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.