Magnetic resonance imaging analysis of left ventricular function in normal and spontaneously hypertensive rats

Abstract

We have used magnetic resonance imaging (MRI) to examine acute morphological changes in the left ventricle throughout the cardiac cycle in normal Wistar Kyoto rats (WKY) and also to follow the development of chronic changes in spontaneously hypertensive rats (SHR). This involved the development of MRI and quantitative analysis techniques for characterizing contractile changes during the cardiac cycle. Images of the cardiac anatomy in two age groups (8 and 12 weeks old) of young anaesthetized adult normal WKY and SHR were acquired in planes both parallel and perpendicular to the principal cardiac axis. Complete coverage of the heart by imaging planes was achieved with high time resolution (13 ms), with typically 12 time frames in the cardiac cycle, using a short echo time (5 ms) multislice gradient‐echo imaging sequence. Imaging was synchronized to the R wave of the electrocardiogram. The image slices could be reconstructed into complete geometrically and temporally coherent three‐dimensional data sets. Left ventricular (LV) volumes were thus reconstructed throughout the cardiac cycle by combining transverse cardiac image sections. This volume analysis revealed structural and functional differences between the normal WKY and SHR in both age groups of 8 and 12 weeks. Measurements from the cardiac images were additionally validated against histological measurements. The SHR showed a raised LV end‐systolic volume and a correspondingly poorer ejection fraction as well as LV hypertrophy when compared with the controls. Left ventricular function in the SHR appeared stable between the two age groups. We developed a simple geometrical model of the left ventricle based on a single longitudinal image section and successfully used this to describe some functional parameters of the left ventricle in the WKY and SHR. This geometrical model has the potential to greatly reduce the imaging time needed to study the beating heart in future serial investigations of cardiac physiology in rats. Our experimental and analytical methods together form a powerful set of quantitative techniques which combine both imaging and functional analysis and will be applicable for future studies of chronic physiological changes in animal disease models.

Retrospective Motion Gating in Small Animal CT of Mice and Rats

“…Also, the cardiac functional parameters of rats fit well with those published: using MRI, Wise and coworkers 33 reported an end-diastolic volume of 0.46 Ϯ 0.03 mL and Nahrendorf and colleagues 34 demonstrated an end-diastolic volume of 316 Ϯ 16.3 L. However, the injection fraction was little higher than in our study with 70.6%. CT studies of rat ventricular volumes are not yet published.…”

Optimization of cardiac cine in the rat on a clinical 1.5-T MR system

“…The following physiological values are presented in Tables 4 and 5 and are in agreement with previous studies made at different field strengths (from 1.5 to 7-T): the ejection fraction [10,12,17,25], left-ventricular diastolic [10] and systolic volumes [10,26], and left-ventricular mass [10,13,25].…”

A model of chronic heart failure in spontaneous hypertensive rats (SHR)

“…In comparison to the WKY/NHsd sham animals, LVEDV was enhanced in the SHR/NHsd sham animals, indicating the enhanced venous tone and reabsorption of sodium and extravascular uid. This was underlined by other authors who have done LVEDV evaluations in SHR/NHsd and normotensive WKY/NHsd rats without MI (Wise et al 1998). Systolic dysfunction was also detected by circumference measurements, indicating enhanced systolic heart sizes.…”