Before​ stethoscopes were invented, physicians would listen to their patients’ hearts by laying one ear directly onto the skin of the chest. We’re accustomed to laying our heads against the breasts of our lovers, our parents or our children, but once or twice when I’ve rushed out on an urgent house call, leaving my stethoscope behind, I’ve had to rediscover the traditional method. It’s an odd sensation – intimate yet detached – to apply your ear to the chest of a stranger. It helps if you stick a finger in the unoccupied ear. Once you tune out all the background noise you begin to hear the sound of blood as it makes its way through the chambers and valves of the heart. The classical belief was that blood travelled to the heart in order to be mixed with vital spirit, or pneuma, rarefied from the air by the lungs. The ancients must have imagined a churning within; air frothing with blood the way wind whips up waves on the sea. The first time I placed my ear to a patient’s chest I was reminded of holding a conch shell as a child, listening to the imagined ocean within.

When any fluid is forced through a narrow opening there is turbulence, and just as a river flooding through a narrow canyon can be deafening, turbulence within the heart generates noise. Medical students are trained to listen very closely to the subtleties of those noises, and to infer from them how narrow – or obstructed – are the canyons of the heart. There are four valves in the human heart. When they close, you hear two separate sounds. The first sound is made as the two largest valves – the mitral and tricuspid – close at the same time during the active part of the beat (known as systole), when blood is forced out of the ventricles and into the arteries. These valves are so broad they have thick cords like harp strings attached to their cusps to reinforce them. The second sound is made by the other two valves – the pulmonary and aortic – as they prevent backflow while the ventricles refill (diastole). Healthy cardiac valves close with a soft percussive noise, like a gloved finger tapping on a leather-topped desk. If they are stiffened or incompetent there are additional sounds: murmurs that can be high-pitched or low, loud or soft, depending on the steepness of the pressure gradient across the diseased valve, and how turbulent the flow.

Starting out in medicine I learned to tell the difference between valve pathologies by listening to a CD of murmurs. I’d put it on while studying, hoping that my subconscious would come to distinguish a ‘seagull’ from a ‘musical’ murmur, recognise the grate of mitral regurgitation from the trill of aortic stenosis. There was something comforting in listening to the gurgle of blood as I worked. I wondered if it recalled the sound of the sea, or hearing a storm outside while wrapped up warm, but the sounds were too rhythmic for that. Perhaps it’s the womb, I thought, a deep memory of my mother’s pulse.

It is the episodic squeezing of our heart, the pressure difference between systole and diastole, that gives rise to the pulses we feel in our wrists, our temples and our throats. The pulse is the defining characteristic of life. Every so often someone comes up with a design for an artificial heart that pumps without need of a pulse. How would it feel, I wonder, to have blood that moved continuously through the body; not the ebb and flood of a tide, but a ceaseless, circular flow?

When language is called ‘clinical’ it is usually to imply that it is without emotion. Yet clinics are often drenched in emotional transactions. In normal life it is unusual to see adults cry, but behind my office door it’s routine. For the most part doctors are not emotionally cold, but become adept at shrugging off the burden of other people’s misery. Clinical language has been drained of emotion not only because it’s a shorthand between peers, but because it is a way of keeping patients’ pain, disappointment and anguish at arm’s length. Balancing empathy and compassion with a degree of detachment and professionalism takes experience as well as emotional intelligence, and no one gets it right every time. Hilary Mantel put it less generously, but more succinctly: ‘Nurses and doctors are an elite, self-selected as sufficiently insensitive to get on with the job.’

The clinical language used to describe the loss of pulse when the heart fails is not subtle. There may be ‘rapid haemodynamic deterioration’: the blood stops moving around the body. Presentation is with ‘dyspnoea, syncope or pain in the praecordium’ (the patient gasps for breath and collapses, feeling as if their chest is being torn apart). Many people who suffer a complete valve failure, if they’re conscious at all, have the conviction that they are about to die. Doctors have a name even for this conviction, and like so much of their jargon, it’s in Latin: angor animi, or ‘anguish of the soul’. In the emergency room that feeling is taken seriously. I remember one woman I attended in the resuscitation room after she collapsed at her 70th birthday party. As the nurses cut off her dress and pearls she gripped both of my forearms and pulled my face down to hers: ‘Help me doctor!’ her eyes staring with horror, ‘I’m dying.’ Her pulse was impossible to find, and she died soon afterwards despite all our efforts to save her.

Since Descartes we’ve had a tendency to believe that from the chin down we are just meat and plumbing. Angor animi suggests that there is more to us than that; that in some way we become aware when a valve is no longer working or that a tear, or ‘dissection’, is developing within the wall of the aorta. As a sensation it carries great predictive power: I have ordered an urgent CT scan of the chest because of a patient’s conviction that they’re about to die.

It isn’t just valve failure that can lead to sudden loss of a pulse: a blockage, or thrombosis, in the flow of blood through the coronary arteries can have the same effect. If the net of fibres co-ordinating ventricular contraction is starved of oxygen the heart muscle may begin to twitch chaotically or ‘fibrillate’; death will follow quickly unless the muscle contractions are electrically shocked back into alignment. Some people remain prone to this fibrillation even after the blockage has been dissolved or forced open by a stent. Pacemakers have been developed that double as defibrillators – it is now possible to carry your own life-support machine, about the size and thickness of a Zippo lighter, tunnelled beneath a pocket of skin on the front of your chest. It nestles comfortably just under the collarbone. A patient of mine who had one, a war veteran, told me he wore it like a medal of honour. ‘Mind you,’ he said, ‘when it fires it’s as if a horse has kicked you back from the grave.’

Robin Robertson, the poet and editor, was born with a heart in which one of the valves – the aortic valve – was composed of only two cusps instead of the usual three. The aortic valve prevents backflow from the aorta into the principal ventricle of the heart. Each valve cusp consists of two elements: a firm nodule and a softer, more flexible crescent-shaped flap of tissue known as the lunule – ‘little moon’. When a healthy valve closes, the three nodules snap together and support the flaps of the little moons, to control the tide of blood. If there are only two cusps, not three, the lunules fit less snugly, which means blood begins to jet backwards into the ventricle. Sometimes this flurry of blood gets loud enough to be felt as well as seen; putting your hand flat against the sternum you can feel a fluttering, or ‘thrill’, through the leaking valve. For the first thirty years of Robertson’s life those two cusps closed seventy or eighty times a minute, a hundred thousand or so times a day, around forty million times a year. Then he developed a ‘seagull murmur’, a name to describe the harshness of the sound, evocative of the squalls of turbulence that had begun to eddy in his heart. His poem ‘The Halving’ describes the operation he had to replace the valve:

General anaesthesia; a median sternotomy
achieved by sternal saw; the ribs
held aghast by retractor; the tubes
and cannulae drawing the blood
to the reservoir, and its bubbler;
the struggling aorta
cross-clamped, the heart
chilled and stopped and left to dry.
The incompetent bicuspid valve excised,
the new one – a carbon-coated disc, housed
expensively in a cage of tantalum –
is broken from its sterile pouch
then heavily implanted into the native heart,
bolstered, seated with sutures.
The aorta freed, the heart re-started.
The blood allowed back
after its time abroad
circulating in the machine.
The rib-spreader relaxed
and the plumbing removed, the breast-bone
lashed with sternal wires, the incision closed.

Four hours I’d been away: out of my body.
Made to die then jerked back to the world.
The distractions of delirium
came and went and then,
as the morphine drained, I was left with a split
chest that ground and grated on itself.
Over the pain, a blackness rose and swelled;
‘pump-head’ is what some call it
– debris from the bypass machine
migrating to the brain – but it felt
more interesting than that.
Halved and unhelmed,
I have been away, I said to the ceiling,
and now I am not myself.

In his poem Robertson describes how his heart was stopped and the circulation and oxygenation of his blood taken over by a machine. A carbon-coated disc, ‘housed/expensively in a cage of tantalum’ was taken from a sterile wrapping and stitched into his cross-clamped aorta. On waking from the surgery he felt disorientated and disembodied: ‘Four hours I’d been away: out of my body./Made to die then jerked back to the world.’ Once the anaesthetics and morphine had drained from his bloodstream he was left with a pain that ripped through his sternum whenever he moved; raw bone grating on bone. When that began to ease, a paralysing darkness began to settle over his mood: ‘Over the pain, a blackness rose and swelled;/“pump-head” is what some call it/ – debris from the bypass machine/migrating to the brain.’

No one knows why some individuals experience ‘pump-head’: a disturbance of mood and cognition brought on by having your blood moved beyond the confines of the body, but a charge nurse in a cardiothoracic intensive care unit told me that up to a third of her patients experience it. Many are violent as they come round; security guards have to hold them down as they are sedated with powerful antipsychotic medication. Some are merely quiet, ‘not themselves’ as she put it to me: as if they have to grow re-accustomed to their bodies. Some become inappropriate and disinhibited; she told stories of vicars making ribald jokes and genteel ladies issuing foul-mouthed curses.

Some think that when the aorta is cut, amputating the heart from its vessels, tiny fatty particles fly off into the arteries of the brain like flocks of birds, and are trapped there in a fine net of capillaries. Some believe that bubbles from the machine disturb the delicate balance of cerebral blood flow. Others have suggested that inflammatory processes within the brain, little understood, are set in motion by the trauma of having your chest prised open and your ribs wedged apart (‘held aghast’ as Robertson superbly puts it). Bypass machines cool the blood, and some think that ‘pump-head’ is a by-product of cooling the brain. But there is another theory: bypass machines have been in use for more than sixty years, but they still can’t closely mimic a natural pulse from the heart. It may be that the heart’s internal rhythm is essential to our wellbeing; our brains, and our sense of self, may depend on it.

It’s nearly four hundred years since William Harvey realised that classical beliefs about the heart were wrong and that it works as a two-way pump. Before his De Motu Cordis was published in 1628, ideas hadn’t moved on since Roman times. In fact, we still often speak as if classical beliefs were true, and the heart generated not only our pulse, but also our spirit. A heartless person is someone without conscience, even without a soul. We speak of heartache, and of following our heart’s desire; we feel a conflict between our hearts and our minds, as if reason lay in the brain, but the heart were the helmsman. ‘Pump-head’ could be a manifestation of bubbles, of cooling, of fat, of inflammation of the brain, but to Robertson, the experience of having his heart stopped and his blood circulated through a machine was ‘more interesting than that’. It left him feeling ‘halved and unhelmed’; ‘I have been away, I said to the ceiling,/and now I am not myself.’

Cardiopulmonary bypass machines have much in common with classical ideas about the function of the human heart. Blood is drawn from the large veins in the chest then sucked into a chamber where it is able to absorb oxygen (or ‘vital spirit’). The early machines bubbled oxygen through a reservoir of blood in the sort of churning Aristotle imagined took place in the ventricles. But since the mid-1970s we have suspected that it’s better to keep blood and air apart, separated by a synthetic, disposable membrane.

Once it has passed through the oxygenator, the blood is squeezed through a tube by a roller, or drawn by a centrifugal pump. From there it is forced through a series of bubble filters and coolers, and then through sensors that analyse the blood for acidity, oxygenation and saltiness. It can be piped back into the body through a cut in the aorta just above the heart, but also at the carotid in the neck, or the femoral artery in the groin. From the perspective of the human body as plumbing, it doesn’t make any difference where you put it back in.

In the 1990s a series of scientific papers appeared claiming that patients suffered less from ‘pump-head’ if the blood from the machine was delivered to them in heart-like pulses, rather than in a steady flow. Capillaries and cells perform the silent industry of life at the microscopic level; in the brain their function is intimately related to thought and personality. The evidence suggests that they prefer the blood that nourishes them to come in pulses. Even the best bypass machines manage only a clumsy approximation to the pressure pulse of a beating heart.

A few days after I heard Robertson read his poem a pregnant woman came to my clinic. She hadn’t felt her baby move for a day or so, and wanted me to reassure her by listening for its heartbeat. Normal stethoscopes are no use for listening to the heartbeat of a baby in the womb; the sound is too fast, quiet and high-pitched. Midwives often use an electronic Doppler probe to find the foetal heart, but I used a modified tube called a Pinard stethoscope, like an old-fashioned ear trumpet, wedged between one ear and the swollen contour of the woman’s belly. The best place to lay the trumpet end is where you think you’ve felt the convex curve of the baby’s spine. Even with one finger in my other ear it took a while to find the heart – an agonising couple of minutes for the mother. But there it was: a rhapsodic, syncopated interleaving of her heartbeat with her baby’s. The foetal heartbeat was distinct, fluttering fast like a bird over the oceanic swell of the mother’s pulse, an allegro played over an adagio. I paused for a moment listening to the two rhythms within one, two lives within one body.

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