Coronary artery disease (CAD) is one of the most common heart diseases. More than 3.5 million cardiac catheterizations are performed in Europe every year, of which more than half are not followed by treatment.

The main findings of the European Commission-funded DISCHARGE Trial – a collaborative multinational research project, were published recently in the New England Journal of Medicine. They show that non-invasive computed tomography (CT) of the heart is a reliable, non-invasive method for diagnosing or excluding CAD.

Canon Medical interviewed Viktoria Wieske, Radiologist at the Coordination Center of the study, within the Charité University Hospital, Berlin, Germany. She has played an important role in the study, along with Professor Marc Dewey, Deputy Director of the Radiology Clinic at the Hospital, who led the study. A total of 3,561 patients from 26 clinical centers across 16 European countries were enrolled in the trial. All patients presented with an indication for a cardiac catheterization based on the presence of chest pain. Another key inclusion criterion was the presence of a medium pre-test probability (10-60%) for a CAD.

How did the study go?
Both recruitment and the CT examination were carried out in an interdisciplinary collaboration between radiologists and cardiologists. The requirement was that representative physicians from both departments were involved. In our coordination center, the patients came partly via the outpatient center. Some were patients that received clinical treatment here. They were then randomized into one of two groups - CT or Cardiac catheterization. The patients then randomly received either a CT scan or a Cardiac catheterization.

CT is a safe alternative to cardiac catheterization for patients suspected of having CAD. The main clinical questions were specifically: “What are the long-term clinical outcomes after 3.5 years?” And “Are there differences in the CT group compared to the cardiac catheterization group?” So far, it has been unclear what the long-term clinical results are for patients with suspected CAD, if the initial diagnosis is made with CT instead of cardiac catheterization.

The results clearly show: Severe cardiovascular events (defined as heart attacks, strokes or deaths from cardiovascular diseases) occurred in 2.1% of the patients in the CT group and in 3.0% of the patients in the cardiac catheterization group during the study period. There were no statistically significant differences in the major cardiovascular endpoints between the two groups. Another important finding was that the frequency of serious procedure-related complications was lower in the initial treatment after the CT (0.5%) than in patients who underwent cardiac catheterization (1.9%).

How was the study coordinated between 26 European centers across 16 countries?
That was indeed a challenge. Just preparing the study and setting it up in the centers took years. With the help of a very structured procedure, we brought all the centers up to date. With the development of standardized, pragmatic guidelines for action, a common guideline was established in all centers and served as a universal quality standard. It wasn't easy, because, for example, we are still a long way from comprehensive CT care everywhere. In addition, the local standards based on the European guidelines for stable chest pain differ from country to country and, thus, the diagnostic procedures in the clinics. So, we defined clear requirements that all centers have fulfilled. For example, there had to be CT experts trained by us in every site. Among other things, at the beginning of the study, a cardiac CT workshop took place here in Berlin at the Charité Hospital, in which at least two colleagues from each center took part. We held regular cross-center discussions on the phone and via video. So, before the study started, we were all on the same page in terms of recruitment, diagnostics, technique, and structure for collecting data. This is a very important prerequisite for the meaningfulness of the study results.

What international attention is the study attracting?
There are numerous diagnostic studies on CT. Notable previous randomized studies are the Scottish SCOT-HEART study (Scottish Computed Tomography of the HEART) and the US PROMISE study (Prospective Multicenter Imaging Study for Evaluation of Chest Pain). In principle, however, many nationaland international experts have been waiting for these results, as this study is the most important randomized building block to demonstrate that there are no differences between CT and cardiac cathterization in the major cardiovascular endpoints over a long follow-up period in patients with stable chest pain and an intermediate pretest probability for the presence of CAD.

How could the study results change clinical workflow?
If CT becomes recognized as an appropriate procedure [for diagnosis or exclusion of CAD], and is covered nationwide by health insurance, demand will increase significantly. A future challenge will be to provide sufficient infrastructure, so that all patients in Germany who benefit from a CT can also receive it from excellently trained staff. It is noteworthy that the German Radiological Society has already trained more than 1,000 certified cardiovascular radiologists.

Another aspect, which is also extremely important to us radiologists: There must be a corresponding indication. The goal should always be to select the patients accordingly. The primary aim of CT diagnostics is to filter out CAD patients, who do not need revascularization, but whose symptoms of chest pain can, for example, be treated well with medication.

The radiation exposure is comparably low with the new CT systems, as with diagnostic Cardiac catheterization. The argument from earlier times that a CT examination per se always involves more X-ray radiation definitely no longer applies to the new devices.

What do patients gain from the DISCHARGE study?
The findings of the study bring several advantages for the patients. If the results contribute to CT of the heart is being fully covered by health insurance, the ideal, gentle, non-invasive diagnostic method for excluding CAD would be available for everyone by use of CT. The examination is carried out on an outpatient basis. It only takes a short preparation for premedication and education. After the examination, people go home, just like after a normal doctor's appointment.

What CT systems do you use?
For the study, we worked here at the Berlin Coordination Center with the volume CT Aquilion ONE from Canon Medical. Of course, you can also do diagnostic heart CT angiographies on the 64-row system. With the 320-row, however, we have the best opportunity in terms of technical requirements to respond to all patients with the most diverse individual characteristics. With the Aquilion ONE we can perform all CTs well and get excellent diagnostic images, even with difficult heart rates under certain conditions. The coronary arteries, for example, can be visualized very well even in very obese patients. In addition, dense calcifications can also be assessed with the reconstruction possibilities of the Aquilion ONE.

Will this CT procedure be reimbursed by health insurance soon?
Under the new European guideline from 2019/20, it is already firmly anchored as a possible initial non-invasive imaging. In Germany, we still lack full approval for reimbursement in every case. In individual cases and individual case reviews, remuneration is possible with prior approval, but these are exceptions. The Joint Federal Committee is currently examining the inclusion of the procedure in standard care.

What is your vision for CT?
If CT is included in standard care, an increased examination volume is to be expected. A uniform indication for an adequate treatment is also decisive for this procedure, incorporation of the procedure into the diagnostic workflow of CAD in patients with stable chest pain, and a medium pre-test probability of the presence of CAD, as well as the use of radiological expertise for the quick and reliable evaluation of the examinations.