Innovation Fast and Slow: The Case for Coronary CT Angiography

by | Sep 19, 2020 | Blog

Evidence of the clinical effectiveness of coronary CT angiography (CCTA) in evaluating patients with coronary artery disease has been building for several years. In Sept. 2020, the Journal of the American College of Cardiology (JACC) published a report representing a consensus of attendees at an ACC Summit on CCTA advances. This report, Current Evidence and Recommendations for Coronary CTA First in Evaluation of Stable Coronary Artery Disease, summarizes evidence from the UK SCOT-HEART trial, the US PROMISE trial, and other studies demonstrating patient benefits from a CCTA-first strategy. The report argues that “the current aim of diagnosis of stable chest pain in patients with possible obstructive coronary artery disease must change from detection of a myocardial perfusion abnormality to detection of coronary atherosclerosis” [1] They conclude “this important scientific advance must become the critical focus of testing” [1]. The report recommends that CCTA be used as the default test for evaluating most patients with stable chest pain.

Innovation, Fast and Slow

The SCOT-HEART trial showed a 41% reduction in deaths from myocardial infarction (MI) when comparing patients whose care was informed by CCTA versus standard care [2]. CCTA is vastly underutilized, with a SPECT to CCTA ratio of 58:1 reported in a 2016 study [3]. Instead, patients are often put on treadmills and subjected to intense workouts during exercise echocardiography tests, or nuclear stress testing. These tests can be quite expensive for patients, especially for those with high deductible health plans. With mounting evidence of its diagnostic superiority, why isn’t CCTA being used widely?

In Atul Gawande’s influential article Slow Ideas published in the New Yorker’s Annals of Medicine series, Gawande poses the question “Why do some innovations spread so swiftly and others so slowly?” He contrasts the adoption of surgical anesthesia and antiseptics in 19th-century medical practice in the US. Before anesthesia, surgery was a horrific experience for all participants, especially the patients. The first-time gas was used to render a patient unconscious during surgery was at Massachusetts General Hospital in Oct. 16, 1846. This was published in the Boston Medical and Surgical Journal on Nov. 18, 1846 [4]. By February of the following year, surgeons were administering ether to patients in most regions of the world. A mere four months had passed before widespread adoption took place.

Gawande contrasts this with the prevention of infection through the use of carbolic acid by surgeons to clean wounds – and their hands and instruments. Joseph Lister published his study demonstrating his ground-breaking results in The Lancet in 1867. However, unlike anesthesia, the widespread adoption of sterile techniques in surgery took decades to become routine. Dr. Gawande’s key insight from this comparison is instructive. Gawande identifies two key differences between these two ground-breaking innovations. The first difference is that anesthesia attacked a visible and immediate problem–surgical pain–while Lister’s antiseptic revolution combatted a less visible problem–infection. The second insight is that of these two innovations, only one made things immediately easier for doctors, which is why anesthesia was adopted in weeks and it took a generation for antiseptics and sterile technique to take hold. The CCTA-first approach advocated for in the Poon report may be vulnerable to the second pattern because of the longer periods involved with treating coronary artery disease and the economic incentives to keep doing functional testing. It is encouraging to see professional associations such as the European Society of Cardiology, the American College of Cardiology, and the Society for Coronary Computed Tomography calling attention to this issue.

Barriers to CCTA Adoption and the Road Forward

The ACC Summit report described above details four barriers to adoption, including:

  1. Widespread availability of nuclear medicine cameras and stress echocardiography labs
  2. Fellowship programs that predominantly emphasize functional testing over anatomical testing
  3. Lack of medical and technical expertise in using CCTA
  4. Large reimbursement disparities between CCTA and other cardiac imaging tests

Upton Sinclair famously said, “It is difficult to get a man to understand something when his salary depends on his not understanding it.” As evidence mounts in the US and EU for using CCTA as a first-line diagnostic for patients with suspected coronary artery disease and professional societies incorporate this evidence into their guidelines, this may change. Payers may eventually recognize this evidence and tip the scales to encourage care paradigms that lower cost and improve clinical outcomes.

Bibliography

[1] Poon, M., Lesser, J.R., Biga, C., Blankstein, R., Kramer, C.M., Min, J.K., Noack, P.S., Farrow, C., Hoffman, U., Murillo, J., Nieman, K., & Shaw, L.J. (2020). Current Evidence and Recommendations for Coronary CTA First in Evaluation of Stable Coronary Artery Disease. Journal of the American College of Cardiology. 76)11), 1358-136.
[2] Newby, David & Williams, Michelle & Hunter, Amanda & Pawade, Tania & Shah, Anoop & Flapan, Andrew & Forbes, John & Hargreaves, Allister & Leslie, Stephen & Lewis, Steff & Mckillop, Graham & Mclean, Scott & Reid, John & Spratt, James & Uren, Neal & Steering, Trial & Timmis, Adam & Berry, Colin & Steedman, Tracey. (2015). CT coronary angiography in patients with suspected angina due to coronary heart disease (SCOT-HEART): An open-label, parallel-group multicentre trial. The Lancet. 385. 10.1016/S0140-6736(15)60291-4.
[3] Levin, D.C., Parker, L., Halpern, E.J., & Rao, V.M. (2016). Recent Trends in Imaging for Suspected Coronary Artery Disease: What is the Best Approach? Journal of American College of Radiology. 13(4):381-386. Doi:10.1016/j.jacr.2015.11.015
[4] Gawande, A. (2013). Slow Ideas. The New Yorker, Annals of Medicine. Available from: https://www.newyorker.com/magazine/2013/07/29/slow-ideas

Photo Attribution

1. 1weezie23 / CC BY-SA (https://creativecommons.org/licenses/by-sa/3.0) 2. Blue0ctane at English Wikipedia / Public domain