Hospital Variation in the Use of Noninvasive Cardiac Imaging and Its Association With Downstream Testing, Interventions, and Outcomes

Study Questions:

What is the variation in hospital utilization of noninvasive cardiac testing in patients presenting with suspected myocardial ischemia, and the impact on downstream coronary arteriography interventions and readmission for acute myocardial infarction (AMI)?

Methods:

Data on 549,078 patients at 224 hospitals were extracted from the Premier, Inc., hospital database. All patients were seen in the emergency department, observation unit, or inpatient ward and were identified as having had at least one cardiac biomarker and a principal discharge diagnosis relevant to chest discomfort, evidence of cardiac ischemia, and/or a comorbidity associated with coronary disease. Patients subsequently proven to have AMI were excluded. At each hospital, the number of patients who received noninvasive imaging for evaluation of cardiac ischemia was identified and the subsequent rates for hospital admission, coronary arteriography, and revascularization were determined. Readmission for AMI within 60 days to the same hospital was also tabulated. Hospitals were stratified by quartiles (Q) of noninvasive imaging.

Results:

A total of 113,602 imaging studies were performed in the cohort, 80.4% of which were myocardial perfusion images, 16.6% echocardiograms, and 1.2% coronary computed tomography angiograms. Imaging rates ranged from 0.2% to 55.7% (median 19.8%). Imaging rates for Q1-Q4 were 6%, 15.9%, 23.5%, and 34.8%. Bed size, access to observation beds, urban versus rural location, and teaching status were similar among the four quartiles. Higher quartile hospitals were more likely to be located in midwest and northeast geographies (p < 0.001). Considering Q1-Q4 of imaging utilization, the rates of coronary arteriography were 1.2%, 2.2%, 3.3%, and 4.9%, with revascularization occurring in 0.5%, 0.9%, 1.2%, and 1.9% (p < 0.001 for both). Revascularization rates per imaging study were 7.6% in Q1 and progressively declined to 5.4% in Q4 (p < 0.001). Similarly, revascularization per angiogram was 41.2% in Q1 and progressively declined to 38.8% in Q4 (p < 0.001). Readmission with AMI within 60 days was 0.3% in each of the four quartiles.

Conclusions:

There is substantial variation in use of noninvasive cardiac testing in patients presenting with suspected myocardial ischemia. Higher imaging rates were associated with higher coronary arteriography rates, but not with higher rates of therapeutic intervention or lower readmission rates for AMI.

Perspective:

This large database survey including over 500,000 patients in 224 hospitals demonstrated substantial variation in the use of noninvasive testing (predominately myocardial perfusion imaging) in patients presenting with symptoms for which myocardial ischemia was suspected. Within the limits of available data, the authors have modeled the likelihood of receiving cardiac imaging and demonstrating that 23% of the variations in rates of cardiac imaging are related to hospital-specific variation rather than clinical or patient-related variables. They further calculated that a pool of identical patients presenting at different hospitals could have as high as a two-fold difference in the likelihood of receiving noninvasive cardiac testing. Multiple previous studies have suggested an overutilization of cardiac noninvasive cardiac testing and have previously attributed it to hospital variation as well as practice variation. This large database study confirms an observation of a presumed excess of cardiovascular testing, but does not provide data to further elucidate the specific cause, with respect to further details of practice pattern, financial incentive, etc. The higher rates of angiography associated with higher rates of noninvasive testing with an actual drop in the percentage of patients requiring intervention, suggests that the lower threshold for cardiac testing resulted in more patients with low pretest likelihood being evaluated, which results in a subsequent higher rate of false-positive imaging results. While not addressed in this manuscript, an obvious next step would be to further find the characteristics of decision making in the low and high utilization hospitals with respect to specific guidelines, heterogeneity of practice patterns, and other factors.

Clinical Topics: Invasive Cardiovascular Angiography and Intervention, Noninvasive Imaging, Atherosclerotic Disease (CAD/PAD), Interventions and Coronary Artery Disease, Interventions and Imaging, Angiography, Computed Tomography, Echocardiography/Ultrasound, Nuclear Imaging

Keywords: Myocardial Perfusion Imaging, Coronary Artery Disease, Myocardial Infarction, Myocardial Ischemia, Biological Markers, Coronary Angiography, Tomography, X-Ray Computed, Emergency Service, Hospital, Angioplasty, Balloon, Coronary, Echocardiography


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