Cardiac imaging can be 'gatekeeper' for implantable heart-shocker

American Heart Association
Tuesday, 7 October 2003

High-tech images of the heart and its surrounding blood flow can help identify patients who will benefit most from implanted electronic devices that treat heart rhythm disturbances, according to a report in today's rapid access issue of Circulation: Journal of the American Heart Association.

Researchers used single photon emission computed tomography (SPECT) and echocardiography (ultrasound images of the heart) to assess peoples' hearts in a three-year study of patients who survived life-threatening ventricular arrhythmias. They found that patients with the most scarring on the heart and the most reduction in left ventricular ejection fraction (LVEF) were at the highest risk for recurrent arrhythmias.

They say that identifying high-risk patients with this imaging technique could lead to more efficient use of life-saving but expensive implantable cardioverter-defibrillators (ICDs).

"Patients with extensive scar tissue and LVEF less than or equal to 30 percent are at high risk for [arrhythmia] recurrences, and ICD implantation may be preferred in these patients," said co-author Alida E. Borger van der Burg, M.D., and colleagues at two Dutch medical centers.

"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 ICDs," said Jeroen J. Bax, M.D., a cardiologist at Leiden University in Leiden, the Netherlands, and co-author of the report.

Survivors of cardiac arrest related to ventricular arrhythmias have a high risk of recurrent arrhythmia and cardiac arrest. Most of the affected patients had coronary disease, but the exact cause of ventricular arrhythmias in these patients is unclear, the investigators said.

Treatment of coronary disease with bypass surgery or catheter-based procedures that restore blood flow through arteries can reduce the risk of recurrent arrhythmias, but a substantial number of patients still die from cardiac arrest. ICDs have proven effective in preventing recurrent arrhythmias and cardiac arrest, but the best candidates for the devices have yet to be determined.

Scar tissue from a heart attack increases the risk of sudden death and might be one factor that identifies patients who are most likely to benefit from an ICD.

"More scar tissue reflects more severe damage in the heart, and frequently patients with more scar tissue have suffered more than one heart attack," Bax said. "LVEF 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 researchers evaluated 153 patients who had survived an episode of sudden cardiac arrest. All the patients had coronary disease.

The investigators used SPECT to determine the extent of scarring and evaluate blood flow (perfusion) to the heart. They used echocardiography and/or SPECT to evaluate LVEF. Selected patients had revascularization procedures when the evaluations identified areas of viable (unscarred) heart tissue that were receiving reduced blood flow. Most of the patients (72 percent) received an ICD.

During follow up for three years, 15 patients died. Eleven of the deaths were heart-related (one sudden death and 10 due to progressive heart failure). Recurrent ventricular arrhythmias occurred in 42 patients, 36 of whom had ICDs implanted. Eight of the 42 patients died, and in seven of the eight cases, the patient died following a recurrent arrhythmia.

The analysis showed that more extensive scarring and more severely reduced LVEF were the only significant predictors of increased risk. Of the patients who survived without recurrence of arrhythmias, 63 percent had extensive scarring, compared to 88 percent of the patients who died or had recurrent arrhythmias. Recurrence-free survivors had a median LVEF of 35 percent, compared to 30 percent for patients who died or had recurrent ventricular arrhythmias.

Undergoing a procedure such as angioplasty or stenting to improve blood flow to the heart significantly improved the odds of survival.

The investigators recommend a specific approach to evaluating patients who survive sudden cardiac arrest that includes evaluation by echocardiography, SPECT imaging during rest and exercise, and cardiac catheterization to evaluate the heart and blood vessels for blockages and other abnormalities. Procedures to improve blood flow to the heart (such as angioplasty or stenting) should be performed in patients who have blockages or who have areas of viable heart tissue that would benefit from improved blood flow.

Patients who have arrhythmias that can be induced by electronic stimulation probably should receive ICDs. If a patient has extensive scar tissue and a low LVEF, an ICD might be indicated even in the absence of inducible arrhythmias.

Co-authors are Ernest J. J. Pauwels, M.D.; Ernst E. Van der Wall, M.D.; Martin J. Schalij, M.D.; and Eric Boersma, Ph.D.

For more information, or to contact American Heart Association, see their website at: www.americanheart.org