P73: Subclavian Artery Cannulation For Left Ventricular Unloading During Extracorporeal Membrane Oxygenation Support

Abstract

Background: Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is an effective mechanical circulatory support for cardiac insufficiency following cardiac surgery especially cardiac surgery with extracorporeal circulation, which can quickly restore the perfusion of vital organs. However, retrograde blood flow in the aorta during VA-ECMO may lead to increased left ventricular (LV) afterload, elevated LV filling pressure, mitral insufficiency, and elevated left atrial pressure, which may subsequently result in reduced coronary blood flow and pulmonary edema, thus aggravating the patient’s condition. Therefore, LV unloading is necessary during VA-ECMO. The optimal approach for LV unloading remains undefined, but the percutaneous access has been increasingly used over time. To addresss this issue, we have attempted to use cannulation of the subclavian artery for left ventricular unloading during VA-ECMO. This study aims to describe our method and report the preliminary results in three patients. Methods: Three patients with low cardiac output syndrome after cardiac surgery. All 3 patients had difficulty weaning from cardiopulmonary bypass (CPB) due to overfilling and contractile weakness of the heart, low mean arterial pressure<80mmHg, and left atrial pressure of >20 mmHg. Decision was made to start ECMO support immediately, and LV unloading was initiated via cannulation of the subclavian artery (Table 1). Given the differences in the surgical approaches and condition of patients, three methods were used to achieve LV unloading via the subclavian artery.Methods of LV unloading with cannulation via the subclavian artery during VA-ECMO in three patients with low cardiac output syndrome after cardiac surgery: 1) VA-ECMO with LV unloading via subclavian artery; 2) femoral vein-to-subclavian artery VA-ECMO with LV unloading via a 4-branched graft; 3) LV bypass via femoral artery-subclavian artery. Results: In all patients, the subclavian artery cannula was withdrawn at postoperative days 2-3, and ECMO was successfully weaned on postoperative day 4. One patient developed cardiac tamponade within 24 hour of surgery, echocardiography showed an LVEF of 55%. During an exploratory thoracotomy, a large amount of blood clot about 500 mL was found in the pericardium and removed, and the patient recovered uneventfully. Table 2 summarizes the postoperative courses of the 3 patients with different LV unloading methods. Conclusion: This study partly illustrated that LV drainage via the subclavian artery could safely and effectively reduce the LV load, prevent VA-ECMO-related complications, and minimize the risk of trauma and infection during LV examinations. Certainly, whether the subclavian artery approach is the optimal strategy for LV unloading as well as patient risks and benefits remains to be further investigated.Figure 1. ECMO + LV unloading schematic diagram of Case 1 (femoral artery + femoral vein+ subclavian artery)Figure 2. ECMO + LV unloading schematic diagram of Case 2 (femoral artery + femoral vein + four branches aortic graft)Figure 3. LV unloading schematic diagram of Case 2 (femoral artery + subclavian artery)