Changes in Abdominal Aortic Diameter in Response to the Cold Pressor Test and Nitroglycerin: A New Noninvasive Model for the Assessment of Endothelial‐Dependent and Endothelial‐Independent Vascular Relaxation

Coronary vascular responses to the cold pressor test (CPT) have been shown to parallel changes caused by infusion of acetylcholine. Whereas the CPT is a method of assessing endothelial-dependent vasodilation, nitroglycerin produces endothelial-independent vasodilation. We performed histological studies on autopsy specimens of abdominal aorta and demonstrated that it is predominantly muscular artery. To test the hypothesis that vasodilatory responses of the abdominal aorta to interventions would parallel those of peripheral vessels, 33 normal males without hypertension, diabetes, or hyperlipidemia, and 10 younger male smokers had ultrasound imaging of the abdominal aorta conducted in the control state, 2 minutes after immersion of the hand in cold water and 10 minutes after rewarming the hand (i.e., cold pressor test). The internal diameter of the abdominal aorta at the onset of the QRS complex was determined for each intervention by averaging 4 beats. It was found that the cold pressor test and nitroglycerin resulted in similar degrees of dilation of the abdominal aorta in nonsmoking subjects, and that these responses were attenuated in smokers. Thus, both endothelial-dependent and endothelial-independent vascular relaxation were impaired in smokers.