Athletic heart syndrome
Encyclopedia
Athletic heart syndrome, also known as athlete's heart or athletic bradycardia, is a medical syndrome in which the human heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
is enlarged due to significant amounts of exercise. Common in athletes who exercise more than an hour almost every day and occasionally in heavy weight trainers, this syndrome is believed to be a benign condition but may be hard to distinguish from other serious medical conditions.
Description
During intensive prolonged endurance- and strength-training, the body signals the heart to pump more blood through the body to counteract the oxygen deficit building in the skeletal muscles. Enlargement of the heart is a natural physical adaptation of the body to deal with the high pressures and large amounts of blood that can affect the heart during these periods of time. After time, these pressures cause the muscle mass, wall thickness, and chamber size of the left ventricleLeft ventricle
The left ventricle is one of four chambers in the human heart. It receives oxygenated blood from the left atrium via the mitral valve, and pumps it into the aorta via the aortic valve.-Shape:...
of the heart to increase.
Cardiac output
Cardiac output
Cardiac output is the volume of blood being pumped by the heart, in particular by a left or right ventricle in the time interval of one minute. CO may be measured in many ways, for example dm3/min...
, the amount of blood that leaves the heart in a given time period (i.e. liters per minute), is proportional to both the chamber sizes of the heart and the rate at which the heart beats. With a larger left ventricle, the heart rate can decrease and still maintain a level of cardiac output necessary for the body. Therefore, it is very common for athletes to have lower resting heart rates than nonathletes.
Symptoms and Diagnosis
There are no symptoms for people with athletic heart syndrome, although an indicator would be a consistently low resting heart rate. AHS is usually diagnosed during a routine screening or during tests for other medical issues. An enlarged heart can be seen on an echocardiogram or sometimes a chest X-rayChest X-ray
In medicine, a chest radiograph, commonly called a chest X-ray , is a projection radiograph of the chest used to diagnose conditions affecting the chest, its contents, and nearby structures...
. Due to the similarities between AHS and more serious cardiac problems, an electrocardiogram
Electrocardiogram
Electrocardiography is a transthoracic interpretation of the electrical activity of the heart over a period of time, as detected by electrodes attached to the outer surface of the skin and recorded by a device external to the body...
(ECG) and exercise stress echo tests are sometimes performed. AHS and left ventricular hypertrophy
Left ventricular hypertrophy
Left ventricular hypertrophy is the thickening of the myocardium of the left ventricle of the heart.-Causes:While ventricular hypertrophy occurs naturally as a reaction to aerobic exercise and strength training, it is most frequently referred to as a pathological reaction to cardiovascular...
are usually indistinguishable via EKG, however LVH is usually dismissed in the young and fit.
The EKG can detect sinus bradycardia
Sinus bradycardia
Sinus bradycardia is a heart rhythm that originates from the sinus node and has a rate of under 60 beats per minute.-Signs and symptoms:The decreased heart rate can cause a decreased cardiac output resulting in symptoms such as lightheadedness, dizziness, hypotension, vertigo, and syncope...
, a resting heart rate of fewer than 60 beats per minute. This is often accompanied by sinus arrhythmia. The heartbeat of a person with AHS can sometimes be irregular while at rest, but usually returns to normal after exercise begins.
One common cardiovascular disease that has similar EKG reads is hypertrophic cardiomyopathy
Hypertrophic cardiomyopathy
Hypertrophic cardiomyopathy is a disease of the myocardium in which a portion of the myocardium is hypertrophied without any obvious cause...
, which is characterized by the thickening of the heart's walls. This genetic disorder is found in 1 out of 500 Americans and is responsible for thousands of sudden death cases every year. Of all sudden death cases, only about 8% are exercise-related. The following table shows distinguishing characteristics of the two conditions.
| Feature | Athletic Heart Syndrome | Cardiomyopathy |
|---|---|---|
| Left ventricular hypertrophy Ventricular hypertrophy Ventricular hypertrophy is the enlargement of ventricles in the heart. Although left ventricular hypertrophy is more common, enlargement can also occur in the right ventricle, or both ventricles.- Physiology :... |
< 13 mm | > 15 mm |
| Left ventricular end-diastolic diameter | < 60 mm | > 70 mm |
| Diastolic Diastole Diastole is the period of time when the heart fills with blood after systole . Ventricular diastole is the period during which the ventricles are relaxing, while atrial diastole is the period during which the atria are relaxing... function |
Normal (E:A ratio > 1) | Abnormal (E:A ratio < 1) |
| Septal hypertrophy | Symmetric | Asymmetric (in hypertrophic cardiomyopathy) |
| Family history | None | May be present |
| BP Blood pressure Blood pressure is the pressure exerted by circulating blood upon the walls of blood vessels, and is one of the principal vital signs. When used without further specification, "blood pressure" usually refers to the arterial pressure of the systemic circulation. During each heartbeat, BP varies... response to exercise |
Normal | Normal or reduced systolic BP response |
| Deconditioning | Left ventricular hypertrophy regression | No left ventricular hypertrophy regression |
Features Distinguishing Athletic Heart Syndrome From Cardiomyopathy
Prognosis and Treatment
Although the heart experiences structural changes (i.e. wall thickening) that are common with some cardiac disease, no unfavorable effects are evident. 80% of people affected by this syndrome show a decrease in such structural changes and in bradycardia with detraining. Unfortunately, the lack of long-term data limits the ability to determine whether or not the remaining 20% of people who do indeed have residual chamber enlargement have experienced any negative side effects.No treatment is required for people with athletic heart syndrome. In some cases, 3 months of deconditioning are required in order to distinguish AHS from cardiomyopathy, though this may be met with resistance since training is an integral part of an athlete's life.
See also
- Left ventricular hypertrophyLeft ventricular hypertrophyLeft ventricular hypertrophy is the thickening of the myocardium of the left ventricle of the heart.-Causes:While ventricular hypertrophy occurs naturally as a reaction to aerobic exercise and strength training, it is most frequently referred to as a pathological reaction to cardiovascular...
- CardiomyopathyCardiomyopathyCardiomyopathy, which literally means "heart muscle disease," is the deterioration of the function of the myocardium for any reason. People with cardiomyopathy are often at risk of arrhythmia or sudden cardiac death or both. Cardiomyopathy can often go undetected, making it especially dangerous to...
- Aerobic exerciseAerobic exerciseAerobic exercise is physical exercise of relatively low intensity that depends primarily on the aerobic energy-generating process. Aerobic literally means "living in air", and refers to the use of oxygen to adequately meet energy demands during exercise via aerobic metabolism...
- Exercise intensityExercise intensityExercise intensity refers to how much work is being done when exercising. The intensity has an effect on what fuel the body uses and what kind of adaptations the body makes after exercise . Intensity is the amount of physical power, expressed as a percentage of maximum, the body uses in performing...