CTCA Does Not Reduce Time to Diagnosis in Suspected ACS

Roxanne Nelson RN, BSN

October 09, 2019

SAN FRANCISCO — CT coronary angiography (CTCA) used early in the assessment of patients with a suspected acute coronary syndrome (ACS) does not reduce the time to definitive diagnosis or discharge, findings from the PROTECCT trial suggest.

The mean hospital stay for patients who received CTCA was 7.42 hours, compared with 8.05 hours in the control group, and it did not meet statistical significance (P = .132).

The cost of hospitalization was also similar between the two group: £1285 vs £1108 (P = .641).

"Therefore, our study does not support the use of CTCA to further stratify patients who are deemed at intermediate risk of ACS based on EKG and biomarker profiles," said lead author Divaka Perera, MD, FRCP, professor of cardiology, King's College London, and consultant cardiologist, Guy's & St Thomas' Hospital, London.

The findings were presented at Transcatheter Cardiovascular Therapeutics 2019.

The definition of a myocardial infarction has evolved, Perera explained, and central to this definition is the assessment of biomarkers using high-sensitivity troponin, which is certainly the case in Europe. According to guidelines from the European Society of Cardiology (ESC), this is one of the mainstays of making a diagnosis.

Detection of an elevated troponin value above the 99th percentile upper reference limit is defined as myocardial injury. "The problem is that as the high-sensitivity assays have improved, we've been able to detect lower and lower levels," Perera said. "In a nutshell, as the assays have improved, sensitivity has increased but at the cost of specificity."

Or, as it has been eloquently put, he noted, "when troponin was a lousy assay, it was a great test, but now that it's becoming a great assay, it's getting to be a lousy test."

Perera emphasized that one single value can no longer be used to make a diagnosis of myocardial infarction. "We have a specificity-based value and a sensitivity-based value and we can rule in and rule out," he said, but there's a region in between that "needs to be adjudicated, and that really is at the heart of this study."

CTCA Use Not Supported

PROTECCT (Prospective Randomised Trial of Emergency Cardiac CT) was conducted to evaluate the use of CTCA in the early assessment of patients with suspected acute coronary syndrome, and to see if its use would decrease the time needed to make a definitive diagnosis or patient discharge.

The cohort involved 250 patients with an intermediate troponin level who were randomized to a CTCA-guided group plus standard of care (SOC) or a CTCA-blinded group plus SOC.

For patients in the experimental group, if stenosis was less than 25%, then an alternative diagnosis or discharge would be explored. If the stenosis was 25% or greater, then acute coronary syndrome was not excluded and the patient would receive further clinical management deemed appropriate by the treating physician.

The primary end point of the study was median hospital length of stay, and secondary end points included mean cost of in-patient stay, including patient investigations and management, rates of invasive coronary angiograms, death, ACS, and revascularization during index hospital visit.

Patients in both groups were similar and about 20% had diabetes with a "smattering" of other risk factors, including hypertension and being a current smoker, noted Perera.

In the control group, four cases were unblinded.

When looking at outcomes, the researchers found that the addition of CTCA to the acute triage and management of patients with suspected ACS did not reduce median hospital length of stay or translate to in-patient healthcare cost savings.

There was a difference in subsequent cardiac referral favoring the CTCA group: 40 (32%) and 40 (68%; = .01). "This does merit closer investigation," said Perera.

He pointed out that there was an "interesting pattern, if you look at length of stay by CTCA result." If the CTCA was normal or there was a minimal stenosis, the time to discharge was shorter. But if it was a more significant stenosis, then it actually caused a problem for the physicians and the time to discharge was delayed.

For example, patients with a normal CTCA have an average length of stay of 6.68 hours, but those with stenosis of 50% to 69% have a length of stay of 8.32 hours (normal 1% to 24% vs ≥25% stenosis; P < .001).

In a subset of 145 patients, most (n = 99) did not have high-risk plaque features. Some had one high-risk plaque feature (n = 42), and only four had more than one. No correlation was observed between the presence of those features and either the admission troponin or the delta troponin on repeat testing.

Overall, the findings do not support the use of CTCA in this setting, and Perera added that anatomic CTCA parameters (severity of stenosis, calcium score, high-risk plaque features) were not related to initial high-sensitivity cardiac troponin T.

In a discussion of the study, session comoderator Pieter C. Smits, MD, director of the Interventional Cardiology Department, Maasstad Hospital, Rotterdam, the Netherlands, commented that this is a "negative study in the end, but CT angiography has some additional benefits. You can diagnose embolism, dissections, or even a stomach hernia, which can cause chest pain."

Smits then asked Perera if he feels that there is still a need for CTCA in the emergency room.

"We did find in our cohort that in the blinded arm, one in 25 had a noncardiac diagnosis," Perera responded. "But being that this is a low-risk cohort, I don't know if we can recommend it."

Perera has no disclosures.

Transcatheter Cardiovascular Therapeutics (TCT) 2019. Presented September 28, 2019.


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