Friedreich’s ataxia is caused by a deficiency of the frataxin protein. This can result in a condition called cardiac neuropathy. It involves damage to the nerves that innervate the heart and changes in cardiac muscle that lead to cardiomyopathy, or heart muscle disease. Around 75 percent of people with FA develop heart abnormalities.
FA is typically diagnosed between ages 10 and 18. At that time, patients’ heart muscle may have started to thicken but can still function fine. Heart function declines over time, however, and within 10-15 years patients can develop severe heart failure.
Forms of heart disease in FA
Various forms of heart disease accompany FA.
These include hypertrophic cardiomyopathy, or thickening of the walls of the heart; myocardial fibrosis, or fiber-like material forming in heart muscles; and heart failure, which involves the heart failing to pump sufficient blood to sustain normal body functions.
Also common with FA are heart rhythm abnormalities such as tachycardia, or a fast heart rate, and heart block, an abnormality in the way electrical impulses pass through the heart.
The cardiac abnormality most often seen in FA is hypertrophic cardiomyopathy. It involves the thickening and enlargement of ventricular walls, or cardiac muscles. This causes the heart’s blood-filled chambers to shrink, decreasing the organ’s pumping capacity. It often leads to arrhythmias, or irregular heart beats, and to heart failure that kills those with FA. Heart muscle cells adapt to increased demands by increasing their size, a condition scientists call hypertrophy.
A thickened heart continues to maintain systolic function, or contraction of the heart muscle. That means its ability to pump blood is fine. But there is a reduction in the heart’s ability to relax and accept blood, or diastolic function.
FA patients usually develop cardiomyopathy before the age of 40. Consistent with the development of the condition is the fact that most of those who die of cardiac failure do so before age 40.
A hypertrophic heart can eventually lead to irregular heart beats. It adapts to increased demands by beating faster, a condition scientists call tachycardia. This is the only way the heart can adapt since it cannot increase its capacity to accept more blood with each beat.
Because the heart is unable to adjust efficiently to certain demands, arrhythmias can put patients’ lives in danger. Tachycardia can cause loss of consciousness. It can also cause sudden death — at the moment when the heart’s rhythm passes from a normal to a fast beat.
Symptoms of heart disease in FA
The symptoms of declining heart function in FA include extreme fatigue; chest pain; shortness of breath, especially with exertion; lightheadedness; leg swelling; difficulty breathing while lying flat; pooling of blood in the ankles; heart palpitations, or abnormally rapid or irregular heartbeats.
Diagnosing heart disease in FA
Doctors use echocardiography to visualize the structure of the heart, and ECG to evaluate heart rhythm and the heart’s ability to pass electrical impulses. CMRI is a more advanced imaging technique that can show details such as fibrosis, or scarring in the heart.
Even with these imaging tools, in certain cases, doctors may need to obtain a heart tissue sample by biopsy to come up with a definite diagnosis.
Treatment of heart disease in FA
The treatment of patients with FA-associated heart failure or arrhythmia can include conventional heart failure drugs, antiarrhythmic drugs, and implanting devices.
Unfortunately, none of these treatments can stop the progression of heart disease or improve heart function. They can only reduce symptoms.
Drugs called ACE inhibitors such as Capoten (captopril) can help lower FA patients’ blood pressure. The treatments make the heart’s work easier by dilating blood vessels and lowering the pressure against which the heart has to push to pump blood out.
In small studies, the antioxidant idebenone has helped thin heart walls by a small amount, leading to a small improvement in heart function.
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