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Patients on extracorporeal membrane oxygenation (ECMO) for cardiac disease frequently have some degree of left ventricular (LV) distension due to incomplete unloading. However, a chronically or excessively volume overloaded and distended LV, with persistently elevated left ventricular end-diastolic pressure (LVEDP) and elevated wall stress, impairs myocardial recovery and the ability to wean off ECMO. The presence of concomitant cardiogenic pulmonary edema, in many cases, also leads to poor patient outcomes. Thus, in order to unload and decompress the left heart, conservative, pharmacologic, interventional and surgical strategies have been described [1, 2].
In this issue, the authors present the use of transseptal balloon atrial septostomy (BAS) and balloon dilation, to vent the left heart, in an adult patient with dilated cardiomyopathy and severe biventricular failure on ECMO, with worsening pulmonary edema. While treatment strategies have been reviewed, the timing, indications and algorithm for left heart decompression for patients on ECMO, especially by percutaneous BAS, remain debatable. Actual treatment strategies remain customized and decided on a case-by-case basis.
With regards to the timing for left heart decompression for patients on ECMO, in one single-center case series (23 pediatric patients), it appears that earlier LA decompression (by all modalities) is associated with better LV recovery and improved likelihood of weaning from ECMO . In another single-center case series (37 pediatric patients), trans-catheter procedures to decompress the left heart were performed in 97% of patients within 24 h of ECMO initiation . In a multi-center case series (64 patients: 32 adult, 32 pediatric) and the only study to include adult patients with available data on timing of intervention, Baruteau et al.  report that the mean ECMO-BAS timing was 1.5 days, with a range of 0 to 12 days. In a literature summary by the same authors, previously reported mean ECMO-BAS timings for pediatric patients ranged from 8 h to 2.5 days.
Interventional approaches to decompress the left heart include cardiac support interventions, such as intra-aortic balloon pumps, and percutaneous techniques to vent the left heart, such as pulmonary artery vents, retrograde transaortic vents, transseptal LA decompression [6, 9] with BAS and LA vent insertion , static over-the-wire [5, 9] balloon dilation, blade balloon septostomy [7, 9] and atrial stenting [9, 10]. The combination of BAS with ECMO has been shown to be safe and efficient in 64 patients in a multi-institutional study . For patients with severe left ventricular failure with a competent mitral valve, the role of BAS is limited to reduction of pulmonary edema. If BAS is not effective to decompress the left ventricle, an early decision of switching from ECMO to a left ventricular assist device would be warranted.
In conclusion, the decision to decompress the left heart in patients on ECMO is a multifactorial one. Evidence-based guidelines, treatment algorithms and consensus statements will be beneficial to guide management. An early decision of interventional approaches such as BAS would be beneficial for some patients, but switching to a left ventricular assist device is needed for most patients with severe left ventricular failure.
The authors declare no conflict of interest.