Branch-First Sun’s Procedure: Early Experience in Patients with Aortic Dissection and Aortic Aneurysm
Aortic arch replacement remains a significant challenge in cardiac surgery, despite advancements in surgical techniques and conceptual understanding. The classic Sun’s procedure, which involves total arch replacement using a four-branched graft with stented elephant trunk implantation, has been established as a standard treatment for type A aortic dissection, yielding favorable outcomes. However, the branch-first technique has emerged as an alternative approach, offering potential advantages in certain clinical scenarios. This article presents an early experience with the branch-first Sun’s procedure in patients with aortic dissection and aortic aneurysm, highlighting its technical details, outcomes, and implications for surgical practice.
Background and Rationale
The classic Sun’s procedure has been widely adopted for aortic arch replacement, particularly in cases of type A aortic dissection. It involves the use of a four-branched graft and stented elephant trunk implantation, performed under cardiopulmonary bypass (CPB) and deep hypothermic circulatory arrest. While effective, this procedure is technically demanding and associated with prolonged CPB and cross-clamp times, which can increase the risk of complications such as coagulopathy and organ dysfunction.
The branch-first technique, on the other hand, aims to simplify the procedure by reconstructing the three arch branches (innominate artery, left common carotid artery, and left subclavian artery) without CPB in most cases. This approach reduces the reliance on hypothermic circulatory arrest and may lead to shorter operative times and improved outcomes. The branch-first Sun’s procedure was introduced at Beijing Anzhen Hospital, and this study reports the early experience with this technique in both elective and emergency settings.
Patient Population and Study Design
From July 2017 to December 2018, 36 consecutive patients with aortic dissection and aortic aneurysm were treated with the branch-first Sun’s procedure at Beijing Anzhen Hospital. The study population included both elective and emergency cases, with a mean age of 51.8 years and a predominance of male patients (86.1%). Comorbidities such as hypertension (80.6%), smoking history (81.5%), and cerebrovascular disease (11.1%) were common among the patients. The diagnoses included aortic dissection (72.2%) and aortic aneurysm (27.8%), with 55.6% of cases performed in an emergency setting.
Surgical Technique
The branch-first Sun’s procedure was performed under general anesthesia, with near-infrared reflectance spectroscopy used for monitoring. A Y-graft (InterGard or Vascutek) was prepared on the table, with the main trunk typically 12 or 14 mm in diameter and the side arm 8 or 10 mm in diameter. The right axillary artery and right femoral artery were cannulated with 22- or 24-Fr cannulas, and a temporal femoral-axillary bypass was established. With a beating heart and without CPB, the three arch branches were sequentially connected to the Y-graft in an end-to-end or end-to-side fashion.
CPB was then initiated by cannulating the right atrium with a two-stage cannula. An ascending graft was selected based on the sino-tubular junction size, and the proximal anastomosis was performed first. When the temperature was lowered to around 28°C, flow to the femoral artery was stopped, while flow to the right axillary artery was maintained at approximately 10 mL/kg/min, with the left radial artery pressure kept at 40 to 60 mmHg. The arch was opened, and the aorta was transected proximal to the innominate artery or between the innominate artery and the left common carotid artery. A frozen elephant trunk (Cronus; MicroPort Medical Co, Ltd) was deployed into the arch and descending aorta, and the proximal sewing ring and native aorta were connected to the distal end of the ascending graft using a continuous suture.
Systemic perfusion was resumed after the distal anastomosis was completed. The main trunk of the Y-graft was trimmed to the proper length, and its proximal end was bevelled. An oval fenestration was created on the right lateral aspect of the ascending graft, and the main trunk was anastomosed with the ascending graft in an end-to-side fashion. Finally, the heart was resuscitated after deairing.
Early Outcomes
The 30-day mortality rate in this cohort was 5.6%, with one patient experiencing a brain infarction (2.8%) and two patients developing temporary paraplegia post-operatively (5.6%). The mean CPB time was 172.4 minutes, and the mean cross-clamp time was 94.3 minutes. The lowest nasopharyngeal temperature was 27.0°C, and the lowest bladder temperature was 28.2°C. Other post-operative complications included renal support (5.6%), return for bleeding (8.3%), ischemic gut (2.8%), and transient psychiatric symptoms (13.9%).
Comparison with Classic Sun’s Procedure
The branch-first Sun’s procedure demonstrated several advantages over the classic Sun’s procedure. In the classic approach, all five anastomoses are performed under CPB, with the sequence being proximal aorta, distal aorta, left common carotid artery, left subclavian artery, and innominate artery. In contrast, the branch-first technique involves bypassing the three arch branches without CPB, reducing the number of anastomoses performed under CPB to three. This modification not only shortens CPB and cross-clamp times but also ensures continuous cerebral perfusion during circulatory arrest, potentially reducing the risk of neurological complications.
In the classic Sun’s procedure, the nasopharyngeal temperature is typically set to 25°C during distal open aortic anastomosis. However, with the branch-first technique, the entire brain is perfused during circulatory arrest, allowing the nasopharyngeal temperature to be elevated to around 28°C. This higher temperature may contribute to less coagulopathy and improved post-operative outcomes.
Discussion
The early results of the branch-first Sun’s procedure are promising, with a 30-day mortality rate of 5.6%, compared to 7.8% in the classic Sun’s group. The reduced CPB and cross-clamp times, along with the higher circulatory arrest temperature, may contribute to the lower incidence of complications observed in this study. The technique’s ability to provide continuous cerebral perfusion during circulatory arrest is particularly noteworthy, as it addresses one of the major challenges in aortic arch surgery.
However, the study has several limitations. It was conducted at a single center with a relatively small number of patients, and there was no long-term follow-up. Future studies with larger patient cohorts and extended follow-up periods are needed to validate these findings and assess the long-term outcomes of the branch-first Sun’s procedure.
Conclusion
The branch-first Sun’s procedure represents a significant advancement in aortic arch surgery, offering a simplified approach with potential benefits in terms of reduced CPB time, higher circulatory arrest temperature, and improved early outcomes. While further research is needed to confirm these findings, the technique holds promise for reducing morbidity and mortality in patients with aortic dissection and aortic aneurysm. The branch-first Sun’s procedure brings us closer to the goals of minimizing CPB time and hypothermia-related complications, paving the way for safer and more effective aortic arch surgery.
doi.org/10.1097/CM9.0000000000000564
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