Myocardial 99Tc - MIBI washout

Ischemic Heart Disease is defined as 'myocardial impairment due to an imbalance between coronary blood flow and myocardial requirements caused by changes in the coronary circulation 1 .Coronary artery disease is thought to arise from normal repair processes in response to chronic injuries to the arterial endothelium.As myocardial oxygen demand increases or coronary blood flow decreases, auto-regulatory mechanisms become active to try to maintain myocardial perfusion at a normal level.In patients with atherosclerotic heart disease, compensatory mechanisms to maintain myocardial perfusion stenosis are already active, so first abnormality to be apparent during ischemia is therefore reduced perfusion to the affected territory 2 .During myocardial ischemia ATP is highly utilized resulting in an increase in its metabolites.This subsequently acts as a vasodilator in an attempt to compensate for the reduced perfusion.Various catabolites such as lactate and hydrogen ions accumulate, and these can also cause coronary vasodilatation.