Oxygenated shunting from right to left: a feasibility study of minimized atrio-atrial extracorporeal membrane oxygenation for mid-term lung assistance in an acute ovine model.

OBJECTIVES: Right ventricular failure is often the final phase in acute and chronic respiratory failure. We combined right ventricular unloading with extracorporeal oxygenation in a new atrio-atrial extracorporeal membrane oxygenation (ECMO). METHODS: Eleven sheep (65 kg) were cannulated by a 28-Fr inflow cannula to the right atrium and a 25-Fr outflow cannula through the lateral left atrial wall. Both were connected by a serial combination of a microaxial pump (Impella Elect(®), Abiomed Europe, Aachen, Germany) and a membrane oxygenator (Novalung(®)-iLA membrane oxygenator; Novalung GmbH, Hechingen, Germany). In four animals, three subsequent states were evaluated: normal circulation, apneic hypoxia and increased right atrial after load by pulmonary banding. We focused on haemodynamic stability and gas exchange. RESULTS: All animals reached the end of the study protocol. In the apnoea phase, the decrease in PaO2 (21.4 ± 3.6 mmHg) immediately recovered (179.1 ± 134.8 mmHg) on-device in continuous apnoea. Right heart failure by excessive after load decreased mean arterial pressure (59 ± 29 mmHg) and increased central venous pressure and systolic right ventricular pressure; PaO2 and SvO2 decreased significantly. On assist, mean arterial pressure (103 ± 29 mmHg), central venous pressure and right ventricular pressure normalized. The SvO2 increased to 89 ± 3% and PaO2 stabilized (129 ± 21 mmHg). CONCLUSIONS: We demonstrated the efficacy of a miniaturized atrio-atrial ECMO. Right ventricular unloading was achieved, and gas exchange was well taken over by the Novalung. This allows an effective short- to mid-term treatment of cardiopulmonary failure, successfully combining right ventricular and respiratory bridging. The parallel bypass of the right ventricle and lung circulation permits full unloading of both systems as well as gradual weaning. Further pathologies (e.g. ischaemic right heart failure and acute lung injury) will have to be evaluated.

Video-assisted pericardioscopic surgery: refinement of a new technique for implanting epimyocardial pacemaker leads.

OBJECTIVE: Current alternative approaches for pacemaker lead implantation imply the breach of the pleural space. Recently, the feasibility of experimental lead implantation by rigid endoscopy has been described. The use of flexible endoscopes and a standardised application has not been realised yet. Our main goal was to compare rigid and flexible endoscopy and to establish a standardised protocol for the implementation of a closed-chest subxiphoid approach for epimyocardial lead implantation. METHODS: Rigid and flexible endoscopes were used for placement of screw-in pacing leads (4-F). A total of 17 adult pigs (80 kg) were anaesthetised and a 10-mm subxiphoid axial incision performed. The pericardium was opened and entered under endoscopic vision. Epimyocardial electrodes were implanted through the endoscope onto all four chambers. Standard haemodynamic measurements and pacing measurements were carried out. RESULTS: Both methods were deployed in the first three individuals. Superior endorsement of rigid endoscopy, due to better orientation and stability, led to its exclusive deployment in the remaining 14 individuals. Access to the implantation sites was quick (<10 min). A plastic cover had to be applied to reduce arrhythmia (VentricularExtraSystoles(bare): 17 ± 2.2 min(-1) vs VentricularExtraSystoles(cover): 5 ± 1.9 min(-1); n = 4). Measured pacing parameters were comparable with classic endocardial-derived thresholds. Post-mortem examination revealed no relevant damage/injury and/or bleeding in the heart and circumjacent tissue. There was no evidence of injury at the implantation sites and the corresponding pericardium. The electrodes showed excellent anchorage inside the myocardial tissue (penetration depths: 3 ± 0.2mm) and resisted high tractive forces. CONCLUSION: Flexible endoscopy is not suitable for exclusive deployment inside the pericardial space, whereas rigid endoscopy presented itself as a safe, fast and simple approach for epimyocardial lead implantation using an insulating trocar. Without cover, malignant arrhythmia constrains the implementation of video-assisted pericardioscopic surgery (VAPS). Subxiphoid VAPS permits optimal lead positioning under direct vision without fluoroscopy, without the breach of the pleural space and with a short procedural duration (<60 min). Our standardised minimal-invasive approach allows visualisation and intervention, potentially of all intrapericardial structures.