No one could say I'm a beauty. I weigh 340 grams, am red brown in colour, and have an unimpressive shape. I am John's dedicated slave- his heart.
I hang by ligaments in the centre of his chest. I am about 15 cm long and, at my widest point, ten cm across- more pear-shaped than valentine. Whatever you may have heard about me from poets, I am not a very romantic character. I am just a hardworking four-chambered pump- actually two pumps, one to move blood to the lungs, the other to push it out into the body. Every day I pump blood through about 96,000 km of blood vessels. That's enough pumping to fill an 18,000 litre tank.
When John thinks of me at all, he thinks of me as fragile and delicate. Delicate! When up to now I have pumped more than 300000 tons of his blood? I work twice as hard as the arm muscles of a heavy weight boxing champion or the leg muscles of a sprinter. Let them try to go at my pace and they would turn to jelly in minutes. No muscles in the body are as strong as I am except those of a woman's uterus as she gives birth. But uterine muscles don't keep at it day and night for 70 years, as I am expected to do.
That, of course, is a slight exaggeration. I do rest between beats,. It takes about three-tenths of a second for my left ventricle to contract and push blood out into the body. Then I have a rest period of half a second. Also, while John sleeps, a large percentage of his capillaries are inactive so, as I don't push blood through them, my beat slows from a normal 72 a minute down to 55.
John hardly ever thinks of me- which is good. I don't want him to become one of those heart neurotics and worry us both into real trouble. When he does worry about me, it is nearly always about the wrong things. One night, as he was drifting off to sleep, John suddenly thought I'd 'skipped' a beat. He was quite worried was I giving out on him? He needn't have been concerned.
From time to time, my ignition system gets momentarily out of tune- just like the ignition system on John's car. I generate my own electricity, and sent out impulses to trigger contraction. But occasionally I will misfire, piling one beat on top of another. It sounds as if I have 'skipped'- but I haven't. John would be surprised how often this happens without him knowing.
Rev Counting. After a nightmare, he sometimes wakes up and worries because I am racing. That's because when he runs in his dreams, I run too. John's worries actually aggravate things- make me go still faster. If he would calm down, so would I. But if he can't, there is a way to slow me down. The vagus nerves act as a brake. They pass up through the neck- behind the ears, at the hinge of the jaw. Gentle massage here will slow my beat.
John blames almost everything on me- from fatigue to dizzy spells. But I have little to do with his fatigue, and his occasional dizzy spells usually trace back to his ears. From time to time he will be sitting at his desk working and will get a sharp pain in the chest. He fears that he is about to have a heart attack. He needn't worry. That pain comes from his digestive tract- payment for the heavy meal eaten a couple of hours earlier. When I am in trouble, I usually send out a pain signal only after undue exertion or emotion. That's the way I tell him I am not getting enough nourishment to cope with the work he is loading on to me.
When I had saved enough money with which to reach Hampton, I thanked the captain of the vessel for his kindness, and started again. Without any unusual occurrence I reached Hampton, with a surplus of exactly fifty cents with which to begin my education. The first sight of the large, three-story brick school building seemed to have rewarded me for all that I had undergone in order to reach the place. The sight of it seemed to give me new life.
How do I get my nourishment? From the blood, of course. But, although I represent only a two-hundredth part of the body weight, I require about one- twentieth of the blood-supply. That means I consume about ten times the nourishment required by the body's other organs and tissues.
But I don't extract nourishment from the blood passing through my four chambers. I am fed by my own two coronary arteries- little branching 'trees' with trunks not much thicker than drinking straws. This is my weak spot. Trouble here is the greatest single cause of death.
It occurred to me at once that here was my chance. Never did I receive an order with more delight.
No one knows how it happens, but early in life- sometimes even at birth- fatty deposits begin to build up in the coronary arteries. Gradually, then can close an artery. Or a clot may form to close it suddenly.
When an artery becomes blocked, the portion of the heart muscle it feeds, dies. This leaves scar tissue- it may be no larger than a small marble, but it can be half the size of tennis ball. How serious the trouble is depends on the size and position of the plugged artery.
John had a heart attack five years ago and didn't even know it. He was too busy to notice that tiny twinge of pain in his chest. The artery that clogged was a small one on my rear wall. It took me two weeks to sweep away the dead tissue and repave the area with a scar not much larger than a pea.
John comes from a family where heart disease has occurred often, so statistics say that I am going to give him trouble too. Of course, he can't do anything about heredity But he can do a lot to minimize risk.
Let's start with overweight. John jokes about his middle-age spread, but it's no laughing matter. Every kilo of excess fat contains some 700 kilometres of capillaries through which I have to push blood, in addition to the work of carrying around each extra kilo.
That brings me to John's blood-pressure. It's 140/90- the upper limit of normal for his age. The 140 measures the pressure I work against while contracting, and the 90 is the pressure while I am resting between beats. The lower figure is the more important. The higher that figure rises, the less rest I get. And without adequate rest a heart simply works itself to death.
There are a lot of things John could do to get his blood- pressure down to safer levels . The first is to get rid of excess weight. He would be surprised at the drop in blood-pressure that would follow.
Smoking is another thing. John smokes 40 cigarettes a day which means he may be absorbing quite an amount of nicotine every 24 hours. This is pretty violent stuff. It constricts arteries particularly in the hands and feet- which raises the pressure against which I must work. It also stimulates me so that I beat more rapidly; a cigarette increases my beat from a normal 72 into the 80's. John tells himself that it is too late to give up smoking- that the damage is done . But, if he could get rid of constant nicotine stimulation, things would be easier for me.
Strife at the Top. John could help me in other ways, too. He is competitive, ambitious- the successful businessman type. He doesn't realize that his constant fretting continually stimulates his adrenal glands to produce more adrenalin and noradrenalin. This has same results as nicotine; tightened arteries, higher blood-pressure, a faster pace for me.
The point is this: if John relaxes, I relax. An occasional nap would help. And he might try some light reading instead of that stuff he brings home from the office.
Exercise is another thing. John is one of those weekend athletes- who take it in big doses. He still likes that rushing up-to-the net bit in tennis: but when he does this, my normal work load is increased by five.