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.