Cardiac Tests Result in More Tests, With Little Answers

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A recent study analysis of more than 220 US hospitals demonstrates wide variation in the use of noninvasive imaging in patients admitted to the emergency department with chest pain. Regardless of the variation, hospitals with high rates of imaging did not have lower MI readmission rates than those with lower rates of noninvasive cardiac imaging.

Yet patients treated at hospitals that were frequent users of noninvasive imaging were more likely to be admitted to the hospital and to undergo coronary angiography.

Our experience is that there are a lot of different approaches being employed by hospitals around the country, some with protocol-based chest-pain centers and others with more ad hoc approaches. And it seems like there is much less discretion in terms of patients who would merit imaging and how best to apply it. We wanted to get some perspective on how much variation there was and whether there was any relationship between the variation and patient outcomes,” said senior investigator from Yale University School of Medicine, New Haven, CT, Dr. Harlan Krumholz.

According to Krumholz the study, recently published online February 10, 2014 in JAMA: Internal Medicine, was meant to offer some data on the nationwide assessment of patients with suspected ischemic heart disease, particularly those with acute coronary syndromes. These patients are often difficult to track because they can be lost to follow-up once they enter into the hospital.

The current analysis is predicated on data from the PREMIER database of 2700 acute-care hospitals in the US. All in all, 549 078 patients from 224 hospitals were included in the study, and the use of noninvasive imaging ranged from 0.2% to 55.7%.

When the hospitals were stratified by quartiles (Q), the use of noninvasive testing was performed 6.0%, 15.9%, 23.5%, and 34.8% in Q1, Q2, Q3, and Q4, respectively. Myocardial perfusion imaging and stress echocardiograms were the most frequently employed imaging tests. In total, 80.4% of the 113 602 imaging tests performed were myocardial perfusion tests, 16.6% were echocardiograms, and 1.2% were computed tomography coronary angiograms (CTCAs).

"We found a remarkable variation in the use of imaging, which is an expensive intervention, and its use was strongly linked to what happened to the patient subsequently. The testing cascade has been discussed in other articles, but this is more proof that the more expensive tests you do the more likely you are to pursue additional tests,” said Krumholz.

When compared with those in Q1, hospitals with the highest rates of imaging (Q4) were more likely to admit patients and conduct coronary angiography. Hospitals with lower rates of imaging performed angiography in 1.2% of patients as opposed to 4.9% in patients treated at hospitals with higher use of noninvasive imaging. The rate of coronary revascularization was also higher among patients treated at hospitals with higher rates of noninvasive imaging.Cardiac-Imaging 500

Yet, in terms of revascularizations per imaging study and revascularizations per angiogram, hospitals in Q1 had significantly better yield than those in Q4.

In spite of the differences in care among hospitals more likely to use imaging, there was no difference in the patients readmitted to hospital within the month or the following month.

"We couldn't find any evidence that patients are being benefited by the approach," said Krumholz, referring to the higher rates of imaging at some hospitals.

“A lot of hospitals don't have any feedback in terms of where they stand in relationship to other hospitals with their use of noninvasive imaging tests. In analyzing the patient characteristics and hospital factors, the group also found that nearly 25% of the between-hospital variation is attributable to institutional factors and not the types of patients treated. Regarding best clinical practices, the study was not designed to determine whether imaging was appropriate, but the researchers contend that patient-case mix would unlikely account for the variation in cardiac imaging rates,” he added.

In an accompanying article, Drs Ezra Amsterdam and Edris Aman from the University of California, Davis point out that accelerated diagnostic protocols (ADPs) involve identifying low-risk patients based on clinical stability, a normal ECG, and a negative biomarker test.

Predischarge testing is then used to identify patients for early discharge, and this could include anything from an exercise treadmill test to CCTA.

"At the University of California, Davis, Medical Center in Sacramento, we practice physician discretion in selecting patients for predischarge testing. In more than 500 patients discharged directly from the unit after evaluation consisting of normal results of electrocardiograms and cardiac troponin tests, there has been only one adverse cardiac event (0.2%) at the 30-day follow-up,” they write.

However, such tactics depends on attaining a detailed family history, an accurate assessment of the ECG, and a reliable assay for cardiac troponin, as well as the willingness of clinicians to implement such an algorithm, especially given the hazards of a missed acute coronary syndrome.

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