Genetic variations contribute to heart rate and risk of sudden cardiac death

A study published in Nature Genetics last week has identified gene variants that affect a person's heart rate, and risk of sudden cardiac death. The team led by Christopher Newton-Cheh at Massachusetts General Hospital (US), found 14 variants in ten gene regions that are associated with differences in a person's heart rate. Some of the variants were previously unknown to be involved in cardiac function. The findings may one day be used to help prevent sudden cardiac death and arrhythmia, by limiting the use of medications that affect heart rate in people with the variants.

Newton-Cheh said: 'It is well established that prolongation of the QT interval in the general population is a potent and heritable risk factor for sudden death. In addition, QT prolongation results from medications can lead to drug-induced cardiac arrhythmias and sudden death'.

QT interval is the time from the beginning of electrical activation of the heart to the end of electrical relaxation, and can be measured on an ECG (electrocardiogram). The researchers studied over 13,000 individuals to find genetic variants that affect QT interval duration. All the participants had their QT interval measured. They also had 100,000's of common genetic variations, or SNPs (single nucleotide polymorphism), analysed. A second independent study in the same journal studied over 15,000 people from Europe and confirmed 12 of the 14 variants, verifying the results.

'While it is commonly a combination of risk factors that contributes to drug-induced arrhythmias - such as older age, female sex, use of other medications, or heart disease - it is certainly possible that common genetic variants will add incrementally to risk prediction' Newton-Cheh said.

It is likely that there will be other genes found that contribute to QT interval. Understanding the mechanisms behind the genes effects will be a big challenge. Five of the gene regions found in this study have never been associated with cardiac function before, so finding out the role of these regions may help researchers understand normal and abnormal human heart biology.