3.1. Vasoactive Inotropic Score

6.1. Isolated Left Ventricular (LV) Dysfunction

• In case of isolated LV dysfunction, without arrhythmia or severe lactic acidosis (<72 mg/dL or <8 mmol/L), primary implantation of an Impella pump (Abiomed, Danvers, MA, USA) should performed.[6,15]
• In patients with a mechanical aortic valve prosthesis or a free-floating thrombus in the LV, a left ventricular Impella is contraindicated. In such cases, primary implantation of v-a ECLS has to be performed. Following this, LV unloading strategies (e.g., IABP, transseptal percutaneous venting, direct LV venting via the LV apex or pulmonary artery) should be discussed.
• The Impella CP (Abiomed, Danvers, MA, USA) is usually implanted percutaneously via femoral artery and can generate a flow of up to 3.5 L/min. For patients with an expected short tMCS duration, sole percutaneous Impella CP implantation can be considered.
• The Impella 5.5 can provide up to 5.8 L/min depending on afterload and has to be surgically implanted through a vascular prosthesis. Axillary artery is the preferred access route, as it allows for early postoperative mobilization of the patient and uncomplicated explantation.
• If the axillary artery is less than 7-mm in diameter, exhibits calcifications or anatomical peculiarities (such as arteria lusoria), implantation of an Impella CP via the axillary artery, possibly on the contralateral side, may alternatively be considered.
• Alternative access routes such as the ascending aorta (in open-chest patients) can be considered.
• We recommend performing surgical implantation via a 10 (8)-mm vascular prosthesis, which is anastomosed in end-to-side fashion to the target vessel.

6.2. Isolated Right Ventricular (RV) Dysfunction

• In patients with an open chest, cannulation of the pulmonary artery can be performed using a vascular prosthesis (10- or 8-mm diameter), which is tunneled out of the chest cavity allowing for thoracic closure and facilitating later explantation. For venous drainage, a cannula is usually placed in the right atrium via femoral or the right jugular vein. Alternatively, if no peripheral access is possible and extended support duration is anticipated, direct cannulation of the right atrium can be performed. In this case, a 14 mm graft is usually anastamosed to right atrium and exteriorized and a 24-26 Fr venous cannula is directly inserted and chest is closed.[9,16]
• In patients with a closed chest, percutaneous cannulation of the pulmonary artery can be performed via the right jugular vein. This can be achieved through two separate cannulas (long standard venous cannulas placed into the pulmonary artery and femoral vein), requiring two separate venous punctures.[16]
• Alternatively, the insertion of a double-lumen cannula (ProtekDuo by LivaNova PLC, London, UK) facilitated right ventricular support through a single puncture of the jugular vein. The tip of the catheter is placed in the main stem or upper right pulmonary artery under fluoroscopic and echocardiographic guidance. This method allows for early mobilization on ongoing right ventricular support.[17]
• The percutaneous Impella RP is inserted into the pulmonary artery via the femoral vein and generates a flow of up to 4.6 L/min. Disadvantages of the Impella RP are a limited support duration, impaired patient mobilization, and the lack of respiratory support.[5] Alternatively, the recently developed Impella RP Flex (Abiomed, Danvers, MA, USA) can be implanted through right jugular vein allowing mobilization of the patients.

6.3. Ongoing CPR

• Establishing rapid circulatory support is essential in patients undergoing CPR. In this case, immediate implantation of veno-arterial extracorporeal life support (v-a ECLS) is recommended.[1,11,15]
• In open-chest patients, cannulation of central vessels (ascending aorta, right atrium) can be considered.
• In patients with a closed thorax, peripheral v-a ECLS cannulation should be performed. Whether percutaneous or open surgical cannulation is chosen depends on the clinical situation, anatomical circumstances of the patient, and the surgeon’s preference.
• In patients with peripheral arterial occlusive disease, surgical exposure of the femoral vessels and surgical implantation should be performed as a primary approach.
• Placement of a peripheral perfusion cannula is recommended, but can be performed shortly after hemodynamic stabilization.

6.4. Severe Cardiogenic Shock

7.1. Discontinuation of Isolated Left Ventricular Impella Support (Figure 2)

• After hemodynamic stabilization and a significant reduction of inotropic medication (with only low-dose vasopressor therapy remaining), a stepwise reduction in support is performed until the P2 level is achieved. This is done gradually with a continuous re-evaluation of hemodynamics over at least 48 hours. Support should not be reduced below the P2 level, as this can cause retrograde flow through the pump into the left ventricle.
• If there are no severe valve pathologies, the LVEF is at least 25–30%, there is a stable rhythm, and no continuous inotropic treatment is needed while on support at the P2 level, the Impella can be removed.
• If this is not the case, alternative treatment concepts such as LVAD, heart transplantation, or palliation should be discussed.
• In case of increasing mitral regurgitation during a reduction of Impella flow, endovascular mitral valve reconstruction can be performed under Impella support.[23]
• If circulatory support is inadequate (increasing catecholamine demand and increasing arterial lactate despite maximum Impella therapy), v-a ECLS implantation for escalation to ECMELLA can be considered, but long-term LVAD therapy should be prioritized.[6]
• In the event of severe respiratory failure, veno-venous extracorporeal membrane oxygenation (v-v ECMO) can be implanted.
• If severe hemolysis, pump thrombosis, or Impella pump failure occur, a switch to a new Impella can be performed, but long-term LVAD therapy should be simultaneously discussed depending on the cardiac recovery potential.

7.2. Weaning from v-a ECLS Support (Figure 3)

• The basic criteria for weaning from v-a ECLS are the same as for weaning from Impella support. After stabilization of the patient's hemodynamic condition, the v-a ECLS flow is gradually reduced to 1.5-2 L over at least 48 hours.
• If the general weaning criteria (no higher-grade valve pathologies, LVEF of at least 25–30%, stable rhythm, no inotropes) are met, v-a ECLS can be explanted.
• In patients on ECLS with unclear neurological status or severe complications, switch to Impella support in setting of bridge-to-decision therapy should be considered.[24]
• Harlequin syndrome (also known as differential hypoxemia) is a rare complication that can occur after onset of the unloading device or during myocardial recovery under v-a ECLS therapy. In severe respiratory failure, poorly oxygenated blood is ejected into the circulation, but remains in the supra-aortic vessels due to retrograde flow and a high afterload generated by v-a ECLS. In this situation, the therapy should be escalated to veno-veno-arterial ECLS. To do this, an additional arterial ECLS line is established in order to transport oxygenated blood to the right atrium. This counteracts differential hypoxemia and reduces the risk of cerebral and coronary hypoperfusion.[25]

7.3. Weaning from ECMELLA Support (Figure 4)

• The basic criteria for ECMELLA weaning correspond to those for v-a ECLS and Impella weaning. Complications on v-a ECLS are common and increase with support duration. Therefore, the concept of ECMELLA weaning focuses primarily on the reduction of v-a ECLS support with potential explantation.
• ECMELLA therapy with femoral cannulation and simultaneous respiratory insufficiency also bears a risk of differential hypoxemia (Harlequin syndrome). In this case, escalating to vv-a ECMELLA should be considered.
• If de-escalation of ECMELLA therapy is not possible, long-term LVAD implantation on ECMELLA can be performed.

7.4. Weaning from Temporary RVAD Support (Figure 5)

• The right ventricle has a significant regenerative potential, but sometimes requires prolonged periods of support. Therefore, implantation of a permanent RVAD or heart transplantation should be considered only after longer periods of support (>30 days).[5] It should also be considered that implantation of a permanent RVAD is a complex off-label procedure with a significant potential for complications.[26]
• We recommend a stepwise flow reduction of the temporary RVAD by no more than 0.5 L/min per day until 2 L/min is reached.
• It is important to underline, that in case of temporary RV support with Impella RP device the flow should not be reduced below 1.5 L/min (P4 level), due to the iatrogenic tricuspid regurgitation caused by the device itself.
• If hemodynamics fail to stabilize at minimal flow, the optimal support level should be established and re-evaluation performed after seven days.
• If weaning from temporary RVAD support is not possible after a total of 30 days, switching to a permanent system and/or listing for heart transplantation should be considered.[10]
• If gas exchange is impaired during temporary RVAD support, the installation of an oxygenator in the extracorporeal circuit should be considered.