CArdiac magnetic resonance perfusioN imaging for SELection of patients for additional invasive evaluation after CT coronary angiography (CANSEL)

Invasive coronary angiography (ICA) has been the standard for coronary artery
disease detection for many years. More recently CT coronary angiography (CT-CA)
has emerged as a safe, non-invasive and accurate diagnostic modality to detect
the presence of coronary atherosclerosis. However both techniques provide only
anatomical information and the functional significance of the anatomical
coronary artery abnormalities may be difficult to determine. At the time of
catheterisation, the functional significance of a coronary stenosis can be
determined by measuring fractional flow reserve (FFR). FFR is derived from a
ratio of the mean distal coronary artery pressure to the aortic pressure during
maximal vasodilatation. It is a well established technique with proven clinical
value.
Compared to the invasive FFR measurement, non-invasive stress testing and
myocardial perfusion studies may also aid clinical decision making in
determining the significance of coronary stenosis. Given the increasing use of
CT-CA, such non-invasive functional assessment may avoid the need for ICA in a
significant proportion of patients.
One commonly-used non invasive test is myocardial single photon emission
computed tomography (SPECT). Myocardial SPECT has high sensitivity and
specificity for detection of significant coronary stenosis, but it exposes the
patient to radiation, has low spatial resolution, and is time consuming for the
patient. Stress echocardiography has similar sensitivity and specificity
compared to SPECT, but it is more operator dependent and adequate echo windows
may not be available in ~ 5% of patients.
Myocardial perfusion can also be determined non-invasively by first pass
contrast magnetic resonance imaging, and this may be a good alternative to
myocardial SPECT and stress echocardiography.
Advantages of MRI compared to SPECT include improved spatial resolution and the
avoidance of radiation exposure, and MRI may provide a quantitative analysis
comparable to FFR measurements. Furthermore, the combination of CT-CA and a MRI
perfusion study could provide a comprehensive, non-invasive evaluation of the
extent and significance of coronary artery disease. Presently only 1/3 of all
patients referred for invasive analysis after abnormal CTCA findings have a
positive FFR. A significant improvement in specificity would reduce the number
of unnecessary invasive evaluation in the future but still have a high negative
predictive value.

To validate MR myocardial perfusion by first pass magnetic resonance with
adenosine stress in patients with suspected coronary artery stenosis as
identified by CT-CA, using FFR as the reverence method.

We will evaluate the diagnostic accuracy of first pass magnetic resonance in
patients with suspected coronary artery disease on CT-CA.
We intend to include seventy-five patients who have suspected obstructive
coronary artery disease as determined by CT-CA as part of an evaluation for
their chest pain syndrome. These patients undergo ICA as part of their clinical
work-up. This includes measurement of FFR by local clinical protocol; FFR will
be done when the stenosis calculated with quantitative coronary angiography
(QCA) is between 30% and 90% of the lumen of the vessel. Prior to ICA, we will
determine myocardial perfusion by first pass magnetic resonance.

Participating in the study will involve data collection and MR imaging with
low-dose adenosine stimulation. MR imaging itself has no known risks. Contrast
agent gadolinium diethyltriaminepentaacetic acid has minimal adverse effects in
the population to be studied (note especially the exclusion of patients with
insufficient renal function). The risk inherent in administration of low doses
of adenosine is minimal. During the MRI imaging there will always be a
physician present to answer any questions and/or provide medical attention if
necessary. The physician is trained in CPR. ECG monitoring leads will be
applied for continuous rhythm control and a brachial blood pressure curve for
regular blood pressure measurements. Nitroglycerine will be present in case the
patient has angina pectoris. There is a crash car at the Department of
Radiology to stabilize the patient to his/her way to the CCU, if necessary.