Magnetic Resonance (MR) Imaging of the cardiac venous system and MR-guided intubation of the coronary sinus in swine: a feasibility-study

Introduction

Procedures like cardiac resynchronization therapy (CRT) or percutanous transcatheter mitral annuloplasty where improved 3-dimensional knowledge about cardiac and cardiac vein anatomy is needed may benefit from magnetic resonance (MR)-guidance.

Purpose

The aim of this study was to visualize the coronary sinus using MR imaging and to demonstrate the feasibility of MR-guided intubation of the cardiac venous system (CVS) in swine.

Methods

6 pigs were investigated. All experiments were performed using an interventional 1.5 Tesla MRI system. The CVS was visualized using an inversion-recovery navigator-gated whole-heart steady-state free precession sequence after administration of Gd-BOPTA contrast agent (130-150 slices, voxel size 1.2 × 1.2 × 1.8 mm³, TR/TE 6.4/3.2, flip angle 85°. Parallel imaging was used with a SENSE-factor of 2. The coronary sinus was then intubated under MR-guidance with a passive MR-compatible guidewire modified by incorporation of iron oxide markers for improved visualization and a non-braded Cobra-catheter. MR-guided interventions were monitored using a steady-state free precession real-time imaging sequence. Parameters of the real-time imaging sequence were TR/TE = 2.5/1.25 ms, flip angle 45°, slice thickness 8 mm, matrix 128 × 128 reconstructed to 256 × 256 using zero-filling. Planning of the image planes, especially for the coronary sinus, were performed with the help of the wholeheart acquisition. Time needed was measured for MR-guided intubation of the CVS and compared to the time needed for fluoroscopy guided intubation of the CVS.

Results

The CVS could be visualized in all animals (100%). The diameter of the ostium of the coronary sinus was 7.6 ± 0.75 mm measured using the inversion-recovery 3-dimensional steady-state free-precession balanced wholeheart sequence. Intubation of the coronary sinus and its site branches was also feasible in all cases. Time spent for MR-guided intubation of the CVS was comparable to time spent for fluoroscopy-guided intubation (8.2 ± 2 min versus 8.3 ± 1.3 min; p = 0.92).

Conclusion

MR-visualization and MR-guided intubation of the coronary sinus and its side branches is feasible. The feasibility of MR-guided intubation of the CVS might have some relevance for procedures like CRT, requiring improved 3-dimensional knowledge about cardiac and cardiac vein anatomy as well as information about function, myocardial scar and asynchrony in the near future.