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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