According to a new study from the Duke Clinical Research Institute, Implantable Cardioverter Defibrillators (ICDs) are associated with improved survival among heart failure patients whose left ventricles only pump 30 to 35 percent of blood out of the heart with each contraction.
The findings, published in the June 4 issue of the Journal of the American Medical Association, support existing recommendations to implant ICDs in patients with a left ventricular ejection fraction (LVEF) of 35 percent or lower. The guidelines recommend using ICDs to prevent sudden cardiac death in select patients with a LVEF of 35 percent or less (The American College of Cardiology defines a normal heart’s LVEF as 50 to 70 percent, while a measurement below 50 percent may be a sign of dysfunction or heart failure).
While one might have thought this association would have been proven before it became a recommendation, that was seemingly not the case. Indeed one of the researchers stated that “Until now, the association between the ICD and improved outcomes in patients with a LVEF of 30 to 35 percent was largely implied.”
The study took the form of a retrospective data review, drilling into the U.S. National Cardiovascular Data Registry. The researchers compared individuals in the registry with heart failure patients in the Get With the Guidelines-Heart Failure database who also had a LVEF of 30 to 35 percent but did not have ICDs. They compared all-cause mortality among those with and without ICDs, looking at a total of 3,120 patients with a LVEF of 30 to 35 percent. The analysis was repeated in 4,578 patients with a LVEF of less than 30 percent.
So to the study results, the researchers finding that ICDs were associated with increased survival among heart failure patients with a LVEF of less than 30 percent, with three-year mortality rates dropping from 57.6 percent to 45 percent with ICD use.
The interesting bit comes from those heart failure patients with a LVEF of 30 to 35 percent whose survival was also significantly improved in those with ICDs versus those without ICDs. Three-year mortality rates dropped from 55 percent to 51.4 percent when an ICD was implanted.
“Our findings fill an important gap in knowledge, as most randomized clinical trials of ICDs include heart failure patients with a median LVEF of well below 30 percent,” said Sana Al-Khatib, M.D., MHS, the study’s lead investigator and associate professor of medicine at Duke.
“Given that a large number ICDs are implanted in patients with a LVEF between 30 to 35 percent, understanding outcomes in such patients is important.”