Measurement of left ventricular mass in rats using electrocardiogram-gated magnetic resonance imaging

Abstract

To evaluate the ability of electrocardiogram (ECG)-gated magnetic resonance (MR) imaging to assess in vivo left ventricular (LV) mass in the rat, we studied 20 healthy adult Sprague-Dawley and Fischer 344 rats and 8 additional rats that underwent scanning after induction of volume overload by aortic leaflet disruption. ECG-gated spin-echo pulse sequences were used to acquire a series of 1-mm thick modified short-axis images of the left ventricle. The area enclosed by the endocardial and epicardial borders of the left ventricle was multiplied by the interslice distance and specific gravity of myocardium to obtain calculated slice mass. Total LV mass was obtained by summing the individual slices. The calculated value for LV mass was then compared with the LV mass as determined at postmortem examination. Linear regression analysis showed an excellent correlation of MR-estimated mass (x) with autopsy-measured LV mass (y) (y = 0.90x + 65, r = 0.98). For this method intraobserved and interobserver slice correlations were 0.97 and 0.96, respectively. There was no significant difference in LV mass as determined from a series of diastolic vs. systolic images in a subset of six animals. Over a mean of 6.5 wk of observation, LV mass increased by 40% in the animals subjected to aortic leaflet disruption. These results demonstrate that MR imaging is highly accurate for the non-invasive in vivo assessment of LV mass in the adult rat.

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

“…It confirms a linear correlation between the muscle volumes determined by MRI and the directly determined muscle mass (r = 0·81). Figure 5A suggests a density of LV muscle of 0·94 (± 0·18) g cm¦Å from the slope of the linear regression (y = 0·94 (± 0·18)x + 0·20 (± 0·10) g), consistent with the value of 1·05 g cm¦Å reported previously (Manning et al 1990), with any differences in muscle density being the systematic result of tissue fixation. The latter caused tissue shrinkage and a consequent reduction in tissue mass in both the WKY and SHR.…”

“…Furthermore, the WKY and SHR had approximately the same range of body weights in this study, making a power law relationship unnecessary for showing the relative differences in LV myocardial volume. The LV myocardial volume could be converted to muscle mass by simply assuming a uniform specific gravity of 1·05 g cm¦Å (Manning et al 1990). End-diastolic and end-systolic luminal volumes of the left ventricle increased with age in both groups of rats (Table 1).…”

“…There has been increasing interest in the investigation of animal models of cardiac pathology in small mammals using MRI techniques in combination with conventional analytical and histological investigations (Manning et al 1990;Rudin et al 1991;Rose et al 1994;Laurent et al 1995;Rehwald et al 1997;Franco et al 1997;Lorenz et al 1997;Slawson et al 1997). Some of those studies examine functional parameters of the left ventricle; typically images are acquired in synchrony with the R wave of an electrocardiographic (ECG) signal.…”

Continuous Blockade of L-Type Ca2+ Channels Suppresses Activation of Calcineurin and Development of Cardiac Hypertrophy in Spontaneously Hypertensive Rats

“…MRI studies of rat LV mass were performed as described previously (18). Sodium pentobarbital (25 mg/kg) was used for general anesthesia during the MRI study.…”

Study of the Murine Cardiac Mechanical Function Using Magnetic Resonance Imaging: The Current Status, Challenges, and Future Perspectives

“…Correspondingly, technological advances and developments of novel hardware and pulse sequences were fairly limited, merely revolving on the scalability of existing technology to match smaller field-of-view acquisitions for mouse and rat imaging. Manning et al [Manning 1990] and Shapiro [Shapiro 1994] first reported cardiac MRI-based LV mass estimations, and Siri et al [Siri 1997] the first mouse cardiac imaging results from a 9.4 T system. Subsequent to such early studies were the first quantitative studies of function ] and myocardial mass in diseased mice post-hypertrophy induction using theadrenergic agonist isoproterenol (ISO) [Slawson 1998].…”