Scientists at the Victor Chang Cardiac Research Institute, working with colleagues at the Vanderbilt University Medical Center, have developed a world-first, individualized risk prediction tool for people suffering from a type of heart arrhythmia that can cause sudden cardiac arrest.

This is the first time a gene mutation–specific test has been applied to predict the severity of heart disease. It could also benefit patients suffering from other heart arrhythmias and neurological conditions.

Lead author Professor Jamie Vandenberg, Deputy Director of the Victor Chang Cardiac Research Institute, says that the findings, now published in Circulation, would enable patients with one of the most common inherited heart diseases—Long QT syndrome—to discover how severe their condition was.

Professor Vandenberg says, "Genetic testing for inherited heart diseases has been transformative, but there have been limitations in what it can tell you. It might reveal you have the disease, but there has been no way of using this genetic information to determine how high your risk is for suffering a sudden cardiac arrest.

"This will provide patients and their families with answers and better enable clinicians to tailor treatment appropriately."

Long QT Syndrome is a heart rhythm disorder that can cause sudden cardiac death and generally affects people who are otherwise fit and healthy. About 1 in 2,000 Australians will have this condition.

The researchers investigated 533 genetic variants or mutations associated with Long QT syndrome from 1,458 patients. The mutations affect the function of ion channel gene variants.

The team analyzed every mutation and its function using a high-speed electrical test, and a high-throughput automated patch clamp assay.

They revealed which genetic mutations were the most dangerous by comparing these findings against traditional testing methods and using patient records.

They discovered that some genetic mutations reduced the function of the ion channel by up to 90%, resulting in a 13.3-fold greater risk of major cardiac events (arrhythmia, sudden death). A 75% reduction in function was associated with an 8.6-fold greater risk of major cardiac events.

Fellow author Dr. Chai-Ann Ng of the Victor Chang Cardiac Research Institute says, "We have shown that not every diagnosis of Long QT is equal, and the risk of having a sudden cardiac arrest can vary dramatically depending on the exact genetic mutation.

"Our findings will make a huge difference in how these high-risk patients are cared for in the future. We are also actively working on adapting this test to patients affected by other heart arrhythmias and neurological conditions."