Valved Fontan in Sheep Model: Feasibility and Safety Study

Background: Passive pulmonary flow and venous regurgitation leading to inadequate preload of the systemic ventricle are the known factors limiting the Fontan circulation. The original Fontan operation included the implantation of two valves in the conduit system, but due to the high calcification rate, this idea was abandoned. The modern bioengineering valves promise low rate of degradation. We set out to develop a stable animal model to test the possible advantages of the valved Fontan conduit.

Methods: A study concept was developed, which included (1) perioperative imaging, anesthesia, and postoperative care and monitoring of the animal, (2) surgical concept for a viable Fontan model in the sheep, (3) minimally invasive techniques for fenestration creation, and (4) transvenous GrOwnValve implantation in the Fontan conduit.

Results: In total, 12 animal models were created. Two-day setting with full anesthesia, preoperative CT, and perioperative echocardiography and angiography was established. The surgical method was optimized according to the anatomical characteristics of the ovine cardiovascular system. Surgical procedures were performed off-pump by right or left lateral thoracotomy. The extracardiac Fontan operation (n = 2) was replaced by “one-lung” atriopulmonary connection (RA appendage to the MPA [n = 2] and later to the LPA [n = 2], with subtotal ligation of the RPA) with preservation of unilateral pulsatile lung perfusion. Conduit thrombosis occurred in a sheep with subpulmonary stenosis but was treated with thrombectomy via lateral thoracotomy 1.5 months after the original procedure. Fenestration (n = 5) was created after minimal left lateral thoracotomy by trans-left atrial puncture and balloon dilatation of the perforated interatrial septum, using direct epicardial echocardiography. The GrOwnValve were implanted via a transjugular (n = 2) or transatrial (n = 1) access. The control CT demonstrated the complete thrombosis of the oversized 22-mm valve in one sheep; thus, for the optimal opening of the valve cusps in the 16- to 18-mm conduit smaller valve diameter was applied.

Conclusion: We established the “half-lung” RA-LPA valved Fontan animal model with subtotal banded RPA via left lateral thoracotomy and secondary valve implantation. The next phase of the study should provide longer follow-up of the conduit function and GrOwnValve properties.

Publication History

Article published online:
11 February 2025