P1428Real time guidance for targeted endomyocardial biopsy in a minipig model

Abstract

Background: Endomyocardial biopsies (EMB) are an important diagnostic tool for myocarditis. Despite procedural success, the large sampling error results in the necessity of multiple (>6) biopsies. In cardiac magnetic resonance (CMR) imaging late gadolinium enhancement (LGE) depicts areas of affected myocardium. Thus, targeted biopsy under real-time magnetic resonance image guidance might reduce sampling error. Methods: Seven minipigs (MP) of the Goettingen strain underwent radiofrequency (RF) (2x30s, max. 30 W, temperature 60–64 °C) ablation in the left ventricle. Two focal lesions were induced (lateral wall in five apex in two animals). Biopsies were taken immediately after lesion induction using a 7 F conventional bioptome under fluoroscopic guidance (FLG) at the ablation site. Afterwards the CMR and lesion visualization by LGE was performed on a 3T MRI scanner. The lesions were biopsied under CMR-guidance using a MR-compatible bioptome (fig.1) guided by a steerable catheter. Interactive real-time visualization of the intervention was based on radial FLASH with nonlinear inverse reconstruction (NLINV) (temporal resolution 42 ms). All samples underwent a standard histological evaluation. Results: RF-ablation was successful in all MP. FL- guided biopsies were performed succesfully in 6/6 MP. Detection of RF lesions by CMR detection was successful in 7/7 MP, i.e. at least one lesion was clearly visible. Localization and tracking of the catheters and the bioptome using interactive control of the imaging plane was achieved in 6/6 MP; however in the MP with a large PE after EMB under fluoroscopy no further EMB was attempted for safety reasons. Biopsies under CMR guidance were successfully performed in 5/6 animals, in one MP the bioptome reached the lesion, however the forceps did not cut out a sample. Specimens obtained under CMR guidance contained part of the lesion in 6/15 (40%) myocardial specimens and in 4/5 (80%) animals in which samples were achieved. Conventional biopsies revealed ablation lesions in 4/17 (23.5%) specimens in 3/6 MP (50%). Conclusion: RF-induced focal lesions are a useful tool for CMR-guided biopsy studies in minipigs. In contrast to fluoroscopy, CMR provides excellent visualization of lesions. Interactive real-time MRI allows excellent passive tracking of the instruments and EMB provides significantly superior sampling accuracy compared to FL-guided biopsies. Improvements of MR-compatible bioptomes and guiding catheters are essential before applying this method in a clinical setting.