SAN FRANCISCO, California Electrocardiogram (ECG) parameters and QRS durations (ventricular activity shown in an electrocardiogram) are not specific enough to either include or exclude patients to receive implantable cardioverter defibrillator (ICD) therapy, according to a new sub-study analysis of the Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT) presented at the Heart Rhythm Society's (HRS; Natick, Massachusetts) 25th annual scientific sessions.

The Centers for Medicare & Medicaid Services (CMS; Baltimore, Maryland) has considered QRS duration as a key factor of its coverage criteria for Medicare and Medicaid beneficiaries.

"These findings have important implications for CMS to consider as they reevaluate coverage for ICD therapy," said Michael Cain, MD, president of the Heart Rhythm Society. "QRS duration may no longer be an appropriate indicator of who should be considered a candidate to receive these potentially lifesaving devices."

The SCD-HeFT study, a 2,521-patient trial begun in 1997 that was sponsored by the National Institutes of Health (NIH; Bethesda, Maryland), divided heart failure patients into three groups, all three of which received conventional drug therapy. One was a control group that received conventional drugs. Another group received conventional drugs plus an anti-arrhythmia drug and a third group received conventional drugs plus an ICD. The goal of the study was a 25% drop in mortality from all causes for the groups with ICDs and anti-arrhythmia medication.

At the formal presentation of the trial's results at the American College of Cardiology (ACC; Bethesda, Maryland) scientific session in New Orleans, Louisiana, this past March, researchers presented findings that ICDs lowered the risk of sudden cardiac death by 23% over the length of the five-year study compared to a placebo and, surprisingly, proved better than the widely used anti-arrhythmia drug amiodarone, beating the main goal of the trial. The SCD-HeFT study also found QRS width to be subjective to interpretation bias depending upon where the cut is made. The hazard ratio difference between narrow and wide QRS was found to not support excluding certain subgroups from ICD therapy.

"Within the SCD-HeFT population, we did not find that any particular ECG measure or wide QRS provided specific enough subgroup risk categorization to select or exclude patients for ICD therapy," said Jeanne Poole, MD, presenter for the SCD-HeFT trial and associate professor of medicine and director, Arrhythmia Service and Electrophysiology Laboratory at the University of Washington Medical Center (Seattle, Washington).

Poole examined a sub-group of ECG parameters and QRS durations from SCD-HeFT, the largest sudden death trial, in April and May. At the ACC meeting in March, SCD-HeFT showed that patients who received ICDs had a three-year mortality rate of 17.1% compared to those who received a placebo (22.4%) and those who received amiodarone (24%).