Lyme disease results when a person is bitten by a tick that is infected with the parasite Borrelia burgdorferi. In most cases, Lyme disease can be cured by treatment with antibiotics. If the disease is treated early, all symptoms typically disappear and the disease is completely cured. However, if Lyme disease is not treated, it can cause serious, life-threatening complications affecting the nervous system, heart and lungs, and can cause fatigue and arthritis. In North America, approximately 8 percent of patients with Lyme disease develop heart complications, according to an article published in the "Canadian Journal of Cardiology."

Electrical Abnormalities

The most common heart complication caused by Lyme disease is disruption of the electrical signals that coordinate the beating of the heart, explains the University of Maryland Medical Center. The heart uses electrical signals to make sure that all the cells of the heart beat at the right time in order to push out blood and pull in more blood. When the electrical disturbances are disrupted, doctors call this a heart block. Depending on the exact location of the block within the heart, different types of electrical blocks can occur. Lyme disease often causes an atrioventricular block, which causes symptoms of dizziness, shortness of breath, loss of consciousness, chest pain and heart palpitations.

Swelling of the Heart

Patients with Lyme disease may also experience a swelling of the heart, which is called myopericarditis. When the parasite causing Lyme disease migrates into heart tissue, the immune system tries to attack it by sending many specialized immune cells into the heart to kill the parasite. The influx of these immune cells causes the heart, particularly the small blood vessels that run through the heart, to swell, which is known as inflammation. The swelling of the heart can affect the ability of the heart to beat properly. In some cases, even after the parasite has been killed, the immune system continues to overreact, causing the heart to remain swollen.

Congestive Heart Failure

If Lyme disease remains untreated for a long time, some evidence suggests it may slowly cause heart failure, which is also known as cardiomyopathy, explains the "Canadian Journal of Cardiology." Researchers have not yet clearly established a link between Lyme disease and heart failure; however, some studies have found that patients infected with Lyme disease tend to have a higher incidence of cardiomyopathy than uninfected patients, reports the" Candian Journal of Cardiology." Doctors suspect that the continued damage to the heart caused by the Lyme disease parasite slowly weakens the ability of the heart to pump blood properly.