HEART ATTACK GRILL CARDIAC CORNER IS OUR TURF! Beat It, Heart Attack Shack

The famed Heart Attack Grill in Vegas is blowing a valve over a Tennessee burger joint ... claiming it's blatantly ripping off its death-on-a-plate theme.

The Grill is suing the Heart Attack Shack in Chattanooga for copying its name, its "Flatliner Fries" and even its logo with EKG waves. In the docs, the Grill says the Shack is purposely confusing consumers to make them think the restaurants are related ... and they're not.

According to the suit, the Shack has refused to change a damn thing ... even after the Grill fired off a threatening letter in February.

Now the Heart Attack Grill wants a judge to step in, and give the Heart Attack Shack a cardiac arrest. It also wants a slice of its profits