Hemodynamics of postmyocardial revascularization hypertension

The evolution of hemodynamic variables during the development of postcoronary bypass hypertension was investigated with use of serial cardiac output determination (indocyanine green dye) in 17 patients. Seven of the 17 patients remained normotensive (Group I) during the follow-up period of 4 to 6 hours after operation, whereas 10 (Group II) had a steady increase in blood pressure (173/101 mm Hg +/- 5.9/2.4 [mean +/- standard error] from 132/78 +/- 4.0/2.5 mm Hg immediately postoperatively, P less than 0.001) during the same time interval. Patients in Group I had no significant change in cardiac output, total peripheral resistance or heart rate. In contrast, patients who became hypertensive had a significant increase in total peripheral resistance (47 +/- 2.9 units/m2 from an initial level of 38 +/- 2.5 units/m2, P less than 0.001) with no significant change in cardiac index (2.73 +/- 0.17 versus 2.66 +/- 0.25 liters/min per m2, P greater than 0.10). Their heart rate, which was rapid initially (102 +/- 3.7 beats/min), remained unchanged during the hypertensive episode (103 +/- 3.0 beats/min). The mean rate of left ventricular ejection was not reduced by the increase in pressure and even tended to increase further in all but one patient. Central venous pressure (measured in all patients) and left atrial pressure (measured in eight patients) remained constant throughout the study in both Groups I and II. The results suggest that the mechanism underlying this type of hypertension is a generalized hemodynamic disturbance possibly related to overall sympathetic overdrive rather than the result of improved cardiac performance induced by myocardial revascularization.