TORONTO — The rate at which eligible, appropriate patients with a low left-ventricular ejection fraction miss out on getting an implantable cardioverter defibrillator might be lower than most people think.
After accounting for ineligible patients and those who refused the device, the “true miss” rate, or rate of patients with ejection fractions of 35% or less who failed to get an implantable cardioverter defibrillator (ICD), was 7% in a randomly selected sample of 228 patients who underwent echocardiography scanning during 2005–2007 at Jefferson Medical College, Philadelphia.
This proportion was much smaller than what many experts have estimated. The ICD implant rate in large observational studies has usually been reported as about 25%–40% in patients with left ventricular ejection fractions of 35% or less, Dr. Shaw Natan said while presenting a poster at the 14th World Congress on Heart Disease. At Jefferson, the implant rate in the 228 patients who were the focus of this study was 42%. These rates suggest that more than half of patients with severe left ventricular dysfunction do not get an ICD. That may be true, but assessing each patient individually showed that in most cases there was a good reason for the omission.
“There are many reasons why a patient may not be a candidate” for an ICD, said Dr. Natan, a cardiologist formerly at Jefferson and now at St. Elizabeth's Medical Center in Boston. “You can't simply say that if a patient with an ejection fraction of 35% or less does not get an ICD, it's a miss,” he said in an interview at the congress, sponsored by the International Academy of Cardiology.
The 228 patients in the sample had an average age of 66 (range 29–96), and 68% were men. Their average left ventricular ejection fraction was 21%. Slightly more than half the patients had an ischemic etiology for their heart failure, 26% had a nonischemic etiology, and the remainder had an unknown etiology.
Among the 132 patients in the sample who did not get an ICD, 89 (39% of the total group) were ineligible. This group included 34 who had an inadequate trial of medical treatment or revascularization, 19 who died, 17 who had dementia or a life expectancy of less than 1 year, 10 who were lost to follow-up, and 9 with other reasons.
Of the remaining 43 patients who did not have a contraindication for an ICD, 27 declined the device when it was offered. This left 16 patients (7% of the total number of patients evaluated) who were true misses for an ICD: They had no contraindications and were willing to receive treatment.
The 7% rate of true missed cases was similar for both men and women, and for both whites and African American patients, Dr. Natan said. The rate of missed cases was higher among the patients who had been referred for their echo exam by a noncardiology service (15% miss rate) than among those who had been referred by the cardiology service (5% miss rate). About 80% of the patients had been referred through the cardiology service.