Are cardiologists truly better at appropriately selecting patients for stress myocardial perfusion imaging

Appropriate use criteria (AUC) were developed to aid physiciansin the optimal use of myocardial perfusion imaging (MPI) with single-photon emission computed tomography (SPECT), a pivotal tool in themanagement of patients with known or suspected coronary arterydisease (CAD). AUC for MPI have been widely accepted as a crucialperformance measure, in the United States and worldwide[1–4].Multiple investigators have reported signiﬁcantly higher rates ofinappropriate MPI use among non-cardiologists, namely primarycare physicians (PCPs) [2–8]. This observation was demonstrated inprivate and academic practices across the world, suggesting thatdifferences in expertise or familiarity with AUC is the instigator forexcess inappropriate utilization by non-cardiologists [2–8]. However,these reports did not account for differences in the patient populationcaredfor bycardiologists versus non-cardiologistsresulting from refer-ralbias.It is expected for patients attended to by cardiologist to havegreater prevalence of conditions that favor appropriate adjudicationbytheAUC, suchas known CAD or riskfactors, baselineECG abnormal-ities preventing interpretability for myocardial ischemia (left bundlebranch-block; ventricular-paced rhythm; left ventricular hypertrophywith secondary ST-segment abnormality), or inability to exercise dueto multiple comorbidities [9]. We investigated whether the gap inAUC adherence between cardiologists and PCPs can be explained bydifferences in patient populations rather than disparity in expertise.The study was approved by the institutional review board of RushUniversity Medical Center (Chicago, IL).The study question was investigated using a prospective cohort of1511 patients referred for out-patient, ofﬁce-based, clinically indicatedSPECT-MPI in eleven community practices in the Chicago metropolitanarea (Illinois, United States) between August 15, 2007 and May 15,2010. Twenty-two practitioners (2 cardiologists and 20 PCPs) partici-pated in the study. A detailed description of this cohort is publishedelsewhere [6]. Referral diagnosis, patient demographics, risk factors,and cardiovascular history were prospectively tabulated prior to MPI.The referring physicians' clinical notes (paper or electronic) precedingMPI were reviewed to determine symptoms and the rationale for test-ing. Framingham 10-year global coronary heart disease risk estimateswere calculated [10]. Chest pain syndromes were classiﬁed as: typicalangina, atypical angina, and non-anginal chest pain based on location,exacerbation with exertion and resolution with rest or nitroglycerin[11]. Dyspnea was classiﬁed as “non-anginal chest pain”,consistentwith a similar landmark study [5]. The pre-test probability of obstruc-tive CAD was determined based on age, gender, and chest pain classiﬁ-cation according to Diamond and Forrester tables [11]. Conditionalcomputer-based logic was used to assign each patient a speciﬁcindica-tionandcategorizeMPIstudiesasappropriate,uncertain,orinappropri-ate based on the 2009 AUC [6,9].Among the 1511 MPI studies, 121 (8%) were ordered by cardiolo-gists and 1390 (92%) by PCPs. As shown in Table 1, inappropriate MPIstudies were less frequently requested by cardiologists than PCPs (28%vs. 47%, P b 0.001). However, patients referred by cardiologists wereolder with a greater prevalence of known CAD and CAD risk factors(Table 1). Moreover, patients referred by cardiologists were more fre-quently unable to undergo exercise, mandating a pharmacologic stressmodality, and more likely to have an uninterpretable baseline ECG forstress induced ischemia (Table 1Patients referred by cardiologists).hadhigherincidencesofabnormalmyocardialperfusion,stressinducedischemia, and left ventricular dysfunction (Table 1).Amultivariatelogisticregressionanalysisdemonstratedthatpracti-tionerspecialty(cardiologistvs.PCP)wasnotanindependentpredictorofinappropriateMPIuse[1.17,95%conﬁdenceinterval= 0.61–2.24,P = 0.64], after adjusting for confounders known to impact AUC