ASO is still a challenging operation for less experienced surgeons, even though it has been performed with very low mortality in many high-volume centers. Accurate transfer of the CA is the key component to a successful ASO. Inadequate coronary transfer can lead to early postoperative mortality or late CA-related morbidity.
There are basically two different coronary transfer techniques: open coronary transfer before neoaortic reconstruction (OCR technique) and coronary transfer after neoaortic reconstruction (CRANR technique). The open trap door technique was advocated by Yacoub and Radley-Smith [5] and Brawn and Mee [6]. This coronary transfer technique has been used in many centers, with low operative mortality thus far. In this technique, marking stitches are made at the MPA before inducing cardiac arrest to select accurate sites for CA reimplantation. However, it is not easy for the less experienced surgeons to select the accurate site for coronary reimplantation and it might be further difficult in patients with malaligned commissures or with high take-off CAs. Furthermore, a transferred CA can be distorted during neoaortic reconstruction. The CRANR technique can offer surgeons an easy way for selecting an accurate CA transfer site regardless of malalignment of the facing commissures or abnormal take-off of the CA. Neoaortic reconstruction does not affect CA geometry. The CRANR technique allows easier and more accurate coronary transfer even in the aortocoronary flap technique (Fig. 1c). In the aortocoronary flap procedure, accurate placement of the flap is very important because a small derangement of the flap can cause distortion of one of the two CAs. The CRANR technique allows more accurate placement of the flap at the distended neoaorta. We have adopted the CRANR technique in coronary transfer using aortocoronary flap since September, 2010, when we experienced myocardial ischemia in a patient with intramural CA who underwent aortocoronary flap procedure through OCR. The only disadvantage of the CRANR technique is the possibility of damage in the neoaortic valve when making incisions at the closed neoaorta for coronary transfer. We have overcome this problem by making a marking stitch at the site of the anterior commissural attachment of the neoaorta by inserting needles from inside to outside using a double-armed fine suture before neoaortic reconstruction [4]. This technique was very useful in locating the commissural site of the neoaorta from the outside after neoaorta reconstruction.
We have already reported the differences in the early results between the two techniques in 2005 [4]. In the present study, we added our accumulated data, including those of the aortocronary flap procedure, to the previous data and we also described the long-term data on late coronary problem and neoaortic valve regurgitation.
We performed multivariate analysis for 30-day mortality after ASO. The CPB time and OCR were the risk factors for the 30-day mortality. The odd ratio of the OCR was 16.697. The 30-day mortality in the OCR group was unacceptably high even though the learning curve was taken into account. However, the number of patients with 30-day mortality after ASO using the CRANR technique (3/164, 1.8%) is comparable with the results of previous studies [7, 8]. Among three mortalities, two occurred in patients with aortic arch anomaly. There was only one mortality in ASO without aortic arch repair. We also observed lower 30-day mortality rate in the CRANR group as compared with the OCR group in the patients with aortic arch anomaly. There was no 30-day mortality after ASO in the recent 10 years in this whole series. There has been no report comparing the mortality between OCR and CRANR technique thus far.
Regarding intraoperative and postoperative CA revision, the incidence was higher in the OCR group. In this series, we defined “CA revision” as revision under another CPB. Placement of a simple traction suture to ameliorate distortion of the implanted CA was excluded. In the CRANR group, only one patient with intramural CA, required intraoperative CA revision. We attempted to use individual CA implantation technique for this patient and observed intraoperative ischemia on the left ventricular territory. We placed the left subclavian artery free graft between the left main CA and the ascending aorta. The patient survived the operation. Excluding this patient, there was no intraoperative or postoperative CA revision required in the CRANR group. This means that the CRANR technique is a safe procedure for coronary reimplantation in ASO.
Several studies have reported obstructed CAs in 5 to 7% of survivors [8,9,10,11,12]. Late coronary obstruction after ASO is uncommon and is more frequently anatomic problem. The incidence of CA-related problem is most prevalent in the first 3 months after ASO [13]. One study showed 88.1% ± 6.4% freedom from coronary events at 22 years [14]. We reviewed CA-related late mortality or morbidity in our series. All sudden deaths were assumed to be CA-related deaths because it is very difficult to obtain autopsy data from such patients in our country. There was no sudden death or CA-related late morbidity in the CRANR group. We do not have any routinely scheduled CA evaluation program after ASO. If there is any sign of abnormal echocardiographic findings or cardiac marker elevation, coronary angiography is performed. There has been no late CA-related problem in the CRANR group thus far. Meanwhile, the OCR group not only had higher incidence of intraoperative or postoperative CA revision [5/72 (6.9%) vs 1/164 (0.6%); p = 0.011] but also had higher incidence of CA-related late mortality or morbidity in the OCR group [6.9% (4/58) vs 0% (0/161); p = 0.005]. We observed three cases of sudden death in the OCR group but none in the CRANR group.
Considering the incidence of mild or more neoaortic valve regurgitation after ASO, previous studies showed 3.3 ~ 49.6% of neoaortic valve regurgitation [15, 16]. Many studies [15, 17,18,19,20,21,22] have reported various risk factors associated with the occurrence and progression of neoaortic valve regurgitation, such as the presence of a VSD, bicuspid native pulmonary valve, primary pulmonary valve regurgitation, CA transplantation method, and higher neoaortic root/ascending aorta ratio. In the CRANR technique, we have to make one or two small incisions at the closed neoaorta adjacent neoaortic valve for CA transfer, which can cause postoperative neoaortic valve regurgitation. Thus, we have been using marking stitches around the anterior commissure of the MPA to avoid injury to the valve while making the incisions. We believe this maneuver is highly effective in preventing injury to the neoaortic valve. In addition, we are trying to put the CA button as high as possible to avoid the disruption of the sinotubular junction of the neoaorta. We evaluated the incidences of early and late postoperative neoaortic valve regurgitations, and in the CRANR group, the incidences of mild or more neoaortic valve regurgitation was 15.3% at discharge and the rate of the 5- and 10-year freedom from it was 66.1 and 61.6%, respectively. The incidences of early and late mild or more neoaortic valve regurgitation was not as high as compared with the OCR group. The degree of neoaortic valve regurgitation in our series was mostly mild. Only two patients from the CRANR group had moderate neoaortic valve regurgitation, but both are doing well without valve reintervention. We do not know why the two moderate neoaortic valve regurgitations developed only in the CRANR group.
Study limitations
This study was limited by its retrospective nature. The OCR technique was performed by one surgeon, but the CRANR technique was performed by five surgeons. The modification of the coronary transfer technique was not the sole factor accounting for the improvement of the operative results because not all operative deaths were related to the coronary problem, even though most of them were related. There was a time-frame difference between the two groups. The CRANR technique was adopted when the surgeon already had enough experience in ASO. However, it is clear that the 30-day mortality has been dramatically reduced after adopting the CRANR technique.
