It is important to differentiate if a cardiac enlargement is pathological, or a physiological adaptation to sport practice. Cardiac magnetic resonance is useful to assess myocardial thickness, chamber volumes, tissue composition and anatomy. It allows the location of myocardial fibrosis, which is specific to certain cardiomyopathies, and therefore differentiate at some extent if we are in front of a pathologically enlarged heart. Nevertheless there is not a single diagnostic test to distinguish between an adaptive or pathological heart, and usually the first assessments involve a normal electrocardiography test.
There are also more differences in a hypertrophied heart besides the morphological ones. A pathologically hypertrophied heart tends to consume glucose as substrate, while a healthy heart upregulates the fatty acid oxidation instead. Aerobic exercise has been associated with changes in the substrate utilization and increased myocardial metabolic efficiency, improving the cardiac remodelling associated with chronic hypertension or myocardial infarction. In diabetes aerobic exercise enhances insulin sensitivity and normalises myocardial metabolism.
Among the worst pathologies linked to structural cardiac hypertrophy is the sudden cardiac death (SCD). It has been documented in all type of competitive sports, although generally more commonly in those physically demanding. Besides the sport type, sex and ethnicity are factors involved in the sudden death risk, as it is more likely to happen in male participants (male to female ratio 5:1) and individuals of Afro-Caribbean descent (black to white ratio 8:1).
Although the SCD is less common than other causes of death, its occurrence in sport events, sometimes affecting supposedly young healthy participants, carries a lot of media attention, raising questions on the necessity of pre-activity screening. In young athletes (less than 35 years old) inherited ventricular arrhythmias are the abnormalities behind the SCD, while for older athletes atherosclerotic coronary artery disease is dominant.
As we commented previously a proper diagnosis is a clinical challenge, as erroneous disapproval of physical activity may prevent a healthy individual from the benefits of sports practice. Echocardiography and cardiovascular magnetic resonance are some of the main non-invasive techniques used to diagnose cardiac disease. Nevertheless, these techniques results are limited, as many times they are used in resting conditions. The ideal would be to use them during stress tests, although motion artefacts could be difficult to interpretate. New systems are becoming available, able to work in exercise conditions, that are offering encouraging results in the diagnosis of pathological cardiac conditions.
The therapeutic effects of aerobic exercise could represent a low-cost intervention, with no side effects, to improve the survival rate in cardiac hypertrophies linked to conditions such as hypertension, myocardial infarction or diabetes: RUN GIVES LIFE.
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