This brief news release describes a single positive finding from the 4,000-patient SCOT-HEART study: roughly half of patients with stable chest pain who were randomized to receive computed tomography angiogram (CTA) and standard care had fewer heart attacks over 5 years than those who received standard care alone.
But there’s a flaw in the headline and first sentence of the release. This study shows zero difference in deaths, and as the authors acknowledge in the published study, the entire difference between the groups was driven by non-fatal heart attacks. Another problem with the news release is that these benefits are expressed in dramatic relative terms, instead of the much more modest (and helpful) absolute terms. Readers are left with little guidance regarding what may account for the slight drop, and if this really represents a “major” reduction as claimed by the lead author.
Finally, readers would have been better served if a discussion of alternative screening methods, conflicts of interest, and potential downstream costs and risks had been included. As a positive, the release mentions the potential to avoid invasive testing via angiogram, which has a very real death rate.
What may really be at issue here is whether roughly $1 million scanners are truly better than the non-invasive tests we already have. It remains unclear which patients benefit most from these tests, whether the scans provide actionable information (or simply lead to further confirmatory tests), and what will be their true costs.
The news release mentions that a computed tomographic angiogram (CTA) is cheaper than traditional angiograms but neither a cost or a rough cost comparison of the procedures is given.
There are also other costs to consider since a positive CTA will often lead to further testing. The study (but not the release) explained that further testing was examined as part of the analysis but no difference was observed — that’s one of the strengths of this study.
We’re told the diagnostic procedure:
Supporting data from the study are not provided. It appears the release misinterpreted the results. As noted above, it would have been preferable to include absolute and not just relative numbers.
The release notes that CTA scans are “safer” than angiograms because CTAs don’t require the insertion of tubes into the body.
But no other harms are mentioned and many readers may want to know about radiation exposure and allergic responses to the contrast dye used. According to the study, those who did have a CTA scan ended up having more invasive coronary angiograms and coronary opening procedures in the months following the scan. These procedures carry considerable risks.
The lead author is quoted as saying the study shows a “major” reduction in the future risk of heart attacks, and this has “major” implications for the diagnosis and management of patients with suspected heart disease.
But the 40% drop in heart attacks noted in the 5-year follow-up period is a relative reduction. The absolute decrease measured was from 3.9% to 2.3%, or an absolute drop of 1.6%. That is quite modest.
Also, as mentioned in an editorial accompanying the study, “the benefit seen in the CTA group might be attributable mostly to changes in medical management that were made on the basis of the testing results.”
There is no disease mongering. Some information on the prevalence of heart attacks among the patient population would put the problem in context.
National funding sources of the study are mentioned.
What’s not mentioned is that the lead author quoted in the release receives grant funding from Siemens, a major manufacturer of CTA scanners.
No mention is made of other non-invasive tests used to screen for coronary artery disease, such as calcium scans, exercise ECG’s, echocardiography, and nuclear heart scans to name a few. These alternatives are named in the published study.
It’s not clear from the release just how available CTA scanners are.
The lead author is quoted as saying:
This is the first time the CT-guided management has been shown to improve patient outcomes with a major reduction in the future risk of heart attacks.
There are other studies — most notably the PROMISE trial — which followed patients for just 2 years and found no changes in patient outcomes when comparing CTA with other noninvasive screening tests. This study followed patients for 5 years to see if the differences persisted and they didn’t.
The title is misleading because it implies it’s the scan itself that cuts heart attack risk and save lives.
But the study cannot account for whether this risk reduction — which was quite modest — may be attributable to lifestyle changes subsequent to the scan, or that the findings from the scan lead to more aggressive pharmaceutical management of risk factors. The published study notes that this is likely the case — and that’s the whole point — having more accurate diagnoses may have the downstream effect of better management.