R. Manthana1, M. Kanuparthy1, C. Stone1, N.R. Sodha1, A. Ehsan1, J. Feng1, F. Sellke1 1Brown University School Of Medicine, Providence, RI, USA
Introduction: Endothelial dysfunction is a hallmark of hypertension. Patients with preexisting vascular dysfunction have previously been demonstrated to be at increased risk for complications after undergoing cardiac surgery, particularly when undergoing cardioplegic arrest and cardiopulmonary bypass. Our lab has recently demonstrated that another condition causing vascular dysfunction, poorly controlled diabetes, is associated with coronary arteriolar endothelium-dependent relaxation dysfunction. In this study, we investigate the effects of poorly controlled hypertension on coronary arteriolar responses to the endothelium-dependent vasodilator Bradykinin in the setting of cardioplegic (CP) ischemia and reperfusion and cardiopulmonary bypass (CPB).
Methods: Right atrial appendage tissue from central venous CPB cannulation was collected from patients undergoing cardiac surgery. Using a dual pursestring approach, tissue and coronary arterioles were collected before and after the initiation of CP/CPB from normotensive and uncontrolled hypertensive patients (n = 6/group). Vessels were cannulated and pressurized with warm modified Krebs buffer and vasoactive medications were added to circulating buffer solution. In-vitro relaxation response of pre-contracted atrial coronary arterioles was examined in the presence of Bradykinin (10-10-10-6 M) by videomyography.
Results: At baseline (pre-CP/CPB), relaxation in response to Bradykinin was significantly attenuated in the uncontrolled hypertensive group compared to the normotensive group (p <0.05). The relaxation response to Bradykinin post-CP/CPB was significantly decreased in both the uncontrolled hypertensive group and normotensive group compared to their pre-CP/CPB counterparts (p <0.05). Furthermore, this decrease was greater in the uncontrolled hypertensive group than in the normotensive group (p <0.05).
Conclusion: Our results suggest that patients with poorly controlled hypertension are associated with worsened endothelial dysfunction in coronary microvasculature early after CP/CPB and cardiac surgery. While relaxation in pre-contracted vessels was attenuated after CP/CPB, patients with uncontrolled hypertension suffer from a greater degree of vascular dysfunction.