Effect of Phlebotomy on Coronary Blood Flow in Calves with Brisket Disease 1

Summary

The effect of phlebotomy (average volume 1700 ml) on coronary hemodynamics was evaluated in 11 calves with BD or pulmonary hypertensive heart disease of cattle. CBF was measured by the ¹³³Xenon technique. In the control period the characteristic findings of BD were present: low CO, severe pulmonary hypertension, marked elevation of right ventricular diastolic and moderate elevation of left ventricular diastolic pressures. Following phlebotomy there was a significant increase in CBF, heart rate, CO, RVSW, and CPP accompanied by a significant decrease in CSP, C_avo2, LVEDP and SAP. There was no significant change in MVo₂- The rise in CBF can be explained by the increase in myocardial perfusion pressure whereas the absence of significant change in MV_{o 2} may be related to a balance of the determinants of MV_{o 2}- The changes in CBF and MV_{o 2} must be interpreted by our inability to separate these variables into the contribution from each ventricle.