Images show risk of sudden heart failure

ICDs are used to prevent sudden cardiac arrest in patients with advanced heart disease, but many patients’ devices are never triggered. New research suggests that imaging the loss of nerve function in the heart may identify those patients at greatest risk of developing a life-threatening arrhythmia. The findings from the largest PET imaging study ever done on sudden cardiac arrest were reported this month at the Heart Rhythm Society’s 33rd Annual Scientific Sessions in Boston. University at Buffalo researchers used PET imaging to quantify the patients’ amount of denervated myocardium, where sympathetic nerves in the heart have died or become damaged due to inadequate blood flow. 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, using the radiopharmaceutical 11C-hydroxyephedrine. “The principal question we posed with this study was whether the amount of denervated myocardium could predict sudden cardiac arrest,” says James A. Fallavollita, professor of medicine and the study’s lead author. “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.” “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,” says John Canty Jr., the study’s principal investigator and a professor of medicine. “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, in the future, could be considered candidates for an ICD.” Currently, the main criteria 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. Funded by the National Institutes of Health, the study involved 204 patients from Western New York with advanced heart disease.