Cardiac muscles
The muscles used to produce a heartbeat are called the "heart."
heart
Cardiac Muscle.
Heart muscles are involuntary.
The heart IS a muscle. If you're talking about skeletal muscles, then they are not all at the top of your heart (because what about your abdominal muscles, thigh muscles, calf muscles, etc?)
The Cardiac muscles are found in your heart.
heart muscles
The inflammation of the heart muscles. (Cardio = heart; myo = muscles; -itis = inflammation)
The intercostal muscles. Intercostal means "between ribs".
Heart muscles have their own category and are known as "cardiac muscles." The muscle layer of the heart is known as the "myometrium."
Papillary muscles are found in the heart's ventricles. They control the AV valves.
Your hands have voluntary muscles and your heart is an involuntary muscle.