EVALUATION OF THE AUTONOMIC CARDIOVASCULAR-RESPONSE IN ARNOLD-CHIARI DEFORMITIES AND COUGH SYNCOPE SYNDROME

Objective: To study the autonomic control of heart rate in patients wi th Arnold-Chiari deformity types I and II who exhibit the signs and sy mptoms of cough syncope syndrome. Design: Prospective, clinical descri ptive study. Setting: University clinical research center. Patients: N ine patients with Arnold-Chiari deformity and cough syncope syndrome. Interventions: None. Main Outcome Measures: Changes in heart rate, blo od pressure, and electrocardiograms for power spectral analysis of hea rt rate variability were studied in the supine and standing positions, preoperatively (n=9) and postoperatively (n=5). Results: Preoperative ly, 8 (89%) of 9 patients increased their heart rate after postural ch ange from supine to standing (mean+/-SD Delta=13+/-13 beats per minute [bpm]). Postoperatively, 4 (80%) of the 5 patients exhibited a greate r increase in standing heart rate (mean Delta=19+/-16 bpm) compared wi th preoperative values. Changes in systolic, diastolic, and mean blood pressure with postural change were variable. Preoperatively, all pati ents exhibited abnormal control of heart rate in response to postural change. Three patients (33%) showed an abnormal decrease in low-freque ncy heart rate power (mean Delta=-27+/-35 bpm(2)); the remaining 6 (67 %) demonstrated an abnormal increase in high-frequency heart rate powe r (mean Delta=25+/-41 bpm(2)). All patients were clinically asymptomat ic at 2 months after surgery. A normal spectral response to postural c hange was demonstrated in heart rate power in all 5 patients who were reevaluated postoperatively, with an increase in low-frequency power ( mean Delta=33+/-21 bpm(2)) and a decrease in high-frequency power (mea n Delta=21+/-23 bpm(2)) Conclusions: Patients with cervicomedullary an atomic abnormalities caused by Arnold-Chiari deformities may exhibit a bnormal autonomic control of heart rate, and the autonomic control of their heart rate returns to a normal pattern after surgical palliation in conjunction with resolution of clinical symptoms.