Personalized genetic information and risk assessment for heart disease

The traditional method of assessing risk for heart disease has been useful for prediction at population level but loses its predictive power at the individual level.

Recently, the use of genomics in medicine has gained a foothold. I summarize two studies here that demonstrated this.

Genetic variants for sudden cardiac arrest

A recent paper reviewed genetic variants that cause sudden cardiac death (SCD). More than 300,000 people die in the US each year as a consequence of SCD. Most of these deaths are related to underlying heart conditions such as coronary heart disease (CHD). The paper, too, points out the shortcomings of the traditional risk assessment methods.

“The conventional coronary risk factors and presence of congestive heart failure are associated with SCD in the general population but have poor ability to predict SCD at the individual level because of their prevalence and comparatively modest effects on risk.”

Some conditions, characterized by structural heart problems are found to be mostly due to genetic mutations. These conditions include:

• Hypertrophic Cardiomyopathy
• Arrhythmogenic Right Ventricular Dysplasia
• Dilated Cardiomyopathy
• Inherited Arteriopathies

The study concluded:

Developing an understanding of genetic contributions to SCD may prove important in the management of genetic SCD syndromes, the development of novel therapeutics, and risk stratification in the general population, thereby improving our ability to predict and ultimately prevent this tragic outcome.

Genetic variants for coronary heart disease

This new study by researchers at the Baylor College of Medicine in Houston demystifies the genetics of CHD. According to the study

“identifying a single, common variation in a person’s genetic information improves prediction of his or her risk of a heart attack or other heart disease events and thus, choice of the best treatment accordingly.”

The DNA variation that the researchers pinpointed at the 9p21 chromosomal region is not a mutation. It is a genetic variant, which means that each of has it, but slightly different in each individual.

The study looked at 10,000 middle-aged Americans as part of the Atherosclerosis Risk in Communities research. Study participants were classified based on traditional risk factors as follows:

• Low risk participants are those having a less than 19% chance of having coronary heart disease (CHD) in the next decade.
• Intermediate risk participants are those with a 10 to 20% likelihood to have CHD in the next ten years.
• High risk participants are those with the likelihood of 20% or more to have CHD in the next 10 years.

Looking at the genetic information, however, gives a completely different picture. Many of the participants with the genetic variant had risk profiles higher than initial categorization and had to be reevaluated. Those who have intermediate risk profiles are especially affected because they could easily move up the risk ranking.This recategorization improved risk prediction, leading to more optimal preventive measures and treatment.

Recently, personalized genetic information has gone mainstream as more and more companies are offering their services at affordable prices. The start up company 23andme is now offering “retail DNA test” for only $399.00.

But does it really help in the diagnosis and treatment of diseases? It seems that it does, in certain cases, as demonstrated by the review studies above. The 23andme test can supposedly screen for over 90 traits which can reveal a person’s predisposition to certain diseases.

Is personalized medicine up next?

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