Combination of imaging tests identifies people who would most benefit from implantable cardioverter-defibrillators

The combination of single photon emission computed tomography and echocardiography can help identify patients who will benefit most from an implanted cardioverter-defibrillator, according to an article in the October 7th rapid access issue of Circulation.

Dutch researchers evaluated 153 patients who had survived an episode of sudden cardiac arrest. All patients had coronary disease. Single photon emission computed tomography was used to determine the extent of myocardial scarring and adequacy of coronary perfusion. Either tomography or echocardiography was used to evaluate left ventricular ejection fraction. Selected patients received a revascularization procedure. Of the 153 patients, 110 (72 percent) received an implantable device.

During the 3-year follow-up, 15 patients died. Of these deaths, 11 were heart-related (1 sudden death and 10 due to progressive heart failure). Recurrent ventricular arrhythmias occurred in 42 patients, 36 of whom had an implanted device; 8 of the 42 patients died, and in 7 of those cases, the patient died following a recurrent arrhythmia.

Analysis showed that more extensive scarring and more severely reduced ejection fraction were the only significant predictors of increased risk. Of the patients who survived without recurrence of arrhythmias, 63 percent had extensive scarring compared with 88 percent of the patients who died or had recurrent arrhythmias. Recurrence-free survivors had a median ejection fraction of 35 percent compared with 30 percent for patients who died or had recurrent ventricular arrhythmias. A revascularization procedure significantly improved the likelihood of survival.

“Patients with extensive scar tissue and left ventricular ejection fraction less than or equal to 30 percent are at high risk for [arrhythmia] recurrences, and [implantable cardioverter-defibrillator] implantation may be preferred in these patients,” said coauthor Alida E. Borger van der Burg, M.D.

“This [evaluation] is very important because it can help guide patient management and might serve to some extent as a gatekeeper for the use of implantable cardioverter-defibrillators,” said Jeroen J. Bax, M.D., lead author of the study.

Scar tissue from previous myocardial infarction increases the risk of sudden death and might be one factor that best identifies patients who are most likely to benefit from an implanted device. Bax said, “More scar tissue reflects more severe damage in the heart, and frequently patients with more scar tissue have suffered more than one heart attack. Left ventricular ejection fraction also reflects the extent of scar tissue, so that the more scar tissue that is present, the more severe the left ventricular dysfunction is.”

The investigators recommend a specific approach to evaluating patients who survive sudden cardiac arrest that includes evaluation by echocardiography, tomographic imaging during rest and exercise, and cardiac catheterization to evaluate the coronary arteries for blockages and other abnormalities. Revascularization procedures should be performed in patients who meet eligibility criteria for the procedure.

Patients who have arrhythmias that can be induced by electronic stimulation probably should receive implantable cardioverter-defibrillators. If a patient has extensive scar tissue and a low ejection fraction, a device might be indicated even in the absence of inducible arrhythmias.





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