Loading…
A quantitative description of dynamic left ventricular geometry in anaesthetized rats using magnetic resonance imaging
We report a functional application of magnetic resonance imaging (MRI) for the quantitative description of left ventricular geometry through systole and diastole in normal anaesthetized Wistar rats that might be applicable for the analysis of chronic changes resulting from pathological conditions. I...
Saved in:
Published in: | Experimental physiology 1997-09, Vol.82 (5), p.887-904 |
---|---|
Main Authors: | , , , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that cite this one |
Online Access: | Request full text |
Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
Summary: | We report a functional application of magnetic resonance imaging (MRI) for the quantitative description of left ventricular
geometry through systole and diastole in normal anaesthetized Wistar rats that might be applicable for the analysis of chronic
changes resulting from pathological conditions. Images of cardiac anatomy were acquired through planes both parallel and perpendicular
to the principal cardiac axis at times that were synchronized to the R wave of the electrocardiogram. The images of the transverse
sections were assembled into three-dimensional representations of left ventricular geometry at consecutive time points through
the cardiac cycle. This confirmed the geometrical coherence of the data sets, that each slice showed circular symmetry, and
that the images were correctly aligned with the appropriate anatomical axes. Different models for the three-dimensional geometry
of the left ventricle were then tested against the epi- and endocardial surfaces reconstructed from images of the transverse
sections of the left ventricle in both systole and diastole using least-squares minimizations in three dimensions. In agreement
with previous reports in the human heart, an elliptical figure of revolution offered an optimal fit to the epicardial and
endocardial geometry for the rat heart in diastole. This was in preference to models that used spherical, quartic or parabolic
geometries. However, in contrast to contraction in the human heart, all these geometrical representations broke down during
systolic ejection in the rat heart. We therefore introduced a more general hybrid model which described left ventricular geometry
in terms of the variation of the radii r(z), independently determined for each slice, with its position z along the principal
cardiac axis. The resulting function r(z) could then be described by a simple ellipsoid of revolution not only during diastole,
but also throughout ventricular ejection. The findings also ruled out alternative geometrical representations. It was then
possible additionally to reconstruct the luminal and total left ventricular volumes, wall thicknesses and ejection fractions
through the cardiac cycle and to confirm that the predicted total ventricular wall volume was conserved throughout the cardiac
cycle. Our hybrid model of cardiac geometry may thus be useful for non-invasive serial studies of chronic pathological changes
that use the rat as a model experimental system. |
---|---|
ISSN: | 0958-0670 1469-445X |
DOI: | 10.1113/expphysiol.1997.sp004071 |