Obesity is an independent risk factor for the development of coronary heart disease (CHD). Furthermore, after the diagnosis of CHD obesity is associated with accelerated progression of CHD. Overweight and obesity also predispose to insulin resistance and type 2 diabetes mellitus (T2DM) which, in turn, accelerates the progression of CHD and worsening prognosis
Coronary heart disease is a major cause of higher mortality among obese individuals. In a population study of 750,000 men and women, mortality was nearly 50% greater among men and women 30-40 % above ideal weight as compared to control subjects.
Relations between categories of body mass index (BMI), cardiovascular disease risk factors, and vascular disease endpoints were examined prospectively in Framingham Heart Study participants aged 35 to 75 years, who were followed up to 44 years. The primary outcome was new cardiovascular disease, which included angina pectoris, myocardial infarction, coronary heart disease, or stroke. Analyses compared overweight (BMI [calculated as weight in kilograms divided by the square of height in meters], 25.0-29.9) and obese persons (BMI > or =30) to a referent group of normal-weight persons (BMI, 18.5-24.9).
Hyperlipidemia contributed to coronary atherosclerosis and Coronary heart disease.
90 % of the transmural acute myocardial infarcts are caused by an occlusive intracoronary thrombus overlying an ulcerated or fissured stenotic plaque.
Occlusion of the major coronary artery results in ischemia throughout the anatomic region supplied by that artery (area at risk), most commonly sub endocardium. Ischemic myocardium than undergoes progressive biochemical, functional, and morphological changes. The biochemical consequence of the ischemia is the onset of anaerobic glycolysis within seconds leading to inadequate production of high-energy triphosphate(ATP )and accumulation of lactic acid. Striking loss of contractility happens within 60 seconds.
Ultrastructural changes develop within few minutes like cell and mitochondrial swelling, glycogen depletion. These early changes are reversible. However, Coagulation necrosis Irreversible changes, in myocytes after 20-40 minutes in severe ischemia (flow <10 %of normal ) can occur.
With more extended ischemia, a wavefront of cell death moves through the myocardium to involve progressively more of the transmural thickness of the ischemic zone. Various factors affect plaque formation and infarction 3-6 hrs. The factors like location, severity, and rate of development of atheroscelerotic obstructions, size of vascular bed perfused by obstructed vessel, duration of occlusion, oxygen need of the myocardium, extend of collateral blood vessels affect the overall ischemia of the heart vessels.
Myocardial ischemia also leads to Arrhythmias which can cause death.
Risk factor reduction strategies employed for CHD such as exercise and more broadly, cardiac rehabilitation (CR) specifics regarding the treatment of obesity in CR under the Physical Activity Guidelines for Americans recommends a minimum of 150 minutes per week / 45 minutes per day of moderate exercise for preventing many chronic diseases.
Studies have shown a favorable effect of weight loss on the development of CHD in high-risk individuals and on prognosis within the CHD population. The first is an observational study of intentional weight loss among patients recruited to receive nutritional counseling from a dietitian to support the medical recommendation to lose weight. Among 1,669 patients, intentional weight loss predicted a lower incidence of CHD over 4 years. In another analysis of 377 CR participants, the effect of weight loss on a composite outcome of total mortality, acute myocardial infarction, stroke, or hospital admission for congestive heart failure was studied. Patients who lost 1 kg or more in CR (cardiac rehabilitation )had a 24% rate of the composite outcome compared with a 37% rate for individuals that did not lose weight (P<0.05).
Hence the overweight category is associated with increased relative and population attributable risk for hypertension and cardiovascular sequelae of cardiovascular hypertension. Interventions to reduce adiposity and avoid excess weight may have large effects on the development of risk factors and cardiovascular disease at an individual and population level.