Extracorporeal Life Support system ECLS is a cardiac assist device based on the heartlung machine HL

1
Extracorporeal Life Support system (ECLS) is a
cardiac assist device based on the heart-lung
machine (HLM) that supports the circulation
temporarily (fig. 1). Postcardiotomy patients,
who are not weanable from the HLM because of low
output, are possible candidates.
Data are obtained by 1) interviewing
perfusionists, 2) studying records of ECLS
patients and 3) literature study.
Table II
The present parameters used to evaluate the heart
function are listed in table I. Unfortunately
these parameters have several disadvantages such
as invasive, non-frequently measured, preload
dependency, or poorly monitored.
During ECLS, evaluation of cardiac function is
hindered because the parallel ECLS pump affects
the measurements. Goal of this study was to find
better quantification methods to evaluate the
heart condition during ECLS. Therefore, first an
inventory of the current parameters is made. This
is used to design additional quantification
methods to investigate the recovery of the heart
during ECLS. This enables to tune the ECLS to
cardiac capacity.
A first alternative index to evaluate the heart
function is contractility. This can be determined
from a Pressure Volume loop (fig. 2) by
placement of a conductance catheter in the
ventricle. A change (induced or natural) in the
circulation constructs the second loop.
Current measurements are not sufficient to
support the heart optimal. A more profound idea
about the condition of the heart can contribute
in tuning ECLS for cardiac function and in
deciding the moment of weaning. The use of
interventions to obtain the parameters described,
seems promising.
A second option is the use of the Starling curve
(fig. 3) to determine its slope as a
contractility index. At least two points of the
curve must be measured. An intervention in
preload (ideally not changing afterload) is most
suitable to realize this.
A third approach is studying the response of the
heart on a quick change in the pump flow. The
response can for example be evaluated using the
Pao (fig. 4).
Table I Parameters to assess cardiac function