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Heart failure is a progressive condition in which the heart's muscle becomes weakened after injury and gradually loses its ability to pump enough blood to supply the body's needs. Many people don't even know they have it because its symptoms are often mistaken for signs of getting older. Heart failure usually does not develop overnight - it's a progressive disease that starts slowly and gets worse over time.

Heart failure is often divided into systolic dysfunction and diastolic dysfunction.  Both can cause similar symptoms of fatigue, fluid retention and shortness of breath.  With systolic dysfunction, the pumping function of the heart is diminished. With diastolic dysfunction, the capacity of the heart to relax during the filling period is diminished.

The most common cause of systolic dysfunction (also called dilated cardiomyopathy) in this country is coronary artery disease and myocardial infarction (heart attack). Other etiologies are post-partum (after pregnancy), secondary to drugs (including chemotherapeutic agents), infections, familial (genetic: FDC- familial dilated cardiomyopathy) and substance abuse (cocaine or alcohol).  For many patients, the etiology cannot be determined and, by exclusion, they are characterized as idiopathic dilated cardiomyopathy (IDC)

Genetic counseling is available at our center. The most important step in a genetic evaluation of dilated cardiomyopathy (DCM) is a careful family history of any evidence of heart failure - especially with patients classified as idiopathic.  At this point in time, over twenty (20) genes have been implicated in DCM. These genes include, but are not limited to: ACTC (cardiac actin), MYBPC3 (myosin binding protein C), MYH6 (a-myosin heavy chain), MYH7 (b-myosin heavy chain), TNNT2 (troponin T), TPM1 (a-tropomyosin), PLN (phospholambin) and TNNI3 (troponin I). DCM genes are found with some of the muscular dystrophies (DMD- dystrophin).

The genes associated with FDC appear to be inherited as autosomal dominant, but there is also evidence of autosomal recessive, x-linked and mitochondrial inheritance. Given incomplete gene penetrance, variable expression and the wide variety of possible implicated genes (plus allele heterogeneity), the prudent course of screening now would appear to be electrocardiogram (ECG) and echocardiogram (ECHO) for first degree relatives of patients with IDC or FDC.  Although genetic analysis is available, not even absence of mutations in all of the implicated genes would exclude FDC. This is because  many cases of FDC are not, as of yet, attributable to any of the known genes, thus making genetic testing insensitive.

Nevertheless, there may be occasions when genetic testing would be of use for example, when the phenotype is severe, and a family wants to investigate whether it has been transmitted to the offspring.

This is a rapidly changing field of inquiry: new data and new knowledge are rapidly accumulating to help better understand the genetics of FDC.

Bibliography:

  1. Burkett EL, Hershberger RE. Clinical and genetic issues in familial dilated cardiomyopathy. J Am Coll Cardiol 2005;45:969-81.
  2. Ross J. Dilated Cardiomyopathy – concepts derived from genetic deficient and transgenic animal models. Circ J 2002;66:219-24.
  3. Kushner JD, Nauman D, Burgess D, Ludwigsen S, Parks SE, Pantely G, Burkett E, Hershberger RE. Clinical characteristics of 304 kindreds evaluated for familial dilated cardiomyopathy. J Cardiac Failure 2006;12:422-29.
  4. Deo R, MacRae CA. The genetics of cardiomyopathies: What Clinicians should know. Current Heart Failure Reports 2007;4:229-35.