Reply to Mishra and Yiu. Intracoronary shunt for prevention of air embolism

Abstract

We thank Dr Mishra and Yiu for their comments [1] and interest in our case report of carbon dioxide (CO2) embolism induced myocardial ischaemia by CO2 blower during off-pump coronary bypass surgery [2]. We agree with their opinion that insertion of an intra-coronary shunt may abolish the risk of CO2 embolism. As they described in their letter, insertion of an intra-coronary shunt had been demonstrated to provide a bloodless surgical field and some degree of nutritive distal flow at the same time. However, opinions still divide whether to advocate routine use of intra-coronary shunt for the added technical complexity and possibility of endothelial denudation raising concerns for long-term graft patency. Although the newer modified shunt design may decrease the degree of endothelial damage, current evidence is still limited to higher incidence of endothelial injury compared with external soft snares in human coronary arteries [3]. Moreover, favourable results supporting the use of intra-coronary shunt with regard to left ventricular function, cardiac enzyme release have only been demonstrated during grafting of left anterior descending artery [4]. It has also been demonstrated that humidified gas insufflation compared with non-humidified gas insufflation, as used in our case, attenuated the endothelial injury [5]. Thus, it is not clear whether endothelial injury induced by insertion of intra-coronary shunt per se is less than that induced by the use of high-flow humidified CO2 blower. Therefore, considering the rare occurrence of CO2 embolism as reported in our case, we cannot advocate the routine use of intra-coronary shunt whenever CO2 blower is used solely for the purpose of preventing CO2 embolism unless the intra-coronary shunt was otherwise necessary. Yet, we agree with their opinion that intra-coronary shunt could be an option in selected cases when proximal soft snares are not feasible for the presence of previously inserted stent or calcium deposition when using a gas blower besides the usual indication of critical stenosis without well-developed collateral formation