The Heart: A Flesh and Blood Examination

September 18, 2014 | Posted in: Science

Two views of an ox's heart, Da Vinci, 1513. This was the first anatomically accurate illustration of a heart.

Two views of a heart, Leonardo Da Vinci, 1513. The first known heart drawn as we would anatomically recognize it today.

“Let us contemplate, you and I, the bloody electric muscle. Let us consider it from every angle. Let us remove it from its bony cage, its gristly case, and hold it to the merciless light, and turn it glinting this way and that, and look at it as if we have never seen it before, because we never have seen it before, not like this… Let us consider it as the most crucial and amazing house, with its four rooms and meticulous plumbing and protein walls and chambered music.”
Brian Doyle, The Wet Engine

 

In my first post on the heart we explored the figurative ways we humans understand our hearts: as the wellspring of love, the seat of the soul, the realm of knowing and wisdom beyond the rational mind. But what of the physical properties of the heart? Truly the palpable, bloody, muscular mass of our heart is wondrous in its own right, no flights of fancy needed. So, this post will be a more somatic examination (indeed, we could say it’s not for the faint of heart), the chance to face the corporeal side of our hearts and understand better how on earth this fleshy pumping organ does its necessary work.

“[The average adult human heart] weighs eleven ounces. It feeds a vascular system that comprises sixty thousand miles of veins and arteries and capillaries. It beats a hundred thousand times a day. It shoves two thousand gallons of blood through the body every day. It begins when a fetus is three weeks old and a cluster of cells begins to pulse with the cadence of that particular person, a music and rhythm and pace that will endure a whole lifetime.” Doyle

The heart is a hollow muscle separated into four chambers, all engaged in an endless dance of inflating and deflating. When a new life is taking shape in its mother’s womb, the heart is the very first organ to develop, beginning as the size of a pin head. It grows as we grow, from infancy to adulthood, until it reaches about the measure of a clenched fist. In utero, the mother provides the blood needed to bathe and oxygenate this new-forming life, and our mother’s heartbeat is the first music we all hear, soon followed by our own. This beating, caused by the powerful contraction and expansion of the muscles of the heart, is responsible for the crucial circulation of oxygenated blood through the entirety of our bodies, for the entirety of our lives.

And the journey of our blood through the sixty thousand miles of rivers and streams that make up our body’s circulatory system is on average completed within a single minute: 60,000 miles in 60 seconds! The entire circumference of the earth is just under 25,000 miles, meaning that if you took all the arteries, capillaries, and veins in your body and lined them up end to end they would stretch around the earth twice and then some. All of this incredible distance and speed beautifully nested within the small fleshy confines of your body.

Human blood. Photo-micrographs created by Arthur E Smith, featured in Nature Through Microscope & Camera (1909) by Richard Kerr.

Human blood magnified 1000x. Photo-micrograph created by Arthur E Smith, featured in Nature Through Microscope & Camera (1909) by Richard Kerr.

The odyssey of the blood cells that travel these epic rivers of arteries and veins deserve a poet to sing their praises, and Brian Doyle is just the man:

“[B]lood that has been plucked and shucked of its oxygen by the body straggles back into the right atrium, the capacious gleaming lobby of the heart. This tired blood, dusty veteran of an immense and exhausting journey, shuffles forward to and through a small circular door in the wall, a door with three symmetrical flaps: the tricuspid valve. This circular door opens into another big room, the right ventricle; but at the very instant the right ventricle is filled to capacity with tired blood the entire ventricle contracts! slamming in on itself, and our tired heroes are sent flying through the pulmonary valve and thence into the pulmonary artery, which immediately branches, carrying the blood to the right and left lungs, and there, in the joyous airy countries of the blood vessels of the lungs, your blood is given fresh clean joyous oxygen… as much as those heroic blood cells can hoist aboard their tiny cellular ships, and now they resume their endless journey… carrying your necessary elixir back to the looming holy castle of the heart, which they will enter this time through the left atrium, whose job is to disperse and assign the blood to the rest of the body, to send it on its quest and voyage and journey to the vast and mysterious wilderness that is You…”

The heart contracts and releases, contracts and releases, keeping our blood cells flowing on their endless oxygen-bestowing journey, faster or slower depending on our level of physical exuberance.  The heart’s architecture comes with special cardiac cells in its fleshy walls that relay electrical signals to keep the muscular contractions of the heart in time with the needs of the body. This electrical system is known as the cardiac conduction system, and it’s what an EKG (that beeping-graph-making-machine present in every hospital show ever) measures to give us information on the workings (or failings) of the heart. This biological electrical system is what creates the heart’s electromagnetic field, which is 5,000 times stronger than the field created by the activities of the brain.

For most of human history, our hearts were so strongly linked to the belief in the soul that it was seen as sacrilegious to cut them open, even in an effort to discover their inner workings. Even more heinous was the idea of taking the heart of one human and placing it in the body of another. This ultimate taboo persisted right up until December 3, 1967 when doctor Christiaan Barnard performed the very first human heart transplant. His country of South Africa had no laws barring the procedure (unlike nearly every other country at the time) and Barnard was eager to transition from practicing heart transplants on dogs to humans (disturbingly, the history of this medical procedure, like most others, is rife with victims).

Who was the willing patient to undergo a procedure never tried on a human before? Why, a man with nothing to lose of course. His name was Louis Washkansky, who at the age of 53 had for seven years suffered from incurable heart disease and diabetes, and who, at the time of the operation, had a heart that could only offer him a few more weeks worth of beats. The donor was a young woman who was rendered brain-dead when struck by a vehicle in Cape Town the day before: Denise Darvall, whose father consented to have her still healthy heart given a new body, a second chance to render life.

La Autopsia, Enrique Simonet, 1890.

La Autopsia, Enrique Simonet, 1890.

Barnard had this to say when he cut open the chest of Washkansky and gazed down on his ruined heart:

“Louis Washkansky’s heart came into full view—rolling in a rhythm of its own like a separate and angry sea, yellow from the storms of half a century, yet streaked with blue currents from its depths—blue veins drifting across the heaving waste and ruin of a ravaged heart… The split chest-cage hung open, motionless as a sundered rock. Separate and alone within the hush of its dark cavity, the great heart twisted on itself as though seeking some exit, only to return with a sudden shudder as the left ventricle once more—how many millions times had it happened?—sought to expel its own private lake of blood, its scarred and ruined muscles closing in a sudden spasm, then collapsing in a moment of exhaustion, a moment seized by the upper atrium to send down still more blood into the unemptied lake below where the life of Louis Washkansky lay trapped, beyond the reach of knife or prayer. So it went, rolling and heaving, one beat after another, like a boxer about to collapse in the ring, fighting on, throwing out punches without strength . . . we had arrived in time to see . . . the dying of a fighting heart.”
Excerpt from The Book of the Heart, Louisa Young

Aided by his brother, Barnard switched the battered heart of the aged man with the sprightly heart of the deceased young woman. In a transplant, once the healthy heart is secured in its new chest, it “rises back to life like bread rising, like a soufflé coming up, like a sea creature, a jellyfish ballooning as it pulses through the ocean. It fills up with life, heat, blood—and then it kicks off into its ancient, eternal rhythm: ba-dum, ba-dum, rolling in its cave…” (Young). The cardiac conduction system self-starts the heart, and indeed the brain and all the rest of the body are only bystanders as the heart begins once more to conduct its own rhythm.

Washkansky’s new heart bought him eighteen days, and then he succumbed to pneumonia. But the transplant had worked, and in the following year a hundred more hearts were moved from one chest cavity to another, with two-thirds of these recipients dying within three months. Many of the deaths were caused by the immune system rejecting the new heart, but doctors persisted and in the 1980’s the immunosuppressant ciclosporin was developed, increasing the number of successful transplants.

Woodcut of the heart, by Aoki Shukuya, from the early Japanese anatomical atlas Kaishi Hen (Analysis of Cadavers), 1772.

Woodcut of the heart, by Aoki Shukuya, from the early Japanese anatomical atlas Kaishi Hen (Analysis of Cadavers), 1772.

Even after heart transplants were shown to be moderately successful, the taboo of treating the human heart as simply an organ to swap out for another was so strong that many countries took decades before allowing the procedures. Japan took until 1997 to legalize heart transplants. Medically, this surgery is only done as an absolute last resort: the risks are still great and the rewards only worth it for those who’re otherwise in near perfect health. Today, about 85% of those who undergo heart transplants live over a year post-surgery, and 65% now live over five years.

As the number of successful transplants has grown, more people are experiencing a literal change of heart and living with the daily aftereffects. And since we are dealing with the heart, an organ ever torn between our understanding of its carnal workings and the figurative qualities we intuitively associate with it, things can get a little weird. More on this in our final post on the wonders of the heart.

The following books informed this post:
The Wet Engine, Brian Doyle
The Book of the Heart, Louisa Young

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