Wednesday, September 18, 2013

CTCA Is Better Than Wishing & Hoping

CT coronary angiograms have infiltrated the Emergency Department, with trials such as ACRIN-PA, CT-STAT, and ROMICAT II demonstrating their utility – primarily sensitivity – for the rapid detection of coronary artery disease.  It comes as a surprise to no one that an angiogram demonstrating a total absence of coronary artery disease confers an excellent short-term prognosis.  The downside, of course, is cost, contrast, radiation, and the suggestion that low-risk patients might be harmed by additional, unnecessary testing.  However, enthusiasm for the procedure abounds.

This is an observational study from Thomas Jefferson University looking at consecutive Emergency Department patients referred for CTCA, prospectively collecting variables to calculate TIMI and GRACE risk scores.  No clearly defined primary outcome is provided, but it seems these authors aimed to demonstrate that CTCA would correctly detect severe coronary disease (>70% stenosis) and better prognosticate adverse outcomes than the TIMI and GRACE risk scores.  They enrolled 250 patients, lost 29 to follow-up, and reported six adverse cardiovascular events within 30 days – 2 MIs, 2 ACS, and 2 revascularizations.  All six were TIMI 1 or 2, had relatively middling GRACE scores, and had extensive CAD detected on CTCA.  Overall, 17 patients had significant CAD (>50% stenosis) detected, and increasing TIMI and GRACE scores did not correlate with its presence or absence.  Therefore, these authors feel CTCA is an appropriate diagnostic study and is superior to clinical assessment and risk scores.  They even go so far as to disparage Rita Redberg's editorial in the New England Journal of Medicine that questioned whether any cardiovascular imaging was indicated before low- and intermediate-risk chest pain patients left the Emergency Department.

They seem, unfortunately, to turn a blind eye to their inability to appropriately select patients for imaging, with only a 6.8% yield for significant stenosis, fewer than half of whom even progressed to a cardiac outcome.  I also take issue with the 2 patients they classified as ACS – they didn't receive revascularization and didn't have an MI – so what were they?  Either way, we're looking at great expense in a cohort with only 1.4-2.4% incidence of positive cardiac outcome within 30 days.  Additionally, the comparison to TIMI and GRACE is a straw-man comparison to instruments proven to have poor predictive value in Emergency Department populations.

This is simply another trip down the quixotic zero-miss path to destruction, even going so far as to fearmonger with liability claim cost statistics.  Rather, it's clear we're simply doing a terrible job searching for the needle in the haystack – and the vast majority of these patients are safe for appropriate follow-up after initial Emergency Department assessment.  Rather than use this article to justify admission for CCTA, I would present this data to your patients in the context of shared decision-making and educate them regarding the high costs, abysmal yield, and poor specificity of the test used in this context.

"Cardiac risk factors and risk scores vs cardiac computed tomography angiography: a prospective cohort study for triage of ED patients with acute chest pain"
http://www.ncbi.nlm.nih.gov/pubmed/24035047

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