A cardiac MRI technique that provides a spatially matched 3D fused volumetric image of myocardial scar and the coronary arteries can be helpful for patients undergoing cardiac resynchronization therapy (CRT) or coronary artery revascularization, according to a study in the September issue of the Journal of the American College of Cardiology: Cardiovascular Imaging.
James A. White, MD, and colleagues at the University of Western Ontario in Canada said that pre-procedural fused volumetric imaging of both myocardial scar and coronary vasculature may benefit pre-procedural planning and patient selection in populations referred for CRT, CABG or coronary angioplasty.
In bypass or angioplasty procedures, if surgeons see scar in a myocardial region corresponding with stenotic vessels, they will not proceed with the procedure because no benefit will be expected, according to White. Similarly, CRT pacemaker leads delivered to regions of scarred myocardium may prevent any benefit from this therapy.
The investigators performed 55 studies in patients referred for either CRT (42) or coronary artery revascularization (13). Coronary-enhanced and scar-enhanced imaging were performed on a 3T MRI scanner using the same cardiac-gated, 3D, free-breathing cardiac MR scanner during and 20 minutes following slow gadolinium infusion.
Combined 3D coronary and scar imaging was successful in 49 studies. Researchers obtained a quality score of 2 (0 to 4) for 97 percent of proximal- and mid-coronary artery and vein segments.
White and colleagues suggested that coronary image quality might be improved through the use of 32-channel coil technology, "which has recently been shown to be beneficial for coronary imaging at 3T field strengths."
The mean quality score of 3D scar imaging was 2.8 and was scored as 2 in 86 percent of patients with myocardial scar. All patients with a scar quality score of 2 had successful image fusion.
"This study is the first to demonstrate the feasibility of matched, isotropic 3D imaging of coronary vasculature and myocardial scar using a single imaging modality," the authors said. "This suggests a potential of this technique to meaningfully assist in the planning of vascular-based therapies reliant upon regional myocardial scar for clinical success."
The presence of one or more vascular targets with underlying transmural scar was seen in 17 of the 36 patients with fused imaging. This group consisted of nine of 23 patients referred for CRT and eight of 13 patients referred for coronary artery revascularization.
Physician surveys demonstrated incremental clinical impact in 67 percent of these 36 patients. Procedures were canceled (clinical impact score of 4) owing to the results of imaging in six patients: two planned for CRT and four planned for coronary artery revascularization.
The mean impact score for therapeutic decision making was 2.8 and 3.1 in CRT and coronary artery revascularization patients, respectively.
"This is the first time we have been able to visualize myocardial scar and the heart's blood vessels at the same time," said White. "We are able to construct a three dimensional model of a person's heart to immediately understand the relationship between the heart's blood vessels and related permanent injury. This will help direct surgeons and cardiologists to better target the blood vessels that lead to muscle capable of responding to their therapy, rather than to muscle that is irreversibly diseased."