Objectives The in vivo murine models of myocardial infarction (MI) and ischaemia/reperfusion (I/R) are widely used in research of coronary heart diseases. Comparison of infarct size (IS) is an important indicator of assessment of heart injury. However, the impact of vascular patterning of the coronary system on IS in post-MI mice has been rarely systematically investigated.

Methods We displayed left coronary artery (LCA) in the hearts of C57BL/6J mice by air embolism and operated the left anterior descending coronary artery (LAD) ligation at 1-2 mm from the edge of left atrium under stereomicroscope. IS and cardiac function were analysed by Evans blue-2,3,5-triphenyl tetrazolium chloride (TTC) double staining and echocardiography, respectively.

Results In this study, C57BL/6J mice exhibited remarkable variations in LAD anatomy, including multiple branches and length. Moreover, difference of IS and cardiac function between individuals has been observed.

Conclusions This study demonstrated difference of LAD patterning widely presents between individuals of C57BL/6J mice and directly affects post-MI IS and cardiac function. These findings suggest stereomicroscope with high resolution and accurate location should be used in surgical operation of MI and I/R models, and the earlier evaluation by echocardiography is necessary after ligation and/or before interference.