Differences between cardiac myocytes and fibroblasts - Unsure of how to tell the difference (Mar/01/2005 )

Hi Everyone,
I was wondering if anyone knows of a definitive way to tell the difference between myocytes and fibroblasts in neonatal rat cultures. I know that beating is a hallmark of course, but I was wondering if there are other indications.

Thanks

Cardiomyocyte you can stain with anti-desmin antibody
Fibroblasts are vimentin-positive
Use immunochemistry or fluorescence