It would be easier to count the cells using higher magnification, and possibly easier on bright-field optics, either of which may make it easier to distinguish the live from the dead cells and cell fragments. 

I counted two of the 9 large squares and found about 66 live cells in one and about 80 in the other, so somewhere around 7.8 x 105 live cells/ml.  But that is quite tentative at this low magnification. On phase contrast the live cells have a bright ring round them while the dead cells look more like dark shadows, and the fragments look the same as dead cells only smaller.  Likewise on bright-field the dead cells look like shadows, fainter than the live ones.

Thanks for the reply - it is true that it is easier to verify life cells and remove the debris from the calculation. In microscopy I prefer fluorescence method using acridine orange (AO) and propidium iodide (PI). In this case I am curious to find out how many cell counts each one, knowing using the same instruments - as many songs as many dances / Many men, many minds /So many countries, so many customs.

If you use ImageJ you can see a big panoramic image at high resolution. It was stitched from 9 image stacks, arranged with ImageJ/Fiji plugin. I used phase contrast objective 10x /0.30 Ph1 DLL and the picture is little big [1.7Mg]. 

Thanks for that.  ResearchID does not allow very much zoom, but  following your comment I can see that more resolution is possible by downloading the image and viewing it with more zoom (eg in Photoshop). 

Yes, there are various stains for dead/damaged cells, including Trypan blue (which one can view with bright-field optics, often more convenient than fluorescence) , and that might give you the best accuracy if your suspensions often have a lot of dead cells like this.  Do you expect all the cells to be cardiomyocytes here, or may there also be other cells present?  I could imagine that the elongated cells are cardiomyocytes, with a lot of actin and myosin giving a degree of stiffness of shape.

The cells come from primary cultures of neonatal mouse hearts, dissociated using Worthington Isolation System kit and the cardiomyocyte was purified using magnetic Neonatal Cardiomyocyte Isolation Kit from Milteny. This means that are no fibroblast cells there. Elongated cells are adult cardiomyocytes. Because are very young cells (pet age 3 days) those that are small are also young CM, that means they are beating in petri dishes (tromponin +, gata4 +, etc) also few stem cells ( i.e. sca -1+).