Cut beef heart into 1-inch chunks while partially frozen (this makes grinding easier). Grind into a medium bowl. You can also reduce the heart pieces in a food processor. Pulse in very short bursts, checking every two pulses for consistency. Scrape down the processor bowl between pulses. Do not over process.
Add ground beef and with two forks toss together with ground heart combining the two. Form into 4-ounce patties.
To cook on the stove: heat cast iron or other skillet on medium high heat until hot. Sprinkle surface of skillet with generous dusting of salt. Add patties and cook for two minutes. Turn the patties over and cook for two minutes. Turn patties again and cook for two minutes. Check temperature with instant read thermometer, inserting the tip of the thermometer horizontally through the patties: 125 degrees for medium rare, 130 for medium and 135 to 140 for medium well. Continue cooking until desired temperature is reached. Serve with toppings of your choice.