Posted on 05/14/2012

BUFFALO, NY--Research by University of Buffalo (UB) cardiologists suggests that imaging for loss of nerve function in the heart may help identify patients who are at high risk of sudden cardiac arrest and therefore most likely to benefit from an implantable cardiac defibrillator (ICD). ICDs are used to prevent sudden cardiac arrest in patients with advanced heart disease.

“Since many patients who suffer a cardiac arrest do not have severely depressed heart function, PET (Positron Emission Tomography) imaging may be able to identify high-risk individuals who could be considered candidates for an ICD,” says John M. Canty Jr., MD, Albert and Elizabeth Rekate Professor of Medicine, and the study’s principal investigator.

Largest Ever PET Study on Sudden Cardiac Arrest

“Since many patients who suffer a cardiac arrest do not have severely depressed heart function, PET imaging may be able to identify high-risk individuals who could be considered candidates for an ICD,” said Canty.

The UB PAREPET study, or Prediction of Arrhythmic Events with Positron Emission Tomography, is the largest PET imaging study ever done on sudden cardiac arrest.

UB researchers used PET imaging to determine how much sympathetic nerve damage or death occurred in a patient’s heart due to inadequate blood flow, a condition known as denervated myocardium.

This was accomplished by imaging the heart’s ability to take up a radioactive tracer of norepinephrine, the neurotransmitter released from the heart’s neurons.

Linking Denervated Myocardium with High Risk

“The principal question we posed with this study was whether the amount of denervated myocardium could predict sudden cardiac arrest,” explains James A. Fallavollita, MD, professor of medicine and lead author on the study. “We found that when at least 38 percent of the heart was denervated, there was a significant increase in the risk of sudden cardiac arrest.”

Canty, who also serves as chief of cardiovascular medicine at UB, adds: “Ultimately, we wanted to develop an approach that could tackle the problem of identifying a larger portion of the patients with coronary artery disease who are at risk of developing sudden cardiac arrest.”

Currently, the main criterion for determining who gets an ICD is a measurement of heart function called the ejection fraction, which is the percentage of blood pumped by the heart with each beat.

Individuals with an ejection fraction of 35 percent or less are considered candidates for ICDs because they have a significant risk of sudden cardiac arrest.

A Clear Example of Translational Medicine

Funded by the National Institutes of Health, PAREPET involved 204 patients from Western New York with advanced heart disease.

Findings from the study were reported on May 10 at the Heart Rhythm Society’s 33rd Annual Scientific Sessions in Boston.

“This research is a very clear example of translational medicine, with a project being taken from bench-to-bedside by the same investigative team,” says Canty.

“In our preclinical research, we studied factors that lead to sudden cardiac arrest in animals, which led directly to the human study. This important finding may ultimately impact the care of patients with heart disease.”

SOURCE: University of Buffalo