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Archives of cardiovascular diseases
Volume 104, n° 5
pages 303-305 (mai 2011)
Doi : 10.1016/j.acvd.2011.03.090
Received : 30 December 2010 ;  accepted : 10 Mars 2011
Mechanical circulatory assistance in children
Assistance circulatoire pédiatrique
 

Philippe Mauriat a, , Nadir Tafer a, Philippe Pouard b
a Service d’anesthésie-réanimation II, hôpital Haut-Lévèque, Pessac, France 
b Département d’anesthésie-réanimation, hôpital Necker Enfants-Malades, Paris, France 

Corresponding author.

Keywords : Mechanical circulatory assistance, Children, Extracorporeal membrane oxygenation, Ventricular assist device

Mots clés : Assistance circulatoire mécanique, Enfant, ECMO, Assistance ventriculaire

Abbreviations : ECMO, VAD


Background

For the past two decades, circulatory assistance in paediatrics has much improved and is evolving from classical extracorporeal membrane oxygenation (ECMO) to pulsatile assistance. ECMO is still widely used for short-term assistance, mostly after cardiac surgery, whereas pulsatile support is for the most part indicated as a bridge to transplantation. Both techniques are within the realm of current strategies to treat cardiac failure.

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.

Indications

Circulatory assistance is indicated, when ‘maximal inotropic support’ is being reached, with the aim of improving the ongoing lack of tissue perfusion. If circulatory failure is reversible, circulatory assistance will be needed for a short period of time, in which case it may be provided by standard ECMO. For irreversible or long lasting failure, a pulsatile ventricular assist device (VAD) will supply the best mechanical circulatory support.

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.

Choice of mechanical circulatory support

In acute settings (cardiac arrest or acute refractory cardiac failure), ECMO is often the first choice because of its rapid availability, and in older children it may be delivered by percutaneous venous and arterial cannulation. An ECMO circuit can be functional and relatively safe for two or three weeks. In the absence of respiratory failure, when the cardiac failure is gradual or when recovery needs a longer timeline, a paracorporeal VAD provides numerous benefits. The patient can be extubated, fed normally and may exercise and walk short distances. Team experience, familiarity with the devices, and pump and circuit availability are also involved in the choice of the mechanical support.

Echocardiographic monitoring of mechanical circulatory support

Echocardiography is the gold standard technique for mechanical circulatory support monitoring [1]. Firstly, it rules out any residual lesions before initiation of the support [2]. Secondly, it is instrumental in assessing cardiac anatomy and function, including preload, filling characteristics, diastolic and systolic function, pressures, presence of regional dyskinesia and valvular status. Echocardiography can confirm the indication for mechanical circulatory assistance and also identify whether assistance is required to one or both ventricles. In addition, it can establish the need for a complementary left vent to properly unload the left-sided heart, unless an atrioseptostomy is performed. Daily echocardiography should be carried out to assess the positioning of venous and arterial cannulae and their relation with the valves [3]. Echocardiography can also evaluate the adequate venting of the left and/or right chambers. Serial evaluations will help to diagnose complications early: presence of thrombuses, closed aortic valve leaflets for ‘over-assistance’ or pericardial effusion. Finally, echocardiography can appraise myocardial remodeling and recovery to guide the progressive and careful weaning of the assistance. For this purpose, it is essential to examine the contractility index independently of the preload [4].

Outcomes

Outcomes vary with pre-ECMO status and the aetiology of the failure. Associated acidosis and renal failure increase the risk of mortality. Analysing the Extracorporeal Life Support Organization data, ECMO survival at discharge was 38% when used to support cardiopulmonary resuscitation, increasing to 42% for cardiac disease [5]. During ECMO, renal failure, pulmonary haemorrhage, neurological injury and a pH<7.2 are associated with higher mortality. In this setting, the survival rate seems associated with manpower availability and philosophy about the use of extracorporeal life support. The rescue team has to be able to set an ECMO support within 10 to 15minutes, 24hours a day (ECMO to support cardiopulmonary resuscitation [E-CPR]). [6]. The team also needs to be empowered to reject the indication for ECMO if the predefined criteria are not met [7].

Data related to the Berlin Heart VAD implantation showed that the cause of unresponsive cardiac failure was congenital cardiac disease in 25% of cases. The median duration of circulatory support was 55 days (range, 1–432 days) and in this series, 42% of patients were transplanted and 21% were successfully weaned from pulsatile support, with a survival rate of 81.1±5.8% at 30 days and 51.4±9.3% at one year. The mortality rate was significantly higher in children with congenital heart disease [8].

In children who have undergone transplantation, the United Network of Organ Sharing database showed that 431 of 2352 recipients (18%), between 1995 and 2005, required post-transplantation circulatory support: 9.5% received a VAD, 6.8% ECMO support and 0.8% an intra-aortic balloon pump. Compared with those who did not require support, the mechanically-assisted patients had the same in-hospital length of stay and the survival rate at five and 10 years was the same, with better outcome for the VAD compared with ECMO [9].

Mechanical circulatory support devices are further developing and improving; currently, a small implantable turbine is being experimentally tested to assist failing complex Fontan-like circulations [10].

Conclusions

To summarize, mechanical circulatory support with ECMO or a VAD is becoming an invaluable tool in the care of children with severe refractory cardio-circulatory failure. The quality of the results and outcomes depends on the team expertise, manpower and financial resources. For these reasons, only few centers may be capable of offering the permanent availability of a rapid deployment ECMO/VAD team.

Disclosure of interest

The authors declare that they have no conflicts of interest concerning this article.

References

Catena E., Paino R., Milazzo F., and al. Mechanical circulatory support for patients with fulminant myocarditis: the role of echocardiography to address diagnosis, choice of device, management, and recovery J Cardiothorac Vasc Anesth 2009 ;  23 : 87-94 [cross-ref]
Chaturvedi R.R., Macrae D., Brown K.L., and al. Cardiac ECMO for biventricular hearts after paediatric open heart surgery Heart 2004 ;  90 : 545-551 [cross-ref]
Thomas T.H., Price R., Ramaciotti C., and al. Echocardiography, not chest radiography, for evaluation of cannula placement during pediatric extracorporeal membrane oxygenation Pediatr Crit Care Med 2009 ;  10 : 56-59 [cross-ref]
Marcucci C., Lauer R., Mahajan A. New echocardiographic techniques for evaluating left ventricular myocardial function Semin Cardiothorac Vasc Anesth 2008 ;  12 : 228-247 [cross-ref]
Thiagarajan R.R., Laussen P.C., Rycus P.T., and al. Extracorporeal membrane oxygenation to aid cardiopulmonary resuscitation in infants and children Circulation 2007 ;  116 : 1693-1700 [cross-ref]
Alsoufi B., Al-Radi O.O., Nazer R.I., and al. Survival outcomes after rescue extracorporeal cardiopulmonary resuscitation in pediatric patients with refractory cardiac arrest J Thorac Cardiovasc Surg 2007 ;  134 : 952-959[e2].
Kelly R.B., Harrison R.E. Outcome predictors of pediatric extracorporeal cardiopulmonary resuscitation Pediatr Cardiol 2010 ;  31 : 626-633 [cross-ref]
Fan Y., WengF Y.G., Xiao Y.B., and al. Outcomes of ventricular assist device support in young patients with small body surface area Eur J Cardiothorac Surg 2011 ;  39 (5) : 699-704Epub 2010 Sep 29.  [cross-ref]
Davies R.R., Russo M.J., Hong K.N., and al. he use of mechanical circulatory support as a bridge to transplantation in pediatric patients: an analysis of the United Network for Organ Sharing database J Thorac Cardiovasc Surg 2008 ;  27 (135) : 421-427[e1].
Bhavsar S.S., Kapadia J.Y., Chopski S.G., and al. Intravascular mechanical cavopulmonary assistance for patients with failing Fontan physiology Artif Organs 2009 ;  33 : 977-987 [cross-ref]



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