An enlarged heart can signal disease, or simply years of endurance training
Cardiomegaly, the medical name for an enlarged heart, usually means the organ has been forced to work too hard by high blood pressure, valve disease or blocked arteries. Yet endurance athletes can develop a bigger heart as a healthy adaptation. Telling the two apart matters, because one form can lead to heart failure.
The problem is partly mechanical. Heart muscle contracts when two protein filaments, actin and myosin, slide past and pull on each other inside the muscle fibres. As an overworked heart stretches, those filaments overlap less and cannot grip effectively, so the fibres shorten poorly and each beat pushes out less blood to the lungs and body. An enlarged heart is also more prone to forming clots in its lining, which can travel and disrupt blood flow to other organs.
Many cases have no identified cause. The most common known ones are inherited conditions, high blood pressure, which can thicken and eventually weaken the left ventricle, and coronary artery disease, where blocked blood supply kills tissue and forces surrounding muscle to compensate. Other culprits include fluid around the heart, iron overload and Chagas disease, a major cause in Latin America. Some women develop an enlarged heart around the time of giving birth. Many people have no symptoms at all; in others, palpitations and severe breathlessness appear once pumping suffers, and studies link the condition to a higher risk of sudden cardiac death.
Athletic heart syndrome is the benign version, seen in people who train hard for more than an hour a day. It reflects natural remodelling and is usually reversible, though screening is still recommended to rule out dangerous hidden conditions. At the other extreme, autopsies of several rock drummers who died from overdoses, including Taylor Hawkins of Foo Fighters, found enlarged hearts, possibly worsened by drug use combined with the strain of drumming.
A simple X-ray measurement still helps flag the condition. The cardio-thoracic ratio compares the heart's width with the width of the chest cavity, and a figure above 50% raises suspicion. It was first proposed in 1919 to screen military recruits. Echocardiograms, electrocardiograms and MRI then help pin down which chambers are enlarged and why.
Source: Cardiomegaly
