Infections Associated with Cardiovascular Implantable Electronic Devices: Mortality and Costs

Therapy involving cardiovascular implantable electronic devices (CIEDs) has been shown to reduce morbidity and mortality, but the benefits can be offset by complications including infection. Researchers have published data showing that the rate of CIED infection is increasing faster than the rate of CIED implantation, but to date there have been only limited data on the risk-adjusted mortality and cost associated with CIED infections or a possible association of those outcomes to different types of CIEDs.

Researchers recently conducted a retrospective analysis to define the risk-adjusted mortality and cost specific to type of CIED as well as the cost allocation associated with hospitalizations for CIED generator implantation, replacement, or revision with infection. They reported results of the analysis online in Archives of Internal Medicine [doi:10.1001/archinternmed.2011.441]. The primary study measures were risk-adjusted total and incremental admission mortality, long-term mortality, admission length of stay (LOS), and admission cost associated with infection.

The researchers utilized data for the 2007 calendar year for inpatient admissions from the 100% Medicare Standard Analytic File Limited Data Set version for inpatient admissions for the 2007 calendar year; the analysis identified all relevant study admissions using the corresponding International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) procedure codes for pacemakers (PMs) and implantable cardioverter/defibrillators (ICDs), cardiac resynchronization therapy devices with defibrillator (CRT-D), or cardiac resynchronization therapy devices without defibrillator (CRT-P). The analysis excluded admissions that were limited to electrode implantation, replacement, or revision; admissions that included other major cardiac procedures were also excluded to avoid counting costs for major procedures unrelated to CIED infection.

There were 200,219 admissions in the final study cohort: 65.6% were PMs (n=131,342); 18.8% were ICDs (n=37,642); 13.6% were CRT-D (n=27,261); and 2.0% were CRT-P (n=3974). Overall, 2.9% of the admissions (n=5817) included infection; >90% of infections were identified with ICD-9-CM codes corresponding to infection with a cardiac (33%) or vascular (2%) device, septicemia (37%), endocarditis (8%), bacteremia (7%), and shock (3%). Following adjustment for demographics and comorbidities, infection was associated with a significant increase in admission mortality rate (rate ratios, 4.8-7.7; standardized rates, 4.6%-11.3%; P<.001) and long-term mortality (rate ratios, 1.6-2.1; standardized rates, 26.5%-35.1%; P<.001), depending on the type of CIED. Approximately half of the incremental long-term mortality occurred after discharge.

For all types of CIEDs, the risk-adjusted LOS mean ratio (with infection/without infection) remained greater than unity (2.5- to 4.0-fold; all P<.001). However, compared with ICDs and CRT-D, the LOS mean ratio was significantly smaller for PMs. The standardized adjusted total and incremental LOS with infection were 15.5 to 24.3 days and 9.4 to 18.2 days, respectively. Depending on CIED type, standardized adjusted incremental and total admission costs with infection were $14,360 to $16,498 and $28,676 to $53,349, respectively. Intensive care and pharmacy accounted for more than half of the total incremental cost with infection for all CIED types; the largest incremental cost with infection was for intensive care, accounting for 41% to 50% of the difference.

Limitations cited by the authors included using ICD-9-CM codes for identification of cardiac or vascular device infection, the inability of the study to include CIED infections for which reimplantation was not performed or was performed during another encounter, the possibility that costs may have been underestimated, and the possible underestimation of the incremental admission mortality and cost with infection. In summary, the researchers said, “infection associated with CIED procedures resulted in substantial incremental admission mortality and long-term mortality that varied with the CIED type and occurred, in part, after discharge. Almost half of the incremental cost was for intensive care.”