Pilot Study Demonstrates Feasibility Of MRI-Guided Catheterization

A small pilot study has demonstrated that it may one day be possible to replace x-rays with MRI to guide some cardiac catheterization procedures.

As reported in the European Heart Journal, researchers at the National Heart Lung and Blood institute (NHLBI) performed x-ray and MRI-guided transfemoral right heart catheterization in 16 patients (four with shunt, nine with coronary artery disease, three with other indications). Each patient first underwent catheterization under x-ray guidance, which was then repeated twice with MRI, once using an air-filled balloon-tipped catheter and once using a gadolinium-filled balloon-tipped catheter.

In all but one patient complete guidewire-free catheterization was successful with both techniques. The researchers said that MRI using gadolinium-filled balloons was “at least as successful as X-ray in all procedure steps, more successful than MRI using air-filled balloons, and better than both in entering the left pulmonary artery.” Procedure time was not significantly longer with MRI. “Catheter conspicuity was best under X-ray and next-best using gadolinium-filled MRI balloons,” the researchers reported.

“This could be the first chapter of a big story,” said Robert S. Balaban, scientific director of the NHLBI’s Division of Intramural Research, in an NHLBI press release. “It provides evidence that clinical heart catheter procedures are possible without using radiation, which could be especially valuable in areas such as pediatrics.”

The authors acknowledge an important limitation of their research: “We do not believe coronary artery interventional procedures are a realistic possibility because of inadequate spatial and temporal resolution. However, we do believe structural heart interventions to be realistic therapeutic targets, including delivery and repair of cardiac valve devices, non-surgical access and closure of large transthoracic cardiac access ports, repair of other cardiac structural defects, and enhanced image guidance of peripheral artery interventions such as recanalization of chronic occlusion.”

Here is the NHLBI press release:

NIH pilot study shows feasibility of MRI to guide heart catheter procedures
Heart catheter procedures guided by magnetic resonance imaging (MRI) are as safe as X-ray-guided procedures and take no more time, according to a pilot study conducted at the National Institutes of Health. The results of the study indicate that real-time MRI-guided catheterization could be a radiation-free alternative to certain X-ray-guided procedures.
A report of the study, which was conducted by researchers within the intramural program of the NIH’s National Heart, Lung, and Blood Institute (NHLBI), is available online in the European Heart Journal.
“This could be the first chapter of a big story,” said Robert S. Balaban, Ph.D., scientific director of the NHLBI’s Division of Intramural Research.  “It provides evidence that clinical heart catheter procedures are possible without using radiation, which could be especially valuable in areas such as pediatrics.”
MRI creates pictures of internal tissues using magnetic fields, unlike X-ray which uses ionizing radiation. In general X-ray fluoroscopy pictures have higher resolution but less detail than MRI pictures.
The research team performed transfemoral catheterization (guiding a catheter from the large vein in the leg to the heart) in 16 patients to examine the right side of the heart, including the attached veins and the pulmonary arteries. The study volunteers all needed catheterization for heart and valve disease.  The researchers performed the procedure in the 16 patients using X-ray guidance, and then repeated it twice using real-time MRI guidance of a balloon-tipped catheter filled with air or with a contrast agent.
The MRI and X-ray catheterizations were successful in 15 of the 16 participants. One patient had required the use of a wire to help guide the catheter under X-ray, and currently no guidewires are available that work under an MRI.
The average procedure time for the two approaches was comparable—about 20 minutes. The team expected the MRI-guided procedure to take much longer because an MRI-compatible catheter can be harder to see in an MRI-generated image than a conventional steel catheter can be in an X-ray-generated image.
“Developing safe and conspicuous catheter devices for MRI is the chief obstacle to overcome before this approach can be widely applied at hospitals,” said study lead Robert J. Lederman, M.D., a senior investigator in the NHLBI’s Cardiovascular and Pulmonary Branch. “But with improved tools and further improvement of the procedure, real-time MRI catheterization may become a realistic option for many people.”
Lederman’s research group is still performing MRI catheterization on additional patients, and is currently designing improved catheters and other tools that will be more visible under MRI to help move this technology forward. In addition to guiding catheter procedures, the NHLBI team also hopes to use MRI to guide non-surgical catheter treatments in the future.
This study was funded by NHLBI Division of Intramural Research grants Z01-HL005062-08, Z01-HL006039-01, Z01-HL006041-01, and Z01-HL006061-01. More information about this clinical study can be found athttp://clinicaltrials.gov/ct2/show/NCT01287026
For more information, or to schedule an interview, please contact the NHLBI Communications Office at 301-496-4236 ornhlbi_news@nhlbi.nih.gov. Film and visuals related to this study are also available upon request.
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