Variations in expression and treatment of transient neurocardiogenic instability.

Whereas previous reports describe the head-up tilt test for the diagnosis of neurocardiogenic syncope, this study focuses on the events leading up to syncope. These events are part of a spectrum of neurocardiogenic instability; syncope is the extreme end point. This report is based on tilt studies of 108 patients, aged 4 to 22 years (mean 13), with histories of either unexplained syncope or episodes of visual blackout without loss of consciousness. The tilt study was positive in 74% of the patients. Five stages of neurocardiogenic instability were identified, ranging from excessive fluctuations in heart rate to full syncope. Uncommon reactions during the tilt study include dissociation of hypotension, bradycardia and vagal symptoms and extended asystole (greater than 6 seconds). Therapy with beta 1-selective blockers was highly successful in suppressing symptoms of neurocardiogenic instability. Repeat tilt testing with beta blockade has resulted in either normal or markedly improved stability in heart rate and blood pressure. Neurocardiogenic instability is a common condition occurring between age 10 and 20 years. It appears to be self-limited.