Once again, a randomized study shows that coronary CT can make sense in stable, previously undiagnosed coronary artery disease. Despite significantly fewer coronary angiographies, the rate of cardiovascular events was not higher in a collective with intermediate pretest probability.

The randomized, non-blind multicenter study CONSERVE, now published in the journal “JACC Cardiovascular Imaging”, took place in 22 hospitals in India, North America, East Asia and Europe. Recruitment focused on South Korea, USA and Italy in Europe.

It was a study that was deliberately planned pragmatically and close to clinical reality. A total of 1631 patients with stable, previously non-invasively diagnosed CHD participated. The patients had to show an indication for elective coronary angiography according to ACC/AHA recommendations. However, it was not exactly specified how this should look like. In addition to patients with ischemia, there were also patients with “only” highly suspicious symptoms. The vast majority of patients had an intermediate pre-test probability with regard to the diagnosis of CHD.

Only 23% with invasive clarification in the CCTA group

The patients were then either sent to the catheter laboratory without further diagnosis, or a CT coronary angiography (CCTA) was performed beforehand. Calculated over one year, 23 percent of the patients in the CCTA group received invasive clarification with coronary intervention if necessary. In the group with immediate coronary angiography, 4 percent of patients were reinvestigated within one year. 11 percent and 1 percent, respectively, of all patients in the CCTA group received PTCA and bypass after one year, compared with 15 percent and 3 percent, respectively, in the immediate invasive group.

The key question, of course, was whether the less invasive group had more severe adverse cardiovascular events (MACE). MACE were defined as death, myocardial infarction, unstable angina, stroke, urgent or emergency coronary revascularization, and all types of cardiovascular hospitalization.

Non-inferiority of CCTA-based strategy proven

There was a precision landing on this primary endpoint: In both groups, MACE events occurred after a median of 12.3 months in 4.6 percent of patients. There were also no differences in various secondary clinical endpoints. This demonstrated the non-inferiority of the CCTA-based strategy.

As expected, the CCTA arm showed a slightly higher rate of patients in whom the attending physicians initiated some kind of non-invasive secondary diagnosis. The difference was significant, but not huge. Re-ischemia tests were performed on 14 percent of patients in the CCTA group and 11 percent of patients in the primary invasive group (p=0.04).

Clinically, at the end of the follow-up period, 60% of patients in the CCTA arm and 62% of patients in the coronary angiography arm were free of angina pectoris. The difference was not significant. The median radiation dose for coronary angiography was 7 to 9 mSv, depending on the institution. For CCTA, a median dose of 6.5 mSv was required.