Suture Forces in Undersized Mitral Annuloplasty: Novel Device and Measurements

Abstract

Purpose: Demonstrate the first use of a novel technology for quantifying suture forces on annuloplasty rings to better understand the mechanisms of ring dehiscence. Description: Force transducers were developed, attached to a size 24 Physio™ ring, and implanted in the mitral annulus of an ovine animal. Ring suture forces were measured after implantation and for cardiac cycles reaching peak left ventricular pressures (LVP) of 100, 125, and 150 mmHg. Evaluation: After implanting the undersized ring to the flaccid annulus, the mean suture force was 2.0±0.6 N. During cyclic contraction, anterior ring suture forces were greater than posterior ring suture forces at peak LVPs of 100 mmHg (4.9±2.0 N vs. 2.1±1.1 N), 125 mmHg (5.4±2.3 N vs. 2.3±1.2 N), and 150 mmHg (5.7±2.4 N vs. 2.4±1.1 N). The largest force was 7.4 N at 150 mmHg. Conclusions: Preliminary results demonstrate trends in annuloplasty suture forces and their variation with location and LVP. Future studies will significantly contribute to clinical knowledge by elucidating the mechanisms of ring dehiscence while improving annuloplasty ring design and surgical repair techniques.

How Local Annular Force and Collagen Density Govern Mitral Annuloplasty Ring Dehiscence Risk

“…[17] Transducers are designed to report suture tension as a positive force tracing. Before use in this study, the transducers were calibrated with known forces exceeding those anticipated in vivo , as previously described.…”

“…All in vivo experimental procedures for ring implantation (1C–D) and measurement were performed as we previously described. [17]…”

Bench Models for Assessing the Mechanics of Mitral Valve Repair and Percutaneous Surgery

“…11). 45 Similar to the methods illustrated in Fig. 7, a fluid bulb and aortic cross-clamp are used to statically pressurize the LV prior to evaluating select experimental endpoints.…”

Real-time recording of annuloplasty suture dehiscence reveals a potential mechanism for dehiscence cascade

“…We recently demonstrated novel transducers capable of quantifying tension in individual sutures in the beating heart, post-mitral annuloplasty. 2 We have expanded these methods to evaluate the effects of ring size, shape, and ventricular function on suture forces, to identify physiologic and device-specific factors that may affect suture dehiscence risk. As part of this study, a Profile3D ring (size:26; Medtronic, Dublin, Ireland), instrumented with transducers, was implanted in a healthy 45kg subject (annulus size:30).…”

“…Implantation (Figure 1) was analogous to clinical annuloplasty, using ten 2-0 Ti·Cron TM sutures (Covidien, Dublin, Ireland) with approximately 10mm suture width and 1.5mm depth; transducers did not affect ring or suture function. 2 Animal care complied with protocols approved by the Institutional Animal Care and Use Committee at University of Pennsylvania, according to guidelines for humane care (National Institutes of Health Publication 85–23, revised 1996).…”