A case report of unexpected right-to-left shunt under mechanical support for post-infarction ventricular septal defect: evaluation with haemodynamic simulator

Background Post-myocardial infarction ventricular septal defect (PIVSD) is a complication of acute myocardial infarction with high mortality. A percutaneous left ventricular assist device, Impella, is currently used in maintaining haemodynamic stability in PIVSD. Case summary A 65-year-old man was transferred to our hospital for treatment of acute myocardial infarction of the proximal right coronary artery. Percutaneous intervention was performed but haemodynamic instability continued. At 10 days after onset, the patient was diagnosed with PIVSD by echocardiogram. To stabilize haemodynamics, we initiated venoarterial extracorporeal membrane oxygenation (ECMO). Three days after ECMO initiation, pulmonary congestion increased and an echocardiogram revealed closed aortic valve and spontaneous echo contrast at the aortic root. After an Impella 2.5 was inserted for unloading of the left ventricle, the oxygenation level and cardiac function rapidly declined. Unexpectedly, an echocardiogram showed a right-to-left shunt (to-and-fro pattern) via PIVSD. By increasing the ECMO and decreasing Impella flow, the shunt flow changed to left-to-right, and oxygenation level and cardiac function improved. Ten days after ECMO was started, elective surgical repair was successfully performed. Conclusion ECPELLA (ECMO + Impella) can offset the adverse effects of isolated ECMO support and reduce the PIVSD shunt flow. However, the risk of right-to-left shunt has not been reported, and ECPELLA caused a right-to-left shunt with deoxygenated systemic perfusion in the present case. A simulation study indicated that the right ventricular failure in PIVSD may pose a risk for right-to-left PIVSD shunt under Impella support.