Transient Orthostatic Hypertension During Head-Up Tilt Test In Young Adults: A Phenotype Of Blood Pressure Variability

Purpose: The mechanisms underlying orthostatic hypertension (OHT) remain poorly understood. The authors evaluated the cardiovascular, cerebrovascular dynamics, and autonomic response to head-up tilt test (HUTT) in young adults with symptoms of orthostatic intolerance and transient OHT. Methods: Forty-four female subjects were included (34 +/- 13 years old) and categorized in three groups after a 30-minute 70 degrees passive HUTT: symptomatic patients with OHT (surge of systolic blood pressure >= 20 mm Hg for at least 5 minutes at any given time during HUTT), orthostatic intolerance (symptomatic patients without orthostatic blood pressure changes), and healthy asymptomatic control subjects. Results: At baseline, OHT patients had lower systolic blood pressure than orthostatic intolerance patients (103 +/- 8 vs. 116 +/- 10 mm Hg, p < 0.01) and lower baroreflex sensitivity than control subjects (15.8 +/- 8.3 vs. 27.1 +/- 11.7 ms/mm Hg, p = 0.01). On tilt, cardiac output decreased in OHT patients from 6.1 +/- 1.4 L/minute during baseline to 5.2 +/- 0.8 L/minute after 10 minutes of HUTT (p = 0.01). In OHT patients at 30 minutes of HUTT, sympathetic efferent heart activity was higher (77.4 +/- 14.9 normalized units or nu) than orthostatic intolerant patients (63.5 +/- 11.8 nu, p = 0.02) and control subjects (65.8 +/- 11.2 nu, p = 0.05). Cerebrovascular resistance in OHT was higher than control subjects after 30 minutes (2.2 +/- 0.8 vs. 1.6 +/- 0.3 cm/second, respectively, p = 0.02). Conclusions: This study demonstrates that transient OHT can occur at any given time during HUTT. These patients exhibit a decrease in cardiac output and a hyperadrenergic response to tilt.