eComment: Outcome of extracorporeal membrane oxygenation in pediatric cardiac surgery – impact of residual lesions Free

The report of Loforte and colleagues [1] shows the increasing use of extracorporeal membrane oxygenation (ECMO) in postcardiotomy pediatric patients. As their work shows, significant morbidity and mortality, with an overall survival rate of 40% can be expected in this patient population. The cost of ECMO use and relatively poor outcomes make appropriate patient selection a desirable goal. But as the authors [1] observe, the indications for postcardiotomy ECMO must often be based on clinical judgment, and thus uniform selection criteria for postcardiotomy pediatric patients being considered for ECMO salvage remain elusive.

Nevertheless, the primary aim of cardiac ECMO remains unchanged – unloading the heart to decrease its work so as to allow recovery of cardiac function from injury within a short time frame. ECMO is thus best used in the patient with a good potential for myocardial recovery in a matter of days. Hemodynamically significant residual lesions unresolved by the cardiac repair profoundly undermine this potential for recovery. The most common residual lesions after congenital heart surgery are residual shunts, obstructed ventricular outflow pathways, and atrioventricular valve regurgitation. These may be the result of incomplete/imperfect repairs or undiagnosed but hemodynamically significant lesions existing preoperatively. Residual lesions may be present in as many as 15% of pediatric postcardiotomy patients placed on ECMO; a third of these residual lesions may not be diagnosed preoperatively [2]. In the presence of such residual lesions, the likelihood of recovery of cardiac function on ECMO is slim; an already compromised myocardium stands little chance of recovering from the additional hemodynamic burden imposed by significant residual lesions. Not surprisingly, the presence of residual lesions has been found to be an important adverse factor for ECMO survival [2, 3]. On this basis, complete surgical repair must be ensured before ECMO is applied. Every effort must be made to rule out hemodynamically significant residual lesions before ECMO salvage is contemplated. Postcardiotomy residual defects must be considered contraindications to ECMO. From the study of Black and colleagues [3], excluding children with residual defects resulted in successful weaning from ECMO in almost 70% of cases, with almost all recovery occurring within the first six days of ECMO.

Summarily, a complete preoperative diagnosis ensures that all hemodynamically significant lesions are addressed intraoperatively to facilitate a complete repair. When patients cannot be separated from bypass, a thorough search must be made for residual lesions which must be addressed to improve ECMO outcomes.

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