To achieve good outcomes during aortic surgery with circulatory arrest, such as open distal anastomosis for type A acute aortic dissection, a secure and non-bleeding anastomosis must be achieved rapidly to ensure brain protection. Typically, a two-step method is adopted that involves aortic stump reinforcement and graft anastomosis, which can prolong both the surgical duration and circulatory arrest time. The extent of aortic replacement and surgical duration have been reported as significant risk factors for hospital mortality [1] -[5] because patients may be unable to tolerate the surgical stress of deep hypothermia (DHT), long durations of cerebral exclusion, or cardiopulmonary bypass. Additionally, prolonged surgery can increase mortality through coagulopathy, cerebral ischemia, infection, or multiple organ failure. This is supported by Cook et al. [6] who reported that decreasing the systemic temperature to below 22˚C may be unnecessary and associated with a higher incidence of neurologic injury during DHT. A low invasive quick repair (LIQR) technique was reported by Hata et al. [7] [8] who found that 20 min of mild hypothermic circulatory arrest (rectal temperature, 28˚C) without any cerebral perfusion is safe, and resulted in better clinical outcomes than with cooling to DHT without selective cerebral perfusion. We believe that it is possible to reduce the length of the procedure further by combining aortic stump reinforcement and graft anastomosis in a single step by using our Branched Graft Inverting (BGI) technique which will lead to shorter circulatory arrest times and less marked hypothermia that is closer to normal physiological levels.

The use of an inverted graft that was invaginated into an injection syringe before being atraumatically injected into the aorta, yielded promising results [9] . Therefore, we have developed a modified BGI technique under mild hypothermia that uses an inserter to enable us to set the graft in proper position in fast and secure way and perform reinforcement of the aortic stamp and graft anastomosis to be completed simultaneously. This was expected to result in shorter circulatory arrest times and to allow for modification of the cerebral protection strategy. Furthermore, we anticipated that the inserter would allow the procedure to be performed without damaging the fragile dissected aorta. Our best efforts are necessary to avoid further damage because the dissected aorta may dilate and progress to a dissected aortic aneurysm over time. We also anticipate that the proposed technique should result in less bleeding, because the device is expected to protect against the damaging effects of graft insertion.

The extent of aortic replacement and surgical duration are significant risk factors for hospital mortality [1] -[5] . This initial report has demonstrated that the modified BGI technique enabled us to reinforce the aortic stump while simultaneously performing distal graft anastomosis. Thus, we were easily able to accomplish secure and reproducible distal anastomosis. As evidenced by the low morbidity and zero mortality, the procedure appears to be safe. Of note, we experienced no difficulties with bleeding, which meant that no patients underwent re-ex- ploration for this complication.

It is possible that our results were favorable because of the target level and duration of hypothermia. Indeed, we had no bleeding or neurological complications as stated. The evidence now suggests that decreasing the systemic temperature to below 22˚C may be unnecessary and associated with a higher incidence of neurologic injury during DHT [6] . There was little difference between the circulatory arrest times for the distal anastomoses: we found that a circulatory arrest time of approximately 20 min was sufficient to close non-bleeding anastomoses, and that at least 20 min was needed for minimally bleeding anastomoses. This is consistent with the findings of Hata et al. [7] [8] who reported the safety and superiority of circulatory arrest for 20 min at 28˚C. At our institution, the patients were cooled to a rectal temperature of 26˚C. Furthermore, an additional right hemisphere perfusion was adopted to increase the procedure safety during prolonged circulatory arrest. The clinical outcomes were promising, and revealed no mortality, neurological dysfunction, or complications directly related to the procedure.

Although this modified BGI technique can lessen the impact of surgery and hypothermia related stress, it cannot be used for severely atherosclerotic or “shaggy” aortas because of the risk of embolism. However, it is sometimes difficult to insert an inverted graft into a fragile dissected aorta, and the aortic arch can be damaged if the graft is inserted without care. The use of an injection syringe for graft insertion in non-bleeding anastomoses was successful in this regard. This is because the inverted graft is invaginated into an injection syringe and atraumatically injected into the aorta [9] .

Finally, this study does have limitations. Notably, the sample size was small (n = 8), the study was not controlled, and we performed no statistical analysis. Consequently, the present data are insufficient to claim definitively that this procedure is effective. However, this study does provide the foundation for further investigation.

Our technique offers an easy, secure, and reproducible method for performing non-bleeding distal anastomosis. We could secure non-bleeding anastomosis within 20 min, ensuring safe circulatory arrest under mild hypothermia. Shorter circulatory arrest times and mild hypothermia probably contributed to the low rate of postoperative complications. Therefore, we consider that under mild hypothermia, this technique was useful for ascending aortic replacement in type A acute aortic dissection. However, further studies with larger cohorts that compare outcomes against the standard procedure are necessary to confirm these initial findings.

The author declares no conflicts of interest.