Although the benefit of percutaneous coronary interventions (PCIs) for patients presenting with acute coronary syndromes (ACS) has been established in numerous studies, the role of PCI in stable coronary artery disease (CAD) remains controversial. With the publication of the Clinical Outcomes Utilizing Revascularization and Aggressive Drug Evaluations trial and the appropriate use criteria for coronary artery revascularization, we sought to examine the impact of these treatment strategies and guidelines on the current practice of PCI in United States. We conducted a serial cross-sectional study with time trends of patients undergoing PCI for ACS and stable CAD from 2007 to 2011. The annual rate of all PCI decreased by 27.7% from 10,785 procedures per million adults per year in 2007 to 2008 to 7,801 procedures per million adults per year in 2010 to 2011 (p = 0.03). Although there was no statistically significant decrease in the PCI utilization for ACS from 2007 to 2011, PCI utilization for stable CAD decreased by 51.7% (from 2,056 procedures per million adults per year in 2008 to 992 procedures per million adults per year in 2011, p = 0.02). Hospitals with a higher volume of PCI experienced a more significant decrease. Decrease in PCI utilization for stable CAD was statistically significant for patients with Medicare and private insurance/health maintenance organization (44.5%, p = 0.03 and 59.5%, p = 0.007, respectively). In conclusion, the rate of PCI decreased substantially starting from 2009 in the United States. Most of the decrease was attributed to the reduction in PCI utilization for stable CAD.
Highlights
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Percutaneous coronary intervention (PCI) use for stable ischemic heart disease decreased significantly from 2007 to 2011.
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Large hospitals experienced the greatest decrease in the rate of PCI utilization.
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Higher annual PCI volume was associated with significant decrease in the PCI use.
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The use of fractional flow reserve steadily increased from 2009 to 2011.
Given the invasive nature of the procedure and the cost of percutaneous coronary interventions (PCIs), the American College of Cardiology and the American Heart Association in conjunction with other national cardiovascular societies have developed the appropriate use criteria (AUC) for coronary artery revascularization in January 2009. A recent study of patients undergoing PCI from the National Cardiovascular Data Registry (NCDR) 2009 to 2010 has demonstrated that only 50.4% of nonacute indications were deemed appropriate, whereas nearly all acute PCIs were classified as appropriate. Similarly, data from the New York State Percutaneous Coronary Interventions Reporting System from 2009 to 2010 showed that a significant number of PCIs were either inappropriate or uncertain. With improving medical therapy for coronary artery disease (CAD), publication of the Clinical Outcomes Utilizing Revascularization and Aggressive Drug Evaluations (COURAGE) trial, introduction of drug-eluting stents (DESs), and the national cardiovascular societies’ efforts through AUC, we examined the impact of these recent clinical treatment strategies and guidelines on the temporal trends in PCI utilization from 2007 till 2011, in patients with acute coronary syndromes (ACS) and stable CAD.
Methods
Data were obtained from the Agency for Healthcare Research and Quality Healthcare Cost and Utilization Project—Nationwide Inpatient Sample (NIS) files from 2007 to 2011. The NIS is a 20% stratified sample of all nonfederal US hospitals and, in 2011, contained de-identified information for 38,590,733 discharges from 1,049 hospitals and 46 states. Discharges are weighted based on the sampling scheme to permit inferences for a nationally representative population. Each record in the NIS includes all procedure and diagnosis International Classification of Diseases codes recorded for each patient’s hospital discharge.
From January 2007 through December 2011, hospitalizations leading to PCI were selected by searching for the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) procedure codes 00.66, 36.01, 36.02, 36.05, 36.06, 36.07, and 36.09 in any of the 15 procedure fields in the database. Patients who were admitted with ACS were identified using the ICD-9-CM codes 410.x. and 411.1. Patients with stable CAD were selected by using the algorithm of Mohan et al. Patient- and hospital-level variables were included as baseline characteristics. Hospital-level data elements are derived from the American Heart Association Annual Survey Database. The Agency for Healthcare Research and Quality co-morbidity measures based on the Elixhauser methods were used to identify co-morbid conditions. Utilization of fractional flow reserve (FFR) and intravascular ultrasound was identified by the ICD-9-CM codes 00.59 and 00.24, respectively. The ICD-9-CM code for FFR was implemented in 2008 by Center for Medicare and Medicaid Services. Therefore, only the data from 2009 to 2011 were available for the analysis.
We calculated the procedure rates as the weighted number of PCI procedures divided by 20% of the total number of US adults during the same periods. Estimates of the US adult population from 2007 to 2011 were obtained from the US Census Bureau. Trends in the annual rates of PCI for ACS and stable CAD were assessed using time series modeling. Rates of PCI for ACS and stable CAD over time were compared in subgroups based on hospital characteristics according to hospital teaching status, region, hospital size, and hospital volume status. Hospital volume status was defined by quartiles based on the volume of PCI performed from 2007 to 2011. The first quartile was defined as centers with the lowest PCI volume. In addition, the rates of PCI utilization were analyzed for subgroups of patients based on gender, race, and insurance status.
For descriptive analyses, we compared baseline characteristics and hospital characteristics between ACS and stable CAD. Continuous variables are presented as medians; categorical variables are expressed as frequencies (percentages). To compare baseline characteristics and in-hospital care patterns with respect to ACS and stable CAD, either Mann-Whitney Wilcoxon nonparametric tests or the Student t test was used for continuous variables, and Pearson chi-square tests were used for categorical variables. All statistical tests were 2-sided, and a p value of <0.05 was set a priori to be statistically significant. All the analyses were conducted using SAS, version 9.2 (SAS Institute, Cary, North Carolina), and SPSS, version 20 (IBM Corporation, Armonk, NY).
Results
For each year from 2007 to 2011, the NIS data set included discharges from all hospitals that performed PCI, which increased from 347 hospitals in 2007 to 387 hospitals in 2011. Of 196,461,055 discharge records reviewed from 2007 to 2011, a total of 3,305,578 patients underwent PCI, of which 66.9% were for ACS and 33.1% were for stable CAD. Table 1 compares baseline characteristics for the ACS and stable CAD groups. The stable CAD population was slightly older, more likely to be women, and more likely to have hypertension, diabetes mellitus, or peripheral vascular disease and Medicare coverage. PCI utilization for stable CAD was more common in teaching hospitals.
| Characteristics | Stable Coronary Artery Disease (N = 1,094,788) | Acute Coronary Syndrome (N = 2,210,790) | p Value |
|---|---|---|---|
| Age, mean ± SD (years) | 66.1 ± 11.5 | 63.6 ± 12.8 | <0.001 |
| Women | 34.4% | 33.4% | <0.001 |
| White | 77.7% | 78.1% | 0.003 |
| Hypertension | 74.3% | 69.0% | <0.001 |
| Diabetes mellitus, uncomplicated | 32.7% | 28.4% | <0.001 |
| Diabetes mellitus, complicated | 3.9% | 4.1% | <0.001 |
| Chronic renal failure | 11.0% | 10.7% | <0.001 |
| Heart failure | 0.9% | 1.0% | <0.001 |
| Chronic pulmonary disease | 15.2% | 16.0% | <0.001 |
| Obesity | 12.2% | 12.9% | <0.001 |
| Coagulopathy | 1.6% | 2.7% | <0.001 |
| Neurological disorder | 2.6% | 3.3% | <0.001 |
| Anemia | 7.3% | 9.7% | <0.001 |
| Collagen vascular disease | 1.6% | 1.9% | <0.001 |
| Valvular heart disease | 0.2% | 0.3% | <0.001 |
| Peripheral vascular disease | 12.7% | 10.0% | <0.001 |
| Teaching hospital | 56.3% | 53.8% | <0.001 |
| Median length of stay (days) | 1.0 | 3.0 | <0.001 |
| Median charge ($) | 45,503 | 54,456 | <0.001 |
| Hospital bedsize | 0.001 | ||
| Small | 7.2% | 6.7% | |
| Medium | 19.2% | 20.4% | |
| Large | 73.5% | 73.0% | |
| Hospital region | <0.001 | ||
| Northeast | 22.1% | 17.4% | |
| Midwest | 25.0% | 26.1% | |
| South | 36.8% | 39.4% | |
| West | 16.0% | 17.2% | |
| Median income of the zip code | |||
| 1 st Quartile | 26.1% | 27.3% | 0.001 |
| 2 nd Quartile | 26.5% | 27.3% | |
| 3 rd Quartile | 24.5% | 24.6% | |
| 4 th Quartile | 22.9% | 20.8% | |
| Payer | <0.001 | ||
| Medicare | 57.3% | 47.2% | |
| Medicaid | 5.1% | 6.1% | |
| Private/HMO | 32.6% | 36.1% | |
| Self-pay | 2.5% | 6.6% |
The annual rate of all PCIs ( Figure 1 ) decreased by 27.7% from 10,785 procedures per million adults per year in 2007 to 2008 to 7,801 procedures per million adults per year in 2010 to 2011 (p = 0.03). There was a slight increase from 2007 to 2008 in the overall utilization of PCI, but this is followed by a significant reduction in the utilization of PCI from 2009 to 2011. Although there was no statistically significant decrease in the PCI utilization for ACS from 2007 to 2011, PCI utilization for stable CAD started to decrease in 2009 with a substantial decrease in 2010 ( Figure 1 ). Table 2 demonstrates a ∼50% reduction in the annual incidence of PCI after 2008.
| Indication | Quartile | 2007 | 2008 | 2009 | 2010 | 2011 | p Value | % Change ∗ |
|---|---|---|---|---|---|---|---|---|
| Overall | 5297.5 | 5487.8 | 4929.9 | 3932.8 | 3868.8 | 0.03 | −27.7% | |
| Stable coronary artery disease | First | 15.4 | 22.0 | 36.8 | 32.6 | 19.8 | 0.6 | +40.3 |
| Second | 172.7 | 167.7 | 169.2 | 134.9 | 107.1 | 0.03 | −28.9 | |
| Third | 494.2 | 426.8 | 349.9 | 262.3 | 228.5 | 0.001 | −46.7 | |
| Fourth | 1372.2 | 1439.2 | 1105.1 | 621.9 | 636.6 | 0.02 | −55.2 | |
| Total | 2054.5 | 2055.7 | 1658.0 | 1051.7 | 992.0 | 0.01 | −50.3 | |
| Acute coronary syndrome | First | 64.4 | 85.7 | 127.1 | 125.2 | 88.2 | 0.4 | +42.2 |
| Second | 392.6 | 424.3 | 412.8 | 406.0 | 408.0 | 0.8 | −0.4 | |
| Third | 856.8 | 847.2 | 871.2 | 760.4 | 765.7 | 0.1 | −10.4 | |
| Fourth | 1929.2 | 2074.9 | 1860.8 | 1589.5 | 1614.9 | 0.07 | −20.0 | |
| Total | 3243.0 | 3432.1 | 3271.9 | 2881.1 | 2876.8 | 0.09 | −13.7 |
∗ % Change indicates the change in volume 2 years before and after the publication of the appropriateness criteria (i.e., from 2007 to 2008 vs 2010 to 2011).
Given the 10% increase in the number of hospitals performing PCI from 2009 to 2011, the decrease in the rates of PCI reflects a 20.3% reduction in the median caseload of 1,379 per hospital in 2007 to 1,098 cases in 2011. The majority of reduction is due to the decrease in the PCI utilization for stable CAD (median caseload of 509 per hospital in 2007 to 223 cases in 2011; Figure 1 ).
Figure 2 demonstrates the rates of PCI utilization over time in key subgroups for stable CAD population based on teaching status, region, hospital size, and PCI volume. A steady decrease in the frequency of PCI from 2008 to 2011 was observed in both academic and nonacademic hospitals (54.2%, p = 0.02 and 48.3%, p = 0.01, respectively). It is notable that nonacademic hospitals began with significantly higher volume in year 2007 and experienced a more precipitous decrease from 2008 to 2011. PCI utilization for ACS decreased moderately in both academic and nonacademic hospitals from 2008 to 2011 (14.7% and 17.3%, respectively).
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