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Published on: October 26, 2017
Cine-MRI assessment of cardiac function in mice anesthetized with ketamine/xylazine and isoflurane
F Kober1, I Iltis, P J Cozzone
1Centre de Résonance Magnétique Biologique et Médicale, Faculté de Médecine, 27 Bd Jean Moulin, 13005, Marseille, France. frank.kober@medecine.univ-mrs.fr
Abstract:
Since small-animal MRI generally requires anesthesia, the effect of the anesthetic regimen on the explored organ(s) has to be taken into account for study interpretation. In this work, we assess the influence of ketamine/xylazine and isoflurane anesthesia on left-ventricular (LV) function in the mouse in vivo by cine-MRI. Three groups of animals were anesthetized with ketamine/xylazine (n = 13) and two different concentrations of isoflurane (1.25%, n = 12 and 2.00%, n = 12) delivered in O2/N2O mix. Long- and short-axis cine-MRI was performed to measure end-diastolic volume, stroke volume, ejection fraction and LV wall thickness. Ketamine/xylazine significantly reduced heart rate, cardiac output and wall thickness, but increased stroke volume and end-diastolic volume compared with both isoflurane groups. No differences across all groups were observed in ejection fraction or systolic wall thickening. Breath rate under isoflurane was significantly lower and concentration dependent, whereas heart function was independent of concentration in all measured parameters. These findings are in agreement with echocardiography and catheterization studies. Isoflurane is advantageous for MR studies because it better maintains cardiac function. Taking into account previously obtained myocardial perfusion measurements, isoflurane concentration should, however, be maintained at the minimum required for a stable sleep even if cardiac function is unaffected by higher isoflurane concentrations.
Insights
Anesthesia impacts small animal MRI studies. Isoflurane better preserves mouse left-ventricular function compared to ketamine/xylazine, making it preferable for cardiac MRI research.
Area of Science:
- Cardiovascular Research
- Medical Imaging
- Anesthesiology
Background:
- Anesthesia is crucial for small-animal MRI but can affect physiological measurements.
- Understanding anesthetic effects on cardiac function is vital for accurate in vivo MRI interpretation.
Purpose of the Study:
- To compare the effects of ketamine/xylazine and isoflurane anesthesia on left-ventricular (LV) function in mice using cine-MRI.
- To determine the optimal anesthetic regimen for preserving cardiac function during small-animal MRI.
Main Methods:
- Mice were anesthetized with ketamine/xylazine or two concentrations of isoflurane (1.25%, 2.00%).
- Cine-MRI was used to measure LV end-diastolic volume, stroke volume, ejection fraction, and wall thickness.
- Physiological parameters including heart rate and breath rate were monitored.
Main Results:
- Ketamine/xylazine significantly reduced heart rate and cardiac output, while increasing end-diastolic and stroke volumes compared to isoflurane.
- Left-ventricular ejection fraction and systolic wall thickening were not significantly different across anesthetic groups.
- Isoflurane anesthesia maintained cardiac function independently of concentration, though breath rate was concentration-dependent.
Conclusions:
- Isoflurane is advantageous for cardiac MRI studies in mice due to its better preservation of left-ventricular function.
- While higher isoflurane concentrations did not affect cardiac function, the minimum effective concentration is recommended for concurrent myocardial perfusion studies.
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