Effect of cough on heart rate and blood pressure in patients with "cough syncope"

Background: "Cough syncope" is uncommon, and its mechanism remains controversial. Objectives: This study evaluated susceptibility to cough-triggered neural reflex hypotension-bradycardia among cough syncope patients. We hypothesized that individuals with cough syncope would manifest not only more profound cough-triggered hypotension than do other fainters but also an inappropriate chronotropic response accompanying cough-induced hypotension, thereby supporting the notion that a neural reflex hypotension-bradycardia contributes to the condition. Methods/Results: Three patient groups were studied. Group 1 patients (n = 9) had "cough syncope." The remaining patients had recurrent faints of other causes: group 2 (n = 13) had a positive head-up tilt test, and group 3 (n = 18) had a negative tilt test. With cough, group 1 patients exhibited a greater drop in systolic pressure (-51 ± 19.3 mmHg) than did either group 2 (-23 ± 11.1 mmHg, P < .04) or group 3 patients (-28 ± 12.4 mmHg, P < .05). Recovery time to normalization of systolic pressure was greater in group 1 (25 ± 9.1 seconds) than in group 2 or 3 (8 ± 2.7 seconds and 9 ± 6.1 seconds, respectively, both P < .01 vs group 1). The expected positive chronotropic response accompanying cough-induced hypotension was diminished in group 1 patients (0.16 ± 0.21 bpm/ mmHg) compared with that in either group 2 (0.74 ± 0.60 bpm/mmHg, P < .05 vs group 1) or group 3 (0.33 ± 0.15 bpm/mmHg, P = .06 vs group 1). Conclusion: Cough syncope patients not only exhibit more pronounced hypotension in response to cough than other fainters, but they also manifest an inappropriate cough-triggered blood pressure-heart rate relationship. These findings argue in favor of the importance of a neurally mediated reflex contribution to symptomatic hypotension in cough syncope.