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What is the impact of obesity on cardio-vascular disease? – Part 2

Impact of obesity on cardio-vascular disease

• The higher prevalence of cardiovascular disease in obese individuals is indirectly mediated, to a large extent.
• This is by the increased frequency of various well known risk factors like hypertension, diabetes, and dyslipidemia.
• This could be either individually or as part of the metabolic syndrome.
• There are several ways in which obesity directly affects the cardiovascular system.
• Obesity also poses considerable challenges to making a precise cardiovascular diagnosis.
• This is because of limitations in physical examination as well as with various investigations.

These tests are like:
• Electrocardiograms (EKGs)
• Imaging studies
• Cardiac catheterization

What is Pathophysiology of the Circulatory System in Obese Patients?

• The adipose tissue has a resting blood flow of 2 to 3 mL/100 g/min, but can increase up to 10-fold.
• This occurs usually after food intake.
• However, with increasing obesity the perfusion per unit mass decreases.
• It falls from 2.36 mL/min to 1.53 mL/min when the percentage of fat increases from 20% to 36% of the body weight.
• So the increase in cardiac output is not directly proportional to the total fat.
• The increased cardiac output in obese patients is to meet the metabolic demand of the adipose tissue.
• It is achieved mainly through an increase in stroke volume.
• The left ventricular chamber dilates to accommodate the increased venous return.
• This, in turn, develops an eccentric type of hypertrophy to keep the wall stress normal.
• The left atrium also enlarges in obese individuals and is initially caused by the increased blood volume and venous return.
• Later, other factors like left ventricular hypertrophy and diastolic dysfunction may also be responsible for increased left atrial size.
• Left ventricular filling pressure increases with exercise, often to more than 20 mm Hg.
• This is even if it is normal at rest.
• The left ventricle undergoes hypertrophy of the eccentric type.
• Cardiomyopathy of obese individuals (adipositas cordis) is caused by a direct effect of obesity on the heart.
• Initially, the increase in the fat content of the heart is because of a metaplastic phenomenon.
• It is not an infiltrative process.
• Various tissues of heart, like the sinus node, atrioventricular node, right bundle branch, and the myocardium near the atrioventricular ring, are replaced by fat cells.
• These can occasionally cause conduction defects like sinoatrial block, bundle branch block, and, rarely, atrioventricular block.
• Subsequently, irregular bands of adipose tissue may separate and cause pressure-induced atrophy of the myocardial cells.
• These adipose cells may also secrete locally active molecules like adipokines.
• These molecules indirectly cause injurious effects on the adjacent myocardial cells.
• Accumulation of triglycerides in nonfat cells like myocytes can also directly cause cell dysfunction because of lipotoxicity.

Congestive Heart Failure

Several factors primarily caused by obesity are like:
• Increased blood volume
• Elevated cardiac output
• Left ventricular hypertrophy
• Left ventricular diastolic dysfunction
• Adipositas cordis
– Adipositas cordis play a role in causing heart failure.
– This is in addition to indirect effects mediated through other frequently coexisting conditions. They are like:
• Diabetes
• Hypertension
• Coronary artery disease

Clinical assessment for heart failure is often difficult in obese patients for several reasons.
• Dyspnea during exertion and leg edema can occur even without congestive heart failure.

Obesity: Impact on Cardiovascular Disease Mayo Clinic Healthy Heart for Life! The Adaptation Diet

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