Exercise as it relates to Disease/Bradycardia in athletes

Bradycardia means to have an abnormally slow heart rate. Heart rate is determined by beats in a minute. An average resting heart rate for adults is between 60-100BPM (beats per minute). If your heart rate is below 60 BPM then you are deemed to have bradycardia. Bradycardia can be quite normal and healthy; sometimes bradycardia can be a sign of being very physically fit. However bradycardia can also be due to different types of heart disease and issues with the heart’s neural signaling.

Sinus Bradycardia
Sinus Bradycardia is when your heart rate is below 60 BPM. It is called Sinus Bradycardia because it is caused by the sinus node of the right atrium. Sinus Bradycardia is not a change in rhythm, it is simply slowed down. Sinus Bradycardia can also be known as athlete’s heart and is the most common form of Bradycardia in athletes. This is because Sinus Bradycardia can be directly linked to having exceptional physical fitness. Most athletes have a resting heart rate between 40-60 BPM giving them the bradycardia diagnosis. We would mostly find Sinus Bradycardia in endurance athletes. This is because endurance sports are heavily reliant on the respiratory and cardiac system to pump oxygenated blood around the body to saturate the muscles with oxygen and remove them of toxins. Sinus Bradycardia in athletes is due to the heart adapting to the physical stresses that it is put under by the athlete’s physical activity. This causes the heart to become more efficient producing a greater stroke volume, which in return allows the heart to circulate the same amount of blood with fewer contractions.

Cardiac causes

 * Ischemic heart disease
 * Vascular heart disease
 * Valvular heart disease
 * Degenerative primary electrical disease
 * Fit healthy heart (athletes heart)
 * Increased stroke volume

Non-cardiac causes
The causes act in three different mechanisms: decreased automaticity of the heart, conduction blocking, or defect pacemakers and rhythms.
 * Recreational drug use
 * Metabolic or endocrine issues (especially in the thyroid)
 * Electrolyte imbalance
 * Neurologic factors
 * Autonomic reflexes
 * Prolonged bed rest
 * Autoimmunity
 * Good physical fitness

Symptoms

 * Fatigue
 * Dizziness
 * Lightheadedness
 * Fainting or near-fainting spells
 * In extreme cases, cardiac arrest may occur.
 * no symptoms in a health trained heart. e.g. Athletes

Treatments
Treatment may not be required if there is no underlying disease, the heart responds to exercise normally and there is no sign of low cardiac output. Treatment options:
 * Atropine
 * Inotrope
 * Pacemaker (single-chamber and dual-chamber pacemaker)
 * In extreme cases heart transplant is required
 * supplemental oxygen

Readings
http://www.bhf.org.uk/heart-health/conditions/abnormal-heart-rhythms.aspx

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1767992/