Genetic Variations and the Risk for Alcohol-Induced Weakness of the Heart

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The summary below is from the full report titled "Angiotensin-Converting Enzyme Gene Polymorphism Is Associated with Vulnerability to Alcoholic Cardiomyopathy." It is in the 3 September 2002 issue of Annals of Internal Medicine (volume 137, pages 321-326). The authors are J Fernández-Solà, JM Nicolás, J Oriola, E Sacanella, R Estruch, E Rubin, and A Urbano-Márquez.

What is the problem and what is known about it so far?

Excessive alcohol consumption is known to cause weakness of the heart muscle, a condition called cardiomyopathy. However, because not all alcoholic persons develop cardiomyopathy, some researchers have suggested that a person's risk for this complication depends on his or her genetic make-up. Packets of genetic material, known as genes, occur in pairs, and each parent contributes half of the pair to the child. Although genes from each parent may be identical, they often differ slightly—these variations are called alleles. Alleles can lead to slight variations in the chemicals produced by heart muscle tissue. One chemical suspected of having a role in alcoholic cardiomyopathy is angiotensin-converting enzyme (ACE). Because of the occurrence of different ACE alleles, different forms of ACE can be present in cardiac muscle. These forms of ACE can be identified in a laboratory.

Why did the researchers do this particular study?

To find out whether alcoholic persons with a particular ACE allele were more likely to develop cardiomyopathy than those with other ACE alleles.

Who was studied?

30 alcoholic persons with moderate to severe cardiomyopathy and 27 alcoholic persons without cardiomyopathy. All participants were well nourished.

How was the study done?

Participants with cardiomyopathy were matched to participants without cardiomyopathy on the basis of similar lifetime alcohol intake. All patients were questioned about symptoms of cardiomyopathy and had a test of heart muscle strength. Genetic testing was done on blood samples to determine the types of ACE alleles present.

What did the researchers find?

Except for the presence or absence of cardiomyopathy, the two groups were similar. Thirty-six percent of patients with cardiomyopathy had an I ACE allele, and 65% had a D allele; those without cardiomyopathy had almost exactly the opposite proportion (63% had an I allele and 37% had a D allele). Eighty-nine percent of patients with a double dose of the D allele (one from each parent) had developed cardiomyopathy compared with only 34% of patients with at least one dose of the I allele. Patients with a double dose of the D allele were more than 16 times more likely to develop cardiomyopathy than those who did not have a double dose.

What were the limitations of the study?

Because all patients in the study were well-nourished, middle-class people from a single ethnic community, they may not have been representative of all alcoholic persons.

What are the implications of the study?

Alcoholic persons with certain types of genetic make-up may be much more liable to develop cardiomyopathy than others. As a result, these individuals should receive special medical attention for detection and treatment of early signs of cardiomyopathy.