Miller, Todd D.

The Impact of Ordering Provider Specialty on Appropriateness Classification In prior studies, our laboratory applied the ACCF/ASNC AUC for SPECT MPI to several cohorts of patients in Mayo Clinic Rochester. The purpose of this study was to re-examine our data to test the hypothesis that the specialty of the ordering provider affected the appropriateness. We compared the ordering providers specialty with appropriateness determined in prior studies. The study group consisted of 281 patients who underwent stress SPECT MPI studies in May 2005 and 282 patients in October 2006 (before any quality improvement initiatives were begun at Mayo). Appropriateness categories were assigned by 2 experienced nurses from the CV Research Studies Unit not affiliated with the nuclear laboratory. Patients who were studied for pre-operative evaluation (n = 20) or post myocardial infarction (n = 7) were excluded because they comprised less than 5 percent of the patients. Pre-operative testing in our institution is done primarily by stress echocardiography. The final study group consisted of 526 patients. Excluding the 64 unclassified patients, AUE categories were appropriate (75 %), uncertain (13 %), inappropriate (12%). Results by ordering provider are shown in the figure, where CV = Cardiovascular MDs, ED = Emergency Department MDs, IM = General and Internal Medicine MDs, RN = Registered Nurses, and SP = other Specialty MDs. There was no significant association (p = 0.19); Chi-square analysis between appropriateness and specialty groups. In a clinical practice where pre-operative testing using SPECT is infrequent, the rate of inappropriate studies was similar for all ordering providers. Quality improvement efforts in similar practices will likely require a broad focus on all ordering physicians/nurses.

Background: Between 1990-2006, there was a tremendous increase in utilization of single photon emission computed tomography myocardial perfusion imaging (SPECT). Characteristics of the observed increase of SPECT utilization have never been studied. Methods: Using the Mayo Clinic nuclear cardiology database, we examined all SPECT tests performed between 1/1/1991-12/31/2007 in patients without prior coronary artery disease (CAD). Patients with history of CAD, left bundle branch block, paced rhythm, bicycle/ rest-only tests, cardiomyopathy, valvular heart disease, and technically unsatisfactory studies were excluded. The study cohort was divided into 4 time periods: 1991-5, 1996-2000, 2001-5, and 2006-7. Results: There were 29255 eligible SPECT tests (mean age 62.4 ± 12y, 54% men). Annual utilization of SPECT studies increased from 682 in 1992 to a peak of 2738 in 2002, and then decreased to 2134 in 2007, Fig 1. There were very modest changes in CAD risk factors over time. Testing of asymptomatic patients nearly doubled (21.9% in 1991-5 to 42.7% in 2006-7). Tests on patients with typical angina decreased dramatically (18.3% in 1991-5 to 5.3% in 2006-7), Fig 2. Summed stress score, summed difference score, and high risk SPECT tests decreased over time, Fig 3. Normal SPECT studies and negative study ECG increased for both pharmacologic and exercise tests. Conclusions: In Mayo Clinic Rochester, annual SPECT utilization in patients without prior CAD increased between 1992 and 2002, but then decreased in advance of national trends. Normal tests increased, while summed stress score, summed difference score, and high risk tests all decreased. These data suggest that SPECT was increasingly utilized in patients with a lower prevalence of CAD.

Background: Over the past 20 years, there has been an increasing decline in the prevalence of abnormal stress single-photon emission computed tomography myocardial perfusion imaging (SPECT) studies among patients with no history of coronary artery disease (CAD). The trend of SPECT studies among patients with known CAD has not been evaluated before. Methods: Using the Mayo Clinic nuclear cardiology database, we examined all stress SPECT tests performed between 1/1991-12/2012 in patients with prior history of CAD defined as having prior myocardial infarction, percutaneous coronary intervention, and/or coronary artery bypass grafting. Patients with left bundle branch block, paced rhythm, bicycle or rest-only tests, cardiomyopathy, valvular heart disease, and technically unsatisfactory studies were excluded. The study cohort was divided into 5 time periods: 1991-5, 1996-2000, 2001-5, 2006-10, and 2011-12. Results: There were 19373 eligible SPECT tests (mean age 66.2 ± 10.9y, 75.4% men). Annual utilization of SPECT studies in patients with history of CAD increased from an average of 495 tests per year between 1991-1995 to a peak of 1425 in 2003; and then decreased to 552 tests in 2012. Asymptomatic patients comprised 33% in 1991-1995, peaked at 48% in 2006, and then decreased back to 31% in 2012. Over time, patients with typical angina decreased while patients with dyspnea increased, P <0.001 (Fig 1). The percentage of high risk SPECT tests significantly decreased, and the percentage of low-risk SPECT tests significantly increased despite the overall decline of SPECT utilization between 2003 and 2012. Almost 80% of all tests performed in 2012 had a low risk summed stress score compared to 29% in 1991, P <0.001 (Fig 2). Conclusions: In Mayo Clinic Rochester, annual SPECT utilization in patients with prior CAD increased between 1992 and 2003, but then decreased significantly after 2003. Fewer patients had typical angina while patients with dyspnea increased over time. High risk SPECT tests declined while low risk tests increased dramatically. These data suggest that stress SPECT was being increasingly utilized in CAD patients without typical angina who are at low risk.

Background : Unrecognized myocardial infarction (UMI), as diagnosed by surveillance electrocardiography (ECG), has the same poor prognosis as recognized (RMI), independent of ejection fraction or ischemia. The value of post UMI risk stratification by infarct size is unknown. Methods : The study group consisted of 5430 patients who underwent 2 day stress (exercise n = 191, pharmacologic n = 155) and rest Tc-99m sestamibi SPECT studies. UMI was diagnosed if ECG showed Q wave MI in the absence of history of MI. SPECT infarct size was quantitated based on a 60% of peak counts threshold method and was expressed as a percentage of the left ventricle (% LV). The association between infarct size and mortality was adjusted for clinical and exercise test prognostic scoring systems. Results : The population consisted of 346 UMI, 628 RMI, and 4456 patients without MI (No MI). Compared to No MI, mortality risk was increased in UMI (RR 1.7, 95% CI 1.6–1.9; p < 0.001) and RMI (RR 1.6, 95% CI 1.4–1.9; p < 0.001) patients. In the UMI group, infarct size was significantly associated with mortality ( p < 0.001), which persisted after adjustment for Mayo prognostic score alone (available in all patients) ( p < 0.001) and for Mayo prognostic score, Framingham risk score, and Duke treadmill score (data available in 137 patients) ( p < 0.001). For every 10% LV increase in infarct size, mortality risk increased 30% (RR = 1.3, 95% CI 1.2–1.5) (see figure ). Conclusions: In patients with UMI, larger quantitated SPECT infarct size predicts increased mortality independent of clinical and exercise test prognostic scoring systems. This finding supports the use of infarct size imaging for risk stratification of UMI patients.

Introduction: The physiologic relevance of myocardial bridging (MB) that is found on invasive (ICA) and CT coronary angiography (CTA) is not known. Myocardial perfusion imaging (MPI) may be useful in objectively assessing altered myocardial blood flow associated with MB. We studied the prevalence of ischemia on MPI and mortality among patients with MB. Methods: Patients with MPI studies within 6 months of MB identified on ICAs (2002-2014) or CTAs (2005-2014) at the Mayo Clinic were retrospectively studied. Exclusion criteria included a history of myocardial infarction (MI), coronary artery bypass grafting and hemodynamically significant coronary artery disease (CAD, coronary artery stenosis ≥ 50%) were excluded. Results: 1116 individuals had MB on ICA out of which 300 had MPI studies. 511 individuals had MB on CTA out of which 63 had MPI studies. After excluding patients with CAD, 114 patients with MB identified on ICA and 31 patients with MB identified on CTA remained for analysis. Patients in the ICA and CTA cohort were the same age (60±13 years for ICA vs 60±12 years for CTA cohort, p=0.9). The ICA cohort was likely to include smokers (47 vs 26%, p=0.03) and those with hyperlipidemia (67 vs 45%, p=0.03). The prevalence of ischemia on MPI was similar in the ICA and CTA cohorts (42 vs. 44%, p=0.5). After a median follow-up of 1166 days, the ICA cohort had 12 patient deaths (8%). There was no death in the CTA cohort. The presence of ischemia on MPI was not associated with increased mortality on long-term follow-up (Log Rank p=0.9). Conclusions: Ischemia on MPI is commonly found in patients with MB who do not have significant CAD. While patients with MB identified on ICA are more likely to have traditional CAD risk factors, the prevalence of ischemia on MPI was similar when compared to patients with MB on CTA. In this small retrospective study, ischemia identified on MPI was not associated with increased mortality.

Background— The Bypass Angioplasty Revascularization Investigation trial demonstrated that symptomatic diabetics with multivessel coronary artery disease had a survival advantage with initial coronary artery bypass grafting (CABG) versus percutaneous coronary intervention (PCI). No published study has examined different treatments and outcome in asymptomatic diabetics. Methods and Results— This study group consisted of 826 asymptomatic diabetics (age 62±12 years; 76% men) without known coronary artery disease who had abnormal myocardial perfusion during stress single photon emission computed tomography (SPECT). SPECT images were classified as low-, intermediate-, and high-risk. Early revascularization (CABG or PCI ≤4 months after SPECT) was performed in 76 patients. Survival (follow-up, 5.3±3.3 years) was compared in patients treated with CABG, PCI, or medical therapy. Revascularization (CABG or PCI) was performed in 54 of 261 patients with high-risk scans and was independently associated with improved survival (χ 2 =4.55; P =0.03 after multivariate adjustment). Subset analysis demonstrated that the survival advantage was confined to patients treated with CABG (n =39), with a 5-year survival CABG at 85%, PCI at 72%, and medical therapy at 67% ( P =0.02 for 3 groups). Although CABG was associated with better survival, mortality remained high (3% per year). There was no survival advantage by treatment for patients with less-severe SPECT abnormalities. Conclusions— These nonrandomized data suggest that CABG improves survival in asymptomatic diabetic patients with high-risk SPECT, although revascularization was performed infrequently in these patients. These results parallel those of the Bypass Angioplasty Revascularization Investigation trial in symptomatic diabetic patients.

Background— There has been a gradual decline in the prevalence of abnormal stress single-photon emission computed tomography (SPECT) myocardial perfusion imaging studies among patients without history of coronary artery disease (CAD). The trends of SPECT studies among patients with known CAD have not been evaluated previously. Methods and Results— We assessed the Mayo Clinic nuclear cardiology database for all stress SPECT tests performed between January 1991 and December 2012 in patients with history of CAD defined as having previous myocardial infarction, percutaneous coronary intervention, and coronary artery bypass grafting. The study cohort was divided into 5 time periods: 1991 to 1995, 1996 to 2000, 2001 to 2005, 2006 to 2010, and 2011 to 2012. There were 19 373 patients with a history of CAD who underwent SPECT between 1991 and 2012 (mean age, 66.2±10.9 years; 75.4% men). Annual utilization of SPECT in these patients increased from an average of 495 tests per year in 1991 to 1995 to 1425 in 2003 and then decreased to 552 tests in 2012 without evidence for substitution with other stress modalities. Asymptomatic patients initially increased until 2006 and then decreased. Patients with typical angina decreased, whereas patients with dyspnea and atypical angina increased. High-risk SPECT tests significantly decreased, and the percentage of low-risk SPECT tests increased despite decreased SPECT utilization between 2003 and 2012. Almost 80% of all tests performed in 2012 had a low-risk summed stress score compared with 29% in 1991 ( P <0.001). Conclusions— In Mayo Clinic, Rochester, annual SPECT utilization in patients with previous CAD increased between 1992 and 2003, but then decreased after 2003. High-risk SPECT tests declined, whereas low-risk tests increased markedly. Our results suggest that among patients with a history of CAD, SPECT was being increasingly utilized in patients with milder CAD. This trend parallels reduced utilization of other stress modalities, coronary angiography, reduced smoking, and greater utilization of optimal medical therapy for prevention and treatment of CAD.