Cardiac Tests in ED Patients Not Tied to Better Outcomes

Norra MacReady

June 27, 2017

Routine cardiac testing may not be indicated for patients who come to the emergency department (ED) with chest pain and few other risk factors, new data suggest.

In an analysis of patients with similar comorbidities and risk factors, invasive and noninvasive cardiac tests were not associated with a reduction in hospital admission for acute myocardial infarction (AMI) at 1 year compared with patients who did not undergo those tests, Alexander T. Sandhu, MD, and colleagues report in an article published online June 26 in JAMA Internal Medicine.

"Our results show that cardiac testing is overused and reinforces the need to evaluate which, if any, patients with chest pain without evidence of ischemia benefit from noninvasive testing," they write.

These data "are consistent with a rapidly expanding evidence base that challenges the current paradigm of early noninvasive testing after an ED evaluation for suspected [acute coronary syndrome]," Benjamin C. Sun, MD, and Rita F. Redberg, MD add in an accompanying editorial.

However, Dr Sandhu, from the Veterans Affairs Palo Alto Health Care System in California and the Center for Health Policy and Center for Primary Care and Outcomes Research, Department of Medicine, Stanford University, Stanford, California, and coauthors caution that these findings apply only to a relatively young and healthy population and may not be generalizable to other patients.

Weekdays vs Weekends

Using data from the MarketScan Commercial Claims and Encounters database (Truven Health Analytics), the researchers conducted a retrospective analysis of ED visits between 2011 and 2012 by patients 18 to 64 years of age with a diagnosis of chest pain or angina pectoris. Exclusion criteria included clear evidence of AMI or any other diagnosis that could account for the chest pain.

Previous studies have shown that noninvasive testing among patients seen in the ED for chest pain greatly increases subsequent testing and treatment, but does not alter risk for AMI admission. However, because these studies have been observational, rather than randomized, some researchers have expressed concern that there is residual confounding that cloud the findings.

Therefore, Dr Sandhu and colleagues used a technique known as instrumental variable analysis to address the unmeasured confounding inherent in observational studies. It is known that people who come to the hospital on weekdays are more likely to undergo cardiac testing than those with similar risk factors and comorbidities who arrive on the weekend, because of issues of staffing and resource availability. In the instrument analysis, the team used day of presentation as a basis for comparing patients who were and were not tested, as this factor is independent of patient characteristics.

The final sample consisted of 926,633 privately insured patients, including 536,197 women (57.9%), with an average age of 44.4 years. "Patients presenting on Monday to Thursday were more likely to receive cardiovascular testing within 2 or 30 days (18.2% and 26.1%) than those presenting on Friday to Sunday (12.3% and 21.4%)," the authors write.

Patients who underwent testing within 30 days were more likely to be older (mean age, 49.7 years vs 42.6 years among patients not tested) and male (47.5% vs 40.4%), and to have cardiac risk factors such as hypertension (47.8% vs 38.2%). However, there was no significant difference in these attributes between patients visiting the ED on weekdays or weekends.

In the instrument analysis, adjusted for demographic variables and comorbidities, patients tested within 2 days of the ED visit did not undergo more coronary angiography than those not tested, but they were more likely to undergo revascularization (15.0 additional revascularizations per 1000 patients; 95% confidence interval [CI], 5.6 - 24.4 additional revascularizations). Despite that increase, there was no significant difference in AMI admission at 1 year (2.3 per 1000 patients tested; 95% CI, −3.2 to 7.8 AMI admissions).

Similarly, testing within 30 days was associated with increases in angiography (36.5 additional angiograms per 1000 patients tested; 95% CI, 21.0 - 52.0) and revascularization (22.8 per 1000; 95% CI, 10.6 - 35.0 additional angiograms), but no difference in AMI admissions at 1 year (7.8 per 1000; 95% CI, −1.4 - 17.0 AMI admissions).

"Testing was consistently associated with more revascularization in patient subgroups with higher baseline cardiac risk," the authors write. "However, there were no subgroups in which testing was associated with a reduction in AMI admissions."

Testing May Be Overused

The findings support the idea that noninvasive testing of patients thought to have acute coronary syndrome does not improve outcomes, Dr Sun, from the Department of Emergency Medicine, Oregon Health and Science University, Portland, and Dr Redberg, from the Division of Cardiology, University of California, San Francisco, write in their editorial.

"This clinical strategy is characterized by enormous costs, substantial practice variation, and absence of efficacy data," they warn. In addition, noninvasive testing places patients at risk for radiation exposure, as well as more invasive procedures. "We strongly advocate for randomized clinical studies that will provide definitive guidance for this prevalent, high-risk, and vexing clinical problem."

Study limitations include the possibility of untested subgroups who may benefit from testing; failure to include less-tangible benefits of testing such as patient reassurance; limiting the analysis to privately insured people younger than 65 years of age, and lack of mortality data, Dr Sandhu and coauthors write.

Also, these findings "would not be directly applicable to a higher-risk subgroup that always receives testing regardless of day of presentation."

Nevertheless, "testing was not associated with a reduction in subsequent AMI admissions and further research is needed to evaluate whether a benefit is present in higher risk subgroups," they conclude. "We believe the current evidence supports a shift in the treatment of these patients; shared decision-making with patients should be considered a viable alternative to routine cardiac testing in the absence of robust evidence to support its benefit."

The authors and the editorialists have disclosed no relevant financial relationships.

JAMA Intern Med. Published online June 26, 2017. Article abstract, Editorial extract

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