As grisly as this may seem, it was studies like this that allowed us to develop things such as the artificial heart.
And although some of it is no doubt fake, alot of it is real.
No one knows, is the problem. Nothing in the film nor any of the research claims can be verified as authentic. The experiments were really carried out, but met with very little success. Dog's heads were "revived" but only for a matter of minutes before they technically died again. The scientific consensus is that this movie is completely faked and exaggerated to show a degree of success that the real-life experiments never actually achieved.
This is real weird to me. I looked up all the terms but it didn't show up before. Maybe because I didn't type in dogs instead of dog and russia but not soviet. Anyway, it's still creepy as fuck.