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provided by Elsevier - Publisher Connector Journal of the American College of Vol. 56, No. 16, 2010 © 2010 by the American College of Cardiology Foundation ISSN 0735-1097/$36.00 Published by Elsevier Inc. doi:10.1016/j.jacc.2010.03.093

Cardiac Testing

Patterns of Cardiac Stress Testing After Revascularization in Community Practice

Bimal R. Shah, MD, MBA,*† Patricia A. Cowper, PHD,* Sean M. O’Brien, PHD,* Neil Jensen, MHA,‡ Matthew Drawz, MBA,‡ Manesh R. Patel, MD,* Pamela S. Douglas, MD,* Eric D. Peterson, MD, MPH* Durham, North Carolina; Singapore, Republic of Singapore; and Minnetonka, Minnesota

Objectives The purpose of this study was to determine the pattern of cardiac stress testing after coronary revascularization in community practice.

Background The American College of Cardiology Foundation appropriate use criteria provide guidance for the use of cardiac stress imaging after coronary revascularization. However, little is known regarding the use of routine cardiac stress testing in coronary artery bypass grafting or percutaneous coronary intervention patients as well as their downstream use of invasive procedures after noninvasive testing in community practice.

Methods Use and timing of stress testing more than 90 days after revascularization in patients 18 to 64 years of age were determined from a national health insurance claims database from July 1, 2004, through June 30, 2007. Subsequent rates of angiography and repeat revascularization after stress testing also were examined.

Results Of 28,177 patients undergoing revascularization (21,046 percutaneous coronary intervention procedures and 7,131 coronary artery bypass grafting procedures), 59% had at least 1 cardiac stress test within 24 months. Sixty-one percent of patients with percutaneous coronary intervention and 51% of patients with coronary artery bypass grafting had undergone testing by 24 months. Nuclear imaging was the predominant testing method. The incidence of testing was found to increase at both 6 months and 12 months after revascularization, suggest- ing an association with elective follow-up office visits. Furthermore, testing varied according to geographic loca- tion. Of those tested, only 11% underwent subsequent and only 5% underwent repeat revascularization.

Conclusions Although there is limited consensus as to the appropriate role of elective stress testing after coronary revascular- ization, more than one half of all patients in community practice had at least 1 stress test within 24 months of revascularization. Yield on such testing was low: only 5% of patients tested ultimately required repeat revascu- larization. These findings support the need to define better the role of stress testing after recent revascularization. (J Am Coll Cardiol 2010;56:1328–34) © 2010 by the American College of Cardiology Foundation

Noninvasive stress testing, with or without imaging meth- physician service in recent years (1,2). This growth has come ods such as , nuclear imaging, and mag- without sufficient evidence to determine the impact of netic resonance, improves assessment of cardiac anatomic testing on clinical outcomes (3,4). and pathologic features. Although these testing methods To help guide diagnostic imaging use, the American can assist in patient management, there has been rapid College of Cardiology Foundation (ACCF) has recently expansion in their use over time, and noninvasive imaging developed appropriate use criteria (AUC) (5–7). The has been among the fastest growing components of any ACCF AUC aim to assist clinical decision-making by outlining available evidence coupled with expert consensus on the optimal use of imaging in various clinical situations. From the *Duke Clinical Research Institute, Duke University Medical Center, Durham, North Carolina; †Duke–National University of Singapore Graduate Med- See page 1335 ical School, Singapore, Republic of Singapore; and ‡UnitedHealthCare, Minnetonka, Minnesota. Supported by UnitedHealthCare. Neil Jensen and Matthew Drawz are employees of UnitedHealthCare. Dr. Cowper has received research grant support One area with limited data in the ACCF AUC was the from UnitedHealthCare. All other authors have reported that they have no relation- ships to disclose. routine use of stress testing with imaging (nuclear, echocar- Manuscript received December 20, 2009; accepted March 10, 2010. diography) after revascularization. However, expert consen- JACC Vol. 56, No. 16, 2010 Shah et al. 1329 October 12, 2010:1328–34 Cardiac Stress Testing After Revascularization sus concluded that stress testing generally was inappropriate functional capacity assessments Abbreviations within 2 years for percutaneous coronary intervention and were not counted as a post- and Acronyms (PCI) and within 5 years for coronary artery bypass revascularization stress study. American College ؍ ACCF grafting (CABG), unless prompted by symptoms or other The indications for stress testing of Cardiology Foundation appropriate use ؍ change in clinical status (7). were identified using ICD-9 AUC Having access to an administrative database from a codes recorded at the time of the criteria coronary artery ؍ large national health insurer, we sought to assess clinical stress test. CABG practice patterns and frequency of stress testing use in The first identified PCI or bypass grafting Current Procedure ؍ patients after coronary revascularization. We also as- CABG procedure for each pa- CPT sessed patient and geographic variation in these testing tient was considered the index Terminology electrocardiographic ؍ patterns. Finally, we examined downstream angiography revascularization. Multiple revas- ECG

International ؍ and repeat revascularization rates that resulted from cularization procedures within a ICD-9 initial stress testing. single encounter were considered Classification of Diseases- as a single revascularization event 9th Revision-Clinical for the current analysis. For each Modification Methods percutaneous ؍ patient, we extracted physician PCI coronary intervention Data source. Data were obtained from UnitedHealth- claims for all stress tests, coro- Care’s administrative billing records for more than 17.7 nary angiographies, and coronary million members enrolled in employer-sponsored plans revascularizations as well as inpatient and outpatient hospi- from July 1, 2004, through June 30, 2007. All claims tal revascularization and angiography claims occurring after (inpatient and outpatient hospital encounters, physician the index revascularization procedure. Patients were in- claims) and enrollment information were provided for cluded in the primary analysis if they survived 90 days after UnitedHealthCare patients who underwent coronary revas- revascularization without a competing event (death, angiog- cularization with either CABG or PCI during this period. raphy, or repeat revascularization) or loss of coverage. Hospital claims included International Classification of Statistical analysis. Characteristics of patients undergoing Diseases-9th Revision-Clinical Modification (ICD-9) diag- revascularization with PCI or CABG were examined. Time nosis and procedure codes, Current Procedure Terminology to the first stress test occurring 90 days after the index (CPT) procedure codes, dates of service, discharge disposi- revascularization episode was examined using cumulative tion, and zip code of provider. Physician claims included incidence functions that accounted for administrative cen- ICD-9 diagnosis codes, CPT procedure codes, and dates of soring and treated coronary angiography, repeat revascular- service. Death dates from the Social Security Death Master ization, and death as competing risks. In addition to File also were provided for the sample. To ensure continu- examining overall stress testing incidence, stress echocardi- ous longitudinal follow-up, for the small number (3%) of ography and stress nuclear and ECG stress testing were patients with discontinuous enrollment periods, only the analyzed separately. These analyses were repeated after first enrollment period was considered. stratifying by sex, age, comorbidities identified by ICD-9 Revascularization procedures were identified using CPT codes at the time of index revascularization, and core-based and ICD-9 codes (PCI, 92980 through 92982, 92973, statistical area. The core-based statistical area is a standard 92984, 92995 through 92996, G0290 through G0291, regional classification based around an urban center with a 36.0x, 00.66; CABG, 33510 through 33529, 33533 through population of at least 10,000 (8). The univariate association 33536, 36.1x, 36.2, 36.31, 36.32). Patients with revascular- between cumulative incidence and variables of interest was ization claims that appeared in either the hospital or assessed using the Gray test (9). physician claims but not in both sources were excluded from For patients undergoing stress testing, we analyzed the the analysis because of incomplete data capture. rates of coronary angiography within 30 days of stress Stress testing. Cardiac stress and imaging tests were iden- testing as well as the rate of repeat revascularization within tified by CPT codes (electrocardiographic [ECG] stress, 30 days of coronary angiography. The 30-day follow-up 93015 through 93018; nuclear, 78460 through 78461, windows were chosen to capture sequential procedures most 78464 through 78466, 78468 through 78469, 78472 likely to result from testing. To determine the effect on the through 78473, 78481, 78483, 78491 through 78492, analysis of excluding stress tests within 90 days of the index 78494; stress echocardiography, 93350). ECG stress and revascularization, we removed the 90-day allowance in a nuclear imaging procedures performed within 72 h of each sensitivity analysis and examined all stress tests after the other were considered a single stress nuclear event. ECG revascularization date. stress and echocardiographic testing performed on the same The Duke University Institutional Review Board re- day were considered a single stress echocardiography event. viewed and approved the study design. All statistical anal- Cardiac stress tests occurring within the first 90 days after yses were performed using SAS software version 9.2 (SAS revascularization were assumed to be performed for the Institute, Cary, North Carolina) and R Project for Statisti- purposes of , staging of procedures, or cal Computing software version 2.11.0 (10). 1330 Shah et al. JACC Vol. 56, No. 16, 2010 Cardiac Stress Testing After Revascularization October 12, 2010:1328–34

PatientTime of CharacteristicsCoronaryPatient Revascularization Characteristics at the at the InternationalRevision-ClinicalStress Testing Classification After Modification Revascularization of IndicationsDiseases-9th for Initial Table 1 International Classification of Diseases-9th Time of Coronary Revascularization Table 2 Revision-Clinical Modification Indications for Initial Stress Testing After Revascularization All PCI CABG p Value All PCI CABG (7,131 ؍ n) (21,046 ؍ n) (28,177 ؍ n) (2,473 ؍ n) (9,315 ؍ n) (11,788 ؍ Age (yrs) 55 Ϯ 655Ϯ 656Ϯ 6 Ͻ0.001 (n Female 21 22 18 Ͻ0.001 Ischemic disease (414.0X) 73 73 71 Acute myocardial 29 32 20 Ͻ0.001 Chest pain 24 24 23 infarction (786.50, 786.51,786.59) Region Ͻ0.001 (413.X) 6 6 5 Northeast 10 10 8 Chest pain or angina 29 30 28 South 49 48 51 (786.50, 786.51,786.59, 413.X) Midwest 29 29 28 Shortness of breath (786.05) 4 4 5 West 13 13 12 Acute 221 (410.XX) Diabetes mellitus 19 19 20 0.13 Acute coronary syndrome (411.1) 1 1 1 Congestive 6 4 11 Ͻ0.001 Other 10 9 12 Hyperlipidemia 44 48 31 Ͻ0.001

Previous myocardial 6 6 5 0.05 Values are expressed as a percentage of total number of stress tests after revascularization. infarction Percentages do not sum to 100% because of multiple indications per stress test. History of stroke 1 1 2 Ͻ0.001 Abbreviations as in Table 1. Peripheral vascular 212Ͻ0.001 disease patients tested, respectively. When tests within the first 90 Chronic obstructive 8614Ͻ0.001 days after revascularization were included in a sensitivity pulmonary disease analysis, the 24-month cumulative incidence of stress test- Renal failure 0.9 0.8 1.2 Ͻ0.001 ing after revascularization was 61%, with 62% and 58% of Tobacco use 14 15 9 Ͻ0.001 PCI and CABG patients being tested, respectively.

All values are expressed as percentages unless otherwise specified. The distribution of testing method used and multiple CABG ϭ coronary artery bypass grafting; PCI ϭ percutaneous coronary intervention. stress testing rates after revascularization are shown in Table 3. Results Nuclear imaging was the most frequently used testing method after revascularization, particularly among patients Patient cohort. We identified 36,598 members at least 18 with PCI. Eleven percent of all patients with revasculariza- years and younger than 65 years of age with a revascular- tion had a second stress test performed within 24 months ization with CABG or PCI during the study period. Of without an intervening angiography or repeat revasculariza- these patients, 28,177 patients (21,046 with PCI and 7,131 tion procedure. PCI patients had a shorter median time to with CABG) had a minimum of 90 days of follow-up first stress test than CABG patients (380 days vs. 610 days). without a competing risk within 90 days of their first Within 24 months of revascularization, 5% of patients revascularization. The mean follow-up available for patients underwent angiography without prior stress testing (6% and undergoing revascularization was 404 Ϯ 254 days. Table 1 provides characteristics of patients at the time of the index coronary revascularization based on ICD-9 classification of comorbid diagnoses. Patients undergoing PCI were more likely to be female, have a diagnosis of hyperlipidemia, and smoke tobacco, whereas patients undergoing CABG were more likely to have a diagnosis of congestive heart failure and chronic obstructive pulmonary disease. Table 2 shows ICD-9 diagnosis codes for initial stress testing after revascularization stratified by revascularization procedure. There was no clinically significant difference in the indications for testing between the 2 groups, but coding for clinical symptoms accounted for approximately one third of all testing. Pattern of stress testing. Figure 1 depicts the cumulative incidence of initial stress testing between 90 days and 24 months after revascularization. The 12-month cumulative Figure 1 Cumulative Incidence of Cardiac Stress Testing After Coronary Revascularization incidence of testing was 36% overall, with a rate of 39% and 28% in PCI and CABG patients, respectively. Fifty-eight Graph showing the cumulative incidence of stress testing between 90 days and 24 months after revascularization overall and by revascularization type. percent of patients undergoing revascularization underwent CABG ϭ coronary artery bypass grafting; PCI ϭ percutaneous coronary at least 1 cardiac stress test within 24 months of coronary intervention. revascularization, with 61% and 51% of PCI and CABG JACC Vol. 56, No. 16, 2010 Shah et al. 1331 October 12, 2010:1328–34 Cardiac Stress Testing After Revascularization

StressAfter Index Testing CoronaryStress Incidence Testing Revascularization at 24Incidence Months at 24 Months CumulativeatSelect 24 Months Patient Incidence After Subgroups Revascularization of Stress Testing in Table 3 Cumulative Incidence of Stress Testing After Index Coronary Revascularization Table 4 at 24 Months After Revascularization in Select Patient Subgroups All PCI CABG Stress Testing (7,131 ؍ n) (21,046 ؍ n) (28,177 ؍ n) Any stress test 58 61 51 Patient Characteristics Incidence (%) p Value Stress echocardiography 7 7 6 Sex Nuclear stress imaging 50 52 42 Female 58 0.62 Exercise 6 6 8 Male 59 Repeat stress testing 11 12 9 Age (yrs) Ͻ45 59 0.04 Data are expressed as percentages of the total revascularization population. 45 to 54 59 Abbreviations as in Table 1. 55 to 64 58 3% for PCI and CABG, respectively) and 4% of patients Diabetes mellitus underwent repeat revascularization without prior testing. Yes 56 0.005 The incidence of death (without intervening stress, angiog- No 59 raphy, or revascularization) at 24 months was 0.7%. Congestive heart failure Figure 2 shows the additional proportion of patients Yes 52 Ͻ0.001 undergoing stress testing in successive 30-day intervals after No 59 Hyperlipidemia revascularization, stratified by revascularization type. Two Yes 61 Ͻ0.001 periods were observed to have increased testing after revas- No 56 cularization, 180 to 210 days and 360 to 390 days, with the Previous myocardial infarction greatest increase in the proportion of patients having their Yes 56 0.62 first stress test occurring at 180 to 210 days after PCI. No 59 Factors affecting patterns of stress testing. Table 4 shows Tobacco use stress testing incidence in patients stratified by sex, age, and Yes 57 0.02 comorbid conditions at the time of index revascularization. No 59 Testing declined slightly with age. However, patients with- Renal disease out diabetes and congestive heart failure had clinically Yes 53 0.53 significant higher rates of testing those with disease. Testing No 59 patterns varied moderately among core-based statistical areas, with the proportion of patients undergoing stress testing without subsequent angiography or repeat revascu- Yield of stress testing. Of patients undergoing stress test- larization ranging from 51% to 71% at 24 months (p Ͻ ing within 2 years, 11% had a subsequent coronary angio- 0.001) (Fig. 3). gram within 30 days of testing. Of those patients undergo- ing stress testing followed by coronary angiography, only

Figure 2 Additional Proportion of Patients With Stress Testing After Revascularization Figure 3 Geographic Variation in Stress Testing After Revascularization Graph showing additional proportion of patients undergoing stress testing in successive 30-day intervals after revascularization. Each value marked on the Graph showing geographic variation in stress testing at 24 months after revas- horizontal axis represents the lower bound of the 30-day interval (90 refers to cularization in core-based statistical areas with at least 300 revascularization 90 to 119 days, 120 refers to 120 to 149 days, etc.). Abbreviations as in patients. Dotted horizontal line represents incidence of stress testing after Figure 1. revascularization for the entire study cohort (59%). 1332 Shah et al. JACC Vol. 56, No. 16, 2010 Cardiac Stress Testing After Revascularization October 12, 2010:1328–34

46% (48% of PCI and 37% of CABG patients), or 5% of all guidelines, variation in use may be influ- patients tested, underwent repeat revascularization. enced by physician attitudes and training, patient prefer- ences, inappropriate use, and other nonclinical factors not Discussion captured in an administrative dataset. However, our study straddled the publication of the various ACCF AUC Although the routine use of stress testing within 2 years of statements, limiting our ability to determine the effect of revascularization is considered inappropriate by recent these guidelines on cardiac testing patterns. ACCF AUC (5–7), more than 50% of patients of a large Undoubtedly, some portion of testing identified in this national insurance provider had at least 1 stress test between analysis corresponds to clinical follow-up, where cardiac 90 days and 2 years after coronary revascularization in symptoms are more likely to be elicited and reported. community practice. Further, we observed a bimodal pat- Surveillance testing and testing in patients with silent tern in stress testing in PCI patients, with the highest before revascularization likely also account for incidence of testing observed at 6 and 12 months after some of the testing. We observed that the rate of testing revascularization. Of the patients tested, only approxi- seems to be higher for patients undergoing PCI. The higher mately 1 in 10 went on to subsequent diagnostic coronary rates in patients with PCI may be related to concerns of angiography, and only 1 in 20 patients underwent repeat restenosis or incomplete revascularization in these patients revascularization. as compared with patients undergoing CABG. Unfortu- The variation in cardiac imaging and procedures in the nately, we have limited information on symptoms and U.S. was previously analyzed in Medicare claims data clinical indications beyond ICD-9 diagnosis codes at the through the Dartmouth Atlas Project (11). These investi- time of stress. As a result, our results should be considered gators found that geographic variation in use of imaging hypothesis generating with regard to appropriateness of procedures was as high as 10-fold and that the most testing. However, if we compare our 40% stress test inci- significant predictor of imaging use was where a patient dence 1 year after PCI with data from the National Heart, lived. Furthermore, they found that there was not an inverse Lung and Institute dynamic registry indicating that relationship between invasive and noninvasive testing to 18% of PCI patients report angina symptoms at the 1-year suggest that these tests were interchangeable, and in fact, follow-up (17), we can surmise that testing occurred more more noninvasive testing led to more invasive investigations. frequently than would be predicted from symptoms alone. Other studies have similarly shown up to 4-fold geographic The finding that only 10% of patients with stress testing variation in the use of echocardiography (12). Similar data undergo coronary angiography suggests that testing in this are present for use of coronary angiography, with the population identified a very small proportion of patients that presence of the technical capability to perform a cardiac either had positive stress test results or other indications for catheterization being more predictive than any clinical further invasive investigation. In patients who proceeded to factor (13), and significant geographic variation in cardiac diagnostic angiography after testing, less than half under- angiography after acute myocardial infarction (14). went repeat revascularization. As a result, the overall diag- We found in a large national claims database that stress nostic yield of stress testing to identify patients requiring testing use after coronary revascularization also shows geo- repeat revascularization seems very low even in regions with graphic variations, and that such patterns still persist more high testing rates. These findings suggest that an opportu- than 10 years after their initial description. We found up to nity exists to improve the selection of patients that should a 50% difference in rates of testing between regions. Unlike undergo post-revascularization testing. The ACCF AUC prior work in this area, we were able to describe the provide guidance for indications for testing, thereby allow- temporal trends in stress testing in a non-Medicare popu- ing allocation of testing resources to those patients most lation. To the best of our knowledge, our study is the first to likely to benefit from further invasive testing and repeat demonstrate 2 periods of increased testing incidence at 6 revascularization (16,18,19). and 12 months after revascularization that seem to corre- Cardiologists are under considerable scrutiny for overuse spond to elective outpatient follow-up visits. Furthermore, of imaging and testing (20–23). Variation in clinical prac- our finding that for every 2 patients undergoing diagnostic tice matters because uncertainty about the appropriate angiograms, only 1 revascularization occurs after stress application of stress testing leads to more testing overall testing parallels findings previously reported in the Dart- (12). False-positive testing and testing in inappropriate mouth Atlas project, in which national invasive imaging and populations leads to increased costs and risks for patients, revascularization patterns also were examined (15). reduces the accuracy of tests (24), and may impact overall Recent single-center investigations have shown that in- quality of care negatively. Additionally, mounting evidence appropriate stress testing rates approach 20% for both stress suggests that excessive testing results in unnecessary and nuclear and stress echocardiography tests (16). It is reason- nontrivial radiation exposure (25,26). Finally, the lack of able to assume that the frequency and variation in testing evidence to date that imaging significantly improves clinical found in our study is reflective of the uncertainty of evidence outcomes requires that ordering physicians prudently assess to direct clinical decision-making. Beyond the lack of how the proposed testing would change care decisions (3). JACC Vol. 56, No. 16, 2010 Shah et al. 1333 October 12, 2010:1328–34 Cardiac Stress Testing After Revascularization

Study limitations. There are limitations to the current 5. Cardiac Imaging Writing Group, Hendel RC, Berman analysis that should be considered. First, our observations DS, et al. ACCF/ASNC/ACR/AHA/ASE/SCCT/SCMR/SNM 2009 appropriate use criteria for cardiac radionuclide imaging: a report are derived from an administrative dataset, limiting the of the American College of Cardiology Foundation Appropriate Use granularity of clinical data. We relied on ICD-9 codes to Criteria Task Force, the American Society of Nuclear Cardiology, the identify comorbid conditions at the time of revasculariza- American College of Radiology, the American Heart Association, the American Society of Echocardiography, the Society of Cardiovascular tion; these codes may represent outcomes of the procedure Computed Tomography, the Society for Cardiovascular Magnetic as opposed to pre-existing conditions. We do not have Resonance, and the Society of Nuclear Medicine. Circulation 2009; information on symptoms after revascularization, stress 119:e561–87. 6. Hendel RC, Patel MR, Kramer CM, et al. ACCF/ACR/SCCT/ testing before patients’ initial coverage date, and whether SCMR/ASNC/NASCI/SCAI/SIR 2006 appropriateness criteria for stress testing altered medical management in patients. cardiac computed tomography and cardiac magnetic resonance imag- Additionally, our findings are based on 1 national insurer of ing: a report of the American College of Cardiology Foundation Quality Strategic Directions Committee Appropriateness Criteria working-age adults and the geographic markets in which it Working Group, American College of Radiology, Society of Cardio- operates, perhaps limiting the generalizability of our results vascular Computed Tomography, Society for Cardiovascular Magnetic to older patients, other regions, and other reimbursement Resonance, American Society of Nuclear Cardiology, North American Society for Cardiac Imaging, Society for Cardiovascular Angiography environments. and Interventions, and Society of Interventional Radiology. J Am Coll We could not identify early testing carried out for Cardiol 2006;48:1475–97. appropriate indications, such as clearance for cardiac reha- 7. Douglas PS, Khandheria B, Stainback RF, et al. ACCF/ASE/ACEP/ ASNC/SCAI/SCCT/SCMR 2007 appropriateness criteria for trans- bilitation or workforce participation. However, we excluded thoracic and transesophageal echocardiography: a report of the Amer- all stress tests occurring within 90 days of revascularization, ican College of Cardiology Foundation Quality Strategic Directions the period during which such testing is most likely to occur. Committee Appropriateness Criteria Working Group, American So- ciety of Echocardiography, American College of Emergency Physi- As a result, our estimate of stress testing incidence is cians, American Society of Nuclear Cardiology, Society for Cardio- conservative. vascular Angiography and Interventions, Society of Cardiovascular Computed Tomography, and the Society for Cardiovascular Magnetic Resonance. J Am Coll Cardiol 2007;50:187–204. Conclusions 8. U.S. Census Bureau. Current Lists of Metropolitan and Micropolitan Statistical Areas and Definitions. Available at: http://www.census.gov/ Our findings provide a perspective on the real-world pat- population/www/metroareas/metrodef.html. Accessed December 7, 2009. terns of stress testing after revascularization and, more 9. Gray RJ. A class of K-sample tests for comparing the cumulative importantly, on the geographic variability and yield of incidence of a competing risk. 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