Re: Could a person get a 'cramp' in their heart/cardiac muscle?

Hi John,

As such there is no indication that the heart muscle can suffer a "cramp" in the true sense of the word. A cramp in skeletal muscles is due to imbalance between supply of fresh blood and calcium metabolism. When the demand on a skeltal muscle exceeds its blood supply a cramp can occur. Also cramps can occur in the face of normal blood supply if the calcium metabolism is so altered that the supply of calium to muscle fibers is low.

Now cardiac (heart) muscle is different in that it has a much more extensive blood supply per gram of heart muscle. As such, when there is no narrowing of heart (coronary) arteries, as in normal individuals, it is virtually impossible to cramp the heart muscle. However, when coronary arteries begin to narrow, and this narrowing reaches a critical point (> 70 % narrowing of the vessel's lumen) then it is relatively easy to over come the blood supply of the heart in even normal stress conditions. This leads to pain in the heart muscle which we call angina, and can lead to malfunction of the heart muscle, which we call heart attack. When the blood supply is so low that the heart muscle can not live the muscle tissue dies, leading to scar formation, and is never replaced by the human body. In contrast, skeletal muscle can be rebuilt to some extent after damage.

So the true cramp does not occur in heart muscle - where the muscle goes into a constant contraction. Remember heart muscle is not only a muscle but also an electrical conductive tissue. Electrical imbalances also accompany the blood deficieny and can cause aberrant electrical conduction which can mimic cramps, but they are again not true cramps.