Commentary: Carbon dioxide embolism during vein harvesting—Directed transesophageal echocardiography for diagnosis and hemodynamic rescue

John G. Augoustides, MD, FASE, FAHA

Central Message.

Massive carbon dioxide embolism is a rare complication of endoscopic saphenous vein harvest. Transesophageal echocardiography can guide diagnosis and management.

See Article page 183.

Endoscopic saphenous vein harvesting has matured as a minimally invasive technique for vascular conduit during coronary artery bypass grafting.¹ The complications of this technique include gas embolism.2, 3, 4 The roles of transesophageal echocardiography in the management of this catastrophic complication can be lifesaving.^3,4

The case reported by Kawabori and colleagues⁵ in this issue highlights the central role of transesophageal echocardiography in this setting. During conduit harvest, significant carbon dioxide embolism resulted in cardiac arrest. The vigilant team instituted prompt cardiopulmonary bypass and echocardiographic-directed management. The case was complicated by right ventricular failure, requiring aggressive pharmacologic support and delayed sternal closure. The patient had a complete recovery, with no neurologic sequelae.

How might this case inform the conduct of endoscopic vein harvest in light of the current literature? One option is to avoid an endoscopic approach in select patients, given its reported reduced graft patency.⁶ This decision could be guided by a new risk score for saphenous vein graft failure.⁷ Further trials will refine the conduct of saphenous vein harvest to enhance patency, including attention to a no-touch technique.^8,9

What are our options when an endoscopic approach is selected for vein harvest? Clearly, meticulous technique with careful carbon dioxide insufflation remains essential.1, 2, 3 Transesophageal echocardiography can allow rapid diagnosis of gas embolism, as exemplified by this case.⁵ Although this diagnostic modality is still debated in coronary artery bypass grafting, it should be available to evaluate hemodynamic compromise.^3,4,10 The midesophageal bicaval view can capture the passage of gas emboli and suggest the likely source.3, 4, 5 If the gas emboli access the right atrium through the inferior vena cava, the source is below the diaphragm.^5,11 If the gas emboli access the right atrium from the superior vena cava, the source is above the diaphragm.3, 4, 5

Furthermore, in gas embolism, the right atrial pressure is commonly elevated.3, 4, 5 Right coronary ischemia is common, resulting in bradycardia and right ventricular failure.3, 4, 5 The right atrial hypertension may stretch a patent foramen ovale to allow right-to-left shunting, which can be reduced with medical and surgical interventions.3, 4, 5^,12, 13

So, where do we go from here? This complex case has focused attention on transesophageal echocardiography for hemodynamic rescue in carbon dioxide embolism.⁵ It can reliably diagnose this complication and guide an integrated management response.3, 4, 5 In this case, the heart team proceeded with bicaval cannulation for cardiopulmonary bypass. The inferior vena caval cannula coupled with a snare provided a prompt route for clearance of gas emboli. The data from transesophageal echocardiography can also guide the escalation of support for the failing ventricle.^14,15

In conclusion, Kawabori and colleagues⁵ are to be congratulated for highlighting the integrated management of carbon dioxide embolism. The vigilant heart team should include transesophageal echocardiography in the response to this complication.3, 4, 5 A multimodal approach is typically required for hemodynamic rescue and subsequent ventricular support.3, 4, 5^,14,15 Future trials will likely refine the conduct of endoscopic vein harvesting, which may further minimize the risk of this complication.