Mitral cerclage annuloplasty, a novel transcatheter treatment for secondary mitral valve regurgitation: initial results in swine

Abstract

Objectives: We developed and tested a novel transcatheter circumferential annuloplasty technique to reduce mitral regurgitation in porcine ischemic cardiomyopathy.

Background: Catheter-based annuloplasty for secondary mitral regurgitation exploits the proximity of the coronary sinus to the mitral annulus, but is limited by anatomic variants and coronary artery entrapment.

Methods: The procedure, "cerclage annuloplasty," is guided by magnetic resonance imaging (MRI) roadmaps fused with live X-ray. A coronary sinus guidewire traverses a short segment of the basal septal myocardium to re-enter the right heart where it is exchanged for a suture. Tension is applied interactively during imaging and secured with a locking device.

Results: We found 2 feasible suture pathways from the great cardiac vein across the interventricular septum to create cerclage. Right ventricular septal re-entry required shorter fluoroscopy times than right atrial re-entry, which entailed a longer intramyocardial traversal but did not cross the tricuspid valve. Graded tension progressively reduced septal-lateral annular diameter, but not end-systolic elastance or regional myocardial function. A simple arch-like device protected entrapped coronary arteries from compression even during supratherapeutic tension. Cerclage reduced mitral regurgitation fraction (from 22.8 +/- 12.7% to 7.2 +/- 4.4%, p = 0.04) by slice tracking velocity-encoded MRI. Flexible cerclage reduced annular size but preserved annular motion. Cerclage also displaced the posterior annulus toward the papillary muscles. Cerclage introduced reciprocal constraint to the left ventricular outflow tract and mitral annulus that enhanced leaflet coaptation. A sample of human coronary venograms and computed tomography angiograms suggested that most have suitable venous anatomy for cerclage.

Conclusions: Transcatheter mitral cerclage annuloplasty acutely reduces mitral regurgitation in porcine ischemic cardiomyopathy. Entrapped coronary arteries can be protected. MRI provided insight into the mechanism of cerclage action.

Conflict of interest statement

Conflicts of Interest and Relationship with industry: JHK, OK, RJL are co-inventors in patent applications related to cerclage and coronary artery protection assigned to NIH.

MS was a student employee of Siemens Corporate Research.

Figures

Figure 1

Schematic, imaging guidance, and necropsy of cerclage annuloplasty. (A) shows the mitral annulus from the cardiac apex and (B) with free walls of right atrium and ventricle removed. A guidewire through the coronary sinus enters a basal septal perforator vein and traverses a short distance of septal myocardium. Wire 1 follows a right ventricular cerclage trajectory into the right ventricular outflow tract, and wire 2 a longer trajectory to reenter the right atrium directly. The guidewire is replaced with a suture and tension applied to both ends and fixed near the coronary sinus ostium. (C–E) shows XFM procedure guidance. MRI-derived contours include LV and RV endocardium (blue and yellow), LV epicardium (green), and aortic root (red). (D) shows live X-ray fluoroscopy and (E) the corresponding XFM display. The guidewire tip (white arrow) crosses septal myocardium and reenters the right ventricle. Registration is maintained even when the table or gantry move. (F) shows the discordant planes of the mitral annulus (blue) and cerclage annuloplasty (red). Necropsy findings are shown immediately after right ventricular (G) and right atrial (H) cerclage with the RV free wall removed. In (G) the suture (arrow) emerges from the septum and returns to the right atrium across a tricuspid commissure. In (H) a suture emerges (arrow) near the cavo-tricuspid isthmus, alongside the coronary sinus end of the same suture (dotted arrow). Panels A,B,F courtesy of Lydia Kibiuk, NIH Medical Arts.

Figure 2

Coronary artery entrapment and protection. (A,B) A typical great cardiac vein configuration passing outside a circumflex artery branch. (C) Cerclage would compress the underlying artery. (D) A protection device along the cerclage suture redistributes compressive forces away from coronary artery. (E–H) circumflex coronary artery pressure during cerclage tension without (E,G) and with (F,H) a protection device in place. (E) Angiographic stenosis (arrow) induced by cerclage and (F) the same segment during cerclage tension with a protection device (dashed arrow) in place. (G,H) Distal coronary artery pressure (Pd, depicted in green, axis on left, mm), the aortic pressure (Pa) in red, and their ratio in yellow (axis on right, displayed as fractional flow reserve). Without a protection device (G), the distal coronary pressure falls by more than half when cerclage tension (400g) is applied. (H) With the protection device in place, there is no distal pressure drop after cerclage tension is introduced (dotted arrow) until tension is sufficiently high (solid arrow) to impede mitral inflow. Panels A–D courtesy of Lydia Kibiuk, NIH Medical Arts.

Figure 3

Effect of graded tension on annular dimensions and leaflet tenting. (A) Progressively increased cerclage tension reduces the annular septal-lateral dimension, perpendicular to the line of mitral coaptation. (B) With progressive tension, the decline in cerclage diameter is directly related to the decline in septal-lateral dimension. (C) Reduced cerclage diameter is directly related to the reduction in mitral valve tenting area, an index of mitral regurgitation.

Figure 4

Representative dynamic pressure-volume loops before (A) and after (B–D) progressive application of cerclage tension in naïve swine. There is no significant change in the end-diastolic (upper slope) and end-systolic (lower slope) pressure-volume relationships as tension is introduced. 600g tension was found to reduce annular circumference sufficiently to impede transmitral inflow. In this animal cerclage does not acutely alter ventricular volumes.

Figure 5

Mitral regurgitation before (A,C) and after (B,D) application of cerclage tension. Arrowheads 1 and 2 indicate the anterior and posterior mitral annulus, respectively. Arrowheads 3 and 4 indicate the anterior and posterior course of the cerclage annuloplasty. Arrows indicate the twin jets of mitral regurgitation in this MRI in an animal with a regurgitant fraction of 0.43. After tension is applied, the regurgitant fraction fell to 0.08, and jets are no longer visible. Note the anterior displacement of point 4 and its altered configuration in relation to point 2 (animated in video 1). Note also that regurgitant jets of dephased spins in steady state free precession MRI under-represent mitral regurgitation compared with echocardiography. (C,D) show combined motion (tagged) and velocity-encoded MRI during systole before (C) and after (D) application of cerclage tension in another animal, animated in video 2. Mitral regurgitation is evident as a blue jet in (C, black arrow) and nearly extinguished in (D). The posterior cerclage wire (black spot indicated by white arrow) is displaced toward the septum when tension is applied. Late gadolinium enhancement and reduced myocardial contraction are evident from prior posterobasal infarction.

Figure 6

Quantitative (A) and qualitative (B) measures of mitral regurgitation before and after application of cerclage tension.

Figure 7

Dynamics of mitral annulus measurements over time before (solid line) and after (dotted line) cerclage tension is applied. The time scale is normalized for a single cardiac cycle beginning with the QRS gating signal for MRI. Cerclage reduces annular circumference (A), commissural width (B), and septal-lateral distance (C) but increases annular height to commissural width ratio (AHCWR, a measure of annular flattening, D). All vary throughout the cardiac cycle and continue to vary despite application of annular tension. (E–F) depict the annulus (black) and leaflet (colored) morphology derived from MRI before (E) and after (F) application of cerclage tension. The posterior annulus (arrow) is displaced caudally toward the posterior papillary muscle when cerclage tension is applied. This is animated in videos 3 and 4.

Figure 8

Reciprocal constraint of the left ventricular outflow tract and mitral annulus after cerclage annuloplasty. The combined diameter of the two structures remains constant throughout the cardiac cycle. During diastole, the anterior mitral leaflet is relatively unconstrained. During systole, the outflow tract enlarges and displaces the anterior mitral valve leaflet posteriorly (* = p

Figure 9

Representative human venograms. (A) A pressurized venogram in a patient undergoing cardiac resynchronization therapy. A basal septal perforator vein was evident (arrow) in all 8 patients with evaluable angiograms. (B) A CT angiogram showing a basal septal perforator vein (arrows) apparently suitable for cerclage.