation. We studied the influence of intravenous cannulatio n alone on responses to head-up tilt in ten healthy elderly subjects. All remained asymptomatic during tilt when non-cannulated whilst five developed symptomatic hypotension following cannulation. Thus, intrava scular instrumentation influences responses to head-up tilt in elderly subjects; the significance of positive responses obtained using intra venous isoprenaline in this age group requires further evaluation.