Abstract 14055: Increased Coronary Myogenic Tone in Patients With Poorly Controlled Hypertension

Abstract

Background: Both animal and clinical studies have demonstrated that hypertension is associated with altered vasomotor tone. However, the direct effect of well-controlled and poorly (un)controlled hypertension on the myogenic tone of human coronary arterioles is inadequately investigated. Objective: We investigated the effect of well-controlled and poorly (un)controlled HTN on the myogenic tone of human coronary arterioles. Methods: Coronary arterioles pre-cardiopulmonary bypass were dissected from harvested atrial tissue samples of eligible patients. Patients were categorized as having normal blood pressure, or well-controlled or poorly-(un)controlled hypertension (n = 5-8/group). Myogenic tone in response to stepwise increases in intraluminal pressure was studied between pressure steps. The microvascular reactivity in response to the selective α-adrenergic agonist phenylephrine was also assessed via vessel myography. Results: Increased myogenic tone was reflected by a decreases in microvessel internal diameter in all patients. There was a significant increase in myogenic tone in patients with poorly (un)controlled hypertension (0.97±0.05 in diameter ) compared with normotensive patients (1.27±0.14 in diameter, P = 0.001). The contractile response to phenylephrine was significantly enhanced in patients with poorly (un)controlled hypertension compared with normotensive patients (P<0.001). However, there were no significant differences in the myogenic tone or phenylephrine-induced vasomotor tone between normotensive patients and patients with well-controlled hypertension (P>0.05 respectively). Conclusion: Poorly (un)controlled hypertension is associated with increases in coronary arteriolar myogenic and vasomotor tone, which may contribute to the increased coronary vasospasm seen in this population.