A work-performing heart preparation for myocardial performance analysis in murine hearts

The mouse has become the animal of choice for genetic manipulations resulting in altered myocardial function, but assessment of cardiac function is extremely difficult due to the animal's size. This study was designed to establish a work-performing isolated mouse heart preparation to objectively investigate myocardial performance in murine hearts. Isolated work-performing cardiac functional studies were performed on a modified Langendorff apparatus using 15 mice [25 to 28 g, +/-0.4 (SEM)]. The hearts were instrumented with a transonic flow meter and micromanometers to measure on-line aortic flow (AF), aortic pressure, and left atrial pressure (preload). A VAX cardiac function analyzing system was used to determine cardiac parameters including heart rate, contractility (max dP/dt), stroke volume (SV), and stroke work (SW) at various preload levels compared to a baseline preload of 5 mm Hg before and after 7 min of warm ischemia. AF increased from 1.01 ml/min (+/- 0.26) at 5 mm Hg of preload to 4.15 ml/min (+/- 1.03, P < 0.05) at 20 mm Hg of preload and decreased to 3.64 ml/min (+/- 0.62) at 25 mm Hg. SV, dP/dt, and SW increased with higher preload levels. There was a significant decrease in cardiac function postischemia.

A valid isolated work-performing preload-dependent murine heart preparation involving minimal instrumentation of the heart is established to measure cardiac function and myocardial performance. Significant ischemia-reperfusion injury occurred after 7 min of ischemia. This model is a reliable and objective tool by which to evaluate murine cardiac function and to study ischemia-reperfusion injury.