Strengths and Limitations
This was the first study to use a non-invasive tool such as
echocardiography to comprehensively quantify LV systolic performance
during ex situ perfusion in two different working modes in a large
animal model. Previous studies have assessed LV function during ESHP
using conductance catheters and limited their investigations to SAM. Our
experimental model closely mimics the clinical scenario of standard ESHP
and assessment, ensuring more readily translatable findings.
Nevertheless, this work has a number of limitations. First, our sample
was very small. As such, conclusions regarding the use of
echocardiographic assessment of LV performance during SAM and PAM should
be considered as hypothesis generating work. Second, the
echocardiographic measures in vivo are not entirely comparable to those
during ESHP given the different setup and loading conditions. Third,
although we tried to provide precise loading and inotropic conditions
during the functional assessment, we did not closely control heart rate
which may have caused increased variability in some of the parameters
evaluated. Fourth, for a comparison between SAM and PAM, the assessment
of myocardial function should be done in an closer interval of time and
randomizing the technique utilized first. Different degrees of LV
dysfunction should also be included. Finally the RV function, which
plays a key role in post-transplant heart failure, was not evaluated due
to technical challenges in providing controlled RV afterload during
ESHP.