Geert Kleinnibbelink

RV Function after Preload Manipulation 7 165 increase in peak RV longitudinal strain. The slope of the systolic phase of the strain-area loop (i.e. Sslope) during preload elevation was significantly smaller than during preload reduction (-1.8±0.7%/cm 2 vs . -2.9±0.9%/cm 2 , P < 0.05). A potential explanation of this finding is that as preload and stroke volume decreases there is a larger contribution of longitudinal fiber shortening with possible less dependency on circumferential fiber shortening to facilitate systolic volume ejection. This also may explain the paradoxical increase in peak longitudinal strain upon preload reduction as circumferential strain may be disproportionally decreased. Since we were not able to measure circumferential strain, this remains speculative. It is important to acknowledge the complexity of RV function, with changes in stroke volume potentially impacting upon various aspects of cardiac mechanics. This makes it difficult in our study to identify a single or most important factor explaining our observations. Cardiac contractility is presented as the relation between end-systolic area (or volume) versus pressure. Using the non-invasive RV strain-area loop, we explored the ability to assess RV contractility by presenting the relation between end-systolic area versus strain. For this purpose, we used the data before and after balloon inflation. We found an excellent correlation between the slopes of the end-systolic pressure area-relation versus strain area-relation (r=0.98, P < 0.001). This observation provides further support for the ability of strain-area loops to assess RV cardiac function.