Micro-Connector Constructed Coronary Anastomosis - Device development and preclinical validation

Abstract

Coronary artery bypass grafting remains the most effective and durable treatment for severe coronary artery disease, but causes significant patient trauma. Efforts to improve the procedure by avoiding cardiopulmonary bypass and/ or by limiting the access are hampered by the increased difficulties of hand suturing the graft connections. Automated anastomotic devices may address these difficulties, provided that current performance standards are matched. For this purpose, the S micro-stapler has been developed. The device has been designed to minimize tissue trauma as well as intraluminal artefact and to provide an easy deployment procedure. To improve reliability, a specific sequence has been built-in, first presenting the tissue using device expansion prior to stapling. Accepted unconventional anastomosis properties are pulsatility non-compliance, inverted vessel wall apposition and a clipped, blind sac, resulting from converting the side-to-side geometry to an end-to-side configuration. Device dimensions are compatible with the majority of internal thoracic artery (ITA) to left anterior descending artery (LAD) anastomoses. Remote actuation minimizes undue movements during deployment, and allows endoscopic application. The preclinical validation included extensive in vitro tests using porcine as well as human tissue, and met preset standards. Chronic tests of the device compared anastomosis patency, remodeling and hemodynamic function to conventionally sutured controls in the off-pump porcine model. The connector rapidly and consistently produced high quality ITA to LAD anastomoses. Thirteen MHz epicardial ultrasound proved effective for intraoperatively assessing anastomosis quality, despite the presence of a metal connector. Evaluation at up to 6 months using angiography, fractional flow reserve measurements and intravascular ultrasound showed 100% patency with an effective vascular remodeling response, resulting in unobstructed anastomoses with excellent hemodynamic function in all cases. Histology showed a stabilized neo-intima on the inside of the anastomoses that was thinner than in the sutured controls. The device’s performance fully met current standards on patency and function. Unconventional aspects like a noncompliant intraluminal ring and a side-to-side to end-to-side converted configuration did not interfere with favorable anastomosis healing. To chart clinical failure modes and to assess the relevance to the S micro-stapler, all publications up to August 2007 on anastomotic devices that included systematic elective angiographic imaging were systematically reviewed. Marked outcome differences between individual devices were found, but could not be correlated to demographic, operative or follow-up differences, anticoagulation regime or device properties like expansion mode, pulsatility non-compliance, implant material or blood exposed non-intimal surface. Significant device and surgery related issues included graft thrombosis, graft kinking and stenosing intimal hyperplasia. Selected devices performed well, and showed that substantial equivalence to the gold standard of tailor-made, hand-sewn anastomoses is possible for automated, intrinsically standardized systems. The design characteristics of the S micro-stapler are well directed at avoiding the observed patency issues, and support expectations of favorable clinical results. In conclusion, reliable anastomotic technology could be the key to mainstream less invasive and port access CABG procedures on the beating heart. The S micro-stapler has the promise to be such a technology, provided that the favorable preclinical results are validated in humans.