11 Fit Facts About the Heart

Technically, your heart isn't made of gold. And don't wear it in on your sleeve—you’ll make a mess! Just in time for Valentine's Day (and National Heart Month every February), here are 11 scientific facts about your ticker.

1. The most common time for heart attacks to occur is in the morning.
2. The heart is an incredibly strong muscle.
3. Ring finger length has been linked to fewer early heart attacks.
4. The term pacemaker doesn’t just refer to an implanted device.
5. Heart rates vary by sex.
6. The “heartbeat theory” alleges that heart rate can predict a fetus’s sex.
7. Bigger hearts boast slower beats.
8. A mammal’s heart beats about 1.5 billion times in total.
9. A heartbeat’s sound is often described as lub-dub.
10. The first successful heart transplant took place in 1967.
11. Beating heart transplant technology could help solve the organ shortage.

The most common time for heart attacks to occur is in the morning.

Studies conducted in the 1980s showed that most heart attacks occurred between the hours of 6 a.m. to 12 p.m., and some research narrowed the window even further to between 7 a.m. and 9 a.m. The least common time was in the very early morning, usually between the hours of 2 a.m. to 6 a.m.

British researchers have found that the most serious kind of heart attack, a ST-segment elevation myocardial infarction (STEMI), is most likely to happen on Mondays, though the reasons behind the correlation are unclear. More recent studies, however, suggest that environmental and patient lifestyle factors may be weakening these parameters.

The heart is an incredibly strong muscle.

Other muscles in the body are bigger or are able to pull with more force, but the heart is the body’s hardest-working muscle. With every beat, it pumps about 2 ounces of blood, which adds up to roughly 2000 gallons per day.

Ring finger length has been linked to fewer early heart attacks.

Men with long ring fingers are less likely to have early heart attacks, according to a 2001 study in the British Journal of Cardiology. Researchers found that men with ring fingers the same length or only slightly longer than their index fingers have a higher risk of heart attacks in their thirties and forties than men with ring fingers much longer than their index fingers. The reason is testosterone, which is responsible for lengthening ring fingers and protects against heart disease.

The term pacemaker doesn’t just refer to an implanted device.

The pacemaker cells in the right atrium of a healthy heart control the heart rate. An implanted pacemaker relies on electrodes.

Heart rates vary by sex.

The average woman’s heart beats 78 times per minute. The average man’s beats 70 times per minute.

The “heartbeat theory” alleges that heart rate can predict a fetus’s sex.

This old-fashioned theory uses the known difference between average male and female heart rates to predict the sex of babies before they’re born. Supposedly, 150 or more beats per minute predicts a girl, and less than 140 beats per minute is a sure sign of a boy. Doctors claim there's no strong correlation between heart rate and sex in hearts that young, since the so-called normal range of fetal heart rate is between 120 to 160 beats per minute.

Bigger hearts boast slower beats.

The smallest heart in the animal kingdom belongs to species of fairyfly. The insects grow to less than two-tenths of a millimeter, and their hearts, which take the form of a tube in their backs, are microscopic. The Etruscan shrew weighs all of 2 grams and boasts the tiniest multi-chambered heart in any mammal, as well as one of the fastest heart rates on Earth: about 25 beats per second, or 1511 beats per minute.

In contrast, a blue whale’s heart, the largest of any animal, can weigh up to 400 pounds. In 2019, Stanford University researchers announced that they had made recordings of a blue whale’s heart rate in the wild, which revealed just how slow it can go. When the whale was at the surface and replenishing its oxygen, its average heart rate was 25 to 37 beats per minute, but when it dove deep to forage for food, its heart slowed to four to eight beats per minute—and even went as low as two beats per minute.

A mammal’s heart beats about 1.5 billion times in total.

All mammals, including humans, are warm-blooded, hairy vertebrates that nurse their young. Know what else some scientists say they all have in common? A lifetime of about 1.5 billion heartbeats. Obviously, not all creatures have the same lifespan—an elephant lives longer than a cat, for instance—but we share a lifetime heartbeat limit because larger animals' hearts beat slower. Megafauna don't just have more cells. They have more efficient cells.

A heartbeat’s sound is often described as lub-dub.

The two sounds of a heartbeat, which occur in pairs, are produced by the heart’s valves closing as they pump blood through the organ’ four chambers. The first lub-dub is the mitral and tricuspid valves closing, followed by another lub-dub when the aortic and pulmonary valves close.

The first successful heart transplant took place in 1967.

Today, most heart transplants are performed in the United States, but the first successful transplant occurred in South Africa on December 3, 1967. Dr. Christiaan Barnard transplanted the heart of a recently deceased woman into 53-year-old Louis Washkansky, who survived 18 days (he died from infection and pneumonia).

The first heart transplant in the U.S. occurred the same month in Brooklyn, New York. But it wasn't your typical heart transplant—it was performed on an infant, who died nearly seven hours later. The next pediatric transplant didn't happen until 1984 in London. It was ultimately unsuccessful. The same year, U.S. physicians tried another pediatric transplant on an infant called Baby Fae, who was born with a fatal heart defect. Because there weren't any appropriate donor hearts, the surgeon tried the next best thing—a baboon heart. Baby Fae lived for three weeks.

In 1985, Baby Moses became the first infant to undergo a successful heart transplant. Many more babies have survived since. The bigger problem now—for all patients needing transplants—is the limited availability of donor organs.

Beating heart transplant technology could help solve the organ shortage.

The big thing in the cardiology world is the beating heart transplant—and if Edgar Allan Poe were still alive, he'd love it. Harvested hearts start to deteriorate within hours, and the longer they take to transplant, the greater likelihood of the patient’s body rejecting it. Now, transplant technicians are able to perfuse the donated heart with donor blood while it waits to be transplanted, then switch over to perfusion with the patient’s blood during the surgery. The technique keeps donor organs healthier for longer, reduces the chance that they will have to be discarded before transplant, and decreases side effects from the transplant procedure—and helps to save many more lives. If you want to be a part of the solution, sign up to become an organ donor here.

Discover More Amazing Facts About the Body:

A version of this story was published in 2013; it has been updated for 2025.