Troponin testing does not reliably detect coronary artery disease in patients with SVT
Many laboratory tests are routinely ordered for reassurance. We almost always order a hemoglobin and pregnancy test when a patient has syncope, despite knowing the vast majority will be normal. These tests are accurate and should prompt further investigation if they are abnormal. Unfortunately, that is not the case for the once-vaunted, much-studied troponin. The troponin is a very sensitive test and can be unwieldy in certain hands, and that makes for a dangerous combination.
Indications for ordering troponins have expanded from symptoms such as chest pain and shortness of breath to a variety of others like weakness, confusion, and of course, palpitations. Patients with supraventricular tachycardia (SVT) in particular frequently have troponins drawn. The thought process is to look for myocardial ischemia from an arrhythmic event, as well as a potential cause of the SVT.
Unfortunately, ordering troponins often creates more dilemmas than solutions. More than 50,000 patients will present to U.S. EDs with SVT annually (J Am Coll Cardiol. 1998;31:150; https://bit.ly/3kxOvTt), and 12 to 48 percent will have elevated troponins after SVT. (Can J Cardiol. 2011;27:105; https://bit.ly/3R1rwwk.)
This retrospective review demonstrated that 24 of 73 patients with SVT had positive troponins. All but five of those underwent a stress test and multiplexed ion beam imaging or a coronary angiogram. All tests were negative, and no further treatment was indicated. In other words, patients without coronary artery disease may have an elevated troponin from their SVT and no further workup is required.
Clinicians, not Clicknicians
Multiple case series with fewer than 10 patients each demonstrated similar findings in the early and mid-2000s. Patients present with SVT, a positive troponin is found, and the patient receives a coronary stress test or catheterization. None required further testing or follow-up in four case series, which totaled 15 patients. (Indian Pacing Electrophysiol J. 2008;8:172; https://bit.ly/3D3BcAJ; Cardiology. 2006;106:10; Hawaii Med J. 2006;65:86; Swiss Med Wkly. 2003;133[31-32]:439.)
One retrospective cohort study of 46 patients demonstrated that none of the patients with positive troponins had a major adverse cardiac event, death from any cause, or positive results from cardiac testing three months later. (J Emerg Med. 2018;55:1; https://bit.ly/3HjEFgM.) Another retrospective study of 51 patients confirmed this with no deaths or complications at 30 days after discharge. (Am J Emerg Med. 2011;29:545; https://bit.ly/3D2x6Zg.)
One of the largest studies looking at this issue came from Switzerland, and it was enlightening even though it was not performed in the ED. A total of 326 patients underwent radiofrequency ablation for SVT and coronary angiography during the same session. CAD was found in 14 percent (45 patients). The troponin was elevated in 83 percent of patients who had CAD and in 47 percent of those who did not. (Cardiol J. 2017;24:642.) CAD prevalence is low in patients with SVT, and troponin testing does not reliably exclude or confirm it in these patients.
The major problem with “routine” troponin ordering is that we are not using our brains. There are consequences to ordering more tests—the cost and potential harm to the patient. We are clinicians, not clicknicians.
Clicknicians see patients and click the boxes on the electronic medical record, ordering whatever they think might be remotely helpful. They look for any red-colored values or ones with exclamation points next to them. No thought goes into what is ordered. Then the clicknicians admit the patient for “lab trending.”
Clinicians perform a solid history and physical and consider the risks and benefits of every test they order. Troponin testing should be done for patients with a concerning ischemic history, like persistent chest pain or other anginal equivalent after successful arrhythmia treatment. No troponin testing is needed for patients who have uncomplicated SVT and whose symptoms resolve after cardioversion.
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Dr. Briggsis an assistant professor of emergency medicine at the University of Tennessee Medical Center in Knoxville. He is the founder, a podcast host, and the editor-in-chief of EM Board Bombs (https://www.emboardbombs.com), a multiplatform educational tool designed to provide board prep and focus on what EPs need to know for the practice of emergency medicine. Follow him on Twitter@blakebriggsmd.