The Oldie: Profitable Wonders – December 2009
The Heart
For the Reverend William Paley of ‘Natural Theology’ fame, the mechanics of the living world exhibited ‘every indication of contrivance, every manifestation of design’—which when compared to man’s much humbler efforts (and here Paley cited the complex interdependent components of a watch)’is greater and more to a degree that exceeds all computation’.
At the time it seemed a knock down argument, and indeed there was something exhilarating about living in a world where every aspect of nature spoke of God’s ‘wonder and providence’. But the more that science progressed in describing in ever greater detail the physiological and anatomical aspects of (for example) the eye, the less convincing became Paley’s suggestion that it ‘alone would be sufficient to support the conclusion … as to the necessity of an intelligence creator’. It seemed an absurdity, demeaning indeed, to suppose that He had nothing better to do than concern himself with the minutiae of designing the nuts and bolts of tens of thousands of species,both living and long since extinct. And anyhow who was to tell what the technical advances of the future might bring—and Paley could scarcely have anticipated microelectronics and the silicon chip—that might permit man to equal, or indeed surpass, the Grand Designer’s best efforts?
This latter proposition has recently, and interestingly, been put to the test with the research programme to develop an artificial heart whose (relatively) simple pumping mechanism is no different in principle from the ubiquitous electric pump that powers the household shower.
To be sure, the human heart is a lot more powerful. No bigger than an orange and weighing little more than a pound it generates enough force to propel the body’s five litres of blood through the pipeline of arteries and veins that stretched end to end would stretch from Paris to Moscow—fifteen hundred miles in all. The human heart is also ‘highly efficient’ in the technical sense of performing twice as much ‘work’ in relation to the amount of fuel utilised as any conventional man-made pump. This is due in part to the unique arrangement of the overlying spirals of its muscle fibres which become progressively shorter as they taper down to the tip (in the same way that a number of bricks in each row of a cathedral spire gradually diminished as it tapers upwards), thus squeezing every last drop of blood out of the cavity of the ventricles at each heart beat. And for good measure this masterpiece of engineering efficiency should, with luck, run for the two and a half thousand million cycles of a lifetime without maintenance or lubrication, or the need to replace its four sets of valves which open and close four thousand times every hour.
Starting in the 1960s, the early pioneers of the artificial heart anticipated some difficulty in matching these specifications, but it still took twenty years to come up with the first workable device. This was implanted into a retired American dentist who went on to develop respiratory and kidney failure and blood poisoning before dying four months later. Over the next few years a similar fate befell a further two hundred patients before the American Food and Drug Authority intervened and called a halt.
By now it was clear the task was hopeless—but perhaps it was suggested it might be possible to achieve a compromise with an artificial heart that could act as a stopgap measure. And after forty years and billions of dollars that, it seems, is as far as we are likely to get. The current model weighs twice as much and is a fraction as efficient as nature’s version, its energy supply transmitted through a couple of tubes connected to a console the size of a chest of drawers which can only be moved around on rollers. This clumsy device can sustain the patient for up to two months in hospital until a transplant of nature’s much better version becomes available—that can keep its recipient fit and healthy, climbing mountains or deep sea diving, for twenty years or more.
The pump-like mechanism of the heart is much the simplest of physiological systems, simpler by far than the complexities of brain or kidney or the sense organs such as the eye—that so excited the Reverend Paley’s admiration. So when, as here, the purposeful efforts of today’s bioengineers, employing the most sophisticated medical technology, falls so far short of nature’s model, one can only profitably wonder at what prodigious biological phenomenon—as yet unknown to science— ensures the nuts and bolts of life are indeed constructed to the very highest specifications of automated efficiency.