Relation of Brachial Artery Reactivity to Nitroglycerin and Heart Rate Recovery Following Exercise in Healthy Male Volunteers

The parasympathetic nervous system facilitates peripheral arterial vasodilation and is also responsible for a decrease in heart rate immediately after exercise (heart rate recovery [HRR]). The relation among parasympathetic tone measured by HRR after exercise, endothelium-mediated vasodilation, and nitroglycerin-mediated vasodilation (determined with brachial artery ultrasound) was assessed in 25 healthy young men. One-minute HRR was nonsignificantly related to endothelium-mediated vasodilation (r = −0.35, p = 0.08) but was significantly related to nitroglycerin-mediated vasodilation (r = −0.63, p = 0.0008), a finding that persisted after adjustment for heart rate at rest, insulin resistance, lipid variables, and blood pressure. This suggests that parasympathetic tone may be inversely related to the responsiveness of arterial smooth muscle to nitrates in healthy humans.