Objective: To study the autonomic control of heart rate in patients with Arnold-Chiari deformity types I and II who exhibit the signs and symptoms of cough syncope syndrome.
Design: Prospective, clinical descriptive study.
Setting: University clinical research center.
Patients: Nine patients with Arnold-Chiari deformity and cough syncope syndrome.
Interventions: None.
Main outcome measures: Changes in heart rate, blood pressure, and electrocardiograms for power spectral analysis of heart rate variability were studied in the supine and standing positions, preoperatively (n = 9) and postoperatively (n = 5).
Results: Preoperatively, 8 (89%) of 9 patients increased their heart rate after postural change from supine to standing (mean +/- SD delta = 13 +/- 13 beats per minute [bpm]). Postoperatively, 4 (80%) of the 5 patients exhibited a greater increase in standing heart rate (mean delta = 19 +/- 16 bpm) compared with preoperative values. Changes in systolic, diastolic, and mean blood pressure with postural change were variable. Preoperatively, all patients exhibited abnormal control of heart rate in response to postural change. Three patients (33%) showed an abnormal decrease in low-frequency heart rate power (mean delta = -27 +/- 35 bpm2); the remaining 6 (67%) demonstrated an abnormal increase in high-frequency heart rate power (mean delta = 25 +/- 41 bpm2). All patients were clinically asymptomatic at 2 months after surgery. A normal spectral response to postural change 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 bpm2) and a decrease in high-frequency power (mean delta = -21 +/- 23 bpm2).
Conclusions: Patients with cervicomedullary anatomic abnormalities caused by Arnold-Chiari deformities may exhibit abnormal 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.