For patients who are at the highest risk of sudden cardiac arrest, this is exciting news, as this research may give cardiologists an advanced screening tool to help those in the high-risk category and those most likely to benefit from receiving an implantable cardiac defibrillator (ICD).
ICDs are mainly 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 degradation of nerve function in the heart may identify those patients at greatest risk of developing a life-threatening heart rhythm.
Using Positron Emission Tomography (PET), in the largest PET imaging study ever done on sudden cardiac arrest, researchers were able to measure the amount of nerve damage within the muscular tissue of the heart.
PET imaging is also able to show where nerves have died or become damaged due to inadequate blood flow.
“The principal question we posed with this study was whether the amount of nerve damage in the heart could predict sudden cardiac arrest,” says James A. Fallavollita, author on the study. “We found that when at least 38 percent of the heart was showed signs of nerve damage, there was a significant increase in the risk of sudden cardiac arrest.”
At this time, to determine whether an ICD is needed, doctors take a measurement of heart function called the ejection fraction; the percentage of blood pumped by the heart with each beat. An ejection fraction of 35 percent or less is a strong indicator of sudden cardiac arrest risk; these patients usually require an ICD.
This research is a prime example of translational medicine (the emerging field which focuses on using what is learned in pre-clinical studies to do smarter things in the clinic). In this case, the pre-clinical studies demonstrated that the risk of developing ventricular fibrillation (a deadly heart rhythm) was related to regional nerve damage.
“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,” explains John M. Canty, a principal investigator of the research. “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.”