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Sex Differences in the Use of ICDs for Prevention of Sudden Cardiac Death, 1999-2004: 

Sex Differences in the Use of ICDs for Prevention of Sudden Cardiac Death, 1999-2004 Lesley H. Curtis, PhD Assistant Research Professor Center for Clinical and Genetic Economics Duke Clinical Research Institute

Acknowledgements: 

Acknowledgements Collaborators Sana M. Al-Khatib, MD Alisa M. Shea, MPH Bradley G. Hammill, MS Adrian F. Hernandez, MD Kevin A. Schulman, MD Funding National Institute on Aging (1RO1AB026038-01A1)

Sudden Cardiac Death is a Leading Cause of Mortality: 

Sudden Cardiac Death is a Leading Cause of Mortality 450,000 deaths annually Risk increases with age Higher in men than in women Majority of events occur in the absence of overt heart disease

Prevention of Sudden Cardiac Death: 

Prevention of Sudden Cardiac Death Prevention of a first life-threatening arrhythmia (primary) Prevention of an additional life-threatening arrhythmia in survivors of sudden cardiac death (secondary)

Implantable Cardioverter Defibrillators Can Prevent Sudden Cardiac Death: 

Implantable Cardioverter Defibrillators Can Prevent Sudden Cardiac Death Primary prevention in patients with significant left ventricular dysfunction Multicenter Automatic Defibrillator Implantation Trial (MADIT) I1 MADIT II2 Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT) 3 1Moss AJ et al. N Engl J Med 1996;335:1933-40. 2Moss AJ et al. N Engl J Med 2002;346:877-83. 3Bardy GH et al. N Engl J Med 2005;352:225-37.

Implantable Cardioverter Defibrillators Can Prevent Sudden Cardiac Death: 

Implantable Cardioverter Defibrillators Can Prevent Sudden Cardiac Death Secondary prevention in patients who survive a life-threatening ventricular arrhythmia Antiarrhythmics Versus Implantable Defibrillators (AVID) trial1 Efficacy further established over the past decade2 1The Antiarrhythmics Versus Implantable Defibrillators (AVID) Investigators. N Engl J Med 1997;337:1576-83. 2Ezekowitz JA et al. Ann Intern Med 2003;138:445-52.

ICDs in Medicare Beneficiaries: 

ICDs in Medicare Beneficiaries Coverage has expanded with accumulating evidence, but many eligible beneficiaries do not receive them. Previous studies have documented important differences by sex and race, but they predate recent expansions in coverage

Study Objective: 

Study Objective To examine sex differences in the use of ICDs for primary and secondary prevention of sudden cardiac death from 1999-2004

Slide9: 

Data Medicare inpatient, outpatient, and carrier 5% standard analytic files and the corresponding denominator files Research-identifiable files from 1991 through 2004 Persons living in the U.S. and aged 65 or older on date of cohort entry. Claims filed during periods of fee-for-service coverage

Identifying the Primary Prevention Cohort: 

Identifying the Primary Prevention Cohort Diagnosis of acute MI (ICD-9-CM 412 or 410.xx) and either heart failure (428) or cardiomyopathy (425.4) on an inpatient, outpatient, and/or carrier claim. Date of the second qualifying diagnosis defined the date of cohort entry which was limited to 1999-2004. Excluded patients with a prior diagnosis of cardiac arrest (427.5) or ventricular tachycardia (427.1, 427.41, or 427.42). If subsequently diagnosed with cardiac arrest or ventricular tachycardia, patient progressed to the secondary prevention cohort.

Identifying the Secondary Prevention Cohort : 

Identifying the Secondary Prevention Cohort Diagnosis of cardiac arrest (427.5) or ventricular tachycardia (427.1, 427.41, 427.42) on a single inpatient, outpatient, or carrier claim between 1999 and 2004. Excluded patients with a diagnosis of cardiac arrest or ventricular tachycardia before 1999.

Statistical Analysis: 

Statistical Analysis Used the cumulative incidence function1 to estimate the proportion of patients in each cohort who received an ICD. Censoring occurred when patients switched to managed care or reached the end of the study. Competing risks of mortality (both cohorts) and progression to the secondary prevention cohort (primary only). 1Gray RJ. Ann Stat 1998;16:1141-54.

Statistical Analysis: 

Statistical Analysis Unadjusted relationships between study variables and number of days from cohort entry to ICD placement estimated using Cox model. Estimated independent effect of sex on receipt of ICD using a multivariable Cox model Model included age, race/ethnicity, geographic region, year of cohort entry, and comorbid conditions using coding algorithms described by Birman-Deych1 and Quan2. 1Birman-Deych E et al. Med Care 2005;43:480-5. 2Quan et al. Med Care 2005;43:1130-9.

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Sensitivity Analyses Stratified by age (andlt;75 years vs. ≥ 75 years) Restricted secondary prevention cohort to beneficiaries with a prior cardiac arrest

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Baseline Characteristics

Slide16: 

Cumulative Rates of ICD Use in the Primary Prevention Cohort

Slide17: 

Cumulative Rates of ICD Use in the Secondary Prevention Cohort

Slide18: 

Hazard Ratios in Multivariable Analyses for Men, Stratified by Cohort and Age

Discussion: 

Discussion Why are there significant sex differences in the use of ICDs for the prevention of SCD? Age? Clinical characteristics? Perception of differential benefit given participation of women in landmark clinical trials? Patient preferences?

Limitations: 

Limitations Administrative data lack important clinical information such as data on ventricular function, the nature of the ventricular tachycardia, and the severity of comorbid illnesses. Does not include ICD implantations that occurred during periods of managed-care coverage. ICD implants before age 65 not included in the analysis.

Conclusion: 

Conclusion There were significant sex differences in the use of ICD therapy from 1999 to 2004. Sex differences in the use of ICDs have not lessened over time. The need for an improved understanding of sex differences in patterns of care is urgent.