Mechanical Circulatory Support of the Fontan Circulation: Implantation of the EXCOR Venous Cannula

This article is part of CTSNet’s Guest Editor Series, Insights Into Pediatric Mechanical Circulatory Support. Congenital and pediatric surgeon Dr. Sandeep Sainathan invited accomplished pediatric surgeons from around the world to contribute clinical videos on the surgical aspects of pediatric mechanical circulatory support as a bridge to cardiac transplantation or recovery of cardiac function.    

Introduction 

Mechanical circulatory support (MCS) devices intended for mid- to long-term support are conventionally designed for left ventricular to aortic assistance. Subpulmonary implantation in patients with surgically palliated univentricular heart disease necessitated extensive surgical reconstruction of the cavopulmonary Fontan connection (1). However, the introduction of the EXCOR Venous Cannula in 2021 marks the first available MCS system dedicated to the failing Fontan population (2). This double-inlet inflow cannula is conceptualized for bicaval venous drainage from the total cavopulmonary connection (TCPC) to the supplementary MCS system. 

Case Presentations 

The authors present the implantation technique of the EXCOR® Venous Cannula in two patients receiving combined subpulmonary and subaortic circulatory support with an MCS system. 

Patient 1 was a 12-year-old male (BSA 1.29m2) with hypoplastic left heart syndrome, who had previously undergone staged surgical univentricular palliation. Initially, hybrid stage I procedures consisted of a bilateral pulmonary artery banding and ductus arteriosus stenting seven days postnatally. At two months of age, a comprehensive stage II palliation was performed with a Norwood procedure and unilateral bidirectional Glenn anastomosis. A complete total cavopulmonary connection (TCPC) was established at four years by connection of an 18 mm Fontan tunnel. Due to a progressively dilating ascending aortic diameter, a David procedure and left pulmonary artery patch augmentation were performed at 11 years of age. Periprocedurally, hemodynamic compromise led to a prolonged episode of cardiopulmonary resuscitation and the necessity of extracorporeal membrane oxygenation (ECMO). Following ECMO weaning, systemic ventricle dysfunction persisted and was aggravated by rapid subpulmonary circulatory failure, as well as an accompanying deterioration of end-organ functions. The decision was made to implant an MCS system for midterm support as a bridge-to-candidacy for heart transplantation. 

Patient 2 was a 16-year-old male (BSA 1.17 m2) also with hypoplastic left heart syndrome. Surgical palliation was initiated with a Norwood-I procedure at nine days, followed by a Blalock-Taussig shunt at two months. Cavopulmonary connection was established with a Glenn procedure at 1.5 years and a Fontan tunnel at four years of age. Due to chronic subpulmonary failure, an innominate vein turndown (Hraska) procedure was performed at 15 years of age. Hemodynamically, the systemic ventricular function remained chronically moderately reduced and subpulmonary circulatory failure continued to progress, resulting in protein-losing enteropathy and Fontan-associated liver disease. In this patient, who was in chronic Pedimacs stage III, MCS implantation was planned as a bridge-to-candidacy for potential relisting for heart transplantation. 

Surgical Proceeding 

Preoperative planning to identify the individual total cavopulmonary connection (TCPC) geometries and optimal cannula sizes comprised segmentationand virtual fitting using specialized software.  

The surgical implantation technique was demonstrated based on Patient 2. Through a median resternotomy, cannulation for cardiopulmonary bypass was achieved at the ascending aorta and both venae cavae and the Hraska conduit in Patient 2. Back table preparations of the EXCOR cannulae involved suturing of a 20 mm and 14 mm ring-reinforced GORE-TEX prosthesis to the respective inferior and superior ends of a 14/18 mm EXCOR Venous Cannula. Further graft anastomosis comprised a 14 mm ring-reinforced ORE-TEX prosthesis to the pulmonary outflow graft and a 12 mm Dacron prosthesis to the aortic outflow prosthesis.  

Connection of the EXCOR cannulae was initiated with transection of the Hraska conduit and inferior vena cava. Following cannula insertion, the innominate vein was anastomosed to the superior EXCOR Venous Cannula inlet. Connection of the superior vena cava was established via an end-to-side anastomosis into the GORE-TEX prosthesis. Implantation of the EXCOR Venous Cannula was completed by anastomosis of the inferior vena cava to the inferior cannula inlet. A staged 12/9 mm arterial cannula was anastomosed to the pulmonary artery for pulmonary outflow. Cannulation for the subaortic assist device was achieved with a 12 mm apex cannula for the systemic ventricle and a staged 12/9 mm arterial cannula anastomosed end-to-side to the ascending aorta cranial of the Damus-Kaye-Stansel anastomosis. Subsequently, the cannulae were tunneled through the epigastrium and connected to two 50 ml blood pumps. Subpulmonary and subaortic circulatory support were initiated while concurrently reducing cardiopulmonary bypass flow. Pump settings at implantation were 67 bpm, 105mmHg systolic and -2 mmHg diastolic pressure with a 30 percent systole for the subpulmonary device and 70 bpm, 150mmHg systolic, and -20 mmHg diastolic pressure with 40 percent systole duration for the subaortic pump. Planned delayed sternal closure was performed on postoperative day one. 

Conclusions 

As circulatory assist device implantation into the Fontan circulation used to be utterly challenging, the addition of a Fontan-specific inflow cannula to the EXCOR regime now initialized standardized subpulmonary MCS for univentricularly palliated patients. Its application in bridge-to-candidacy and transplantation setting is hemodynamically effective and applicable for short- to mid-term durations (3, 4). However, intracorporeal cavopulmonary assist devices for long-term support have yet to be introduced. 

References

1. Woods RK, Ghanayem NS, Mitchell ME, Kindel S, Niebler RA. Mechanical Circulatory Support of the Fontan Patient. Semin Thorac Cardiovasc Surg Pediatr Card Surg Annu. 2017;20:20-27. doi:https://doi.org/10.1053/j.pcsu.2016.09.009
2. Berlin Heart GmbH. Berlin Heart today announces CE approval and first implantation of an innovative bridging solution for single ventricle patients. Published online 2021.
3. Michel SG, Menon AK, Haas NA, Hörer J. Cavopulmonary support with a modified cannulation technique in a failing Fontan patient. Interact Cardiovasc Thorac Surg. 2022;35(2):ivac090. doi:10.1093/icvts/ivac090
4. Karner B, Urganci E, Schlein J, et al. First-in-man use of the EXCOR Venous Cannula for combined cavopulmonary and systemic ventricular support in Fontan circulation failure. J Heart Lung Transplant. 2022;41(10):1533-1536. doi:10.1016/J.HEALUN.2022.06.009

Disclaimer

The information and views presented on CTSNet.org represent the views of the authors and contributors of the material and not of CTSNet. Please review our full disclaimer page here.