Gene clue to irregular heartbeats

US researchers have pinpointed a genetic variation associated with abnormal heartbeats, a finding that could help identify people at risk of sudden heart failure. The team, based at Johns Hopkins University (JHU), has shown that different versions of a gene called NOS1AP are linked to unusually long or short 'QT' intervals - an electrical measure of part of a person's heartbeat. The study, published online in the journal Nature Genetics, could lead to new preventative measures to help save the lives of people at risk of sudden cardiac death.

The QT interval measures the length of time it takes the heart to recover from the 'lub' part of the 'lub-dub' pattern of a heartbeat, which corresponds to the pumping of the two bottom chambers of the heart. Previous studies have shown that people with an unusually long or short QT interval are at higher risk of sudden cardiac death. Many different genetic and environmental factors are thought to contribute to irregular heartbeats and the risk of heart failure.

Working with scientists from Munich, Germany, and the long-term US Framingham Heart Study, the JHU researchers set out to identify genetic variations that might influence the QT interval. They studied around 1,800 US and 6,700 German adults, and identified those whose QT interval length was either shorter or longer than the normal range. They then looked at DNA samples from these individuals and a control group, focusing on common genetic variations known as SNPs . One particular SNP, associated with the NOS1AP gene, appears to account for about 1.5 per cent of the QT interval variation between people - implying that several other genes are involved.

The NOS1AP gene was already known to play an important role in nerve cells, but in the latest study, the JHU scientists showed that it is also active in the left ventricle (lower chamber) of the heart. 'In addition to finding a genetic variant that could be of clinical value for sudden cardiac death, this study demonstrates how valuable large-scale genomics studies can be in detecting novel biological targets', said team leader Aravinda Chakravarti. The scientists hope that eventually, being able to identify people predisposed to abnormal heart rhythms could help save lives, through the prescription of drugs that regulate heartbeat and, in some cases, using implantable electrical devices.