Pulmonary vein venting during minimally invasive aortic valve replacement: is it really minimally invasive extracorporeal circulation?

Management and innovation in extracorporeal circulation (ECC) are constantly evolving in an attempt to make ECC systems increasingly minimal and, therefore, more and more physiological [1]. It is in this context that we read with interest the article by Berretta et al. [2] who recorded better results in terms of bleeding events, reduced use of blood products, lower incidence of postoperative atrial fibrillation, and early recovery in patients undergoing minimally invasive aortic valve replacement using minimally invasive ECC (MiECC) compared with conventional ECC. However, MiECC can pose several limitations to the management of minimally invasive aortic valve replacement procedure that should be better discussed. During these procedures, a large amount of blood from the pulmonary veins often returns from the collateral circulation, limiting surgical vision especially in the confined space of the minimally invasive approach. This necessitates the use of a vent in the pulmonary vein, which, however, could ‘activate’ the blood in contact with the air, undermining one of the cardinal principles of the MiECC system, i.e. avoiding air-blood contact. The system proposed by Berretta et al., more than a MiECC, could be better defined as an optimized conventional cardiopulmonary bypass system. Indeed, MiECC should be completed by air-closed venting systems other than those used in conventional surgery; the absence of these represents a limitation to the definition of MiECC [1]. On the other hand, the absence of a vent in the pulmonary vein could limit myocardial protection, by not being able to avoid left ventricular distension, during the administration of cardioplegia in the aortic root in the presence of aortic valve insufficiency. In addition, the absence of a vent in the pulmonary vein could limit the elimination of residual air in the left ventricle to declamping, potentially making the de-airing procedure incomplete. Berretta’s article could have been even more interesting, especially for surgeons who have little experience with these minimally invasive techniques and want to approach these methods, if the tricks and limitations in the management techniques mentioned during minimally invasive aortic valve replacement with MiECC had been described.