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OBESITY:  A HEART FAILURE CAUSE?

Can obesity cause heart failure? The answer, unfortunately, is yes: Through multiple mechanisms, excessive weight may lead to cardiac disease, including ischemic heart disease and congestive heart failure. We will proceed to take a closer look at how this happens.

First of all, excessive weight leads to increased blood volume in the body. This is only natural, since the excess body mass requires adequate blood flow, just like any other body tissue. However, this means the heart must continually pump a larger volume of blood. In other words, the workload of the heart is being increased, proportionally to the degree one is overweight.

Just like any other muscle in the body, the heart muscle responds to this increased workload by becoming hypertrophied, i.e. by increasing its size. This condition is called left ventricular hypertrophy (LVH), and is often associated with some degree of hypertension (increased blood pressure).
Up to a point, the heart can accommodate this and continue to function normally. Later however, the following problem develops: As the heart muscle grows larger, the coronary arteries (the vessels supplying blood to the heart muscle) fail to proliferate at the same rate. Although additional coronary branches are being formed, their number soon becomes insufficient to sustain the increased mass of the heart muscle. Therefore, a relative ischemia (lack of blood) occurs, which tends to become manifest during states of high demand (physical exercise, febrile illnesses, etc). The heart tissue affected by this phenomenon is being damaged over time, and gradually looses is ability to contract normally. Moreover, the hypertrophied cardiac muscle looses elasticity, and therefore fails to relax completely in between cardiac contractions. This causes insufficient filling of the heart muscle with blood prior to a contraction, which in turn decreases the amount of blood pumped out during the contraction.

Over time, this mechanism may result in frank congestive heart failure, a condition where the heart fails to contract properly and therefore cannot deliver the required amount of blood into the body. Under these circumstances, the residual blood volume which the heart fails to pump into the circulation accumulates "behind the heart", in the lungs and other body tissues, causing pulmonary congestion or body swelling (in particular swelling of the lower limbs).

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But that's not all. The process described above is just one way obesity can lead to congestive heart failure. In reality, at least 2 other mechanisms are at work: We all know (or should know) that being overweight is associated with high cholesterol and other lipid abnormalities, as well as with the development of diabetes type 2. In turn, lipid disorders and diabetes type 2 cause the formation of plaque in the blood vessels, a condition commonly known as atherosclerosis. When atherosclerosis affects the vessels in the heart, we talk about coronary artery disease or ischemic heart disease, the culmination of which is a heart attack. A heart attack, or myocardial infarction, occurs when a coronary vessel is fully obstructed by plaque formed locally, or by a clot breaking off from a distant plaque source. Under these conditions, blood flow is interrupted, such that the heart muscle beyond the site of the blockage will be deprived of blood. This in turn results in death of the respective portion of the heart muscle, a process called myocardial necrosis. The dead portion of the heart muscle becomes flabby and inert, and fails to contract as the heart is beating. As such, the heart is loosing part of its contractile power. The necrotic heart portion may also generate abnormal electric potentials, which can lead to cardiac arrhythmias such as atrial fibrillation, atrial flutter, or tachycardia. Cardiac arrhythmias further diminish the ability of the heart to pump blood, since the rapid heart rhythm doesn't allow sufficient time for the heart to fill with blood prior to each cardiac contraction.

It's important to know that diabetes type 2, which is a common condition in overweight persons, has an extremely strong association with ischemic heart disease. That is to say, if a person suffers from diabetes type 2, it's quite likely that person also suffers from ischemic heart disease (coronary artery disease). Oftentimes, patients with diabetes type 2 have silent heart disease, which means there are no clinical symptoms until a potentially fatal heart attack occurs. This is why from a medical point of view, diabetes type 2 is regarded as an equivalent of ischemic heart disease, and a patient suffering from diabetes type 2 is treated as if he or she also suffered from ischemic heart disease.

Note is being made that diabetes type 2 is largely a preventable condition. It usually occurs in individuals who are overweight or obese, and resolves if the individual's weight returns to normal or near-normal. The mechanism of diabetes type 2 has to do with insulin resistance. In other words, overweight or obese individuals become refractory to insulin, the hormone that regulates blood glucose levels. Under these circumstances, a higher amount of insulin is required to keep blood glucose in the normal range.

In conclusion:
It's obvious that excessive weight and obesity play a key role in the development of cardiovascular disorders, including ischemic heart disease and congestive heart failure. In a nutshell, obesity may act as a trigger mechanism for these conditions, which eventually have a snowballing effect, resulting in more and more cardiac damage. Therefore, it's prudent for overweight individuals to work on weight reduction prior to developing any signs or symptoms of heart disease. At the point symptoms occur, the cardiac damage may be irreversible.


 

 

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