Heart issues do not affect all children and adults with CMD. Heart issues occur because the heart is a muscle and people with CMD develop muscle weakness. For reasons that are unclear, some types of CMD develop weak hearts, others do not. The spectrum of heart involvement ranges from:
Congestive heart failure with shortness of breath, requiring medication
Asymptomatic but mild weakness of the heart detected on echo only
Asymptomatic without abnormalities or weakness on heart echo
When the heart becomes weak, it has a hard time squeezing out the blood. Over time, a weakened heart muscle may lead to a flabby enlarged heart that cannot pump well which in turn may lead to congestive heart failure. The best way to clinically follow you or your child to make sure there are no heart issues is to get an EKG (electrocardiogram) and an echo (echocardiogram). Both of these tests are noninvasive, do not cause pain and are performed by a cardiologist (heart specialist) or a technician trained in performing echos.
Since there are no medical guidelines directing people with CMD and their doctors, the decision about how often to obtain an EKG and an echo are made on an individual basis in consultation with the cardiologist. There are certain subtypes that do not have cardiac involvement: Ullrich/Bethlem. For those CMD subtypes with potential heart involvement, one should have at least one EKG and echo performed as a baseline. Below are some reference articles, based on CMD subtype that can be used in discussion with your or your child’s cardiologist to decide how often an EKG and echo should be obtained.
Short runs of atrial tachycardia may begin in the first decade of life and become more persistent over time, resulting in chronic atrial fibrillation. Anticoagulation may be needed.
Progressive AV block may also begin early, and get worse over time. Some patients require pacemakers.
Asymptomatic non-sustained ventricular tachycardia (VT) may be seen on Holter. Sudden death, while rare, has been reported, even with a prior normal ECHO and Holter.
Ventricular systolic dysfunction tends to be a late finding, and may deteriorate rapidly. Diarrhea, edema may be early symptoms of cardiac dysfunction before a noticeable decline in ejection fraction on ECHO. BNP levels may be a more sensitive indicator of heart dysfunction than ejection fraction.
Physiologic stress (surgery, infection) may precipitate a rapid decline in heart function.
Heller, et al. Cardiac manifestations of congenital LMNA-related muscular dystrophy in children: three case reports and recommendations for care. Cardiology in the Young, Dec 2016
Merosin deficient CMD (MDC1A)
Heart failure is rare in merosin deficient CMD. Some with merosin deficient CMD develop mild to moderate left ventricular hypokinesis. The left ventricle is one of the 4 chambers of the heart. Hypokinesis means the muscle walls of the left ventricle appear weakened and have decreased motion.
Spyrou N, Philipot J, et al. Evidence of left ventricular dysfunction in children with merosin deficient congenital muscular dystrophy. AM Heart J 1998 (136):474-6.
Fukuyama: Dilated cardiomyopathy (enlarge heart with heart failure) is common in second decade.
FKRP mutation (MDC1C): FKRP mutations can give rise to entire clinical spectrum from CMD to limb girdle. People with FKRP mutations have a tendency to develop enlarged hearts.
Poppe M et al. The phenotype of limb girdle muscular dystrophy type 2I. Neurology 2003 (60):1246-51.
Brockington M, Blakce DJ, et al. Mutations in the FKRP gene cause a form of congenital muscular dystrophy with secondary laminin alpha2 deficiency and abnormal glycosylation of alpha-dystroglycan. Am J HumGenet 2001 (69):1198-209.