CTA Gives Percutaneous Angiography a Run for Its Money

Neil Osterweil

May 24, 2018

PARIS — A new analysis finds close agreement between coronary CT angiography (CTA) and conventional invasive coronary angiography for their relative ability to aid in treatment decisions about coronary revascularization.

In what investigators are describing as a "virtual randomized trial," Patrick W. Serruys, MD, PhD, from Imperial College London in the United Kingdom, and colleagues compared treatment decisions made by heart teams for coronary artery bypass grafting (CABG) or percutaneous coronary intervention (PCI) based on CTA or standard coronary angiography in patients with three-vessel coronary artery disease.

They found that the Cohen κ, a measure of interrater reliability, was 0.82 (95% CI, 0.73 - 0.91), which is the statistical equivalent of a triple in baseball or, in technical terms, they say, "almost perfect."

The results suggest "the potential feasibility of a treatment decision-making and planning based solely on this noninvasive imaging modality," he said in a late-breaking abstract session here at the Congress of the European Association of Percutaneous Cardiovascular Interventions (EuroPCR) 2018.

Martin B. Leon, MD, from Columbia University Medical Center in New York City, an invited discussant, called the study "provocative, complex, and potentially transformative."

The SYNTAX II scoring system, which integrates the anatomical SYNTAX score derived from CTA with a patient's clinical characteristics and comorbidities provides a noninvasive score that predicts 4-year mortality and can help guide the decision to recommend patients with multivessel disease for CABG or PCI.

Serruys and colleagues conducted the SYNTAX III Revolution trial to see just how closely two separate heart teams — each consisting of a cardiologist, cardiac surgeon, and radiologist — agreed on treatment decisions using CTA or conventional angiography in 223 patients with left main or three-vessel coronary artery disease.

One team was randomly assigned to derive information for the first treatment decision solely from angiography, and the other was assigned to base its decisions solely on CTA.

CTA was performed with a Revolution CT scanner (GE), which has a high spatial resolution and can image the heart in a single beat.

Each team was assigned to use the information from the respective imaging modalities to determine an anatomic SYNTAX score, based on age, sex, creatinine clearance, and left ventricular ejection fraction, and a SYNTAX II score combining the anatomic score and comorbidities (peripheral vascular disease and chronic obstructive pulmonary disease). They then used the score to make a treatment recommendation of CABG, PCI, or clinical equipoise between the two.

Patients with any anatomic SYNTAX score were eligible for inclusion, including those with a score greater than 33, although patients who had prior revascularization were excluded from the study.

The severity and extent of coronary artery disease were assessed by the anatomic SYNTAX score in coronary segments with narrowing, with visual diameter stenosis of more than 50%.

Investigators used fractional flow reserve derived from CTA (FFR­CT)­ to calculate a noninvasive functional SYNTAX score by subtracting non–flow-limiting stenosis from the coronary CTA–derived anatomic SYNTAX score. They then used the functional SYNTAX score to calculate a SYNTAX III score, which Serruys described as "conceptually a combination of coronary anatomical complexity with its physiologic repercussions and patient's clinical characteristics and comorbidities."

The team that was assigned to interpret conventional angiography was able to calculate an anatomic SYNTAX score for all 223 patients. A score based on coronary CTA was calculated for 222 patients, with 1 having missing information because of motion artifact.

The investigators were able to determine FFR­CT for a total of 196 patients. Data were missing for 27 patients because of severe calcification, motion artifacts, low contrast signal, noise, use of an unsupported image reconstruction algorithm, or pixel spacing greater than 0.5 mm.

On the basis of coronary CTA or conventional angiography, the heart teams agreed that CABG was the preferred treatment in 23.4% of cases and that clinical equipoise between the procedures was achieved in 69.4% of cases.

The global agreement between the two modalities was 92.8%, earning the aforementioned "almost perfect" designation.

For the secondary endpoint of revascularization, the teams agreed on the coronary segments to be revascularized in 81.1% of cases. 

Additionally, FFR­CT, which was available for 869 of 1108 total lesions, had a mean value of 0.63 ± 13. FFRCT changed the treatment decision in 7% of patients and in 13 patients changed the initial decision for CABG to the less invasive percutaneous approach.

In the question-and-answer portion following Serruys' presentation, Leon noted that "the heart team makes a binary decision: surgery or PCI equipoise, yet what we're looking at have been continuous endpoints, so how does the heart team decide?"

Serruys replied that "the key point is the SYNTAX II score, which will give you a recommendation based on mortality."

"Obviously if you have a mortality rate of 20% vs 10%, the decision is easy," he continued. "But if the difference is 3% or 2%, this is equipoise, and most of the patients will go to PCI," he said.

Invited discussant Emanuele Barbato, MD, PhD, from the Cardiovascular Center OLV Aalst in  Belgium, asked Serruys whether surgeons in his center would be satisfied with the decision to perform surgery, or would they still require conventional angiography before going forward.

Serruys said that he and his colleagues had polled surgeons at their center one by one to ascertain whether the surgeons would be willing to operate on patients with multivessel disease based on coronary CTA alone.

"The feasibility in this survey was 83%," he said.

Serruys did not disclose a funding source for the study. He reported serving as a consultant to and/or receiving fees or honoraria from Abbott, Biosensors, Medtronic, and others. Leon has received consultant fees/honoraria from Abbott, Boston Scientific, and Medtronic; has ownership interest in Claret Medical; and has received research grants from Edwards Life Science. Barbato has declared that the Cardiovascular Center Aalst receives on his behalf grant support from Abbott, Boston Scientific, Biotronik, and St Jude Medical and consulting fees from St Jude Medical and Boston Scientific.

Congress of the European Association of Percutaneous Coronary Intervention (EuroPCR) 2018. Late-breaking abstract. Presented May 22, 2018.

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