Heart Muscle Viability and Remodeling in Individuals Post-Heart Attack

BACKGROUND: Coronary heart disease is a major health problem in the United States. It is estimated that in 2003, more than 600,000 Americans had a new heart attack, and more than 400,000 experienced a recurrent heart attack. Up to 40% of individuals with a new or recurrent heart attack will show a complete occlusion, or blocking, of the IRA on follow-up angiography. Many people with an occluded IRA post-heart attack are at risk for progressive LV remodeling in the heart, which can lead to congestive heart failure. The NHLBI-funded OAT study is testing the hypothesis that opening an occluded IRA 3 to 28 days following a heart attack will reduce the composite endpoint of mortality, recurrent heart attack, and New York Heart Association class IV heart failure over a three-year follow-up period. OAT has enrolled approximately 1,100 participants at 240 centers in 24 countries. Among the mechanisms proposed to explain the benefit of late revascularization, recovery of LV function and attenuation of LV remodeling due to restoration of blood flow to viable myocardium, or heart muscle, is the most plausible. DESIGN NARRATIVE: An estimated 200 individuals who have had a heart attack will be enrolled in this study. The primary aims of this study are the following: 1) to test the hypothesis that participants who demonstrate preservation of viability within the infarct zone will have less progressive remodeling compared to participants exhibiting predominant infarct, and 2) to test the hypothesis that preservation of viability will modify the treatment effect of randomization to late revascularization in participants with an occluded IRA 3 to 28 days after the heart attack. All participants will have resting gated Tc-99m sestamibi SPECT imaging at baseline, and again 1 year later. Parameters of baseline viability within the infarct zone, and serial measures of LV volume change and function will be centrally assessed by the Cardiac Imaging Core Laboratory at Tufts Medical Center. The major study endpoint to address the hypotheses will be serial change in LV end-diastolic volume, based on the degree of preservation of viability within the defined infarct zone. Sample size calculations will be based on data evaluated by the same group from a similar number of participants studied at a similar number of clinical sites.