Reconstruction of the pulmonary artery usually indicates that tumors or lymph nodes adhere to or invade the PA in the hilum and preclude complete resection by simple lobectomy. The PA can be compromised to various degrees, from partial filtration to a more extensive and even circumferential invasion or grow inside of the lumen. This heterogeneous presentation require different types of techniques, like tangential resection with direct repair, patch reconstruction, end-to-end anastomosis or interposition of a prosthetic conduit .
Accurate evaluation of the PA involvement has been improved with the help of three-dimensional reconstructions imaging. However, presence of vascular encroachment cannot be defined with interpreting imaging and it is impossible to make a specific PA reconstructive plan preoperatively. The most appropriate technique option of reconstruction is usually chosen during the operation on the basis of how much the vascular is invaded, and this crucial decision may take a long time and many efforts. Once face this situation surgeons should be encouraged to avoid the easier choice, pneumonectomy.
In our experience and in agreement with others [7, 8], it is much more frequently to perform PA reconstruction on the left side and for squamous cell carcinoma (SCC). SCC is more often to be seen in central type NSCLC because larger bronchi are usually the primary sites of this type tumor. And it often metastasizes to hilar lymph nodes early in its course. Compared with the right side, both superior and posterior side of left upper bronchus is surrounded by the PA. Due to this anatomical reason, direct invasion by primary tumor or metastasis lymph nodes originating in the lung hilum is more likely to occur on the left side. Similar to lobotomies, the 3 pneumonectomies were also on the left side. In addition, the left recurrent laryngeal nerve is also easier to be injured compared with right side, care should be taken when using energy equipment and extra extend retraction should be avoid.
Induction chemotherapy is usually used for patients with N2 or chest wall invasion , and it is usually more technically demanding after induction therapy, because of the deleterious effects on bronchial healing, vascular fragility and local devasculation. Safety can be guaranteed once the proximal PA is clamped. If there was no enough room to place the clamp, open the cardiac sac to expose the PA more clearly could be an option. When bronchial sleeve resection is needed, we prefer to protect the bronchial anastomosis by intercostal muscle flap. It can act as a buffer between PA and bronchus, and this buffer should not be too thick. That would elevate pulmonary artery too high and reduce the blood inflow.
We found that tumor or metastatic lymph nodes located in the lower or middle lobe occasionally just invaded the upper lobe along the interlober PA. The upper lobe could be preserved as long as a clean arterial margin could be achieved below the level of the 1st branch (apical and anterior branches) of the pulmonary artery. Complications occurred in 3 out of 6 (50%). They are empyema (n = 1 because of his nephron syndrome), pneumonia (n = 1), and transient atria fibrillation (n = 1). 2 lived more than 5 years, 1 died of myocardial infarction 2 years later, one died of brain metastasis 3 years later and 1 died of respiratory failure 18 months later. One was lost during follow-up. No other authors have reported this kind of technique before. In our limited experience of these 6 patients, the upper lobe can be preserved with this viable option. The blood supply for the upper lob is sufficient just relying on the 1st branch of pulmonary artery. Patients had better postoperative pulmonary function and improved quality of life. However, more cases are needed when analyzing the long-term outcome. The temporary intra-artery conduit technique brought us some conveniences and the patients can recover faster with lower cost. Nevertheless, the potential higher risks in thesis cases are not insubstantial. We only utilize this technique when the circumferential encroachment of the main PA is less than 20%. And CPB should be prepared before and during the operation.
The incidence of complications in our study was 52.2% and was associated with older age (p < 0.0001), Stage III disease (p < 0.0001), induction chemotherapy (p < 0.0001), non-squamous cell carcinoma (p = 0.0006), N2 status (p < 0.0001) and PA extended resection with bronchus sleeve resection (p < 0.0001). Concern about high postoperative complications limited the acceptance of the PA angioplasty . In fact, they are companied with the operation and most of them can be controlled with medication successfully without influence of the 5-year survival. How the incidence of complications significantly predict recurrence was uncertain to the authors. It is possible that the development of complications is a surrogate for patients with more extensive disease (not captured by the staging system), for example, more proximal tumors or magnitude of N1 adenopathy. In these patients, the resection is more difficult, which may lead to a higher complication rate, and the recurrence rate (local and regional) might also be higher. This finding only suggests an association between these two events—not that patients should not have undergone resection—but whether surgical complication caused recurrence is another question to be tested in future studies.
The estimated 5-year survival rate was 50.2%, which is consistent with that reported for standard resection . The results from the present study suggest that stage III,histology type of non-squamous cell carcinoma and patch pulmonary arterioplasty are prominently prognostically related. The 5-year survival for stage III is significantly lower than stage I and II. Although it is more technical demanding after chemotherapy and/or radiation therapy, reconstruction of PA can be carried out safely. So we recommend induction and/or radiation therapy first for the patients with stage III, and those who are proved down-staged would be selected for surgical candidates. Those who progress through therapy are clearly not going to benefit from resection and should be considered inoperable. Decision of operation for patients who had no change after induction is complex. The benefits of resection and benefits of non-operative therapy should be carefully deliberated in multi-disciplinary tumor board and informed to the patents.
Non-squamous cell carcinoma showed more aggressive biological character and generally disseminates outside the thorax somewhat earlier than squamous cell carcinoma. These patients should be considerate as a different group and treated separately. Tineke W.H. Meijera and his colleagues found this was due to the difference in metabolism. Adenocarcinomas may use aerobic glycolysis as an energy source, whereas the metabolism of squamous cell carcinomas seems to rely on mitochondrial oxidation with anaerobic glycolysis under hypoxic conditions. Aerobic glycolytic metabolism is an additive responsible factor for aggressive behavior in NSCLC . This subgroup of tumors may try new treatment approaches first, such as MCT4 inhibitors, and then consider surgery.
When considering appropriate surgical technique, careful examination and precise evaluation of the extent of PA involvement is critical. Errors should be avoided when choosing reconstruction techniques. The goal of the angioplasty was to obtain a suitable length of PA and smooth lumen. Tension and bleeding were probably resulted from inadequate artery length. On the other hand, the axis of PA was more easily twisted due to unnecessary preservation. The vessel twist might impair the blood flow and lead to the stenosis or thrombosis. When upper lobectomy was performed, more attention should be paid to avoid the kinking because of elevation of the lower lobe. Autologous pericardial patch can exceed the length of PA, and there is no posterior suture line on the artery, which can be a buffer against the bronchial stump or anastomosis. However, it is difficult to harvest patches with suitable size. Because it was hard to estimate how much the graft will stretch, shrink kinking or turbulence after the artery was reexpanded .
We recommend aspirin (100 mg per day) for high-risk patients 24 hours after PA plasty. This 24 hours’ time window was used to observe the volume and character of chest drainage to exclude post-operative hemothorax. High-risk patients included hypertension, coronary atherosclerosis, and more than 50 years old. Contraindications are the volume of chest bloody drainage per day is more than 200 ml, peptic ulcer, trend of stoke and allergy to aspirin. In this study, stents or grafts were not used, so we did not have experience of other anti-platelet like clopidogrel. For the issue of preventing pulmonary embolism, Heparin lock flush solution (12500 u diluted with 500 ml sodium chloride solution) was used during operation. Considering the pulmonary artery blood flow was broken off when proximal and distal parts of the PA were both controlled, intravenous heparin sodium (1 mg/kg) was used when applying autologous pericardial patch or circumferential resection.
Complete resection and long-term survival are mainly affected by neoplastic events. PA reconstruction associated with bronchial sleeve resection is a positive prognostic factor in our study. This can be expained by more complete resection percentage and lower risk of recurrence. The study also shows that PA invasions are more longitudinal and circumferential for the patients who received patch angioplasty. Their 5-year survivals are significantly lower than others.