Rapid microcomputed tomography suggests cardiac enlargement occurs during conductance catheter measurements in mice

Abstract

Conductance catheters (CC) represent an established method of determining cardiac function in mice; however, the potentially detrimental effects a catheter may have on the mouse heart have never been evaluated. The present study takes advantage of rapid three-dimensional (3D) microcomputed tomography (CT) to compare simultaneously acquired micro-CT and CC measurements of left ventricular (LV) volumes in healthy and infarcted mice and to determine changes in LV volume and function associated with CC insertion. LV volumes were measured in C57BL/6 mice (10 healthy, 10 infarcted, 2% isoflurane anesthesia) using a 1.4-Fr Millar CC. 3D micro-CT images of each mouse were acquired before CC insertion as well as during catheterization. Each CT scan produced high-resolution images throughout the entire cardiac cycle in <1 min, enabling accurate volume measurements as well as direct visualization of the CC within the LV. Bland-Altman analysis demonstrated that CC measurements underestimate volume compared with CT measurements in both healthy [bias of -18.4 and -28.9 μl for end-systolic (ESV) and end-diastolic volume (EDV), respectively] and infarcted mice (ESV = -51.6 μl and EDV = -71.7 μl); underestimation was attributed to the off-center placement of the catheter. Individual evaluation of each heart revealed LV dilation following CC insertion in 40% of mice in each group. No change in ejection fraction was observed, suggesting the enlargement was caused by volume overload associated with disruption of the papillary muscles or chords. The enlargement witnessed was not significant; however, the results suggest the potential for CC insertion to detrimentally affect mouse myocardium, necessitating further investigation.