Real-time magnetic resonance imaging guidance improves the yield of endomyocardial biopsy

Background

In current practice, the diagnostic yield of endomyocardial biopsy is low because the procedure is performed ‘blind' using X-ray fluoroscopy guidance and because many pathologies affect the myocardium in a patchy distribution. We hypothesized that biopsy performed under direct realtime MRI guidance would have superior diagnostic yield, in an animal model of focal myocardium pathology.

Methods

An active visualization MR conditional bioptome was designed and built for transcatheter endomyocardial biopsy (MRI Interventions, Irvine, CA). A porcine model of focal myocardial pathology that enhances with late gadolinium enhancement imaging and that contained fluorescent tags that are easily identifiable under ultraviolet light was created. Under X-ray fluoroscopy, selective coronary artery catheterization was performed and 3 mL of fluorescent microspheres (NuFlow Hydrocoat, 15μm diameter, 5 million spheres/mL) was infused, followed by 2 mL of 100% ethanol to create a focal lesion. Animals were survived for min 7 days, after which each animal underwent both MRI and X-ray guided biopsy. Specimens were analysed using a Leica MZFIII dissecting microscope under transmitted or ultraviolet light with a 400-480 nm band pass filter.

Results

The bioptome shaft was actively visualized under realtime MR imaging. The jaws appeared as a distinct signal void (arrow, Figure 1A). After administration of systemic gadolinium contrast, the lesion was visible using LGE or inversion recovery real-time MRI (Figure 1B). The bioptome was navigated to the pathology and specimens were collected. Animals were then transferred to an X-ray catheterization laboratory, where ‘conventional' fluoroscopy guided biopsy was performed. Examination of the biopsy specimens under ultraviolet light revealed fluorescent microspheres in 24/27 specimens obtained using MRI guidance compared with 7/28 specimens obtained using X-ray fluoroscopy guidance (Figure 2).

Figure 1

Real-time MRI guided endomyocardial biopsy using an active visualization bioptome.

Figure 2

Biopsy specimens under transmitted and ultraviolet light obtained using either real-time MRI or X-ray fluoroscopy guidance.

Conclusions

Endomyocardial biopsy under direct real-time MRI guidance using an active visualization MRI-conditional bioptome is feasible. Using this bioptome we demonstrate targeted biopsy of focal myocardial pathology. Compared with X-ray fluoroscopy guided endomyocardial biopsy, MRI guidance substantially improves the diagnostic yield in an animal model of focal myocardial pathology.