110 Fun Facts About Heart

How many chambers does the human heart have?

Four. A wall down the middle makes the heart two pumps in one: one half sends used blood to the lungs while the other sends the refreshed blood round the body.

What are the two upper chambers of the heart called?

Atria. The name is Latin for an entrance hall, which is roughly what they are: blood arriving at the heart collects there before being passed down to the pumping chambers below.

An adult's heart is usually described as about the size of which part of its owner's body?

Fist. It weighs only about 300 grams, though years of hard endurance training can enlarge it, a normal change that doctors regularly see in athletes.

A resting adult heart rate above 100 beats a minute is known by which medical term?

Tachycardia. A healthy adult heart at rest beats 60 to 100 times a minute, and fitness pulls the figure down: a well-trained athlete's can idle at 40 to 60.

Which structure acts as the heart's own natural pacemaker?

The sinoatrial node. Left to itself it would fire about 100 times a minute, but the nervous system acts as a brake and holds a resting heart to 60 to 80 beats.

Which chamber of the heart has by far the thickest muscular wall?

Left ventricle. The right ventricle only has to push blood next door to the lungs, while the left must drive it out to the toes and back, and it builds the muscle to match.

What is the name of the sac that surrounds the heart?

Pericardium. When it becomes inflamed, the sharp pain that follows has a telltale quirk: it eases when the patient sits up and leans forward.

Which wall of muscle separates the heart's two lower pumping chambers from each other?

The interventricular septum. A hole in it is one of the most common heart defects babies are born with, and small ones often close on their own as the heart grows.

The myocardium, the middle layer of the heart wall, is made of which type of tissue?

Involuntary striated muscle. It is striped like the muscle of your arm but runs without conscious control, and its cells are packed with mitochondria that keep it supplied with energy around the clock.

Which heart valve sits between the right atrium and the right ventricle?

Tricuspid. Its three flaps are tied by fine cords to small muscles in the ventricle wall, which tighten with every beat to stop the valve being blown inside out.

The heart's mitral valve, named for its likeness to a bishop's mitre, also goes by which name?

Bicuspid. It has two flaps where the heart's other valves have three, and when it leaks, blood slips backwards with every beat and can leave its owner short of breath.

Roughly how soon after conception does a human embryo's heart start to beat?

About 3 weeks. Doctors count a pregnancy from the last period, which makes that week five, and the heart at that point is still a single tube, weeks away from forming its chambers.

Which parasympathetic nerve acts to slow the heart rate?

The vagus nerve. Its name is Latin for wandering, after its long route from the skull to the gut, and pain or strong emotion can fire it hard enough to slow the heart and cause a faint.

The amount of blood the heart pumps each minute, about five litres at rest, is known as what?

Cardiac output. Five litres is roughly all the blood an adult has, so a resting heart turns over the body's entire supply about once a minute.

What is the largest artery in the human body, carrying blood out of the heart's main pumping chamber?

The aorta. Its elastic wall stretches with each beat and springs back while the heart relaxes, which keeps blood moving between beats.

The 'lub' of the heart's 'lub-dub' sound is caused by the closing of which pair?

The mitral and tricuspid valves. They snap shut as the ventricles start to squeeze, and the 'dub' that follows is the aortic and pulmonary valves closing once the squeeze is over.

A heart murmur is a sound produced by what?

Turbulent blood flow. The rough flow is sometimes blood forcing its way through a leaky or narrowed valve, but many murmurs, especially in children, are harmless.

Which instrument did the French doctor René Laennec first improvise from a rolled sheet of paper?

Stethoscope. Too embarrassed to press his ear to a young woman's chest, Laennec listened through the paper tube instead, heard her heart more clearly than ever and went on to build a wooden version.

Which English physician first fully described blood circulation in his 1628 book De Motu Cordis?

William Harvey. He worked out how much blood the heart pumps in half an hour and showed the liver could never make that much, so the same blood had to be going round and round.

Willem Einthoven won the 1924 Nobel Prize in Medicine for his work on which heart test?

The electrocardiogram. His first recording machine weighed some 270 kilograms, and the letters he gave the five deflections of the trace, P, Q, R, S and T, are still used today.

On an ECG trace, the QRS complex represents the electrical depolarization of which part of the heart?

The ventricles. They hold far more muscle than the atria, so their firing draws the tallest spike on the trace, while the atria manage only the small P wave just before it.

On whom did Werner Forssmann perform the first human cardiac catheterization in 1929?

Himself. Forbidden by his boss to try it, he slid a catheter up a vein in his arm, walked to the X-ray room to have it photographed inside his heart, and shared a Nobel Prize in 1956.

In which city did Christiaan Barnard perform the first human heart transplant in 1967?

Cape Town. His patient, Louis Washkansky, lived only 18 days, and Barnard had beaten better-prepared American teams to the operation using a technique two of their surgeons had worked out on dogs.

At which California university did Norman Shumway perform the first adult heart transplant in the United States?

Stanford. Shumway had spent eight years perfecting the operation on dogs, and when early patients died and other American surgeons gave up, his team carried on almost alone for a decade.

What made heart transplants far more common in the 1980s?

Anti-rejection drugs. Cyclosporine, a compound isolated from a soil fungus, curbed the immune system's attack on the new heart, and the number of transplants climbed quickly once it arrived.

Which heart device was first implanted in a patient in Sweden in 1958?

Pacemaker. The first unit failed within hours, yet the patient, Arne Larsson, went on to wear 26 of them and died in 2001 aged 86, having outlived both his surgeon and the engineer who built it.

In 1982 Barney Clark became the first person given a permanent what?

Artificial heart. Clark did not qualify for a donor heart, so the Jarvik-7 was meant to be permanent, and he lived 112 days tethered by air hoses to its bulky drive console.

In a coronary bypass, a vein used as the graft is usually taken from which part of the body?

The leg. Surgeons lift out the great saphenous vein, the longest in the body, through a cut between ankle and groin, then stitch it in as a detour around the blocked artery.

Cardiovascular disease causes roughly what share of all deaths worldwide?

About 1 in 3. That is close to 20 million deaths a year, 85% of them heart attacks and strokes, and the World Health Organization says most could be prevented.

Which is the only continent where cardiovascular disease is NOT the leading cause of death?

Infectious diseases still claim more lives there, though heart disease is climbing fast as diets and cities change.

A heart attack is known medically by what term?

Myocardial infarction. Infarction means tissue death: starved of blood by a blocked artery, the heart muscle begins to die unless the flow is restored quickly.

Which over-the-counter drug is recommended for someone having a suspected heart attack?

Aspirin. It makes platelets less sticky, which slows the growth of the clot blocking the artery, so the advice is to take one while waiting for the ambulance.

Which blood test marker is considered the best indicator that heart muscle has been damaged?

Troponin. The protein is found inside heart muscle cells and leaks into the blood when they are damaged, so a rising level is how doctors confirm a heart attack.

Compared with men, women having a heart attack more often present without which classic symptom?

Chest pain. It is still the commonest symptom in both sexes, but a large American study found women clearly likelier than men to arrive at hospital without it, which can delay their care.

Which explosive has also served since the 1870s as a medicine for angina?

Nitroglycerin. A small dose under the tongue relaxes the blood vessels and eases the heart's workload; Alfred Nobel, who built his fortune on the explosive, called it an irony of fate when doctors prescribed it for his own heart.

The public defibrillators kept in airports, gyms and stations are known by which abbreviation?

AED, for automated external defibrillator. Switched on, it talks an untrained user through each step and delivers a shock only if it detects a rhythm that a shock can correct.

In a cardiac arrest, which chaotic heart rhythm is a defibrillator's shock designed to stop?

Ventricular fibrillation. The pumping chambers quiver uselessly instead of beating, and a shock can reset them; a flatline, by contrast, cannot be shocked back and is treated with CPR and drugs.

In CPR on an adult, where should the heel of the rescuer's hand be placed?

The centre of the chest. The target is the lower half of the breastbone, not the left side where people picture the heart, and each push should go 5 to 6 centimetres deep at about two a second.

Which Bee Gees song does the American Heart Association suggest to keep time for CPR?

Stayin' Alive. Its beat of just over 100 a minute sits inside the 100 to 120 pushes rescuers aim for; Queen's 'Another One Bites the Dust' fits as well, with a less encouraging title.

Untrained bystanders are advised to leave out which part of standard CPR?

Rescue breaths. Pressing alone is easier to do and easier to coach over the phone, so untrained helpers are told to skip them; trained rescuers give 2 after every 30 compressions.

In a blood-pressure reading of 120 over 80, the higher number marks which moment?

When the heart contracts. The lower figure is taken while the heart rests between beats, and both are still given in millimetres of mercury, a relic of the mercury columns doctors once read.

Which cholesterol particle is popularly called 'bad cholesterol' because it deposits in artery walls?

LDL. It delivers cholesterol out to the body's cells, while its 'good' counterpart, HDL, carries the surplus back to the liver for disposal.

The World Health Organization advises adults to get at least how many minutes of moderate exercise a week?

150 minutes. That is a brisk half-hour walk five days a week, and vigorous exercise counts double, so 75 minutes of running does the same job.

What is the most common serious abnormal heart rhythm?

Atrial fibrillation. The affected chambers beat chaotically instead of pumping, so blood can sit and clot inside the heart, and a clot that breaks loose can cause a stroke, which is why many patients take blood thinners.

In the stroke-recognition mnemonic FAST, what does the letter T stand for?

Time. The first three letters are signs to look for, a drooping face, a weak arm and slurred speech, and the T is the instruction: call an ambulance at once, even if only one of them shows.

Which animal has the largest heart of any creature on Earth?

Blue whale. On a deep feeding dive its heart slows to as few as two beats a minute, then races at up to 37 when it surfaces, which researchers think is close to as fast as so big a heart can go.

An octopus's two extra hearts pump blood through which organs?

Gills. An octopus has three hearts in all: each gill gets a booster of its own, and the blood they push is blue, because it carries oxygen with copper where ours uses iron.

Which animal's heart must pump at about twice the pressure of a typical mammal's?

Giraffe. Its heart has to drive blood all the way up that neck, and skin stretched tight around the lower legs works like a compression stocking to stop the blood pooling at the bottom.

Which birds' hearts can beat more than 1,200 times a minute in flight?

Hummingbirds. To get through a cold night without feeding they sink into torpor, a brief hibernation in which body temperature plunges and the metabolism slows to a small fraction of normal.

Which hormone, released in moments of fright or excitement, makes the heart beat faster and harder?

Adrenaline. Glands that sit on top of the kidneys pour it into the blood within moments of a scare, and the faster, harder heartbeat rushes extra blood to the muscles in case you need to fight or run.

Egyptian embalmers left the heart inside a mummy but removed which organ through the nose?

The brain. It came out through the nostrils, while the heart stayed in place because, for the Egyptians, the heart was what did the thinking.

The usual rule of thumb puts a person's maximum heart rate at 220 minus what?

Their age. The formula was sketched in 1970 from about ten earlier studies, not from an experiment of its own, and a person's true maximum can easily sit a dozen beats above or below it.

In the fetal heart, what is the opening between the atria that closes soon after birth called?

Foramen ovale. It lets blood skip the unused lungs before birth and normally closes once the baby starts to breathe, though in about a quarter of people the seal is never quite complete.

Which specialized fibers carry the electrical signal through the ventricles to the heart muscle?

Purkinje fibers. They are the fastest conductors in the heart, so the signal reaches every part of both ventricles within a fraction of a second and the walls squeeze together, from the tip upward.

Which 13th-century physician first described pulmonary circulation, contradicting Galen?

Ibn al-Nafis. He argued that the wall dividing the heart is solid, with none of the invisible pores Galen had imagined, so blood can cross from one side to the other only by way of the lungs.

In 2022, David Bennett became the first person to receive a heart from which genetically modified animal?

A pig. Bennett, 57, had terminal heart disease, so Maryland surgeons won special permission to try a heart from a pig with edited genes, and he survived for two months.

Ancient Egyptians believed the heart was weighed against the feather of which goddess?

Maat, the goddess of truth and justice. A heart heavier than her ostrich feather was devoured by the monster Ammit, so its owner never reached paradise.

Which of these animals has a three-chambered heart, letting oxygen-rich and oxygen-poor blood mix?

Frog. Two chambers receive its blood but only one pumps it out, so the two streams partly mix, and frogs top up by absorbing oxygen straight through their skin.

Which people cut out human hearts as offerings to the god Huitzilopochtli?

The Aztecs. They believed the gods' own sacrifice kept the universe going, so the blood offered at Tenochtitlan's Templo Mayor fed the gods and repaid the debt.

Takotsubo cardiomyopathy, named after a Japanese octopus trap, is better known by which name?

Broken heart syndrome. A surge of stress hormones after a shock such as a bereavement is thought to stun the heart so its main chamber balloons like the pot, yet most people recover fully.

Despite how veins look through the skin, what color is oxygen-poor blood returning to the heart?

Dark red is the color of blood that has given up its oxygen, and it turns bright red again once it picks more up. Veins near the surface only appear blue from outside.

In 1984 the newborn known as Baby Fae lived for three weeks with a heart from which animal?

A baboon heart kept Baby Fae alive for three weeks, two weeks longer than any earlier recipient of an animal heart. A year later her surgeon performed the first successful infant-to-infant heart transplant.

The CPR doll Resusci Anne has the face of an unknown young woman said to have drowned in which river?

The Seine gave the doll her model, a death mask known as L'Inconnue de la Seine. Her toymaker inventor chose a woman's face because he thought men would balk at kissing a male mannequin.

Which Greek philosopher dissected animals and decided the heart, not the head, did the thinking?

Aristotle saw that the veins seemed to spring from the heart and concluded it was the body's command post, the origin of movement and feeling alike.

Which sea animal has no heart or blood and senses light and smells through a simple net of nerves?

Jellyfish have no heart, and only about five percent of the body is solid matter; the rest is water. Lifted out of the sea, one collapses into a shapeless blob.

Which composer's heart was carried home to Warsaw in a jar of alcohol while his body stayed in Paris?

Frédéric Chopin asked for it, and his sister Ludwika took the heart to Poland in 1850. It was later sealed inside a pillar of Warsaw's Holy Cross Church.

The adult human heart, about 12 cm long, is often described as roughly the size of which of these?

A closed fist is the classic comparison, though some doctors dispute it and say the heart is likely a little larger. It sits between the lungs in the middle compartment of the chest.

Which character in The Wonderful Wizard of Oz asks the Wizard for a heart and receives one made of silk?

The Tin Woodman gets a silk heart stuffed with sawdust, a placebo from a Wizard who turns out to be a humbug. He was already the most tender of Dorothy's companions.

Which device was first used on a person in 1947, when surgeon Claude Beck restarted a boy's heart?

A defibrillator made its human debut when Beck shocked the heart of a 14-year-old during chest surgery. He believed many stopped hearts were, in his words, too good to die.

Which Renaissance artist built a glass model to watch water and grass seed swirl through a heart valve?

Leonardo da Vinci tested his ideas about blood flow with that model after dissecting and drawing the heart. He also made one of the first scientific drawings of a fetus in the womb.

Which gland, large in childhood and shrinking after puberty, sits just in front of the heart?

The thymus is where the immune system's T cells mature, and in newborns it is bulky enough that surgeons often remove it to reach the heart.

Which author wrote 'The Tell-Tale Heart', in which a killer hears his victim's heartbeat under the floor?

Edgar Allan Poe has his narrator insist he is perfectly sane, then break down and confess to the police because the pounding he imagines grows too loud to bear.

Which tiny mammal, the lightest known by mass, has a heart that can beat about 1,500 times a minute?

The Etruscan shrew weighs about 1.8 grams, as much as a paperclip, and its heart has been clocked at 1,511 beats a minute. That is roughly 25 beats every second.

Which Scottish king's heart was carried into battle in Spain, then buried at Melrose Abbey?

Robert the Bruce asked on his deathbed that his heart be taken to the Holy Land. Sir James Douglas wore it in a silver casket around his neck, but he fell fighting the Moors and it came home to Scotland.

Which garden flower gave doctors digitalis, the heart drug William Withering described in 1785?

Foxglove was a folk cure for the swelling called dropsy before Withering worked out how to use it safely. The plant is poisonous enough that eating it can kill.

Blood returning to the heart from the body carries which waste gas, to be breathed out by the lungs?

Carbon dioxide is swapped for fresh oxygen in the lungs, and the heart then pumps the refreshed blood back out. The body's cells release the gas as they burn fuel.

Which word describes feeling your own heart pound, flutter or skip a beat, often after caffeine?

Palpitations are a symptom rather than a disease. In one study only 43% of cases came from the heart itself, while 31% had a psychiatric cause.

Despite its name, heartburn is caused by stomach acid flowing back up into which organ?

The esophagus is irritated when acid and food flow back up from the stomach, causing a burning felt in the middle of the chest. Angina is one of the look-alikes doctors must rule out.

Which tiny blood vessels, first observed by Marcello Malpighi in 1661, link the arteries to the veins?

Capillaries are the smallest blood vessels in the body and the place where blood trades oxygen and nutrients with the tissues. Their discovery filled the last gap in the circuit of the blood.

Which blood vessel in the neck do medics press to feel for a heartbeat when the wrist gives no sign?

The carotid artery often keeps a detectable beat in patients in shock, after the one in the arms and legs has faded. It is felt just in front of the long muscle running down the side of the neck.

Which bone do surgeons cut down the middle to reach the heart, then wire back together afterward?

The sternum forms the front of the rib cage and normally shields the heart and lungs from injury. The cut that splits it lengthwise is called a median sternotomy.

Which tiny mesh tube is left inside a narrowed coronary artery to prop it open after angioplasty?

A stent acts as a scaffold, and most now release a drug that stops the vessel narrowing again. Doctors first placed them in coronary arteries in 1986.

Which former US vice president received a heart transplant in 2012 at the age of 71?

Dick Cheney spent the wait on an implanted pump that pushed blood so steadily it left him alive without a pulse. The transplant operation itself took seven hours.

Which small aquarium fish, a favorite of research labs, can regrow damaged heart muscle without a scar?

Zebrafish rebuild the heart completely within about two months of an injury. The British Heart Foundation set out to raise £50 million to learn whether people could be helped to do the same.

Which North American amphibian survives winter frozen solid, with its heart stopped and no breathing?

The wood frog can tolerate up to 70% of its body water turning to ice. A frozen one shows no heartbeat, breathing or muscle movement, yet it thaws out alive in spring.

Stephen Hales, who made the first published measurement of blood pressure in 1733, earned his living as what?

A clergyman who spent half a century as curate of Teddington, Hales slid fine tubes into the arteries of animals and measured how high the column of blood rose.

Blood pressure is still recorded in millimetres of which metal, long used inside the measuring gauges?

Mercury rises in a glass column to show the pressure, and gauges built that way are still considered the gold standard. Dial and digital monitors keep the old unit.

What job is done by the heart's real 'heartstrings', the tough cords doctors call chordae tendineae?

Anchoring the valve flaps is their whole job: the cords pull tight with every beat so the flaps cannot be blown inside out and let blood leak backward.

Which Shakespeare play gave English the phrase 'wear my heart upon my sleeve', spoken by the scheming Iago?

Othello opens with Iago sneering that if he ever showed his true feelings he would wear his heart on his sleeve for birds to peck at. He ends the speech with 'I am not what I am.'

Which cholesterol-lowering drugs did Akira Endo first find in a mold on rice from a Kyoto grain shop?

Statins grew out of Endo's hunch that fungi make chemicals to fight off rivals, and he screened 6,000 compounds to find one. They became some of the best-selling medicines in history.

Which racehorse, winner of the 1973 Belmont Stakes by 31 lengths, had a heart estimated at 22 pounds?

Secretariat's heart was never put on a scale, but the vet who examined him judged it about two and a half times the normal size. He said the team just stood there in stunned silence.

Which giant snake's main heart chamber grows about 40 percent heavier after it swallows a large meal?

The Burmese python rebuilds its whole digestive system after a kill, and the bigger heart powers the work. Between meals its stomach and intestines shrink back down.

Heartworm, a parasite that can clog a dog's heart and lung arteries, is spread by the bite of which pest?

Mosquitoes pick up the microscopic young worms with a blood meal and pass them to the next animal they bite. The worms then take six to seven months to mature inside a dog.

Rheumatic fever, which can scar the heart's valves for life, follows a bacterial infection of which body part?

The throat infection is strep, and the fever typically appears two to four weeks later, mostly in children aged 5 to 14. Treating strep with antibiotics lowers the risk.

An echocardiogram builds a moving picture of the beating heart using which of these?

Ultrasound echoes bounce off the heart's walls and valves, and the scan can also track blood moving through the chambers. It is done with gel and a probe held against the chest.

Which Massachusetts city has had its residents' hearts tracked since 1948, coining the term 'risk factor'?

Framingham beat Paintsville, Kentucky, to be chosen as the site, and 5,209 adults signed up. The study has since enrolled their children and grandchildren.

Which sea animal's heart stops every few minutes, then restarts and pumps its blood in the opposite direction?

The sea squirt's heart is a curved tube with a trigger zone at each end, and the two take turns to lead. The animal is named for the jet of water it shoots out when disturbed.

Which theologian, burned at the stake in Geneva, first told Europeans how blood passes through the lungs?

Michael Servetus tucked the finding into a book of theology and died on a pyre of his own books. Most copies were burned, and the three that survived stayed hidden for decades.

Heart pioneer Helen Taussig went deaf, so she learned to read her young patients' heartbeats using what?

Her fingers could feel the rhythm that a stethoscope no longer brought to her ears. Taussig founded the field of children's heart medicine and later campaigned against thalidomide.

In which city did Daniel Hale Williams, founder of Provident Hospital, repair a stabbed man's heart sac in 1893?

Chicago's Provident Hospital, which Williams opened in 1891 as a non-segregated hospital, also trained nurses and doctors. His patient walked out about fifty days after the operation.

Which Houston heart surgeon was saved at age 97 by an artery operation of his own invention?

Michael DeBakey was the oldest patient yet to have the surgery, and a hospital ethics committee had to approve it. He spent eight months recovering and returned to good health.

The lower number in a blood pressure reading comes from which phase, when the heart relaxes and refills?

Diastole takes its name from the Greek for dilation, since the chambers widen as they refill. The squeeze that follows, systole, supplies the higher number.

Which English Romantic poet's heart is said to have refused to burn when he was cremated on an Italian beach?

Percy Shelley drowned when his boat was lost in a storm in 1822, and a friend snatched the organ from the pyre. Some suspect it was really his liver.

Which blood thinner, given to people with artificial heart valves, first went on sale in 1948 as a rat poison?

Warfarin grew out of research into why cattle fed spoiled sweet clover hay kept hemorrhaging in the 1920s. In careful doses, the same anti-clotting effect helps prevent strokes.

Commotio cordis, a cardiac arrest set off by a blow to the chest, most often strikes players of which sport?

Baseball tops the list because a hard ball can strike an unprotected chest. The blow must land within a window of about 40 milliseconds in the heartbeat, which is why it is so rare.

Which US state's tourism campaign swapped the word 'love' for a red heart in a famous logo by Milton Glaser?

New York got its logo when Glaser sketched it in red crayon on scrap paper in the back of a taxi. The campaign it fronts has promoted tourism in the state since 1977.

Which Dr. Seuss character has a heart 'two sizes too small' that grows three sizes by the end of the story?

The Grinch feels the change when the Whos sing on Christmas morning even though he has stolen every present. He decides the holiday means 'a little bit more' than gifts and feasting.

Which mineral raises blood pressure when people eat too much of it?

Sodium in excess makes the muscle in artery walls tighten, which narrows the vessels. Potassium works the other way, and eating more of it lowers blood pressure.

Which term describes an unusually slow heartbeat, often normal in sleeping adults and trained athletes?

Bradycardia joins the Greek words for slow and heart. Doctors generally treat it only when it causes symptoms, since it is common in healthy people.

Which US president suffered a serious heart attack while vacationing in Colorado in 1955, then won a second term?

Dwight D. Eisenhower spent weeks in an Army hospital while Vice President Nixon and senior aides kept the government running. He had seven heart attacks in all before his death.