Invasive cardiovascular magnetic resonance (iCMR) for diagnostic right and left heart catheterization using an MR-conditional guidewire and passive visualization in congenital heart disease

Abstract

Background: Today's standard of care, in the congenital heart disease (CHD) population, involves performing cardiac catheterization under x-ray fluoroscopy and cardiac magnetic resonance (CMR) imaging separately. The unique ability of CMR to provide real-time functional imaging in multiple views without ionizing radiation exposure has the potential to be a powerful tool for diagnostic and interventional procedures. Limiting fluoroscopic radiation exposure remains a challenge for pediatric interventional cardiologists. This pilot study's objective is to establish feasibility of right (RHC) and left heart catheterization (LHC) during invasive CMR (iCMR) procedures at our institution in the CHD population. Furthermore, we aim to improve simultaneous visualization of the catheter balloon tip, MR-conditional guidewire, and cardiac/vessel anatomy during iCMR procedures.

Methods: Subjects with CHD were enrolled in a pilot study for iCMR procedures at 1.5 T with an MR-conditional guidewire. The CMR area is located adjacent to a standard catheterization laboratory. Using the interactive scanning mode for real-time control of the imaging location, a dilute gadolinium-filled balloon-tip catheter was used in combination with an MR-conditional guidewire to obtain cardiac saturations and hemodynamics. A recently developed catheter tracking technique using a real-time single-shot balanced steady-state free precession (bSSFP), flip angle (FA) 35-45°, echo time (TE) 1.3 ms, repetition time (TR) 2.7 ms, 40° partial saturation (pSAT) pre-pulse was used to visualize the gadolinium-filled balloon, MR-conditional guidewire, and cardiac structures simultaneously. MR-conditional guidewire visualization was enabled due to susceptibility artifact created by distal markers. Pre-clinical phantom testing was performed to determine the optimum imaging FA-pSAT combination.

Results: The iCMR procedure was successfully performed to completion in 31/34 (91%) subjects between August 1st, 2017 to December 13th, 2018. Median age and weight were 7.7 years and 25.2 kg (range: 3 months - 33 years and 8 - 80 kg). Twenty-one subjects had single ventricle (SV) anatomy: one subject was referred for pre-Glenn evaluation, 11 were pre-Fontan evaluations and 9 post-Fontan evaluations for protein losing enteropathy (PLE) and/or cyanosis. Thirteen subjects had bi-ventricular (BiV) anatomy, 4 were referred for coarctation of the aorta (CoA) evaluations, 3 underwent vaso-reactivity testing with inhaled nitric oxide, 3 investigated RV volume dimensions, two underwent branch PA stenosis evaluation, and the remaining subject was status post heart transplant. No catheter related complications were encountered. Average time taken for first pass RHC, LHC/aortic pull back, and to cross the Fontan fenestration was 5.2, 3.0, and 6.5 min, respectively. Total success rate to obtain required data points to complete Fick principle calculations for all patients was 331/337 (98%). Subjects were transferred to the x-ray fluoroscopy lab if further intervention was required including Fontan fenestration device closure, balloon angioplasty of pulmonary arteries/conduits, CoA stenting, and/or coiling of aortopulmonary (AP) collaterals. Starting with subject #10, an MR-conditional guidewire was used in all subsequent subjects (15 SV and 10 BiV) with a success rate of 96% (24/25). Real-time CMR-guided RHC (25/25 subjects, 100%), retrograde and prograde LHC/aortic pull back (24/25 subjects, 96%), CoA crossing (3/4 subjects, 75%) and Fontan fenestration test occlusion (2/3 subjects, 67%) were successfully performed in the majority of subjects when an MR-conditional guidewire was utilized.

Conclusion: Feasibility for detailed diagnostic RHC, LHC, and Fontan fenestration test occlusion iCMR procedures in SV and BiV pediatric subjects with complex CHD is demonstrated with the aid of an MR-conditional guidewire. A novel real-time pSAT GRE sequence with optimized FA-pSAT angle has facilitated simultaneous visualization of the catheter balloon tip, MR-conditional guidewire, and cardiac/vessel anatomy during iCMR procedures.

Keywords: Cardiac catheterization; Congenital heart disease; Device tracking; Interventional CMR; Magnetic resonance imaging.

Fig. 1

In vitro phantom testing in a cardiac model (right) filled with normal saline and a 6F gadolinium-filled balloon wedge catheter to determine the ideal flip angle (FA)-partial saturation (pSAT) angle combination for interventional cardiovascular magnetic resonance (iCMR) procedures. Yellow Box– ideal FA-pSAT angle combination for visualization of the balloon

Fig. 2

Figure depicts a novel passive tracking technique using a pSAT angle of 40^° at different flip angles to optimize imaging for iCMR. The upper row shows the gadolinium-filled balloon alone, the middle row shows the gadolinium-filled balloon and MR-conditional guidewire separate but within the same image, and the bottom row shows an MR-conditional guidewire markers within the gadolinium-filled balloon. The imaging acquisition scan duration time (ms) begins to increase at a FA > 45^°. Dashed White Arrow– Gadolinium-filled balloon;Solid White Arrow– MR-conditional guidewire;Thick White Arrow– MR-conditional guidewire markers within the gadolinium-filled balloon.Yellow box- Ideal in-vivo flip angle combination (pSAT angle = 40^°; FA = 35^°) to simultaneously visualize the catheter balloon tip, MR-conditional guidewire, and cardiac/vessel anatomy during iCMR procedures. Note: No decrease in image acquisition time was seen at FA < 45^°

Fig. 3

FDA cleared and CE marked MR conditional wire (0.035″ diameter) with three nanoparticle markers at discrete positions located at the tip, 2 and 4 cm from the end producing significant passive susceptibility artifact. Green Arrow – MR-conditional guidewire artifact in a sagittal view midway up the descending aorta aiding in a retrograde LHC

Fig. 4

Depicts successful iCMR Fontan fenestration test occlusion (FFTO) followed by successful Fontan fenestration device closure (FFDC) in the x-ray fluoroscopy cath lab. a Under iCMR, the Fontan fenestration (FF) was crossed using an MR-conditional guidewire. An MR-conditional guidewire is seen across the Fontan fenestration and in the RA appendage. b The gadolinium-filled balloon was deflated to advance across the FF, inflated again in the right/pulmonary venous atrium and then pulled back to perform FFTO. Cath and CMR hemodynamics were repeated with FFTO. c If deemed appropriate, the subject was transferred to the x-ray fluoroscopy lab for FFDC. Solid White Arrow– MR-conditional guidewire;Dashed White Arrow– Gadolinium-filled balloon

Fig. 5

Coronal interactive series depicting retrograde entry into the LV during a LHC. a The gadolinium-filled balloon (dashed white arrow) is seen at the aortic root as an MR-conditional guidewire (solid white arrow) is seen in the LV. b An MR-conditional guidewire is within the gadolinium-filled balloon (thick white arrow) in the LV. c The gadolinium-filled balloon remains in the LV to measure pressures as an MR-conditional guidewire is withdrawn to the ascending aorta; Dashed White Arrow– Gadolinium-filled balloon;Solid White Arrow– MR-conditional guidewire;Thick White Arrow– MR-conditional guidewire within the gadolinium-filled balloon

Fig. 6

a MR-conditional guidewire (angled-tip Emeryglide MRWire, Nano4Imaging, Aachen, Germany). b Coronal view of an MR-conditional guidewire (solid white arrow) being used to guide the gadolinium-filled balloon (dashed white arrow) for a RHC. c MR-conditional guidewire used for a retrograde LHC. d Gadolinium-filled balloon used for successful Fontan Fenestration Test Occlusion (FFTO). e Depiction of an MR-conditional guidewire being used to guide the gadolinium-filled balloon across a pre-existing atrial communication in order to enter the LA obtaining pulmonary venous saturations. f Series showing the gadolinium-filled balloon crossing a severe discrete CoA with the assistance of an MR-conditional guidewire. g Axial view of the previously depicted FFTO. Dashed White Arrow– Gadolinium-filled balloon;Solid White Arrow– MR-conditional guidewire