Cardiac arrest from massive carbon dioxide embolism during endoscopic saphenous vein harvesting.

TTE images show massive CO2 bubbles in right, left heart, and aortic root during EVH.

EVH is a safe, standard procedure that can cause critical complications. TEE allows early detection of critical conditions.

See Commentaries on pages 186 and 188.

Endoscopic saphenous vein harvesting (EVH) is a safe, well-adopted standard minimally invasive vein harvesting procedure for coronary artery bypass grafting (CABG) surgery that requires carbon dioxide (CO2) inflation. CO2 embolism is a rare reported complication from EVH. If the amount of CO2 embolized is large, the situation can become be critical. Here, we present an educational case that highlights the life-threatening complication caused by EVH, CO2 embolus, which was treated successfully. The accompanying transesophageal echocardiogram (TEE) images describe the event process, showing the path of CO2 bubbles from the right heart to left heart through a patent foramen ovale (PFO).

A 74-year-old woman presented for CABG following an anginal episode with subsequent coronary catherization that showed multivessel coronary artery disease. The EVH procedure proceeded in the usual fashion, using VASOVIEW HEMOPRO 2 (Maquet, Wayne, NJ) in closed tunnel technique with CO2 insufflation pressures of 10 to 12 mm Hg and flow of 3 L/min, until EVH reached the high thigh saphenous vein, at which point sudden-onset hypotension and hypoxemia was noted. During resuscitation, TEE was performed, showing a dilated heart with a large number of bubbles entering the right side of the heart (Figure 1). EVH CO2 insufflation was immediately stopped at this point. The right internal jugular vein introducer skin insertion site was assessed, and no skin integrity issues or stigmata of air entrainment were noted at the insertion site. In addition, none of the stopcocks on the central line were open to air. The bubbles were also seen crossing over to the left atrium via a PFO on TEE (Video 1). The stream of bubbles can be seen entering the aortic root (Video 2), and it is presumed the bubbles caused an air lock to the right ventricle, which increased right atrial pressure resulting in the right-to-left shunt (Figure 1).

Figure 1

Top, TEE bi-caval view of right heart distension and which CO2 bubbles can be seen throughout. Bottom, TEE still image of CO2 in the aortic root, which indicates that there has been transmission of CO2 to the left heart and possible embolization of CO2 into the coronary arteries. TEE, Transesophageal echocardiogram; CO, carbon dioxide.

The patient became bradycardic. Systemic heparin was given. Internal cardiac massage was performed (Video 3). Cardiopulmonary bypass (CPB) was initiated. Bi-caval venous cannulation was performed because of the PFO with associated right-to-left shunt. EVH CO2 insufflation was resumed and a large amount of bubbles was noted to be entering the vacuum-assisted CPB venous drainage via the inferior vena cava (IVC) cannula (Video 4). The IVC was snared to prevent further introduction of bubbles into systemic circulation. Completion of EVH and cessation of CO2 insufflation stopped the drainage of bubbles into the IVC cannula. The surgery continued, cardioplegia was administered, and subsequently the team performed PFO closure and 2-vessel CABG. The vein harvest site had a moderate amount of venous bleeding that required a compression wrapping during the case. The patient required milrinone and epinephrine for inotropic support, with adjunctive epoprostenol therapy for right heart dysfunction. The patient initially was brought out of the operating room in open chest status. The right heart function recovered to normal and the sternum was closed on postoperative day 2. The patient was discharged on postoperative day 7 with intact neurologic status. The patient provided informed consent for the publication of the study data.

Comment

EVH is a safe, widely used method for vein harvesting that has largely replaced open vein harvesting, as EVH produces less postoperative pain and shorter duration of hospital stay. Complications of EVH include seroma/hematoma formation, abscess collection, CO2 embolism, and erythema or cellulitis of the incision site. Erythema has the greatest incidence, in 3.8% of EVH procedures. CO2 embolism has an incidence that is inversely proportional to severity of symptoms, with venous embolism occurring in 17.1% of EVH and massive CO2 embolism, such as in our report, with an incidence of 0.5% (Table 1). This incidence may be an underestimate, as most patients are asymptomatic or minimally symptomatic, and the minority of patients, particularly those with a PFO, are more susceptible to the life-threatening complications as presented here.

Table 1

Recent literature

Study	Year	Sex	Age, y	Insufflation pressure, mm Hg	Observations
Fan et al3	2012	F	55	14	Rise of ETCO2, pulmonary hypertension, cardiogenic shock
Strauss et al6	2016	M	77	14	Auscultation of mill-wheel murmur, TEE visualization

ETCO, End-tidal carbon dioxide; TEE, transesophageal echocardiogram.

Although CO2 embolism is a rare event during EVH, its potential consequences can be devastating. In this case, cardiopulmonary resuscitation via internal cardiac massage was required due to likely air lock in the right heart that caused right ventricular dysfunction and dilation with high filling pressure, creating a right-to-left shunt through an existing PFO with subsequent coronary artery CO2 embolization. Cardiac arrest from EVH was reported in the past; however, real-time echocardiographic imaging has not yet been reported. Our TEE videos show the massive right ventricular embolism entering the left heart through the PFO. Traditionally, end-tidal CO2 concentration has been used to monitor for CO2 embolus, but with the availability of TEE in the operating room setting, end-tidal monitoring is being replaced in favor of TEE. This case highlights the importance of TEE in diagnosing CO2 embolus in a timely manner, thereby allowing the operating room team to rapidly initiate resuscitation. The rapid cessation of CO2 insufflation and initiation of CPB allowed for a positive outcome.

We hope this case report with TEE images demonstrates this potentially critical complication from EVH and can assist in the rapid diagnosis and treatment of CO2 embolism.