Gender and outcomes after primary prevention implantable cardioverter-defibrillator implantation: Findings from the National Cardiovascular Data Registry (NCDR)

Abstract

Background: Clinical trials have demonstrated the benefit of implantable cardioverter-defibrillators (ICDs) for the primary prevention of sudden cardiac death in selected high-risk individuals. Because of small numbers of women enrolled in these trials, outcomes for women after hospital discharge have not been well described. We compared procedure-related complications and outcomes after hospital discharge between men and women undergoing single- or dual-chamber ICD implantation for primary prevention.

Methods: In patients 65 years or older with Medicare fee-for-service coverage, we identified 38,912 initial implants (25% women) who received single- or dual-chamber ICDs for primary prevention between January 2006 and December 2009 in the NCDR and evaluated gender differences in outcomes.

Results: Women had greater comorbidity and more advanced heart failure (HF) at the time of ICD implantation than did men. Device-related complications, death at 6 months, all-cause readmissions, and HF readmissions at 6 months were significantly more common in women (7.2% vs 4.8%, 6.5% vs 5.6%, 37.2% vs 31.7%, and 14.0% vs 10.0% respectively; P < .001 for all). Women continued to have higher odds of procedural complications (odds ratio [OR] 1.39, 95% CI 1.26-1.53, P < .001), 6-month all-cause readmission (OR 1.22, 95% CI 1.16-1.28, P < .001), and 6-month HF readmission (OR 1.32, 95% CI 1.23-1.42, P < .001), with a trend toward higher 6-month mortality (OR 1.08, 95% CI 0.98-1.20, P = .123), compared with men, after adjusting for differences in baseline characteristics and device type (single vs dual chamber).

Conclusions: Among older patients receiving ICDs for primary prevention in clinical practice, women experience worse outcomes than do men. Reasons for gender differences in outcomes are poorly understood and require further investigation.

Figure 1

Study sample. There were 105,698 evaluable Medicare patients in the NCDR who underwent initial ICD implantation from 2006 to 2009 after matching with CMS claims data in the corresponding period. After excluding patients with secondary prevention indications, CRT, cardiac arrest, sustained VT, and syncope, 38,912 implant procedures for primary prevention indications were included in the current analysis.

Figure 2

Mortality rate. The Kaplan-Meier curves illustrate the difference in mortality event-free rates, unadjusted (A) and adjusted (B), in men and women within 6 months. Women had higher unadjusted 6-month mortality rates than did men, with a trend toward higher mortality rates after adjusting for baseline differences.

Figure 3

Heart failure rehospitalization rate. The Kaplan-Meier curves illustrate the difference in unadjusted HF hospitalization event-free rates, unadjusted (A) and adjusted (B), in men and women within 6 months. HF rehospitalization rates at 6 months were higher in women than in men.