In this analysis of over 30,000 Medicare beneficiaries undergoing new cardioverter-defibrillator implantation in fiscal year 2003, we found that 10.8% experienced one or more complications before hospital discharge. On average, the occurrence of any complication increased adjusted hospital costs by ~$7,250, an increase of nearly 20% over an uncomplicated admission. If 100,000 cardioverter-defibrillators were implanted this year with similar results, the incremental cost of these complications would exceed $78 million.
Reported complication rates from cardioverter-defibrillator implantation may depend on the type of device implanted, and may also vary with definitions and the time frame of patient observation (19
). Multicenter studies of early-generation transvenous ICDs reported surgical complication rates of 12% or higher (14
). Common issues were lead dislodgement and wound or pocket problems. More recent ICD trials have reported lower acute complication rates, ranging from 1% to 8% (1
), with the higher estimate including inappropriate shocks before hospital discharge (13
). These recent trial data are concordant with survey data and single-center reports that estimate complication rates after pacemaker implantation of 4% to 7% (12
Although direct comparisons are difficult, the overall frequency of complications in our study appears to be higher than that reported in recent clinical trials. Medicare patients who receive ICDs may, on average, be older and may have a higher prevalence of comorbid disease than typical clinical trial patients. A recent study also documented a relationship between low implant volumes and increased complication rates and found that the majority of implanting physicians in the U.S. had relatively low volumes of cases submitted to Medicare (20
). Thus, higher complication rates may, to some extent, be expected in the Medicare population based on both patient and physician factors.
We did not find a difference in overall complication rates between ICD and CRT-D implants. In contrast, recent trials of CRT-D devices have reported higher (10% to 28%) frequencies of acute complications than those observed in recent ICD trials involving standard single and dual-chamber devices (21
). This could be because only very skilled operators were implanting CRT devices in 2003, or because some CRT-D complications, such as lead dislodgement, may occur after the initial hospital discharge and may therefore have been underestimated by our methods.
The CMS has established a national ICD registry, in part to evaluate whether the costs and outcomes of cardioverter-defibrillator implantation differ in general practice compared with clinical trials (23
). The present data support the rationale for this registry, and can serve as both benchmarks (e.g., for new implanting hospitals or physicians) and as targets for quality improvement. Previous studies indicate that several common complications of cardioverter-defibrillator implantation may be preventable (19
). Our data suggest that dedicated quality improvement efforts could substantially enhance patient safety, and that, in light of their economic impact, successful initiatives to reduce procedural complications could pay for themselves.
Our data may also have implications for cost-effectiveness modeling. Trial-based analyses are able to directly incorporate observed complication costs in their calculations, but complication rates seen in the clinical trial setting are probably not representative of general practice. Model-based analyses, on the other hand, have either incorporated limited data on procedural complications (27
) or have used old data for model inputs (28
). In both scenarios, the true costs of procedural complications may have been underestimated.
Economic analyses of clinical trials also tend to focus on cardioverter-defibrillator implantation as an isolated procedure. This perspective would appear to grossly underestimate the true costs of providing care for the kind of patients in whom cardioverter-defibrillators are currently being implanted. Our data demonstrate that cardioverter-defibrillator implantation is very often performed as one of multiple invasive cardiac procedures during a single hospital admission. Even though we excluded patients with additional cardiac procedures from our analysis, the average hospital costs for our study cohort ($42,000, not including physician fees) were much higher than those used in contemporary ICD cost-effectiveness studies. The costs for hospitalizations in which cardioverter-defibrillators are implanted in addition to other cardiac procedures stand to be substantially higher.
Several important limitations of our study must be acknowledged. Our analyses rely on administrative data, which has well-recognized strengths and weaknesses. Both complications and comorbid illnesses could have been underreported. We made reasonable attempts to avoid confounding explanations for the complications that we defined, but cannot be certain that all of the complications we report were related to the implant procedures. Cardioverter-defibrillator implants performed on an outpatient basis were not included. Potentially important clinical details were also unavailable; for example, the diagnostic code for “mechanical complications” (996.0), is non-specific, making clinical interpretation of its frequency difficult.
Our analysis was also limited to the hospitalizations during which cardioverter-defibrillators were implanted. Our estimates therefore represent a lower bound on the total frequency of cardioverter-defibrillator implant complications and their cost, which would also include physician fees for inpatient care, outpatient care, and re-hospitalizations. Some implant-related complications—in one pacemaker trial, as many as 30%—do not occur or are not recognized until after the initial hospitalization (20
Finally, we estimated costs on the basis of hospital charges and whole-hospital cost to charge ratios. This method may be inaccurate for high-expense items like ICDs. Although hospital costs can be calculated more precisely using alternative methods, such methods are not practical to apply to a large national sample of hospitals.