About a third of referring physicians who responded to a survey about implantable cardioverter-defibrillators (ICDs) provided answers that were out of step with national guidelines in terms of patient selection criteria, according to a study published online Feb. 6 in Heart Rhythm. General cardiologists were more likely than other physicians to answer compatibly with guidelines, but even a portion of the cardiologists responded counter to the expert panel’s patient selection criteria.

The American College of Cardiology, the American Heart Association and the Heart Rhythm Society published evidence-based guidelines in 2008 to help physicians identify patients who would benefit from primary prevention ICDs. University of California, San Francisco researchers Jorge M. Castellanos, MD, of the department of medicine, and Gregory M. Marcus, MD, of the electrophysiology section in the division of cardiology, teamed up with colleagues to investigate the role of referring physicians in what they termed “discordance” with these guidelines.

Using the American Medical Association Masterfile, they mailed a 34-item survey to a national sample of 3,000 physicians between June 3, 2009, and Dec. 11, 2009. They selected three physician specialties that may refer at-risk patients for ICDs: family medicine, internal medicine and general cardiology. The masterfile included all physicians who graduated from U.S. medical schools. The researchers achieved a response rate of 64 percent.

Overall, about a third of the sample provided answers that did not align with national guidelines on patient selection for primary prevention ICDs. Internists and family physicians reported that they managed a median 10 percent of patients with a low left ventricular ejection fraction (LVEF) without referring the patients to a subspecialist. The researchers found that the primary care physicians who assume this care also provided discordant answers about 20 percent to 30 percent of the time.

Some 28 percent of the respondents indicated that they do not refer patients to a subspecialist specifically to be considered for a primary prevention ICD. Among those most likely to refer were cardiologists, physicians with patients older than 60 years and physicians who refer patients to an electrophysiologist. Nonetheless, 7 percent of general cardiologists responded that they do not refer patients for ICDs.

Compared with other physicians, general cardiologists’ answers were more often in line with the guidelines, but:

• Four percent answered that an ICD is never indicated in the absence of malignant arrhythmia;
• Twenty-five percent viewed an LVEF of greater than 40 percent as the appropriate cutoff for a primary prevention ICD; and
• Nineteen percent reported that they referred patients for an ICD within 40 days of an MI.

Even for patients whom physicians think primary prevention ICD is indicated, they responded that they refer a median 85 percent. Reasons for not referring included risk of device infection, painful ICD shocks and patient preference.

“Our survey results suggest that failure to adhere to ICD guidelines is at least in part due to a lack of awareness or failure to understand the guidelines,” Castellanos and colleagues wrote. “Despite clear evidence and expert consensus to the contrary, 15 percent did not believed an ICD was indicated unless there was evidence of ventricular arrhythmia. And, for those that would consider the EF [ejection fraction], more than one third believed an EF of greater than 40 percent would warrant consideration of primary prevention ICD implantation.”

The researchers warned that their study may not be sufficiently powered for measuring independent predictors within specialty groups, and they noted that they could not discern between discordance due to lack of knowledge or informed opinion. They suggested their findings may help identify barriers to the adherence of the guidelines, and provide targets for educational and other opportunities that may lead to improved adherence.