NUCLEAR AND ECHOCARDIOGRAPHIC IMAGING FOR PREDICTION OF REVERSIBLE LEFT-VENTRICULAR ISCHEMIC DYSFUNCTION AFTER CORONARY REVASCULARIZATION -CURRENT STATUS AND FUTURE-DIRECTIONS

Modern therapy of coronary artery disease (CAD) increasingly involves interventional strategies aimed at restoring blood flow to the ischemi c myocardium, The emergence of coronary artery bypass surgery, percuta neous transluminal coronary angioplasty, and more recently thrombolyti c therapy, has helped to change the natural course of ischemic heart d isease and contribute to the overall reduction in the mortality from b oth acute myocardial infarction and chronic CAD. Presumably, the benef icial effects of revascularization result from improving blood supply to dysfunctional but viable regions with subsequent improvement in reg ional and global left ventricular function, Over the past decade, seve ral approaches have been proposed to predict the reversibility of left ventricular dysfunction after coronary revascularization, For the mos t part, these methods rely on assessment of basic cellular mechanisms that are known to play a central role in the recovery of systolic func tion after coronary revascularization. These include sufficient restin g perfusion to provide metabolic fuels and to allow wash-out of toxic metabolites, maintain membrane integrity (which includes the ability t o generate transmembrane ionic gradients and to transport energy provi ding substrates), preserve metabolic machinery (to allow glucose, fatt y acid and oxygen consumption), and recruitable inotropic reserve. Amo ng the available modalities, thallium imaging, positron emission tomog raphy, and low-dose dobutamine echocardiography are currently the most frequently used in the clinical setting. All allow prediction of reve rsible dysfunction with a high degree of sensitivity (greater than 80% ). They seem to vary, however, in terms of specificity, thallium imagi ng showing the lowest (50-55%) and dobutamine echocardiography the hig hest (80-85%) specificity. New promising modalities, such as FDG or MI BI SPECT imaging, contrast echocardiography and integrated backscatter imaging are just ahead and will likely strengthen further our ability to identify jeopardized but viable myocardium.