Published online before print February 9, 2009, doi: 10.1161/CIRCULATIONAHA.108.781138
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(Circulation. 2009;119:952-961.)
© 2009 American Heart Association, Inc.
Health Services and Outcomes Research |
Temporal Changes in Coronary Revascularization Procedures, Outcomes, and Costs in the Bare-Metal Stent and Drug-Eluting Stent Eras
Results From the US Medicare Program
From the Division of Cardiology, University of Connecticut Health Center (J.R.), Farmington, Conn; Cordis Corporation (L.E., L.C.), Warren, NJ; ZD Associates LLC (W.L.-Z.), Perkasie, Pa; and Saint Luke’s Mid America Heart Institute (D.J.C.), Kansas City, Mo.
Correspondence to David J. Cohen, MD, MSc, Saint Luke’s Mid America Heart Institute, 4401 Wornall Rd, Kansas City, MO 64111. E-mail dcohen{at}saint-lukes.org
Received March 19, 2008; accepted November 21, 2008.
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Abstract |
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Background— Although drug-eluting stents have been shown to be cost-effective compared with bare-metal stents for select clinical trial patients, whether these findings apply to the general population is unknown.
Methods and Results— We used data from the Medicare 5% Standard Analytic Files to compare the practice and outcomes of coronary revascularization (by either percutaneous coronary intervention or coronary artery bypass grafting) in the United States between 2001 (pre–drug-eluting stent era, n=14 362) and 2004 (post–drug-eluting stent era, n=16 374). Between 2001 and 2004, the rate of revascularization increased from 837 to 931 per 100 000, whereas the proportion of patients who underwent percutaneous coronary intervention as an initial revascularization procedure increased from 67.5% to 75.2% (P<0.001). Over a median follow-up period of 25.5 months, no significant changes in mortality were found between 2001 and 2004 (13.8% versus 13.3%, P=0.193). Significant decreases were seen, however, in the incidence of repeat revascularization (17.1% versus 16.0%, P=0.012) and myocardial infarction (10.6% versus 8.5%, P<0.001). Over this same time period, total cardiovascular care costs per revascularized patient decreased by $1680 (95% confidence interval $1164 to $2196, P<0.001) whereas total noncardiovascular costs increased by $2481 per patient (95% confidence interval $1844 to $3118, P<0.001). When the impact of overall procedural volumes was considered, aggregate cost to the Medicare program for cardiovascular services increased by $544 million over the 2-year follow-up period. Risk-adjusted results for both the clinical and economic outcomes showed similar trends.
Conclusions— Among the Medicare population undergoing coronary revascularization, the introduction of drug-eluting stents was associated with increased use of initial percutaneous coronary intervention and reduced bypass surgery along with improved clinical outcomes over 
2 years of follow-up. Although total cardiovascular-related costs per revascularized patient decreased over this time period, total cost to the Medicare system still increased owing to greater overall use of revascularization procedures.
Key Words: stents • bypass • population • restenosis • cost-benefit analysis
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Introduction |
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The introduction of drug-eluting stents (DES) has dramatically altered the treatment of coronary artery disease. After their initial approval by the US Food and Drug Administration in 2003, DES were widely adopted by the interventional cardiology community and by 2006 were used in as many as 90% of all percutaneous coronary interventions (PCIs) in the United States.1 Recently, safety concerns related to late stent thrombosis and the possibility of excess mortality in DES patients have increased the need for valid large-scale studies of PCI practice patterns and outcomes.2–4 To date, most studies of the clinical outcomes of DES have been derived from either randomized clinical trials or device-specific registries. The former are frequently limited to narrow patient subsets defined by trial-specific entry criteria and have generally incorporated routine angiographic follow-up, which is known to bias clinical outcomes through the "oculostenotic reflex."5 Device-specific registries may be limited by selection bias and confounding and do not necessarily capture all relevant treatment options, such as coronary artery bypass grafting (CABG) or bare-metal stenting (BMS).
Clinical Perspective p 961
A further limitation of existing data is that the aggregate impact of DES adoption on patterns of revascularization and overall medical care costs remains largely unknown and is a source of continued controversy.6,7 In controlled trials among patients with complex lesions and high rates of BMS restenosis, formal economic evaluations have suggested that DES may be reasonably cost-effective.8,9 On the other hand, studies involving broader populations have suggested that widespread adoption of DES may be a relatively inefficient use of scarce resources, particularly in healthcare systems outside the United States.10,11 Whether these findings apply to US practice is currently unknown.
From a societal perspective, DES may lower healthcare costs through 2 mechanisms. Most directly, DES may lead to lower costs for PCI patients by reducing restenosis and the need for subsequent revascularization procedures compared with BMS.8,9 In addition, by allowing for more complex percutaneous interventions on patients with multivessel coronary disease, the availability of DES might reduce the use of bypass surgery as initial revascularization therapy. Studies of revascularization costs that are limited to direct comparisons of DES versus BMS may thus fail to capture the full economic impact of DES by ignoring the impact of DES on CABG rates. Conversely, it is also possible that a shift in revascularization practices from CABG to PCI may lead to higher costs due to more frequent additional procedures and less complete revascularization.12
To address these issues, we performed a population-based study of the practice and outcomes of coronary revascularization among elderly Americans using data from the US Medicare program. Our objectives were to evaluate the impact of the introduction of DES on treatment patterns, outcomes, and costs of revascularization for the full population of elderly patients undergoing coronary revascularization.
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Methods |
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Data Sources and Study Population
The data sources for the present study were the Medicare Standard Analytic Files from 2000 through 2006. The Standard Analytic Files contain all inpatient, outpatient, skilled nursing, physician, and supplier claims for a 5% random sample of fee-for-service Medicare beneficiaries. Beneficiaries enter the sample on the basis of their beneficiary identification number and remain in the sample until they leave the Medicare program. An encrypted version of the beneficiary identification number is used to identify the same patient across all services and to track longitudinal resource use and outcomes.
For the purposes of the present study, we chose to examine the practice and outcomes of coronary revascularization in 2 years, 2001 and 2004. These years were chosen prospectively to represent periods of relatively "pure" BMS and DES use, respectively, while minimizing the time interval between the periods so as to limit the likelihood that secular changes in other aspects of cardiovascular care would substantially alter outcomes during the period of study. Specifically, the year 2001 was chosen as the "pre-DES" cohort because it was the latest complete year during which only BMS were available both for initial PCI treatment and for treatment of restenosis during the ensuing year. The year 2004 was chosen as the "post-DES" cohort because it was the first full calendar year in which DES were commercially available throughout the year and in sufficient quantities to allow relatively unconstrained utilization.
The population for the present study included all patients 
65 years of age who underwent an index coronary revascularization event (either PCI or CABG) during the 2 study years of interest and who were continuously enrolled in the Medicare Part A fee-for-service program for at least 1 calendar year before and 2 years after the index event. Patients who had undergone a coronary revascularization procedure during the 4 calendar quarters preceding the index revascularization were excluded from the present study. Hospitalizations for coronary revascularization were identified on the basis of International Classification of Diseases, Ninth Revision Clinical Modification (ICD-9-CM) procedure codes 36.1X (for CABG) and 36.0X (for PCI). The index event was considered to be the first occurrence of a coronary revascularization procedure during the calendar year of interest and was categorized as either PCI or CABG. Patients who underwent both PCI and CABG during the index hospitalization (0.7%) were assigned to the PCI group, because we assumed that their bypass operation was most likely to have followed an unsuccessful PCI. Patients who underwent another cardiac surgical procedure (such as valve repair or replacement) during the same hospital admission as the index revascularization procedure were excluded from the analysis.
Assessment of Clinical Outcomes and Costs
We tracked clinical outcomes, resource use, and costs for all patients for 9 calendar quarters after the index event (ie, the remainder of the index quarter during which the initial revascularization procedure was performed and 8 subsequent calendar quarters). This approach was necessary to ensure that all patients were followed up for a minimum of 2 years after the index event. The Medicare Standard Analytic Files do not contain specific healthcare service dates but only report the sequence of events and the calendar quarter in which the service was used. To isolate potential staged revascularization procedures (which are generally performed in the first 1 to 2 months after initial PCI) from subsequent procedures due to restenosis or progressive disease (which tend to occur later), we analyzed clinical outcomes by calendar quarter relative to the index procedure (ie, quarter 1 versus quarters 2 to 9).
Outcomes tracked included death, myocardial infarction (MI), and repeat revascularization procedures. Costs were assessed from the perspective of the Medicare program (using actual payments, including both inpatient and outpatient services, adjusted to 2006 dollars with the consumer price index). Claims were classified as cardiovascular- or noncardiovascular-related with a prospectively defined algorithm based on the ICD-9-CM principal procedure code for hospital inpatient claims and by the Health Care Procedure Coding System for all other claim types (see the Appendix in the online-only Data Supplement for details). Costs did not include any beneficiary cost sharing such as coinsurance or deductibles, although these costs were included in a sensitivity analysis. Outpatient medication costs were not included in the primary analysis, because they were not covered by Medicare in either 2001 or 2004 and therefore were not included in the data files; the cost of dual-antiplatelet therapy was considered explicitly in sensitivity analyses, however.
Statistical Analysis
The focus of the present analysis was the comparison of aggregate clinical and economic outcomes for the overall cohort of revascularized patients between 2001 and 2004. Secondary analyses were performed after stratification by the initial revascularization procedure (PCI or CABG).
Discrete variables are described as proportions and compared with the 
2 test. Continuous variables are described as mean±SD and compared with unpaired t tests. Although the cost data were not normally distributed, given the large sample size, the use of parametric tests is both reasonable under the central limit theorem and generally preferred for economic analyses in which the objective is to provide inference on the expected value of cost.13 We used multiple logistic regression to estimate the independent effect of time period (2004 versus 2001) on clinical outcomes over the follow-up period. These models adjusted for age, race, sex, diabetes mellitus, dialysis, congestive heart failure, chronic obstructive pulmonary disease, prior stroke, and individual components of the Charlson comorbidity score. The results are presented as adjusted odds ratios (ORs) with associated 95% confidence intervals (CIs). Similar risk-adjusted models were constructed for cardiovascular, noncardiovascular, and total costs with adjustment for the same patient factors by multiple linear regression.
In addition to these analyses that were restricted to the population of revascularized patients, we calculated the contribution of revascularization procedures and subsequent cardiovascular care to per capita expenditures for the overall Medicare population by multiplying the cost per revascularized patient by the per capita revascularization rates in each time period. Finally, we estimated the net budget impact to the Medicare program (independent of population growth) by multiplying the per capita costs in each year by the overall number of Medicare beneficiaries in 2001.
Because the present study has 4 main end points, a P value <0.0125 was considered statistically significant with no further correction for multiple comparisons. Databases were constructed with FoxPro (Microsoft Corp, Redmond, Wash), and analyses were conducted with Data Desk version 6.2.1 (Data Description, Ithaca, NY).
The authors had full access to and take full responsibility for the integrity of the data. All authors have read and agree to the manuscript as written.
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Results |
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Patient Characteristics and Treatment Patterns
Baseline characteristics of the population undergoing initial coronary revascularization in 2001and 2004 are summarized in Table 1. Between 2001 and 2004, the overall revascularization rate for Medicare beneficiaries increased by
11% from 837 to 931 per 100 000. Compared with 2001, the 2004 cohort tended to be older and more complex, as reflected by the Charlson comorbidity index. Patients in the 2004 cohort were more likely to be diabetic, to have a history of congestive heart failure, and to have comorbidities of chronic obstructive pulmonary disease and hypertension. Other patient characteristics tended to be similar for patients undergoing coronary revascularization during the 2 time periods. No significant differences were found in peripheral arterial disease or previous stroke or the proportion of patients whose revascularization procedure was performed during a hospitalization for acute MI.
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As expected, the type of initial revascularization procedure changed considerably between 2001 and 2004 (Table 1). Specifically, the proportion of patients who underwent initial PCI increased from 67.5% to 75.2%, whereas the proportion who underwent initial CABG decreased from 32.5% to 24.8% (P<0.001). On a population basis, the overall rate of initial PCI thus increased by 24% (from 565 to 701 per 100 000 beneficiaries), whereas initial CABG decreased by 15% (from 272 to 231 per 100 000 beneficiaries). Among patients undergoing initial PCI in 2004, 75% received at least 1 DES.
Clinical Outcomes
Clinical outcomes for the overall study population over a median follow-up period of 25.5 months (range 24 to 27 months) are summarized in Table 2. No significant change in mortality was found between 2001 and 2004 (13.8% versus 13.3%, P=0.193). Significant reductions, however, were found in the incidence of MI (10.6% versus 8.5%, P<0.001) and the need for repeat revascularization (17.1% versus 16.0%, P=0.012) over this time period.
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Stratified analyses according to choice of initial revascularization procedure (PCI or CABG) and follow-up interval are displayed in Table 3. Between 2001 and 2004, patients undergoing initial PCI had a significant decrease in rates of MI (11.8% versus 9.2%, P<0.001) and repeat revascularization (23.0% versus 19.8%, P<0.001). The reductions in subsequent MI were apparent during both the first quarter of follow-up and the subsequent 8 quarters. In contrast, the incidence of repeat revascularization actually increased modestly during the first quarter (3.9% versus 4.9%, P<0.001), whereas it decreased substantially during the subsequent 8 quarters (20.3% versus 16.1%, P<0.001). No significant differences in mortality were found at any time point during follow-up.
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Economic Outcomes
For the initial hospitalization, mean medical care costs decreased by $1035 per patient (95% CI $725 to $1345, P<0.001) between 2001 and 2004 (Table 2). Over the subsequent 25.5 months, follow-up cardiovascular costs were $644 per patient lower in 2004. As a result, total cardiovascular costs (as assessed from the perspective of the Medicare program) fell by $1680 per revascularized patient between 2001 and 2004 (95% CI $1164 to $2196, P<0.001). In contrast, over the same time period, noncardiovascular costs actually increased by $2481 per patient (95% CI $1844 to $3118, P<0.001). Although total costs for the population of patients undergoing coronary revascularization thus increased by $802 per patient, this difference was not statistically significant (95% CI $124 less to $1728 more, P=0.090).
Stratified analyses by type of revascularization and time period are summarized in Table 3. Between 2001 and 2004, index hospital costs for PCI increased by $572 per patient (P<0.001). Follow-up cardiovascular costs were modestly lower in both the first follow-up quarter (by $341 per patient, P<0.001) and the subsequent 8 quarters (by $1204 per patient, P<0.001), primarily owing to the reduction in the need for additional revascularization procedures. In contrast, costs for patients treated with initial CABG were largely unchanged during both the initial hospitalization and follow-up during the 2 time periods of the present study. Noncardiovascular costs were generally higher in 2004 versus 2001, regardless of the initial revascularization strategy.
Risk-Adjusted Outcomes and Costs
Risk-adjusted clinical and economic outcomes are summarized in Table 4. After controlling for differences in demographic and clinical factors, significant reductions were found in both all-cause mortality (adjusted OR 0.90, 95% CI 0.83 to 0.97, P=0.004) and MI (adjusted OR 0.75, 95% CI 0.69 to 0.81, P<0.001) between the 2001 and 2004 cohorts. Risk adjustment tended to accentuate the difference in cardiovascular costs that was noted in the crude analyses (adjusted cost reduction of $1998), whereas the difference in noncardiovascular costs was attenuated slightly. Similar trends were apparent in separate stratified analyses according to the initial revascularization strategy (Table 5). Among patients treated with initial PCI, significant reductions were found in risk-adjusted rates of each clinical end point, with associated reductions in overall cardiovascular costs as well. Among patients treated with initial CABG, similar trends were apparent, although no differences were found in the incidence of repeat revascularization.
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Sensitivity Analyses: Impact of Alternative Analytic Perspectives and Duration of Dual-Antiplatelet Therapy
Although the primary analysis was performed from the perspective of the Medicare program, the Standard Analytic Files also contain data on beneficiary cost sharing and copayments. When these costs were also included, the main findings of the present analysis were largely unchanged. Between 2001 and 2004, the overall cost of cardiovascular care (including initial treatment) decreased by $1633 per revascularization patient (95% CI $1099 to $2166, P<0.001), noncardiovascular costs increased by $2342 per patient (95% CI $1622 to $3063, P<0.001), and total medical care costs increased by $709 per patient (95% CI –$299 to $1718, P=0.168). After risk adjustment, cardiovascular costs fell by $1945 (P<0.001), noncardiovascular costs increased by $1862 (P<0.001), and overall costs decreased by $83 per patient (P=0.865).
As noted previously, outpatient medications were not covered by Medicare in 2001 or 2004, and therefore, their costs were not reflected in the primary analyses. For this reason, we performed a series of sensitivity analyses to estimate the impact of differing durations of dual-antiplatelet therapy on aggregate costs during the 2 time periods. In our base-case analysis, we assumed that dual-antiplatelet therapy would be prescribed for 1 month after BMS and 6 months after DES placement, because these were the typical durations prescribed in 2004. Under these conditions and based on a monthly cost of $148.23 for clopidogrel, we estimated that the cost of antiplatelet therapy would have been $89 per revascularized patient in 2001 compared with $509 per patient in 2004. When these costs were incorporated in the present analysis, the net difference in unadjusted cardiovascular costs was –$1260, with an adjusted difference of –$1577 (both P<0.001). Under our minimum duration assumptions (BMS=2 weeks, DES=3 months), the difference in risk-adjusted cardiovascular costs between 2004 and 2001 was –$1788 per patient, whereas under our maximum duration assumptions (BMS=1 month, DES=12 months), the adjusted cost difference was –$1092 per patient.
Overall Budget Impact
To estimate the overall impact of these changes on total Medicare expenditures, we multiplied the adjusted cost per revascularized patient (according to year and revascularization type) by the associated per capita revascularization rate in the Medicare population. On a per-beneficiary basis, aggregate costs for coronary revascularization and subsequent cardiovascular care over 2 years were estimated to have increased by 5.8% (ie, $16 per beneficiary) from 2001 to 2004 (Table 6). For the overall Medicare population, this represents increased cardiovascular-related expenditures of $544 million (normalized to the 2001 population). By comparison, over the same time frame, noncardiovascular costs in the revascularized patient population were estimated to have increased by 25.0% (ie, $40 per beneficiary), with an overall budget impact of $1.36 billion.
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Discussion |
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Using data from the Medicare population, the present study demonstrates that among patients over 65 years of age undergoing coronary revascularization, the introduction of DES was associated with a significant increase in use of PCI and a reduction in bypass surgery as an initial revascularization strategy. The increase in the use of PCI procedures was greater than the decreased use of bypass surgery, such that the overall rate of revascularization per Medicare beneficiary increased as well. Accompanying this shift in treatment patterns, between 2001 and 2004, significant improvements occurred in a broad range of outcome measures, including MI and repeat revascularization, over a median follow-up duration of 25.5 months. In risk-adjusted analyses, mortality was reduced as well. Over this same time period, total cardiovascular care costs decreased by
$1700 per revascularized patient, whereas noncardiovascular costs actually increased by more than $2400 per revascularized patient. These findings were generally unchanged (or further accentuated) in risk-adjusted analyses. The present study is thus the first to demonstrate that in a true population-based analysis, the introduction of DES between 2001 and 2004 was temporally associated with both improved outcomes and lower per-patient costs for older Americans undergoing coronary revascularization procedures. Nonetheless, when the higher overall volume of revascularization procedures was also considered, the aggregate cardiovascular cost of revascularization patients to the Medicare program increased by $544 million. The shifting balance of coronary revascularization procedures from bypass surgery to PCI that we observed is not surprising and appears to be an accentuation of a general trend over the past decade.14,15 In particular, several recent studies have documented that since the introduction of DES, the use of PCI to treat patients with multivessel coronary artery disease has increased, with a resulting decrease in rates of bypass surgery.16,17 Although the precise explanation for this observation cannot be discerned from the present data, this trend most likely reflects the increased willingness of interventional cardiologists to perform PCI in patients with more complex disease whose risk of restenosis before the introduction of DES was thought to be prohibitive.
Although numerous previous studies have either compared the outcomes among relatively unselected patients undergoing PCI with DES versus BMS18–21 or performed time-series comparisons of the practice and outcomes of PCI before and after the introduction of DES,22–25 to the best of our knowledge, the present study represents the first examination of the impact of the introduction of DES on the overall practice and outcomes of coronary revascularization in a defined patient population. This approach offers several important advantages over previous study designs. Unlike randomized clinical trials, the present study focuses on a broad, real-world population of patients undergoing coronary revascularization, including both "on-label" and "off-label" applications of DES.26 Moreover, studies that have attempted to compare the outcomes of contemporaneous patients treated with BMS versus DES outside of the clinical trial setting inevitably suffer from selection bias, which is only partially addressed through even sophisticated risk-adjustment methods.27 In contrast, our approach of examining the overall population of patients undergoing coronary revascularization may be less likely to suffer from selection bias, because the underlying demographic and clinical characteristics of patients undergoing revascularization tend to be relatively stable, particularly over the brief time span of the present study. These differences in analytic approach may explain, at least in part, some of the differences in findings between these studies. For example, several recent propensity-matched observational comparisons of DES versus BMS recipients have suggested a mortality benefit with DES,21,24 a finding that was not corroborated by the present study or others that have used similar indirect comparisons.25
Safety of DES
One of the most important findings of the present study was that the introduction and widespread use of DES among older Americans undergoing coronary revascularization was not associated with any evidence of an increased risk of "hard" clinical outcomes (such as death or MI) over >2 years of follow-up. Indeed, risk-adjusted analyses demonstrated that the risk of death and MI in the first 2 years after coronary revascularization was reduced in the post-DES compared with the pre-DES era. These findings are particularly reassuring in light of recent studies demonstrating an increased risk of late stent thrombosis with DES implantation and some studies that suggested increased rates of death or MI among DES recipients.3,28 It is further reassuring that no evidence was found of increased late events despite the shift from CABG to PCI (mainly with DES) as the initial form of revascularization for 8% of the population.
Although the most striking change in clinical practice between 2001 and 2004 was the introduction of DES and their preferential use in patients undergoing PCI, it is important to recognize that other factors may be contributing to the improved outcomes as well. In particular, it is possible that some of the reductions in mortality and MI rates may be due to improved use of secondary coronary prevention measures such as β-blockers and statins over the time frame of the study. The fact that similar relative risk reductions for these end points were observed in both the PCI and CABG populations lends credence to this possible explanation. A recent study of non–ST-elevation acute coronary syndrome patients showed that use of American College of Cardiology/American Heart Association-recommended secondary preventative measures increased from 2002 to 2004.29 Similar trends likely occurred among the Medicare population during the time frame of the present study but could not be assessed directly with our data. It is also possible that extended use of dual-antiplatelet therapy, as is recommended in patients receiving DES, influenced clinical outcomes such as MI and mortality, particularly for those patients treated with PCI.
In addition, some of the benefit we observed at 2-year follow-up may be related to the shift from CABG to PCI, which generally has a superior short-term safety profile, particularly in an elderly population.30 It is not clear whether the reduction in adverse events found in the present study would persist with longer follow-up, because studies comparing PCI to CABG frequently show higher adverse events for CABG in the short-term, with later "catch up" among PCI patients as coronary disease progresses, requiring additional PCI.31–33 Nevertheless, the present data are reassuring that thus far, the observed changes in practice patterns have not been associated with any signal of harm to the aggregate population, particularly in relation to late thrombosis. Because some of the population studies that suggest such harm3,34 do not begin to demonstrate a signal until 6 to 12 months, however, it will be important to continue to monitor this population with longer follow-up.
Impact on Repeat Revascularization
Although a reduction occurred in the need for subsequent revascularization procedures between 2001 and 2004 (particularly among the subset of patients treated with PCI), both the absolute and relative magnitude of benefit were less striking than might have been anticipated from randomized, controlled trials and device-specific registries, which have shown reductions in restenosis and target-lesion revascularization of 60% to 80%.35–37 To some extent, this may reflect the absence of protocol-mandated angiographic follow-up and the associated oculostenotic reflex that is known to accentuate rates of target-lesion revascularization and the apparent benefits of DES.38–40 Moreover, it is important to recognize that the administrative data that we used do not distinguish between repeat revascularization of the original target lesion or vessel (clinical outcomes that are closely linked with restenosis) and revascularization due to progressive disease or even staged procedures. Indeed, data from the Evaluation of Drug Eluting Stents and Ischemic Events (EVENT) registry suggest that approximately two thirds of repeat revascularization procedures during the year after DES implantation are unrelated to the original target lesion (personal communication, N. Kleiman; October 18, 2007). Thus, the higher than expected rate of repeat revascularization may not reflect clinical restenosis but rather the impact of staged procedures as cardiologists approached multivessel disease patients with sequential PCIs rather than CABG operations.22 This hypothesis is further supported by our finding that among PCI patients, the rate of early repeat revascularization actually increased between 2001 and 2004, which suggests the possibility of increased staging of complex revascularization procedures during the DES era. Recently published data from the New York State PCI registry have shown similar results.41
Impact on Costs
The overall economic impact of these changing practice patterns differed according to the analytic construct. From the perspective of the revascularized population, per-patient costs for cardiovascular care actually decreased between 2001 and 2004. There appear to be 2 principal factors that account for these cost savings. First, an $1500 (10%) reduction was found in follow-up costs for cardiovascular care among patients treated with PCI, which largely parallels the reduced need for repeat revascularization procedures in this subgroup. In addition, the shift from bypass surgery (with initial treatment costs of $30 000 per patient) to PCI (with initial treatment costs of $14 000 per patient) in 8% of the revascularized population accounted for a substantial proportion of the observed upfront cost savings as well. This latter factor has been excluded from virtually every other analysis of the economic impact of DES and highlights the importance of considering the broadest possible perspective in any economic evaluation of a "disruptive technology."42
On the other hand, when we considered the perspective of the overall Medicare program, we found that total cardiovascular expenditures over the 2-year follow-up period actually increased by $544 million between 2001 and 2004 because of the increased volume of revascularization procedures performed. Nonetheless, the overall cost increase to the Medicare program was driven to a greater extent by an 25% increase in noncardiovascular expenditures in this population compared with only an 6% increase in cardiovascular costs. These discordant findings (increased total costs to the Medicare program in the setting of decreased per-patient costs) illustrate an apparent paradox associated with the introduction of a technology like DES. With improved clinical outcomes, the cost of treating the individual patient falls; however, these same improved outcomes may encourage wider use of the technology, thereby increasing total expenditures.
The explanation for the increase in noncardiovascular costs is uncertain but may relate in part to more aggressive treatment of comorbid conditions and to general medical inflation. Of note, a separate analysis among an age-, sex-, and race-matched cohort of patients who did not undergo coronary revascularization demonstrated a 13.6% and 31.9% increase in per-patient cardiovascular and noncardiovascular costs over this same time period (data not shown). It is also possible that some of the increase in noncardiovascular costs may relate to an increase in bleeding complications due to prolonged use of dual-antiplatelet therapy after DES implantation. Given the rates of bleeding reported in previous studies of dual-antiplatelet therapy,43,44 however, it seems unlikely that such events would be solely responsible for the >$2400 per-patient increase in noncardiovascular costs that we observed.
Study Limitations
As described above, given the design of the present study, it is not possible to determine whether all of the findings were due to the introduction of DES. Indeed, it is possible that other secular changes in treatment patterns over the same 3-year period could have accounted for some of the clinical and economic benefits we observed. Additionally, we could not track medications or their costs among Medicare patients, which may have altered the cost findings. Nevertheless, it is reassuring that the economic benefits persisted in sensitivity analyses that included up to 12 months (the current recommended duration) of dual-antiplatelet therapy for DES recipients.
It is also noteworthy that DES usage has evolved since the time frame of the present study. In particular, since 2004, concerns have arisen over DES safety and costs that have contributed to a decline in DES use and an increase in BMS use. Thus, caution should be exercised in extrapolating the present findings from the early DES era to current interventional cardiology practice. Future studies will be necessary to determine the effect of more selective DES usage on population-wide clinical outcomes and costs. Finally, the present study is limited by the relatively brief duration of follow-up. Longer-term follow-up will be essential to monitor for adverse events occurring beyond 2 years.
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Acknowledgments |
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Sources of Funding
This study was supported by a grant to Saint Luke’s Mid America Heart Institute from Cordis Corporation.
Disclosures
Dr Cohen has received grant support from Cordis and Boston Scientific (manufacturers of DES). L. Englehart and Dr Cooper are employees of Cordis, Inc. W. Linde-Zwirble currently serves as a consultant to Cordis (for his analytic work on this project). Dr Ryan reports no conflicts.
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