Comparison of drug-eluting versus bare metal stents on later frequency of acute myocardial infarction and death

Propensity Score-Based Methods in Comparative Effectiveness Research on Coronary Artery Disease

This review examines the conduct and reporting of observational studies using propensity score-based methods to compare coronary artery bypass grafting (CABG), percutaneous coronary intervention (PCI), or medical therapy for patients with coronary artery disease. A systematic selection process identified 48 studies: 20 addressing CABG versus PCI; 21 addressing bare-metal stents versus drug-eluting stents; 5 addressing CABG versus medical therapy; 1 addressing PCI versus medical therapy; and 1 addressing drug-eluting stents versus balloon angioplasty. Of 32 studies reporting information on variable selection, 7 relied exclusively on statistical criteria for the association of covariates with treatment, and 5 used such criteria to determine whether product or nonlinear terms should be included in the propensity score model. Twenty-five (52%) studies reported assessing covariate balance using the estimated propensity score, but only 1 described modifications to the propensity score model based on this assessment. The over 400 variables used in the 48 propensity score models were classified into 12 categories and 60 subcategories; only 17 subcategories were represented in at least half of the propensity score models. Overall, reporting of propensity score-based methods in observational studies comparing CABG, PCI, and medical therapy was incomplete; when adequately described, the methods used were often inconsistent with current methodological standards.

Integrity(®) bare-metal coronary stent-induced platelet and endothelial cell activation results in a higher risk of restenosis compared to Xience(®) everolimus-eluting stents in stable angina patients

Drug-eluting stenting (DES) has become a reliable tool for coronary stenting; however, its direct effects on platelet and endothelium function differ from those of bare-metal stenting (BMS). This study involved a periprocedural analysis of various biomarkers of cellular activation after elective DES (Xience(®), Abbott Vascular, Santa Clara, CA, USA) or BMS (Integrity(®), Medtronic, Minneapolis, MI, USA). Forty-nine stable angina patients were recruited: 28 underwent BMS, and 21 received everolimus-eluting stents. Samples were collected (i) prior to stenting, (ii) at 24 hours after procedure, and (iii) after 1 month of dual antiplatelet therapy. Platelet activation was analyzed by surface P-selectin positivity in parallel with plasma levels of soluble P-selectin, CD40L and platelet-derived growth factor (PDGF). Endothelial cell (EC) activation was detected by measuring markers of early (von Willebrand factor) and delayed response (VCAM-1, ICAM-1, E-selectin). Patients were followed for 6 months for the occurrence of restenosis or stent thrombosis. Increased platelet activation was sustained regardless of stent type or antiplatelet medication. Concentrations of most EC markers were more elevated after BMS than after DES. No stent thrombosis was seen, but six BMS subjects displayed restenosis with significantly higher sCD40L (779 [397-899] vs. 381 [229-498] pg/mL; p = 0.032) and sICAM-1 (222 [181-272] vs. 162 [153-223] ng/mL; p = 0.046) levels than in those without complication, while DES patients exhibited significantly decreased PDGF (572 [428-626] vs. 244 [228-311] pg/mL; p = 0.004) after 1 month. Nonresponsiveness to antiplatelet drugs did not influence these changes. In conclusion, the degree of platelet and EC activation suggests that Xience(®) DES may be regarded a safer coronary intervention than Integrity(®) BMS, with a lower risk of in-stent restenosis.

Changes in the Practice of Coronary Revascularization between 2006 and 2010 in the Republic of Korea

PURPOSE

Evidence suggests that technological innovations and reimbursement schemes of the National Health Insurance Service may have impacted the management of coronary artery disease. Thus, we investigated changes in the practice patterns of coronary revascularization.

MATERIALS AND METHODS

Revascularization and in-hospital mortality among Koreans ≥20 years old were identified from medical claims filed between 2006 and 2010. The age- and sex-standardized procedure rate per 100,000 person-years was calculated directly from the distribution of the 2008 Korean population.

RESULTS

The coronary revascularization rate increased from 116.1 (95% confidence interval, 114.9-117.2) in 2006 to 131.0 (129.9-132.1) in 2010. Compared to the rate ratios in 2006, the rate ratios for percutaneous coronary intervention (PCI) and coronary artery bypass graft (CABG) surgery in 2010 were 1.16 (1.15-1.17) and 0.80 (0.76-0.84), respectively. Among patients who received PCI, the percentage with drug-eluting stents increased from 89.1% in 2006 to 93.0% in 2010. In-hospital mortality rates from PCI significantly increased during the study period (p=0.03), whereas those from CABG significantly decreased (p=0.01). The in-hospital mortality rates for PCI and CABG were higher in elderly and female patients and at the lowest-volume hospitals.

CONCLUSION

The annual volume of coronary revascularization continuously increased between 2006 and 2010 in Korea, although this trend differed according to procedure type. A high percentage of drug-eluting stent procedures and a high rate of in-hospital mortality at low-volume hospitals were noted.

Tailoring the endovascular management of transplant renal artery stenosis

In this study we analyze the different types of endovascular interventions (EVIs) in de novo transplant renal artery stenosis (TRAS) and its anatomical subtypes to examine any variation in recovery of allograft function, blood pressure control, EVI patency and allograft survival with respect to EVI type (DES: drug-eluting stent, BMS: bare-metal stent, PTA: percutaneous transluminal angioplasty). Forty-five patients underwent a total of 50 primary EVIs (DES: 18, BMS: 26, PTA: 6). Patients were stratified according to medical co-morbidities, graft characteristics, biopsy results, clinical presentation and TRAS anatomic subtypes (anastomotic: 26, postanastomotic: 17, bend-kink: 2). There was significant improvement in allograft function and mean arterial blood pressure (MAP) control across all interventions (pre-EVI-creatinine [CR]: 2.8 ± 1.4, post-EVI-Cr: 2.1 ± 0.7, p < 0.001; pre-EVI-MAP: 117 ± 16, post-EVI-MAP: 112 ± 17, p = 0.03) with no significant difference among EVI types. There was no significant difference in allograft survival with respect to EVI type. Patency was significantly higher in EVIs performed with DES and BMS compared to PTA (p = 0.001). In the postanastomotic TRAS subtype, patency rates were significantly higher in DES compared to BMS (p = 0.012) in vessels of comparable reference diameter (≤5 mm).

Accounting for the mortality benefit of drug-eluting stents in percutaneous coronary intervention: a comparison of methods in a retrospective cohort study

BACKGROUND

Drug-eluting stents (DES) reduce rates of restenosis compared with bare metal stents (BMS). A number of observational studies have also found lower rates of mortality and non-fatal myocardial infarction with DES compared with BMS, findings not observed in randomized clinical trials. In order to explore reasons for this discrepancy, we compared outcomes after percutaneous coronary intervention (PCI) with DES or BMS by multiple statistical methods.

METHODS

We compared short-term rates of all-cause mortality and myocardial infarction for patients undergoing PCI with DES or BMS using propensity-score adjustment, propensity-score matching, and a stent-era comparison in a large, integrated health system between 1998 and 2007. For the propensity-score adjustment and stent era comparisons, we used multivariable logistic regression to assess the association of stent type with outcomes. We used McNemar's Chi-square test to compare outcomes for propensity-score matching.

RESULTS

Between 1998 and 2007, 35,438 PCIs with stenting were performed among health plan members (53.9% DES and 46.1% BMS). After propensity-score adjustment, DES was associated with significantly lower rates of death at 30 days (OR 0.49, 95% CI 0.39 - 0.63, P < 0.001) and one year (OR 0.58, 95% CI 0.49 - 0.68, P < 0.001), and a lower rate of myocardial infarction at one year (OR 0.72, 95% CI 0.59 - 0.87, P < 0.001). Thirty day and one year mortality were also lower with DES after propensity-score matching. However, a stent era comparison, which eliminates potential confounding by indication, showed no difference in death or myocardial infarction for DES and BMS, similar to results from randomized trials.

CONCLUSIONS

Although propensity-score methods suggested a mortality benefit with DES, consistent with prior observational studies, a stent era comparison failed to support this conclusion. Unobserved factors influencing stent selection in observational studies likely account for the observed mortality benefit of DES not seen in randomized clinical trials.

Cost-effectiveness of drug-eluting stents versus bare metal stents in clinical practice

BACKGROUND

Drug-eluting stents (DES) reduce the need for repeat target revascularization (TVR) compared with bare metal stents (BMS) but are more costly. The objective was to evaluate the cost-effectiveness of DES versus BMS.

METHODS AND RESULTS

We evaluated clinical outcomes and costs of care over 3 years in 1147 undergoing BMS before the availability of DES and 1247 DES patients at Wake Forest University Baptist Medical Center from 2002 to 2005. Costs for index stenting, TVR, and clopidogrel use were assessed. The 2 groups were well matched for baseline characteristics. Index stenting costs were $1846 higher per patient for DES versus BMS ($1737 more to $1950 more). At 3 years, absolute TVR rates were 15.2 per 100 DES patients and 24.1 per 100 BMS patients, and as a result, cumulative TVR-related costs were $2065 less per patient for DES versus BMS ($3001 less to $1134 less). Including the cost of clopidogrel, the incremental cost-effectiveness ratio per TVR avoided with DES was $4731 through 1 year, $4703 through 2 years, and $6379 through 3 years.

CONCLUSIONS

At 3 years, the higher index cost of DES versus BMS was completely offset by lower TVR-related costs. However, because of extended clopidogrel use for DES, the incremental cost-effectiveness ratio per TVR avoided ranged from $4703 to $6379 over 3 years. These unadjusted observational findings provide support for the continued use of DES in routine practice but highlight the important impact of prolonged dual antiplatelet use on the cost-effectiveness of this technology.

In-hospital complications and long-term outcomes of the paclitaxel drug-eluting stent in acute ST-elevation myocardial infarction: a real-world experience from a high-volume medical center

BACKGROUND

The paclitaxel drug-eluting stent (Taxus, Boston Scientific) is FDA approved for treatment of coronary artery disease in simple, noncomplex coronary lesions. In this registry, we sought to investigate the procedural success and long-term outcomes of patients receiving the Taxus stent in the setting of acute ST-elevation myocardial infarction (STEMI) in a busy single-center interventional program.

METHODS

This is a single-center retrospective analysis of prospectively collected in-hospital data with postdischarge follow-up achieved by phone calls and review of medical records. Data were audited by an independent monitor, and outcomes were adjudicated by an experienced interventional cardiologist. All patients with STEMI over the period of 2 years (2005 and 2006) with native de novo lesions who received the Taxus stent were included. Patients receiving bare metal stents were excluded. The primary outcome was the combined end point of cardiac death, recurrent nonfatal MI, and target lesion revascularization (TLR) on follow-up.

RESULTS

Of 198 patients included in this study, follow-up data were obtained in 172 (86.9%) patients. The mean age was 63+/-14.9 years. There were 59.1% males. Patients had the following cardiac risk factors: diabetes 20.7%, hypertension 60.6%, hyperlipidemia 87.8%, and current smoking 48%. In-hospital complications included death 5.1%, acute closure with stent thrombosis 1%, vascular complications 2.9%, and cardiogenic shock 6.6%. The mean follow-up period (days) was 317.3+/-239.3. The primary end point of cardiac death, nonfatal MI, and TLR was met in 12.4%. Individual end points on follow-up were cardiac death 2.5%, total death 4.9%, TLR 8.1%, target vessel revascularization 19.9%, stroke 1.2%, nonfatal MI 5%, and acute stent thrombosis 5.5% (definite 4.3%, probable 0.6%, possible 0.6%; Academic Research Consortium definition).

CONCLUSION

The use of the Taxus stent in acute STEMI is associated with a low postdischarge combined end point of cardiac death, nonfatal MI, and TLR and a definite/probable 4.9% in-stent thrombosis rate, which is within the reported range of data published in "real-world" registry.

The Adverse Long-Term Impact of Renal Impairment in Patients Undergoing Percutaneous Coronary Intervention in the Drug-Eluting Stent Era

Background— An observational study determining the long-term impact of chronic kidney disease (CKD) on patients undergoing percutaneous coronary intervention at a tertiary cardiac referral center. CKD is associated with poor in-hospital outcomes after percutaneous coronary intervention, but its effect beyond 1 year, particularly in the drug-eluting stent (DES) era, has not been reported.

Methods and Results— Baseline creatinine was available for 11 953 patients entered into a prospective registry (April 2000 to September 2007). Patients were stratified: those with or without at least moderate CKD (creatinine clearance, <60 mL/min). Follow-up data were obtained through linkage to a provincial registry. Kaplan–Meier analysis was performed. Cox multiple-regression analysis identified independent predictors of late mortality and major adverse cardiac events (MACE) and examined the association between DES use and late outcomes in the presence or absence of CKD. CKD was present in 3070 patients (25.7%). In-hospital mortality and MACE were significantly increased in CKD (3.34% versus 0.44%, P <0.001 and 5.73% versus 2.2%, P <0.001). Survival and MACE-free survival at 7 years were reduced (64.5�1.4% versus 89.4�0.5%, P <0.001; 44.0�1.4% versus 63.4�0.8%, P <0.001). CKD was an independent predictor of late mortality and MACE (hazard ratio [HR]: 2.18, CI: 1.90 to 2.49, P <0.0001; HR: 1.37, CI: 1.25 to 1.49, P <0.0001). DES use was associated with a significant reduction in both (HR: 0.71, CI: 0.60 to 0.83, P <0.0001; HR: 0.70, CI: 0.63 to 0.78, P <0.0001). In patients with CKD, DES use was associated with reduced revascularization (HR: 0.68, CI: 0.53 to 0.88, P =0.004) and reduced MACE (HR: 0.81, CI: 0.69 to 0.95, P =0.011) but not reduced mortality (HR: 0.85, CI: 0.69 to 1.05, P =0.1).

Conclusion— In a large registry of “all comers” for percutaneous coronary intervention, CKD was an independent predictor of adverse late outcomes. DES use may be associated with improved long-term outcomes in this high-risk cohort, but further prospective studies are required.

Using secondary data sources for pharmacoepidemiology and outcomes research

The increased availability of electronic medical records and administrative health care databases is adding to the popularity of pharmacoepidemiology and outcomes research studies. Despite their availability, practitioners may be reluctant to use these databases because they lack familiarity with database research in general. The basic principles of research are the same regardless of the data source, but there are a few special considerations. When using secondary data sources for research purposes, special care must be taken to select an appropriate source to ensure that relevant information is available to answer the research question at hand. Special attention must also be paid to selecting the appropriate codes to represent the outcomes and exposures of interest; therefore, a general understanding of coding schemes is necessary. Although time may be saved by not prospectively collecting data, the process of manipulating the data for analysis in secondary databases can be complex. Analysis of data from secondary sources may require special procedures to overcome the lack of randomization. By familiarizing themselves with these special issues, practitioners can use secondary sources to conduct studies that make valuable contributions to the improvement of patient care.

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

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 approximately 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.

Effect of Length and Diameter of Drug-Eluting Stents Versus Bare-Metal Stents on Late Outcomes

Background— The risk of restenosis and other adverse cardiac events with bare-metal stents (BMS) is increased with smaller stent diameters and longer stent lengths. Drug-eluting stents (DES) may reduce this effect in select patients; however, whether this benefit occurs in high-risk lesions and patients in routine practice is not clear.

Methods and Results— Clinical outcomes (target-vessel revascularization [TVR], stent thrombosis, nonfatal myocardial infarction [MI], and cardiac death) at 2 years stratified by stented length and diameter were compared in 949 consecutive patients who received BMS and 1236 consecutive and comparable patients who received DES for single lesions. The longest tertile of BMS (>23 mm) was associated with increased hazard of TVR, ST, and nonfatal MI or death compared with shorter tertiles of BMS, which was abolished by DES. DES compared with BMS was independently associated with a lower hazard of TVR (HR, 0.34 [0.20 to 0.58]) and nonfatal MI or death (HR, 0.60 [0.39 to 0.92]) in the longest length tertile (>23 mm). No clear association of stented tertile diameter and clinical outcomes for either stent type was observed. However, DES compared with BMS was independently associated with a lower hazard of TVR for all diameter tertiles, and a lower hazard of nonfatal MI or death (0.66 [0.44 to 0.99]) in the largest diameter tertile (>3.4 mm).

Conclusions— Independent of adverse patient and lesion characteristics, DES demonstrated significantly lower hazard of TVR and nonfatal MI or death at 2 years compared with BMS within the longest stented lengths (>23 mm) and largest diameters (>3.4 mm).

Incidence of coronary stent thrombosis based on academic research consortium definitions

Stent thrombosis occurs infrequently after drug-eluting stent (DES) placement, but concerns have surfaced that identification of stent thrombosis based solely on angiography may underestimate the true incidence of this complication. The purpose of this study was to compare rates of stent thrombosis using Academic Research Consortium (ARC) definitions. From April 2002 to February 2005, bare-metal stents (BMSs) and DESs were placed at Wake Forest University Baptist Medical Center. Rates of ARC definite, probable, and possible stent thrombosis were evaluated. Overall, definite stent thrombosis occurred in 1.4% of BMSs and 1.1% of DESs (p = 0.47); probable stent thrombosis, in 1.0% of BMSs and 0.9% of DESs (p = 0.81); definite plus probable stent thrombosis, in 2.3% of BMSs and 1.9% of DESs (p = 0.48); and possible stent thrombosis, in 6.8% of BMSs and 3.5% of DESs (p <0.001). Rates of definite late (31 days to 1 year) and very late (>1 year) stent thrombosis were 0.9% for BMSs and 0.06% for DESs (p <0.001) and 0.16% for BMSs and 0.56% for DESs, respectively (p = 0.13). Rates of definite plus probable and late and very late stent thrombosis were 1.1% for BMSs and 0.19% for DESs (p <0.001) and 0.40% for BMSs and 0.68% for DESs, respectively (p = 0.31). Rates of possible stent thrombosis increased significantly for each thrombosis interval. In conclusion, rates of stent thrombosis using the proposed ARC definition differed by stent type, definition of stent thrombosis, and thrombosis interval. Use of the ARC probable stent thrombosis paralleled rates of definite stent thrombosis alone, but partially masked the occurrence of late (>1 year) stent thrombosis in DESs compared with BMSs.

Survival advantage in Medicare patients receiving drug-eluting stents compared with bare metal stents: real or artefactual?

BACKGROUND

Concerns have been raised regarding late mortality, particularly from late stent thrombosis, from drug-eluting stents (DES). Randomized clinical trials have shown that DES decrease restenosis but do not decrease mortality compared with bare metal stents (BMS). These studies utilized well-defined clinical and angiographic subsets. In the "real world" drug-eluting stents are used in a much broader crosssection of patients. We evaluated mortality in the first year after implantation of DES, specifically the sirolimus-eluting stent (SES), Cypher vs. BMS in "real world" older patients using the Medicare claims database.

METHODS AND RESULTS

Data for the years 2002 (n = 6,890; pre-DES) and 2003 (n = 7,566; first year of DES use) (May through December of each year) were analyzed. BMS and DES groups had similar baseline characteristics except for small but significant differences with BMS patients being somewhat older, having more males and African Americans, and a higher percentage of peripheral artery disease and heart failure while DES patients had a higher percentage of diabetics and patients with prior revascularization procedures. A significant improvement in mortality using both unadjusted and adjusted analyses was observed for DES (6.0% vs. 11.4%, P < 0.0001; hazard ratio 1.98, 95% CI 1.68-2.34). Controlling for comorbidity, extent of disease, and other characteristics by multivariable analysis or by propensity analysis had little impact on these results. On the other hand, there was no change in overall mortality in all stented patients in 2003 compared with all stented patients in 2002.

CONCLUSION

An observed mortality benefit for DES compared with BMS in 2003 was observed, demonstrating the safety of DES, and suggesting the possibility of superiority in outcome in older patients with DES vs. BMS. However, the lack of improved survival from 2002 to 2003 in all stented patients suggests that the mortality advantage with DES finding may be due to unidentified selection biases. Our data suggest that DES in the Medicare population is as safe as, and possibly superior, to BMS for survival over the first year after implantation.

Cocaine use is associated with an increased risk of stent thrombosis after percutaneous coronary intervention

BACKGROUND

The treatment of cocaine-related acute coronary syndromes presents unique challenges. Although percutaneous coronary intervention in cocaine abusers appears to be safe in the short term, longer-term outcomes have not been reported. We postulated that cocaine use would be associated with increased risk for stent thrombosis.

METHODS

We report 30-day and 9-month clinical outcomes including stent thrombosis, myocardial infarction, repeat revascularization, and death in 71 cocaine abusers who underwent percutaneous coronary intervention at our institution (66 of whom received a stent) compared with 3216 control patients. Propensity score-matched analysis was performed to control for statistical bias present in nonrandomized study populations.

RESULTS

Stent thrombosis occurred in 5 (7.6%) of the 66 stented cocaine abusers during the 9-month follow-up period compared to a 0.6% rate of stent thrombosis in the control database, a highly statistically significant difference (P < .001). In the propensity analysis, stent thrombosis occurred in 4 stented cocaine abusers and 0 of 70 matched controls (6.2% vs 0%; P = .04) throughout the 9-month follow-up period. There was no significant difference in overall rates of myocardial infarction, death, or repeat revascularization at 9 months.

CONCLUSIONS

Because of the increased risk of stent thrombosis, consideration should be given to a more conservative approach in cocaine abusers who present with acute coronary syndromes.