I have tried isolating ventricular cardiomyocyte by perfusing type II collagenase through adult mice hearts. When looking at the extracted cells under 20X magnification, I don't see the typical rod-shaped cardiomyocytes I was expecting. Instead I seem to have multiple rounder debris. Was I able to extract the myocytes, but they got damaged during the isolation or am I looking at totally different kinds of cells ?

I know immunostaining would be the way to test, however I do not have the reagents on hand.