Venoarterial extracorporeal membrane oxygenation (ECMO) frequently represents a lifesaving technique in adult and pediatric patients with severe myocardial dysfunction. Cardiogenic shock, difficult weaning from cardiopulmonary bypass, severe acute myocarditis, and refractory cardiac arrest, all represent potential indications for ECMO.
When, during ECMO, left ventricular contractility is profoundly impaired, inadequate right ventricular drainage and bronchial circulation can lead to left ventricular distension, with potential severe consequences, ranging from inadequate “myocardial rest,” to intracardiac clot formation, to pulmonary edema. Hence, it is of paramount importance to ensure an adequate left ventricular drainage, either by improving contractility or by venting the failing ventricle.
Surgical techniques used to vent the left ventricle include direct pulmonary venous and transapical cannulation, although a number of percutaneous techniques have been described, which include blade or balloon septostomy,1,2 axial flow pumps,3 and also a percutaneous transaortic approach,4 as described by our group a few years ago.
In this article, we describe a new technique of left ventricular decompression during ECMO through the percutaneous placement of a venous cannula in the pulmonary artery, in an adult female with profound myocardial depression after acute myocarditis and in the presence of a left ventricular thrombus.
Clinical Summary and Percutaneous Technique
A 43-year-old woman presented to our emergency department with worsening cough and dyspnoea, after 10 days of antibiotic therapy for left basal pneumonia. Her medical history included a total hysterectomy for cancer in the previous year, followed by chemotherapy with cardiotoxic agents. Her cardiac status before the current admission was unknown. Her chest x-ray revealed parenchymal consolidation and bilateral pleural effusions. Hemodynamic status demonstrated a rapid deterioration, without an increase in cardiac enzymes, and a transthoracic echocardiography (TTE) obtained 3 hours after admission showed a dilated and hypokinetic left ventricle, ejection fraction was 10%, and revealed a large intraventricular thrombus adherent to the apex and anterior wall of the left ventricle (Figure 1). The patient was admitted to our cardiac surgery intensive care unit with a clinical diagnosis of cardiogenic shock, sedated, and intubated. Coagulation status revealed overt disseminated intravascular coagulation with elevated d-dimers, low platelet count, and low fibrinogen. Because of refractory cardiogenic shock despite the optimization of medical therapy, the right femoral vein and the left femoral artery were cannulated percutaneously with a 21F and a 15F cannulas, respectively (Maquet, Jostra, Medizintechinik AG, Hirrlingen, Germany), and venoarterial ECMO (PLS system Maquet, Jostra, Medizintechinik AG, Hirrlingen, Germany) was instituted. Extracorporeal membrane oxygenation blood flow was kept to supernormal values to prevent left ventricular ejection and warrant stabilization of the intraventricular thrombus. Transesophageal echocardiography (TEE) was performed to ensure a motionless, closed aortic valve. A Swan-Ganz catheter (Ccombo, Edwards Lifesciences, Irvine, CA) was inserted through the left internal jugular vein under fluoroscopic guidance. Hemodynamic parameters were measured, and a pulmonary and left atrial hypertension was detected (Table 1). Under fluoroscopic guidance, a 6F angiographic catheter was introduced through the right jugular vein with a modified Seldinger technique and advanced in the right pulmonary artery. An Amplatz Ultra Stiff Wire Guide was inserted through the angiographic catheter, which was subsequently removed. A 15F venous cannula (Medtronic Biomedicus 50 cm, Minneapolis, MN) was then advanced over the wire and positioned in the common pulmonary artery (Figure 2), and the Amplatz guide was removed. The venous cannula was subsequently connected to the venous limb of the ECMO circuit. Hemodynamics showed a decrease in the pulmonary and left atrial pressures. Blood gases from the venting cannula were analyzed, revealing a pulmonary inverse flow on day 1 (Table 1), with low pulmonary and left atrial pressures. On day 3, a coronary angiogram was obtained, with no evidence of significant coronary disease. On day 6, the venting cannula was withdrawn to the superior vena cava and removed on day 9. During this period, we had no problems in maintaining the proper position of the vent in the pulmonary artery. An intraaortic balloon counterpulsation (IABP) was inserted to support the failing left ventricle, and levosimendan infusion was started. In the subsequent days, atrial fibrillation and major arrhythmias developed, and test for weaning was not initiated. Step by step is our main strategy for weaning ECMO using TEE or TTE monitoring. This consists of reducing the pump flow to 1.0 L/min/m2 for approximately 40–60 minutes having obtained an activated clotting time (ACT) of 180 seconds. If hemodynamic remained stable, heparin was stopped, and ECMO was removed at the bedside or in the operating room within the next few hours. On day 14, test for weaning was resumed, and ECMO was removed on day 16. The patient was discharged to the Intermediate Care under stable conditions on day 30, when echocardiography demonstrated an improved left ventricular contractility (left ventricle ejection fraction [LVEF], 35%–40%). The left ventricle (LV) thrombus progressively reduced in size and was not visible at discharge.
Venoarterial ECMO is widely used in pediatric and adult patients with cardiogenic shock. When left ventricular ejection is severely impaired or when preventing aortic valve opening is mandatory, left ventricular end diastolic pressure and left atrial pressure can rise and lead to increased wall stress and severe pulmonary edema. Surgical left-heart decompression through the insertion of a left atrial or left ventricular venting cannula carries a high risk of bleeding. Percutaneous venting can be performed with a catheter placed across the aortic valve in adult patients4 or through the atrial septum in children and young adults, with an associated risk of major complication ranging from 3% to 7%.5,6 In a sheep model, Kolobow et al.7 decompressed the left ventricle with a modified Swan-Ganz catheter that caused insufficiency of the pulmonary valve. It is our belief that pulmonary cannulation offers several advantages over the previously mentioned methods, as demonstrated by von Segesser et al.8 in a bovine model. First, unlike septostomy, the placement of a pulmonary arterial cannula allows decompression of the pulmonary circulation when the right ventricular ejection is not abolished. The risk of complications is smaller, when compared with blade septostomy or the placement of a transeptal stent, and the decompression of the pulmonary circulation represents an active process, whereas the decompression with helical spring is passive. Finally, the procedure is performed percutaneously, without the need for surgical manipulation, with the associated risk for bleeding and heart manipulation, and it is less expensive than the application of axial pumps, easier, and faster than all the aforementioned methods.
During our long-lasting experience in treating ECMO patients, surgical venting was performed in several cases, with frequent associated complications, such as bleeding and left ventricular thrombus formation. Venting the left heart in closed chest patients on ECMO is rarely needed, but when it becomes necessary, it represents a lifesaving procedure, and this percutaneous approach represents, in our opinion, a feasible and effective method, particularly in postcardiotomic ECMO patients, where surgical reopening carries a high risk of potentially severe complications.
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