Abstract
Critical to myocardial functional characterization is the assessment of regional stress and strain behavior. This study quantifies in‐vivo left ventricular (LV) epicardial force and strain measurements of the normal murine heart using micro sensors. Male C57BL/6 mice (n=11, mean age=10.5 wks, weight=24.6 g) were intubated and studied under 1.5% isoflurane in 100% O2. Microsurgery allowed the placement of two piezoelectric crystals (od=0.3–0.7 mm, 1–2 mm apart) at longitudinal, basal and mid‐myocardial regions, and a miniature force sensor, between the crystals. The crystals were sutured on the epicardial LV wall, whereas the cantilever force sensor was placed on a platform stand and was connected to the epicardium via a thin silver wire, attached to a silk thread suture inserted superficially on the tissue. Findings demonstrate lack of ischemia (H&E histology) and epicardial longitudinal crystal displacements in the range of 0.19–0.27 mm (n=7), indicative of maximum evoked contractile and relaxation strains of 5–6.8 and 4.6–6.2 % for basal/mid‐ventricular regions. Force results (n=5, uncorrected for baseline offsets) yield mean contractile and relaxation forces of 12.7±1.2 and 12.9±1.4 mN (p=NS), respectively. The potential usefulness of in‐vivo force and strain measurements relates to transgenic and diseased mouse studies, where regional cardiac mechanical properties may be significantly altered.
Published Version
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