VERDICT: High Diagnostic Accuracy for Coronary CT in NSTEACS

Patrice Wendling

February 03, 2020

New data show early coronary CT angiography (CTA) can accurately rule out coronary stenosis in patients presenting with non-ST-segment elevation acute coronary syndrome (NSTEACS), potentially sparing some from subsequent invasive testing and admission.

The negative predictive value (NPV) of CTA to rule out coronary artery stenosis of at least 50% was 90.9% (95% CI, 86.8%  - 94.1%).

NPV was not influenced by patient characteristics or clinical-risk profile, and most false-negative results were in patients who had a single stenosis in small side branches with a luminal diameter of 2.5 mm or less.

The positive predictive value of CTA was 87.9%, sensitivity was 96.5%, and specificity was 72.4%.

The analysis, described as the largest CTA study in NSTEACS to date, was published today in the February 11 issue of Journal of the American College of Cardiology.

"The findings of the VERDICT trial suggest that, in patients with NSTEACS, coronary CTA can be conducted within 2 h of clinical diagnosis to quickly identify patients in whom invasive evaluation will be futile," the authors conclude.

For those found with no significant coronary artery disease (CAD), the strategy could also "reduce the duration of antithrombotic medications and reduce the number of interhospital transportations, which are a major cost in the logistics of handling these patients," senior author Klaus Kofoed, MD, DmSc, Rigshospitalet, University of Copenhagen, told | Medscape Cardiology.

"For the patients where you do find significant coronary artery disease on the CT, I predict that there will be a lot of benefit to be had on the procedural planning of the revascularization," he said.

Current guidelines favor invasive angiography as the primary diagnostic test for patients with ACS, whereas coronary CTA is reserved for those with chest pain who have an intermediate pretest likelihood of CAD.

The recommendations are based on early moderately sized ACS studies using 64-row CT in low-risk cohorts, whereas VERDICT patients were high risk and most were evaluated using 320-detector CT, Kofoed observed.

The VERDICT investigators previously reported that very early angiography within 12 hours of NSTEACS diagnosis did not improve 5-year clinical outcomes compared with standard angiography within 48 to 72 hours.

The new preplanned analysis included 1023 of the 2147-patient randomized cohort who underwent an additional coronary CTA exam prior to angiography. All patients had at positive troponin or ischemic electrocardiographic changes at baseline, and 67% had at least one stenosis on invasive angiography.

"This is really a big step forward because the tendency was always to think that coronary CTA is really only for patients with a low pretest likelihood. Well here, even in a cohort with high pretest likelihood, coronary CT angiography still performs very accurately," Stephan Achenbach, MD, Friedrich-Alexander-University Erlangen-Numberg, Germany, told | Medscape Cardiology.

He agreed that CTA technology and experience has evolved, but said another possible explanation for the high diagnostic accuracy is that among the high-risk cohorts, patients with ACS are more favorable for CT imaging than those with stable CAD. They tend to be younger and to have less coronary calcium and less diffuse disease.

Although use of CTA in this setting could allow for a more economical and rapid workup in the emergency room, Achenbach cautioned that the study was conducted in Denmark, which has very good scanners and infrastructure, and that scans were interpreted off site by a core lab.

"So if somebody comes to the emergency room at 2 o'clock in the morning and the scan has to be done and read immediately, maybe by a nonexpert in cardiac CT, it's a different situation than this trial setting, where the data were read in peace by two experts at some completely different time point," he said.

"So this is still a trial, it's not the real-life situation, but it's a very strong indication that CT can be useful in this context."

The frequency of a nondiagnostic CT scan was 5.2% overall and 3.7% among those in whom 320-slice CT was used. "A combination of several factors gave us this very rewarding result," including the frequent use of 320-slice CT, good heart rate control, and lower calcium scores, Kofoed suggested.

Notably, the high NPV was achieved at a substantially lower radiation dose (5.3 mSv) than in earlier reports of patients with NSTEACS (10 to 21 mSv). The median radiation dose was 4.6 mSv when patients were examined using a 320-slice CT and 12.2 mSv when using a 64-row CT. The median contrast volume was 66.2 mL.

"This is not a strategy that you would favor in patients who have impaired renal function, but for all those who have normal renal function, adding the contrast that is given during CTA is really no big deal," remarked Achenbach, who authored an accompanying editorial.

As for a positive effect on clinical outcomes, he said a randomized trial is needed, but that a benefit is more likely in patients where CT shows there is no stenosis. Data around the SCOT-HEART trial, for example, indicate that doing CT in the workup of stable chest pain identifies patients who have plaque, and that targeting statin therapy to these patients probably reduces the event rate in the coming 5 years.

"So we can imagine — although it's not proven at all — something very similar happens here: patients come to the emergency room, a CT shows there is no stenosis, you don't have to do a cath, but there's a lot of plaque. So we better give the patient some statins, so that the patient doesn't come back 2 or 3 years later with an infarct," Achenbach said.

Kofoed said the investigators are planning a clinical-outcomes trial but have yet to determine the outcomes or number of patients needed. In the meantime, there will be barriers to adoption given the financial and economic implications of the findings.

"Whenever you move between segments of a medical specialty, say invasive vs noninvasive or local vs central, there are some political boundaries," Kofoed observed. "Most invasive people will probably say, well this is a waste of time, we can see everything with invasive [angiography], so why bother doing this. And the local hospitals will say, well we can do this ourselves and keep the patients here, so therefore we would prefer this new approach be implemented."

"My interest mainly is that we, at the end of the day, come up with a better strategy for acute coronary syndrome patients than we have right now," he said.

This study was funded by the Danish Agency for Science, Technology and Innovation and the Danish Council for Strategic Research and The Research Council of Rigshospitalet. Kofoed reports grants from the Danish Research Foundation during the conduct of the study; and grants from the Research Council of Rigshospitalet, AP Moller og hustru Chastine McKinney Mollers Fond, the Danish Heart Foundation, and Canon Medical outside of the submitted work. Achenbach reports having no relevant financial relationships.

J Am Coll Cardiol. 2020;75:453-463 and 464-466. Abstract, Editorial

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