colorimetric assay Introduction br Coronary revascularizatio

Introduction
Coronary revascularization Ischemic cardiomyopathy is caused by occlusive or obstructive coronary artery disease. Ischemic cardiomyopathy is now recognized as the most common cause of heart failure worldwide. It can be described in terms of three pathophysiological processes. (1) Myocardial hibernation. This is caused by reduced coronary blood flow that can be partially or completely restored to normal by myocardial revascularization. (2) Myocardial stunning. The viable myocardium is injured by generation of oxygen-derived free radicals on reperfusion and by a loss of sensitivity of contractile colorimetric assay to calcium. With adequate revascularization, the postischemic contractile dysfunction of the myocardium can be reversed. (3) Myocardial cell death. This is an irreversible state and causes ventricular remodeling and contractile dysfunction. Myocardial revascularization can save a jeopardized but still viable myocardium, but the aims of surgery should be to elicit a significant improvement in heart failure symptoms, survival rate, and left ventricular (LV) function. Appraised by means of positron emission tomography (PET), nuclear thallium studies, or dobutamine echocardiography tests, the presence of a hibernating or viable myocardium is essential for improvement in the left ventricular ejection fraction (LVEF) after surgical revascularization. Recent studies suggest that at least 25% of the myocardium should be viable for revascularization to be successful. In contrast, there is no survival benefit to revascularization for patients with no myocardial viability. Current American College of Cardiology/American Heart Association (ACC/AHA) guidelines for coronary artery bypass graft (CABG) in patients with poor LV function recommend surgery as a Class I indication for patients with left main coronary artery disease or its equivalent as a Class IIa indication for patients with viable noncontracting muscle, and as a Class III indication for those without evidence of ischemia or viability. According to the SHOCK trial (Should We Emergently Revascularize Occluded Coronaries for Cardiogenic Shock), for patients with acute myocardial infarction (MI), the 1-year mortality rate was 42% for CABG, and 56% for medical therapy alone. Furthermore, for patients in cardiogenic shock, the 1-year mortality rate was 56% for CABG and 75% for medical therapy alone. Multiple studies have demonstrated improvements in survival, ventricular function, and functional status after coronary revascularization in patients with ischemic cardiomyopathy (LVEF less than 25%). These series show that the survival rate after CABG ranges from 85 to 88% after 1 year, from 75 to 82% after 2 years, from 68 to 80% after 3 years, and from 60 to 80% after 5 years. Operative mortality ranges from 3 to 12%. Revascularized patients have a better quality of life than patients treated with medical therapy alone and have enhanced mobility, peak oxygen consumption, and functional status. After CABG, the incidence of readmission for congestive heart failure (CHF) is low, and many patients are able to return to work. According to the CABG Patch trial, perioperative mortality was 1.3% in patients without angina or heart failure. Mortality was 4.8% in patients with no angina and New York Heart Association (NYHA) Class I or II heart failure, and 7.4% in patients with no angina and NYHA Class III or IV heart failure. Elefteriades and Edwards reported improvement in LVEF from 23.3 to 33.2% and improvement in NYHA functional class from 3.1 to 1.4. In Meluzin’s prospective study, 133 patients who underwent CABG or percutaneous coronary intervention were randomized into three groups. Group A consisted of 29 patients with a large amount of dysfunctional but viable myocardium, Group B consisted of 60 patients with a small amount of dysfunctional but viable myocardium, and Group C consisted of 44 patients with a dysfunctional and irreversibly damaged myocardium. Group A demonstrated the greatest functional improvement after revascularization, a lower rate of cardiac events during follow-up (two for Group A versus 18 for Group B, p < 0.05, and 17 for group C, p < 0.01), and better cardiac event-free survival according to Kaplan–Meier survival analysis. Another study showed that revascularization resulted in a 34% increase in exercise capacity (from 5.6 to 7.5 metabolic equivalents).