New Way to Assess Risk of Sudden Cardiac Death Studied

BUFFALO, N.Y. -- Sudden cardiac death accounts for nearly two-thirds of cardiovascular mortality, yet few methods exist to identify precisely those at risk.

A new study being conducted in the University at Buffalo is expected to make it easier for clinicians to predict those at high risk of experiencing this potentially catastrophic condition, which results from disruption of normal heart rhythm, and who would benefit from a life-saving implantable defibrillator.

Mary Adams Carey, Ph.D., assistant professor of in the UB School of Nursing and lead researcher on the study, will investigate the potential of using a 12-lead electrocardiograph (ECG) to identify more precisely patients who will benefit from a defibrillator. An ECG records the pathway of electrical impulses through the heart muscle using electrodes, or leads, attached to the chest, arms, and legs.

"Currently, the primary indicator of a person's risk for SCD and the basis for determining who should be fitted with a defibrillator is the left ventricular ejection fraction," said Carey. The left ventricular ejection fraction, or LVEF, is a measure of how much blood the left ventricle of the heart pumps out with each contraction.

"Since only one in five patients may actually benefit from the device, the cost implications of relying solely on LVEF are tremendous," Carey said. "People with implantable defibrillators suffer from stress, and show high rates of depression, anxiety and anger from living with the devices. It's clear we need new approaches to risk-stratify this patient population more precisely."

Carey's research will involve 250 patients already enrolled in a study headed by John Canty, M.D., Albert & Elizabeth Rekate Chair in Cardiovascular Disease at UB. Canty, who is Cary's mentor, is researching the use of positron emission tomography (PET) scanning as a better indicator of potential SCD than LVEF.

The patients who have had a heart attack with poor left ventricular function will undergo a resting ECG and then wear a 12-lead electrocardiogram digital recorder for 24 hours. The results will provide two measures thought to be predictors of SCD risk: total ischemic burden and T-loop morphology.

Total ischemic burden indicates the burden on the heart caused by insufficient blood flow, while T-loop morphology indicates electrical instability.

Participants will be followed for three years to determine who has experienced a defibrillator discharge, indicating normal rhythm was restored, averting sudden cardiac death, or succumbed to sudden cardiac death.

"Each of the measures could be correlated with an adverse outcome to arrive at a scoring system that, after further testing, could be used to identify a subset of patients at higher risk of SCD," Carey said.

"If effective, it would be an inexpensive risk assessment tool to make sure people who need defibrillators the most receive them, while people not likely to benefit from the devices would not have to go through the stress of living with a defibrillator."

The three-year project is funded by a $404,394 K23 grant from the National Institutes of Health. A K23 grant is a Mentored Patient-Oriented Research Career Development Award for training new clinical investigators. This grant will foster collaboration between the School of Nursing and the Division of Cardiology, Cary said.

The University at Buffalo is a premier research-intensive public university, the largest and most comprehensive campus in the State University of New York.