Only a small proportion of the 180 000 patients that are referred to a cardiologist each year in the Netherlands with complaints of angina pectoris or shortness of breath suffer from coronary stenosis in such a degree that revascularisation is required. To identify these patients, multiple diagnostic tests are available. Simple non-interventional imaging tests, such as coronary CT-scan, are safe, relatively cheap and can effectively rule-out coronary artery disease. However, when coronary artery disease is present, coronary CT-scan cannot assess the restriction in blood flow caused by the stenosis. Cardiac angiography with invasive blood flow measurements is required to assess this restriction in blood flow. This is an invasive test, more expensive than CT and it is accompanied by certain risks.

In retrospect, many patients unnecessarily undergo cardiac angiography with, if deemed neccessary, flow measurements. These patients do not need treatment for coronary artery disease. To reduce the number of unnecessary cardiac angiography with flow measurements, new imaging techniques have been developed. These techniques use CT- or angiographic images to calculate the restriction in coronary blood flow and determine the need for treatment. These new imaging techniques have been tested extensively in observational studies. Currently, there is no consensus in the optimal diagnostic pathway resulting in major differences in strategies between hospitals. Moreover,data on cost-effectiveness is lacking.

This study is designed to assess the safety and efficacy of these techniques when used as an addition to coronary CT-scan. Our target population will be patients with complaints of angina pectoris or shortness of breath for which the patients will undergo coronary CT-scan. If the CT-scan shows one or more possibly flow-limiting stenoses, further diagnostic testing is required. These subjects are randomized in one of three possible arms. One arm will receive additional CT-derived calculation of coronary blood flow, one arm will receive angiography-derived calculation of coronary blood flow and one arm will receive standard care. Standard care consists of coronary angiography and invasive coronary blood flow measurements. The results of these tests determine the need for treatment of coronary artery disease. After these tests, subjects are treated according to routine care guidelines. Subjects are requested to complete 5 questionnaires in a 12 month follow-up period. The primary endpoint is a composite of MACE - all-cause mortality, aborted sudden cardiac death, myocardial infarction and unplanned hospitalization for chest pain leading to urgent revascularization during the 12-month follow-up period. Secondary endpoints consist of cost-effectiveness, the number of avoided invasive coronary angiographies and flow measurements and quality of life. The investigators will use hospital patient files and completed questionnaires to collect information about events during the follow-up period until the last included subject has completed their final questionnaire.

The investigators expect that the total number of invasive cardiac angiographies with additional blood flow measurements can be reduced by half with the use of new imaging techniques. The investigators expect that this will lead to a reduction in healthcare costs, complications and a lower burden of diagnostic tests for patients. The investigators do not expect a difference in primary endpoints between the study groups.

In addition to the randomised controlled trial, all eligible subjects whose coronary CT-scan does not show possibly significant coronary artery disease (CAD-RADS 0-2) are included in a patient registry. Because of absent or limited coronary artery disease, additional diagnostic testing is not needed in these patients. These subjects are requested to answer 5 questionnaires in a 12-month period, similar to the subjects included in the RCT-part of the trial. The outcome measures of this part of the trial are similar to those of the RCT. Our primary outcome is the occurrence of MACE-events, secondary outcomes are quality of life and patient satisfaction.