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OBJECTIVE: To better understand cardiac prosthetic valve attachment suture strength and consistency, a micro-transducer system was developed to quantify the pressures between sutured prostheses and underlying heart tissue. The compressional forces within and adjacent to attachment sutures were measured for comparative analyses. Sutures through a flexible prosthetic mitral ring were secured in an ex-vivo porcine heart model simulating a minimally invasive mitral annuloplasty to evaluate sutures knotted with an extracorporeal knot pusher versus an automated titanium fastener.
METHODS: Using standard suture placement techniques, 16 mitral annuloplasty rings were sewn into pig hearts with 8 sutures per ring. Eight rings were secured with hand-tied knots and 8 secured with automated fasteners via a thoracotomy trainer by either a senior cardiac surgeon or a general surgery resident; each operator completed 4 manually-tied rings and 4 automated rings. Six throws were placed per manually-tied knot. The total time to tie and cut each ring’s 8 sutures was recorded. Suture attachment pressures were promptly measured within (intra-suture) and between (extra-suture) each suture loop using the computerized 0.5 x 2.0 mm micro-transducer probe.
RESULTS: The median suture holding pressure for the mitral rings attached with automated knots was significantly greater than that for manually-tied knots (1008.9 vs. 415.8 mmHg, p < 0.001). Fourteen percent of the hand-tied knots had attachment pressures of less than 75 mmHg and 43% were less than 375 mmHg, while none of the automated fasteners measured that low. There was also less variation in the pressures of automated knots than those of hand-tied knots (SD: 401.6 vs. 499.3 mmHg, p = 0.04). Significant time savings occurred with use of automated knots compared to manual tying (13.0 vs. 68.8 sec/knot, p = 0.0012).
CONCLUSIONS: The new micro-transducer technology proved useful for measuring the attachment pressures between cardiac prostheses sutured to heart tissue. Mitral annuloplasty ring sutures knotted with automated titanium fasteners were stronger, more consistent and faster than manually-tied knots.