A WORK-PERFORMING HEART PREPARATION FOR MYOCARDIAL PERFORMANCE ANALYSIS IN MURINE HEARTS

The mouse has become the animal of choice for genetic manipulations re sulting in altered myocardial function, but assessment of cardiac func tion is extremely difficult due to the animal's size. This study was d esigned to establish a work-performing isolated mouse heart preparatio n 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 (SE M)]. The hearts were instrumented with a transonic flow meter and micr omanometers to measure on-line aortic flow (AF), aortic pressure, and left atrial pressure (preload). A VAX cardiac function analyzing syste m was used to determine cardiac parameters including heart rate, contr actility (max dP/dt), stroke volume (SV), and stroke work (SW) at vari ous preload levels compared to a baseline preload of 5 mm Hg before an d 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 signific ant decrease in cardiac function postischemia. Conclusions: A valid is olated work-performing preload-dependent murine heart preparation invo lving minimal instrumentation of the heart is established to measure c ardiac function and myocardial performance. Significant ischemia-reper fusion injury occurred after 7 min of ischemia. This model is a reliab le and objective tool by which to evaluate murine cardiac function and to study ischemia-reperfusion injury. (C) 1996 Academic Press, Inc.