Graded coronary stenosis and coronary flow during acute normovolemic anemia

Abstract Acute normovolemic anemia is associated with increase in coronary blood flow to approximately 185% of control at a hematocrit of 20%, and no significant change in peak reactive hyperemia flow. Other parameters of cardiac function are not significantly changed. The effect of varying degrees of accurately graded coronary artery stenosis was studied in 12 dogs with a normal hematocrit and a hematocrit of 20% achieved by bleeding and simultaneous infusion of plasma. There was no significant change in parameters of cardiac function at normal hematocrit with left anterior descending coronary stenosis of up to 67%. Similarly, cardiac function was not significantly affected by acute normovolemic anemia and up to a 50% reduction in luminal diameter of the left anterior descending (LAD) coronary artery. However, the combination of anemia and a 67% LAD coronary artery stenosis resulted in electrocardiographic evidence of ischemia in the LAD coronary artery territory and mild deterioration of cardiac function. Resting coronary flow was not affected by up to a 67% reduction of lumen diameter (90% reduction in cross‐sectional area) at normal hematocrit, but peak flow after 30 seconds of occlusion was significantly decreased with transient ischemia. At a hematocrit of 20%, resting flow increased as expected in the unobstructed artery and with 50% stenosis, but peak∶resting flow ratio was only 1.34 at 50% stenosis. With 67% stenosis, resting flow was impaired and there was no further increase after a 30‐second occlusion period which frequently led to severe arrhythmias. Acute normovolemic anemia compromises coronary reserve and, in the presence of significant coronary stenosis, leads to myocardial ischemia. It should be avoided in patients with coronary occlusive disease.