The mortality analysis of primary prevention patients receiving a
cardiac resynchronization defibrillator (CRT-D) or implantable
cardioverter defibrillator (ICD) according to guideline indications in
the Improve SCA Study.
Background: Despite a proven mortality benefit in primary prevention
(PP) patients, the utilization of implantable
cardioverter-defibrillators (ICD) and cardiac resynchronization
therapy-defibrillators (CRT-D) remains low in many geographies. Purpose:
The objective of this analysis was to examine the mortality benefit in
PP patients by guideline-indicated device type: implantable
cardioverter-defibrillator (ICD) and cardiac resynchronization
therapy-defibrillator (CRT-D). Methods: Improve SCA was a prospective,
non-randomized, non-blinded multicenter trial that enrolled patients
from regions where ICD utilization is low. PP patient’s CRT-D or ICD
eligibility was based upon the 2008 ACC/AHA/HRS and 2006 ESC guidelines.
Mortality was assessed according to guideline-indicated device type
comparing implanted and non-implanted patients. Cox proportional hazards
methods were used, adjusting for known factors affecting mortality risk.
Results: Among 2,618 PP patients followed for a mean of 20.8 ± 10.8
months, 1,073 were indicated for a CRT-D, and 1,545 were indicated for
an ICD. PP CRT-D-indicated patients who received CRT-D therapy had a
58% risk reduction in mortality compared to those without implant
(adjusted HR 0.42, 95% CI: 0.28-0.61, P<0.0001). PP patients
with an ICD indication had a 43% risk reduction in mortality with an
ICD implant compared with no implant (adjusted HR 0.57, 95% CI:
0.41-0.81, P=0.002). Conclusions: This analysis confirms the mortality
benefit of adherence to guideline-indicated implantable defibrillation
therapy for PP patients in geographies where ICD therapy was
underutilized. These results affirm that medical practice should follow
clinical guidelines when choosing therapy for PP patients who meet the
respective defibrillator device implant indication.