Circulatory assistance as part of cardiac failure management

Most cardiac failure scenarios, mainly after cardiac surgery, result from ischaemia or ischaemic reperfusion injuries. Inotropic support is the cornerstone of therapy to restore tissue perfusion by improving cardiac output. Nevertheless, all the available beta- or alpha-agonist drugs, as well as phosphodiesterase inhibitor-type drugs, increase myocardial oxygen demand and effort. Although these drugs should decrease oxygen demand to restore a balanced cellular metabolism in the ischaemic territories, they worsen energetic loss.

The aim of circulatory assistance is to assist cardiac function by totally or partially providing cardiac output. The flow may be continuous or pulsatile. This circulatory assistance is obtained by venting the cardiac chambers and reperfusing blood into the ascending aorta to providestable systemic and coronary artery flow. The venting of the cardiac chambers decreases wall tension, thus improving coronary flow. Last but not least, by contrast with inotropic drugs, circulatory assistance decreases oxygen demand to allow the myocardium to remodel and recover, if the aetiology of the cardiac failure permits.

Postoperative cardiac failure

Postcardiotomy cardiac failure may result from inadequate myocardial protection, a worsening of preoperative cardiac dysfunction or the presence of residual cardiovascular lesions. For example, after an anomalous left coronary artery from pulmonary artery repair, the hibernating ventricle may be worsened by reperfusion injury stunning, refractory to any inotropic support and leading to ECMO.

Myocarditis

During the acute or fulminant period, the resulting cardiac failure may be refractory to any pharmacological treatment and need ECMO until recovery occurs.

Drug poisoning

ECMO has been shown as a very efficient support after poisoning by beta-blockers, tricyclic drugs or quinidine with severe arrhythmias. It is often required for short runs, while the drug is metabolized and eliminated.

In-hospital and out-of-hospital cardiac arrest

In the case of in-hospital and out-of-hospital cardiac arrest, if the event is witnessed and the patient has the benefit of immediate conventional cardiopulmonary resuscitation, ECMO may improve short- and long-term outcomes. This indication requires extensive human and financial resources.

Bridge to heart transplantation

A large variety of clinical situations may require to be bridged to transplantation: refractory cardiomyopathy, acute myocarditis, failing univentricular circulation, as well as other complex congenital heart diseases. The pneumatic, pulsatile, ‘Berlin Heart’ VAD is being extensively used in children who need long-term support. It is available for children, as well as for neonates, after careful patient selection.

Post-transplantation circulatory assistance

The scarcity of paediatric donors leads to the acceptance of some grafts with altered myocardial function or with a very long ischaemic time. Circulatory assistance may then be necessary to give the myocardium sufficient time to recover. In addition, some children with very high pulmonary vascular resistances may require an isolated heart transplant, because of the lack of heart and lung grafts. In such cases, the risk of right ventricular failure is very high, despite the use of pulmonary vasodilators, and temporary mechanical assistance may be useful to enable the right ventricle to remodel.