Danish study of Non-Invasive testing in Coronary Artery Disease (Dan-NICAD): study protocol for a randomised controlled trial

Abstract

Background: Coronary computed tomography angiography (CCTA) is an established method for ruling out coronary artery disease (CAD). Most patients referred for CCTA do not have CAD and only approximately 20-30 % of patients are subsequently referred to further testing by invasive coronary angiography (ICA) or non-invasive perfusion evaluation due to suspected obstructive CAD. In cases with severe calcifications, a discrepancy between CCTA and ICA often occurs, leading to the well-described, low-diagnostic specificity of CCTA. As ICA is cost consuming and involves a risk of complications, an optimized algorithm would be valuable and could decrease the number of ICAs that do not lead to revascularization. The primary objective of the Dan-NICAD study is to determine the diagnostic accuracy of cardiac magnetic resonance imaging (CMRI) and myocardial perfusion scintigraphy (MPS) as secondary tests after a primary CCTA where CAD could not be ruled out. The secondary objective includes an evaluation of the diagnostic precision of an acoustic technology that analyses the sound of coronary blood flow. It may potentially provide better stratification prior to CCTA than clinical risk stratification scores alone.

Methods/design: Dan-NICAD is a multi-centre, randomised, cross-sectional trial, which will include approximately 2,000 patients without known CAD, who were referred to CCTA due to a history of symptoms suggestive of CAD and a low-risk to intermediate-risk profile, as evaluated by a cardiologist. Patient interview, sound recordings, and blood samples are obtained in connection with the CCTA. All patients with suspected obstructive CAD by CCTA are randomised to either stress CMRI or stress MPS, followed by ICA with fractional flow reserve (FFR) measurements. Obstructive CAD is defined as an FFR below 0.80 or as high-grade stenosis (>90 % diameter stenosis) by visual assessment. Diagnostic performance is evaluated as sensitivity, specificity, predictive values, likelihood ratios, and C statistics. Enrolment commenced in September 2014 and is expected to be complete in May 2016.

Discussion: Dan-NICAD is designed to assess whether a secondary perfusion examination after CCTA could safely reduce the number of ICAs where revascularization is not required. The results are expected to add knowledge about the optimal algorithm for diagnosing CAD.

Trial registration: Clinicaltrials.gov identifier, NCT02264717 . Registered on 26 September 2014.

Keywords: Cardiac magnetic resonance imaging; Coronary angiography; Coronary artery disease; Coronary computed tomography angiography; Fractional flow reserve; Myocardial perfusion scintigraphy.

Fig. 1

Danish study of Non-Invasive testing in Coronary Artery Disease (Dan-NICAD) patient flowchart. CAD, coronary artery disease; CCTA, coronary computed tomography angiography; CMRI, cardiac magnetic resonance imaging; MPS, myocardial perfusion scintigraphy; ICA-FFR, invasive coronary angiography-fractional flow reserve

Fig. 2

Perfusion defect on myocardial perfusion scintigraphy. Myocardial perfusion scintigraphy with Tc-99 m Sestamibi: short-axis and horizontal long-axis images during stress (upper rows) and rest (lower rows). A severe reversible perfusion defect is seen in the anteroseptal area of the left ventricle

Fig. 3

Perfusion defect on coronary magnetic resonance imaging. Coronary magnetic resonance imaging during pharmacological stress induced hyperemia (a) and at rest (b). The patient has an anteroseptal and lateral reversible perfusion defect in the midcardial segments of the left ventricle