Impairment of endothelium-dependent vasodilation of resistance vessels in patients with obstructive sleep apnea.
BACKGROUND
Patients with obstructive sleep apnea (OSA) experience repetitive episodic hypoxemia with consequent sympathetic activation and marked blood pressure surges, each of which may impair endothelial function. We tested the hypothesis that patients with OSA have impaired endothelium-dependent vasodilation, even in the absence of overt cardiovascular disease.


RESULTS
We studied 8 patients with OSA (age 44+/-4 years) and 9 obese control subjects (age 48+/-3 years). Patients with OSA were newly diagnosed, never treated for OSA, on no medications, and free of any other known diseases. All obese control subjects underwent complete overnight polysomnographic studies to exclude occult OSA. Resistance-vessel function was tested by use of forearm blood flow responses to intra-arterial infusions of acetylcholine (a vasodilator that stimulates endothelial release of nitric oxide), sodium nitroprusside (an exogenous nitric oxide donor), and verapamil (a calcium channel blocker). Conduit-vessel function was also evaluated by ultrasonography. Brachial artery diameter was measured under baseline conditions, during reactive hyperemia (with flow increase causing endothelium-dependent dilatation), and after sublingual administration of nitroglycerin (an endothelium-independent vasodilator). Patients with OSA had a blunted vasodilation in response to acetylcholine (P:<0.007), but responses to sodium nitroprusside and verapamil were not significantly different from those of control subjects. No significant difference in conduit-vessel dilation was evident between OSA patients and obese control subjects.


CONCLUSIONS
Patients with OSA have an impairment of resistance-vessel endothelium-dependent vasodilation. This may be implicated in the pathogenesis of hypertension and heart failure in this condition.
Kato
M
M
Division of Clinical and Administrative Pharmacy, University of Iowa Colleges of Medicine and Pharmacy, Iowa City, USA.
Roberts-Thomson
P
P
Phillips
B G
BG
Haynes
W G
WG
Winnicki
M
M
Accurso
V
V
Somers
V K
VK
D000109:Acetylcholine / Q000008:administration & dosage; D000328:Adult; D001783:Blood Flow Velocity / Q000187:drug effects; D001916:Brachial Artery / Q000000981:diagnostic imaging / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004562:Electrocardiography; D004730:Endothelium, Vascular / Q000503:physiopathology*; D005542:Forearm / Q000098:blood supply / Q000000981:diagnostic imaging; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D006940:Hyperemia / Q000503:physiopathology; D007261:Infusions, Intra-Arterial; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications / Q000503:physiopathology*; D017286:Polysomnography; D020181:Sleep Apnea, Obstructive / Q000150:complications / Q000503:physiopathology*; D014463:Ultrasonography; D014655:Vascular Resistance / Q000187:drug effects; D014664:Vasodilation / Q000187:drug effects; D014665:Vasodilator Agents / Q000008:administration & dosage
D014665:Vasodilator Agents; D000109:Acetylcholine