Butter one side of each slice of bread. On the non-butter side spread Russian dressing on each slice. Top with a slice of Swiss cheese, corned and smoked heart, sauerkraut, another slice of Swiss cheese, and finally more Russian dressing. Top with another slice of rye bread.
Heat a medium skillet over medium heat. Place a sandwich in a skillet and cook until golden and cheese is melted, 3 minutes per side.
For the Russian dressing
In a medium bowl, whisk together mayonnaise, ketchup, horseradish, Worcestershire, sugar, and paprika until combined. Season with salt and pepper.