Foolish Heart, Hagfish Hearts

  He had chest pressure. Not that bad, really, he told himself; just an aching, burning feeling which went up into his throat. Something he ate. When the pain worsened, he went into the kitchen and told his wife. She could see he was very ill, but he didn't want her to call an ambulance. He will drive, he said. They drove to the hospital and she asked him to pull up by the front door. We will park in the parking lot, he said. He refused a wheelchair and walked to the emergency room, where they told him he was having a massive heart attack. When he recovered, he went home and continued working around the house as usual, fixing the steps, doing cement work, shoveling snow. He continued to smoke two packs of cigarettes a day. It took him only ten weeks to die.

An old surgeon once told me that the human heart is foolish; born upside down (it folds and partly reverses direction in fetal development) it works constantly and eats poorly (the two coronary arteries are small and susceptible to the blockage which can cause heart attacks).

Since then I have met many hearts. Hearts with frozen aortic valves which blocked blood flow to the body when the left ventricle contracted; hearts with regurgitant mitral valves which let the blood back up into the left atrium with each beat. Heart muscles weakened by multiple heart attacks, by complete clogging of clumsy arteries more fit to supply rib muscle than the muscle.

Our song-poems speak of our heart's foolishness. We lose it, leave it break it, have a total eclipse of it, etc., etc. We know we live only because of a single warm, beating heart, which reminds us of itself when we feel our pulse or put our hand on our chest.

Because of the precocity of our heart, the human egg needs little yolk. The cardiovascular system is the first organ system to function in the embryo, bringing nutrients from the mother's placenta and carrying back waste products. At 18 days a group of cells form a pair of long strands called heart cords. These become tubes and fuse to form a single tube. Then the tube dilates, bends to the right and upward, and the ventricles and atria form via delicately orchestrated partitioning of membranes and programmed cell death. Some cells become muscle, others nerve. The nervous system of the human heart is intricate. The development of the cardiovascular system is nearly complete by the end of the seventh week.

If the heart tube bends to the left instead of the right, the heart will end up on the right side of the chest instead of the left. Such a heart often functions normally, despite being both foolish and backward.

I was angry about our foolish heart until I began studying other hearts. In all creatures, the size of the heart is proportional to body mass, and usually the smaller the heart, the faster the heartbeat: in one minute an elephant heart beats 25 times, the human heart beats 70 times, the shrew heart beats 600 times. One of the most primitive vertebrates, the hagfish, has four types of hearts.

The hagfish is a sea lamprey, an eel-shaped, funnel-mouthed creature that eats live or dead fish. It is still seeking an efficient method of reproduction: while young it is hermaphroditic; when it grows older it is male; in old age, when it grows longer than thirteen inches, it is a female. The huge-yolked eggs of the hagfish are found in lonely clusters of 10-20 on the deep ocean floor, especially around the continental shelf. Hagfish require a soft, salty mud bottom and live in volcano-like mounds.

The circulatory system of the hagfish is a combination of closed and open blood vessels. Its heart system is the most primitive of all vertebrates. It has a regular heart (the brachial heart) and three types of accessory hearts; the portal heart which carries blood from intestines to liver; the cardinal heart which transports blood from the head to the body, and the caudal heart which moves blood from the trunk and kidneys to the body.

The caudal hearts are particularly unique; they each have two muscles attached to a stiff piece of cartilage that separates the heart into two chambers. When the muscle on one side flexes the cartilage that way, the chamber on that side fills and the other side empties and vice versa. By alternating contractions, the cold, salty hagfish blood is pumped from the tail and kidneys back toward the body cavity. None of the hagfish hearts have any nerve activity; they are isolated muscle.

At first thought it seems a wonderful arrangement. With all these hearts beating in concert, the hagfish needn't worry about the vulnerability of a single heart. There are four types of hearts to do the work. Little hagfish husbands can muck happily about the sea bottom, ignoring a mere single failing heart; and hagfish wives need never haggle them.

Perhaps our heart transplantation techniques will eventually give us efficient accessory hearts. Until then we each have one beautiful heart. There is no need to be angry at it; if we but listen it will tell us when it is hurt. Other times, through the nerve connections that increase its rate, it tells us when we are thrilled with deep emotion, when we sense an event of great meaning, when we love. It is not foolish. We dance, it keeps the beat, we can then dance on.

The song-poets lie. The hagfish hearts are cold, primitive, nerveless sexually ambivalent. The old surgeon speaks only in generalities. Our heart isn't perfect, but it has been singly intent on one purpose, warm and true, since we were embryos.

We apologize, heart. Keep up the good work. Don't stop now.

David Schiedermayer, MD
former Professor of Medicine
Division of General Internal Medicine
Medical College of Wisconsin

"Reflections" is a collection of essays by the health professionals of the Medical College of Wisconsin.