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High-resolution magnetic resonance cine imaging (cine-MRI) is a method that allows for a non-invasive assessment of left ventricular function and mass. To perform this quantitation, hearts are imaged from the base to the apex by a stack of two-dimensional images. Thus, analysis of myocardial mass and function by cine-MRI does not rely on geometric assumptions. Geometric and functional parameters, such as end-diastolic volume (EDV), end-systolic volume (ESV) or ejection fraction (EF), are obtained by subsequent image segmentation of the respective cine frames in each slice. While this technique has been well established in clinical practice, it is now rapidly becoming the reference method in experimental cardiovascular MRI for accurate quantification of cardiac parameters, thereby aiding the phenotyping of the increasing number of transgenic and surgical mouse models. However, accurate measurement of cardiac functional parameters requires the images to be acquired in short-axis orientation of the heart, which can be difficult to define, particularly in animals with diseased hearts. Furthermore, data analysis can be the source of a systematic error, mainly for myocardial mass measurement. Here, we describe a protocol that allows for a quick and reproducible approach of obtaining the relevant cardiac views for cine-MRI, and we explain how an accurate experimental image analysis can be performed.

High resolution magnetic resonance (MR) imaging is uniquely suited for cardiovascular phenotype characterization in transgenic mice. Experimental MR scanners with the high magnetic field strength are commonly built with a vertical bore design. The hemodynamic consequences of a prolonged upright body position in anesthetized mice are, however, unknown. Thus, the purpose of this work was to investigate the influence of a vertical body position on murine systemic blood pressure and left ventricular (LV) hemodynamics over time. We studied six C57Bl/6 mice at 14-16 weeks of age (body weight, 24-28 g) under isoflurane anesthesia. Positioned supine on a 37 degrees C warming pad, a microtip catheter was advanced via the right carotid artery into the left ventricle. Continuous registration of LV hemodynamics was performed at rest and after tilting of the table to a 90-degree vertical position. After tilting, there was a transient decrease of LV systolic pressure to 96% of initial values immediately after tilting with return to baseline level within 6 min. Tilting to vertical position had no influence on LV end-diastolic pressure, heart rate, maximal rate of left ventricular pressure increase, and maximal rate of left ventricular pressure decrease. Over a follow-up period of 60 min in vertical position, there were no significant changes in murine hemodynamics. An acute change of body position is fully compensated by a normal orthostatic response in anesthetized mice. Prolonged upright body position exerts no significant changes in murine LV hemodynamics. Hence, high resolution MR studies for cardiovascular phenotype characterization in transgenic mice performed on vertical bore MR scanners allow measurements under physiologic conditions.