Detection of Coronary Artery Disease in Patients With Atrial Fibrillation Using Regadenoson Stress MRI

Scientific Background/Rationale:

Atrial fibrillation (AF) is a large and growing healthcare problem worldwide. Over 7 million people in the U.S. and Europe currently suffer from atrial fibrillation, and this number is expected to double before 2050. The lifetime risk of AF is high: ~24% at age 40, and this risk remains fairly constant at older ages, with 22% lifetime risk at age 80 [1]. AF significantly increases the risk of stroke and mortality, and can greatly limit quality of life. Little research has been done on AF and ischemic cardiomyopathy, though it is a relatively common co-morbidity. CT found increased prevalence (41% vs 27%) of coronary artery disease (CAD) in patients with AF compared to patients with similar pre-test risk but no AF [2]. AF patients with a positive SPECT scan for CAD have a worse prognosis for cardiac events than patients with positive SPECT but without AF [3]. It was recently reported that in a study of 253 AF patients, that AF patients with positive SPECT studies had a very high number of false positives - only 15% of patients had significant CAD by angiography (compared to 67% in the control group) [4, 5]. Just over half of the patients were in sinus rhythm at SPECT, but since similar numbers of positives were seen in each half, the authors did not feel that imaging during AF was the cause of the poor specificity.

Use of MRI for assessment of CAD is a growing area that entails no radiation exposure to the patient. Advances in MRI have made it possible to accurately detect CAD, either as well or better than SPECT in unselected populations [6, 7]. However, adoption of MRI myocardial perfusion scans has been limited in part due to the challenges associated with the use of adenosine. Adenosine requires starting a second IV, and to use either a special expensive MRI-compatible infusion pump to deliver the drug, or long lengths of tubing to run to a pump outside the scanner room. Neither solution is ideal, and regadenoson would not require any such pumps or the starting of a second IV. Here the investigators propose to determine the sensitivity/specificity for dynamic contrast-enhanced myocardial perfusion MRI with the vasodilator regadenoson in a subpopulation of patients - those with atrial fibrillation.

The investigators have a great deal of experience with stress and rest myocardial perfusion MRI. In a preliminary study imaging three patients with AF that then went to X-ray angiography (cath), two of the three subjects had significant stenoses by cath, and one did not. This agreed with the regadenoson stress perfusion MRI findings. These MRI acquisitions were performed on a Siemens Verio MRI scanner. The Verio operates at twice the magnetic field strength (3 Tesla, or 3T) of most MRI scanners, which operate at 1.5T. The higher magnetic field offers images with significantly less noise (almost twice the signal-to-noise ratio).

Objective: To demonstrate sensitivity/specificity comparable to that reported in meta-analyses of non-AF patients and adenosine (90%/80% [6, 7]), in an atrial fibrillation population while using the time-efficient vasodilator regadenoson that requires only a single IV.