Implantable cardioverter defibrillators (ICDs) have been proven effective in reducing mortality in patients with severe systolic heart failure. A recent study used two models—one for heart failure and another for proportional risk—to identify patients less likely to benefit from ICDs.

Lead author Kenneth C. Bilchick, associate professor in cardiovascular division of the UVA Health System, and colleagues published their findings online May 22 in the Journal of the American College of Cardiology.

The team applied the Seattle Heart Failure Model (SHFM) for overall survival and the Seattle Proportional Risk Model (SPRM) for proportional risk of sudden death in a cohort of nearly 100,000 people—10,932 with systolic heart failure and 87,914 with primary prevention non-cardiac resynchronization therapy ICD implants between 2006 and 2009.

“We hypothesized that the SHFM and SPRM scores would identify HF patients who were more likely and less likely to derive survival benefit from an ICD intended for primary prevention of sudden cardiac death,” Bilchick and colleagues wrote.

Patients were divided into four groups to assess the effectiveness of the models: lower SHFM/lower SPRM, lower SHFM/higher SPRM, higher SHFM/lower SPRM, and higher SHFM/higher SPRM.

Patients with a lower predicted mortality (lower SHFM) and a lower predicted proportional risk of sudden death (lower SPRM)— the group with the least survival improvement with ICDs—were projected to minimally benefit with an ICD. These individuals would need to be treated with an ICD for 22.5 years to add 1 year of life.

However, patients with a lower predicted overall mortality (lower SHFM) and a higher SPRM-predicted proportional risk of sudden death—the group with the greatest survival improvement with the ICD—would be projected to add 3.3 years of life from the ICD. These patients would only need to be treated for 4.2 years to add 1 year of life.

“We found that the SPRM and SHFM together provide a useful assessment of overall mortality and expected ICD effectiveness,” wrote Bilchick et al. “The SHFM provides a powerful measure of overall survival, whereas the SPRM provides an effective assessment of how overall survival with the SHFM is modified by ICD implantation.”

The researchers noted the study was limited in its analysis because it was not a randomized clinical trial. Instead, it used patient data from previous trials, as well as registries for the control.

Still, the findings show such predictive tools can help identify those with the most to gain from ICDs.

“Considering the large amount of time and expense presently allocated to patients with ICDs for implantation, post-operative care, and subsequent generator changes, application of these models could more effectively allocate these health care resources and personalize device therapy for the benefit of patients and society,” wrote Bilchick and colleagues.