Conventional full sternotomy in cardiac surgery had the disadvantages of long incision, bleeding and potential mediastinitis. Despite partial sternotomy shortens the incision, the sternal stability is damaged and it requires several months to recover back to normal life after the surgery. In the recent two decades, various minimally invasive techniques were applied in congenital cardiac surgery.(14) Liu et al from Fuwai Hospital(3) reported their experience of oblique lateral thoracotomy in 683 children with congenital heart disease. The ages ranged from 4 months to 7 years, and the main diseases in this series are ASD and VSD. A few TOF patients were also operated by this incision. However, the length of this incision was relatively long, and the incision was close to mammary tissue. Bleiziffer et al. followed 72 female patients who underwent heart surgery from right anterolateral thoracotomy in their puberties, and the authors found that 61% patients developed asymmetric breasts in adult ages, therefore, the authors recommended not to use such incision in adolescent females. However, these surgeries were performed in 1980s, and the minimally invasive techniques were immature at that time,the length of incision was up to 19.2 centimeter(15). To avoid such complications, this group modified their techniques, and reported their results at 2005. The incision was at mid-axillary level and the length was around 4.5-6 cm. Thirty-six children with isolated ASDs were included in this study, and the outcomes were excellent. The youngest patient in this study was 4 years old (5)。Pretre et al from Switzerland reported their experience of using right posterolateral thoracotomy in 80 patients with simple congenital heart disease (4). In the majority of this group, femoral arterial and venous cannulation were used (87.5%). The mid-term follow-up results were good(16). In recent years, several heart centers from China reported various modified minimally invasive methods to operate on simple congenital heart diseases. The most commonly used incision was right sub axillary incision. The incision was modified from oblique shape to vertical direction, and the length of the incision was also shortened. The indications of such minimally invasive surgeries were expanded, and there was a trend of using soft tissue retractor instead of rigid spreader.(13, 17, 18) (9). The safety and efficacy of such strategies were validated, and the outcomes of minimally invasive cardiac surgery in children was not inferior to conventional heart surgery.
The indication of minimally invasive surgery and the choice of incision in children was not yet consistent. The indication in early era was simple ASDs, because the defect was close to the incision, and the exposure usually was very good, so it was easy to repair the defect. However, in patients with VSDs, the surgical exposure was not as good as that in ASD patients, because the VSD was deep and blocked by tricuspid tissues sometime. With the advancement of instruments and techniques in minimally invasive surgery, the indication was expanded in recent years. Anzhen Hospital recently reported a group of infants less than 5 kilograms operated via right sub axillary incision, and the outcomes were the same as those operated from median sternotomy(19). In addition, CAVSD infants were also reported repaired from lateral mini-thoracotomy (9).
An uneventful establishment of cardiopulmonary bypass is the foundation to perform minimally invasive cardiac surgery. The diameters of femoral vessels in infants are too small, and femoral cannulation may lead to high incidence of vascular complications, thus central cannulation is preferred in such patients. The right sub axillary incision can expose ascending aorta, superior vena cava and inferior vena cava very well in most patients. The arterial cannulation site is usually very deep, and aortic cannulation is the most difficult step in most patients. From literature, some authors used forceps to grab the tip of the curve arterial cannula and this facilitate the cannulation; however, it is not easy to master this technique, especially when surgical exposure is not well. We used a straight arterial cannula with a rigid inner cylinder, and put it inside through the arterial incision. The keys of this step are to open the adventitia within the aortic purse string as much as possible, and to rotate the cannula back and forth slightly if we feel resistance. In some elder patients with deep thoracic cavity and small incision, the aorta is punctured by a needle, and a guiding wire is inserted, therefore, arterial cannula is placed by Seldinger technique. The SVC and IVC canulae can be either curved or straight, and we prefer the canula with thin-walled-wire-reinforcement, which is flexible to be positioned.
The key point to ensure precise repair is well surgical exposure, especially when the infra-axillary incision is tiny. To obtain better surgical exposure, recently, Heinisch et al. reported percutaneous cannulation of IVC in 38 pediatric patients, but 13.5% cases had thrombosis at cannulation site.(20) In our infants operated from right sub axillary incision, the IVC cannula can be placed through the sixth intercostal space, and this puncture site can be used to place chest tube at the end of surgery. After cardioplegia is given, the cardioplegia needle and tube are removed, since most simple cardiac defect can be repaired within the protection time of a single dose of cardioplegia. In some patients with VSD, an ice cold saline rinsed gauze is placed behind the heart in the pericardial cavity, and this helps to push the heart close to the incision; with appropriate retraction, the VSD can be exposed well. In case of unrestrictive VSD, patch closure with interrupted stitches is preferred.
However, we found that the infra-axillary incision is convenient in infants and young children, but it is limited in adolescents and adults, since the incision is too far away from the heart. Therefore, we used right anterolateral thoracotomy in such groups of patients. In this study, the mean age and body weight of RALT group is significantly higher than those of RSAVI group. The RALT incision from the fourth intercostal space is close to the heart, and the surgical view is similar to the view from sternotomy. Peripheral cardiopulmonary bypass established by femoral cannulations helps to obtain better exposure from the mini-thoracotomy. In recent years, the SVC cannula was placed through the right jugular vein, and Chitwood aortic cross clamp was used. In addition, thoracoscopy assistance and soft tissue retractor also help us to reduce the incision to as short as 4 cm in length. To be noticed, the skin incision should be at the lower margin of the breast tissue in adult females, and the incision should be far away from the mammary tissue in prepubescent female children.
The above-mentioned two incisions expose ASD and perimembranous VSD well enough to repair; however, it is difficult to expose sub pulmonary VSD. A few heart centers reported their experience of repair doubly committed sub arterial VSD using sub axillary incision. The VSD was repaired either through tricuspid valve or through main pulmonary artery, but the number of such patients are very limited, and the surgeons are very experienced in this field, so the reproducibility is not easy(13, 18). In this study, one infant with sub pulmonary artery VSD underwent repair from right sub axially incision, and the exposure was not good enough for a precise repair. Intraoperative transesophageal echocardiography demonstrated residual VSD, and a second cross clamp was applied to repair the residual defect. After this case, we preferred median sternotomy in infants with sub pulmonary artery VSD. While in adolescents and adults with sub pulmonary artery VSD, a left anterolateral mini-thoracotomy from the second intercostal space was used. In the present study, we reported our preliminary experience in 5 cases. Femoral arterial and venous cannulations were used, and achieved adequate drainage. SVC cannulation is not necessary in most patients, but SVC cannulation is possible through the incision if needed after patient is on bypass. In 2017, authors from China reported this approach to repair sub-pulmonary artery VSD, but it was only used in adults, not in children(21). In 2019, authors from Guangzhou reported an alternative method using minimal mid-partial sternotomy in 13 patients (22). Minimally invasive perventricular closure of doubly committed subarterial VSD was also reported, but this technique lacks of long term follow-up results(2). In our opinion, surgical closure from LALT is preferred in such patient groups. Recently, this LALT incision was also applied to replace pulmonary valve in 7 patients following Tetralogy of Fallot repair by Nellis et al.(23)
The lower weight limit of femoral cannulation is inconsistent. Most surgeons prefer using peripheral cannulation in patients over 30 kg; however, surgeons from Switzerland dissected iliac artery in infants with body weight as low as 10 kg.(16) The reported lowest body surface area using a femoral venous cannulation was around 0.3 square meters, however, the patency of the femoral vein was compromised in 13.5% patients.(20) The cutoff body weight is 20 kg in our institution, and preoperative femoral vessels were evaluated by ultrasound to determine the possibility of femoral cannulation.
This study is limited by its retrospective nature in a single institution, and no comparison was done between minimally invasive approach and sternotomy. Score of pain was not evaluated in these patients, and the follow-up time was relative short. The minimally invasive approaches reported here is not suitable for all congenital heart disease, especially in complicated disease. In infants less than 6 months old, we still prefer median sternotomy due to fragile heart and lung tissues in young infants, while a few centers summarized their experience in such patients.(19, 20) In low body weight patients with doubly committed sub arterial VSD, we also prefer median sternotomy, and finally, if the patient has prior thoracic surgery or has significant adherence in thoracic cavity, sternotomy is preferred too.