Antegrade percutaneous closure of membranous ventricular septal defect using X-ray fused with magnetic resonance imaging

Abstract

Objectives: We hypothesized that X-ray fused with magnetic resonance imaging (XFM) roadmaps might permit direct antegrade crossing and delivery of a ventricular septal defect (VSD) closure device and thereby reduce procedure time and radiation exposure.

Background: Percutaneous device closure of membranous VSD is cumbersome and time-consuming. The procedure requires crossing the defect retrograde, snaring and exteriorizing a guidewire to form an arteriovenous loop, then delivering antegrade a sheath and closure device.

Methods: Magnetic resonance imaging roadmaps of cardiac structures were obtained from miniature swine with spontaneous VSD and registered with live X-ray using external fiducial markers. We compared antegrade XFM-guided VSD crossing with conventional retrograde X-ray-guided crossing for repair.

Results: Antegrade XFM crossing was successful in all animals. Compared with retrograde X-ray, antegrade XFM was associated with shorter time to crossing (167 +/- 103 s vs. 284 +/- 61 s; p = 0.025), shorter time to sheath delivery (71 +/- 32 s vs. 366 +/- 145 s; p = 0.001), shorter fluoroscopy time (158 +/- 95 s vs. 390 +/- 137 s; p = 0.003), and reduced radiation dose-area product (2,394 +/- 1,522 mG.m(2) vs. 4,865 +/- 1,759 mG.m(2); p = 0.016).

Conclusions: XFM facilitates antegrade access to membranous VSD from the right ventricle in swine. The simplified procedure is faster and reduces radiation exposure compared with the conventional retrograde approach.

Figure 1. MRI derived contours

A: Long axis 3 chamber SSFP MRI used to contour VSD (white arrow) and aortic root (black arrow). B: Short axis SSFP MRI used to contour right (yellow) and left (blue) ventricular endocardial surfaces, and left ventricular epicardial surface (green). C: Short axis SSFP MRI used to contour aortic valve annulus (blue) and leaflets (black). D: Surface rendering of MRI-derived contours. The yellow dot indicates the left ventricular apex.

Figure 2. Schematic depictions of conventional and investigational procedure technique

A: Conventional retrograde X-ray technique. 1: Retrograde, transaortic access to the left ventricle; 2: A guidewire crosses retrograde from the left to right ventricle across the VSD; 3: A transfemoral venous snare retrieves the transaortic guidewire from the pulmonary artery; 4: An arteriovenous loop is exteriorized to provide a rail to deliver the rigid VSD delivery sheath; 5: The delivery sheath is positioned antegrade across the VSD; 6: The VSD occlusion device is positioned and released. B: Investigational XFM-guided antegrade technique. 1: With enhanced imaging guidance, the guidewire is passed antegrade from the right ventricle through the VSD into the left ventricle and descending aorta; 2: the delivery sheath is positioned in the left ventricle; 3: the VSD occlusion device is positioned and released. The XFM technique has fewer steps. Courtesy of Lydia Kibiuk, NIH Medical Arts and Photography Branch.

Figure 3. X-ray fluoroscopic landmarks compared with XFM roadmaps

A: X-ray depicts the ventricular septal defect (white arrow) only during radiocontrast injections. Black arrows indicate the external fiducial beads. B: A representative image of direct antegrade VSD guidewire crossing using XFM guidance. XFM roadmap elements include the right ventricular endocardial contour (yellow), the left ventricular epicardial contour (green), the left ventricular endocardial contour (blue), the VSD tract (red outline and black arrow), aortic root (red), and aortic valve (blue annulus with black leaflets). The guidewire (white arrow) is delivered across the VSD and into the aorta using a right-handed 3-dimensional curve right coronary artery catheter. The MRI-derived contours adjust automatically when the X-ray system is repositioned.

Figure 4. XFM positioning of delivery sheath and VSD occluder deployment

A: Antegrade sheath delivery guided by XFM. The sheath is directed toward the left ventricular apex using a flexible guidewire. The XFM roadmap includes right (yellow) and left (blue) ventricular endocardial contours, left ventricular epicardial contour (green), aortic annulus (blue), aortic root (red), and VSD tract (bright red). B: Confirmatory XFM radiocontrast ventriculography before release of VSD occluder device deployed in position. Features include the VSD occluder (white arrow), VSD tract (bright red contour), right (yellow) and left (blue) ventricular endocardial and left ventricular epicardial (green) contours, aortic valve (dark blue) and aortic root (dark red).