POSSIBLE ROLE OF CARDIOAORTIC REFLEXES IN POST-CORONARY BYPASS HYPERTENSION

A study of hemodynamic and humoral characteristics of postcoronary bypass hypertension has been pursued in 85 patients in the immediate postoperative period. Paroxysmal hypertension developed in 69 of these patients. None of the 85 patients had a history of hypertension before operation. Hemodynamic evaluation demonstrated that the increase in blood pressure was associated with an elevation in systemic vascular resistance and a rapid heart rate. The increase in mean arterial pressure correlated significantly with the change in plasma catecholamine levels (r = 0.50, P < 0.05). There was no significant change in cardiac output. Changes in plasma renin activity showed no correlation with the increase in blood pressure. Average values of plasma renin activity on sequential determinations were not significantly different either in those who remained normotensive or in those who became hypertensive. Similarly, blood volume did not seem to play an important role. Baroreceptor sensitivity appeared blunted in both normotensive and hypertensive patients. The increase in systemic catecholamines associated with the increase in blood pressure suggested a sympathetic overdrive. This was further supported by the control of hypertension in 81 percent of patients by unilateral stellate block. The reduction in pressure consequent to the block was associated with a reduction in systemic vascular resistance (P < 0.025). Heart rate slowed slightly but significantly (P < 0.01) after stellate block irrespective of the effect on blood pressure whereas cardiac output did not change significantly. The results suggest that postcoronary bypass hypertension could be due to an afferent sympathetic reflex originating from the heart, great vessels or coronary arteries. © 1979.