<qa>  What is the cause of the conversion?Although VATS lobectomy has been proven to be effective and safe in experienced hands, it is not devoid of risk. Intra-operative surgical complications can be at times catastrophic. Complications include: pulmonary vascular injuries Pulmonary artery PA, pulmonary vein necessitating urgent conversion to open thoracotomy and even death. Causes of conversion included PA injury, difficult anatomy, bulkycalcified lymph nodes, and technical problems including stapler misfire. PA injury alone constituted 37.5 of all conversions. Proper dissection of all tissue around PA branches is sometime difficult especially in the presence of adhesions or large, calcified lymph nodes and may increase the risk of vascular injury. 