Limit to cardiac compensation during acute isovolemic hemodilution: influence of coronary stenosis

A study evaluated the limit to cardiac compensation, during isovolemic hemodilution (HD) in 14 anesthetized dogs. The transmural distribution (endo/epi) of myocardial blood flow (MBF) was estimated using radioactive microspheres. The tolerance of the left ventricle to HD was greatly lowered by critical coronary stenosis, which also inhibited vascular adjustment to HD. During extreme HD, subendocrinal ischemia resulted, when cardiac failure was induced by MBF becoming maldistributed. The rises in MBF were transmurally consistent and adequate to maintain myocardial oxygenation.