NIH pilot shows MRI can accurately guide cardiac caths
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"This could be the first chapter of a big story," Robert S. Balaban, PhD, scientific director of the National Heart, Lung and Blood Institute's (NHLBI) division of intramural research, said in a release. "It provides evidence that clinical heart catheter procedures are possible without using radiation, which could be especially valuable in areas such as pediatrics."
Kanishka Ratnayaka, MD, from NHLBI, and colleagues sought to perform comprehensive transfemoral diagnostic right heart catheterization using MRI guidance.
The researchers recruited 23 patients to participate and 16 ultimately underwent the procedure. They 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. Ratnayaka and colleagues measured success and time required for four procedure steps, and evaluated image guidance in terms of confidence and conspicuity of the catheter.
One patient was unable to undergo complete MRI catheterization, and in two patients, only one of the two MR catheterizations was performed.
The researchers reported that MRI provided continuous visualization of transfemoral catheterization during navigation into all selected vessels and chambers.
Procedure steps required approximately the same amount of time regardless of the image guidance modality. “All three image guidance techniques provided equivalent confidence to operator that [the] catheter was inside [the] targeted chamber or vessel,” wrote Ratnayaka et al.
However, the researchers pointed out a discrepancy between x-ray and MRI guidance. Although the catheter tip and shaft were always visible under x-ray, only the tip was visible under MRI. “We found gadolinium-filled catheters to be more conspicuous and allowed faster navigation, and therefore were more effective than air-filled balloon catheters,” they wrote.
As the researchers considered future applications, they identified the lack of conspicuous and safe catheter devices as the chief obstacle to adoption of MRI catheterization. A potential workaround may be ‘active’ MRI catheters which double as antennas connected to the MR system. Given the limited commercial interest in developing these devices, the NHLBI laboratory is engineering these tools.
Future research projects include routine radiation-free diagnostic right and non-coronary left heart catheterization using active guidewires and passive catheters. While coronary artery interventional procedures may not be feasible, the researchers offered several realistic therapeutic targets: 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.
Ratnayaka and colleagues noted that although MRI catheterization is not ready for prime time, it could become a realistic alternative with improved tools and optimized steps.