Modified cardiopulmonary bypass circuit for transcatheter aortic valve implantation and emergent cardiac surgery

Introduction

Transcatheter aortic valve implantation (TAVI) has revolutionized the treatment of severe aortic stenosis patients, offering a minimally invasive alternative to open-heart surgery. ¹ However, TAVI procedures carry risks, particularly in patients with complex comorbidities or severe hemodynamic instability. ² In these cases, circulatory support is crucial to ensure patient safety and procedural success. Extracorporeal membrane oxygenation (ECMO) has proven valuable for temporary cardiac and respiratory support during high-risk interventions. In some cases, patients may require emergent cardiac surgery (ECS) during or shortly after the TAVI procedure, requiring a transition to cardiopulmonary bypass (CPB). ³ A seamless transition from mechanical circulatory support (MCS) to CPB is challenging but essential in managing complex TAVI cases. Converting patients from MCS to CPB quickly and safely can minimize hemodynamic disruptions, reduce procedural risks, and improve patient outcomes. This transition requires meticulous planning, advanced technical skills, and a deep understanding of both MCS and CPB systems. We describe a modified CPB circuit that enables seamless conversion from completely closed cardiopulmonary bypass (CCCB) circuit to conventional CPB, enhancing procedural safety.

Technique

A total of 634 TAVI procedures were performed from January 2021 to August 2024 in our institution. MCS was applied in 17 patients. Four patients required ECS due to complications which occurred during the procedure. Since January 2024, the CPB circuit has been modified to allow easy transfer between circulatory support and the CPB model. We adopted this technique in four patients, three patients needed prophylactic circulatory support, and one patient required emergency circulatory support. One patient was transferred to the CPB model due to migration of the aortic valve. In the hybrid operating room, the CPB circuit was modified in the sterile field. A 3/8 inch line from the venous return line to the centrifugal pump was inserted using 3/8 Y connectors, bypassing the venous reservoir (Figure 1(a)). 6F sheaths are routinely placed in the femoral artery and vein. If circulatory support is necessary, femoral arterial and venous cannulation can be performed percutaneously. By adjusting the position of the tubing clamp, blood can be directed from the inferior vena cava drainage tube through the bypass tube to the oxygenator. The CPB circuit can be a closed unit (Figure 1(b)). If the patients required ECS, we routinely perform a median sternotomy. Subsequently, an additional 3/8 drainage tube is connected to the superior vena cava cannula. Vacuum assisted venous drainage may be employed for additional drainage if necessary. Then the bypass tube was clamped and full flow was established (Figure 1(c)). When cardiac function was sufficient to separate from circulatory support, CPB was gradually wean off (Figure 1(d)). Femoral arterial cannula can be used during the CPB period or it can remain in place for further ECMO support.OPEN IN VIEWER

In these four patients (3 males) the mean age was 69.25 years (range 62–75 years). In three patients the mean circulatory support time was 23.33 minutes (range 15–35 minutes). In ECS patients, the duration of CPB and aortic cross-clamping were 97 and 52 minutes, respectively. Bleeding and vascular complications were not observed. The study protocol was approved by the Institutional Review Board (Ethical approval number: 202406-02). Individual consent was waived due to the retrospective nature of our study.

Discussion

TAVI has been proved to be a safe and effective treatment for high-risk patients with severe aortic stenosis. ⁴ However circulatory collapse may occur during TAVI, Prophylactic or emergent MCS has been used in 2.8%–9.4% patient.^5,6 ECMO, CPB and Impella are frequently used MCS systems for TAVI support.^7,8 Compared to CPB, ECMO provides respiratory and circulatory support with reduced circuit prime. Impella has the advantages of wide flow rate, forward flow and left ventricular unloading. ⁹ Potential complications associated with the use of Impella include hemolysis, ventricular arrhythmias and perforation of the left ventriclewall. ¹⁰ During the TAVI procedure, aside from the potential use of mechanical assistance, there is also approximately 0.76 %–1.2 % risk of requiring emergency cardiac surgery, which carries a mortality rate of up to 51.9 %.^11,12 When patients require ECS, the process of switching from Impella or ECMO to CPB is complex and time consuming, especially in emergency situation.

CPB was designed for open heart surgery. The CPB system includes a blood reservoir and requires a large priming volume. Additionally, the air-blood interface in CPB can significantly activate the coagulation and inflammatory cascades. High doses of anticoagulation therapy are necessary during CPB procedures. For these reasons, the risk of bleeding complications with CPB is relatively high. CCCB utilizes a centrifugal pump and a membrane oxygenator within a closed, confined circuit, which potentially helps to mitigate inflammatory responses. In the CCCB mode, we maintain an activated clotting time of approximately 200 s. The use of CCCB for intraoperative circulatory support has the potential to reduce bleeding complications, owing to the lower heparin dosage required. The implementation of CCCB may lead to reduced incidence of complications. For patients anticipated to require short-term circulatory support. This circulatory support method not only enhances patient safety but also has the potential to lower healthcare expenditures compared to ECMO and Impella.

Furthermore, the CCCB circuit allows for a seamless transition to CPB mode, enabling the completion of ECS with greater flexibility. The modified modified CPB circuit enables a rapid transition from circulatory support to CPB, reducing procedural steps and enhancing patient safety, ultimately optimizing resource utilization. During TAVI procedures, circulatory support is typically required for 1–2 h, therefore, CCCB may represent a suitable method of mechanical circulatory assistance.^13,14

Several limitations of this study should be noted. The number of patients in this single center study was limited. This technique cannot be applied if the patient’s anatomy is not suitable for femoral arteriovenous cannulation.

Conclusion

In conclusion, the seamless transition from CCCB to CPB during TAVI procedures represents a significant advancement in the management of high-risk patients. The modified CPB circuit has facilitated this transition, enabling clinicians to provide rapid and effective circulatory support when needed. By minimizing hemodynamic disruptions and procedural risks, these advancements have enhanced patient safety. As the field of TAVI continues to evolve, further research will be crucial in optimizing patient care and advancing the boundaries of minimally invasive cardiac surgery.