The idea of the heart as a red cartoon bubble holding our emotions is one we generally let go of in childhood. We learn that the heart is just a bloody machine. The mind is where we feel things.
But there’s truth in that elementary-school version of the heart, too, says Sian Harding, an emeritus professor of cardiac pharmacology at the National Heart and Lung Institute at Imperial College London. In her new book, “The Exquisite Machine: The New Science of the Heart,” the heart researcher argues that this organ is deeply linked to our emotions. That connection can kill you. It can also help keep you alive.
Decades of studying heart failure and other problems have made Harding appreciate how well the heart does its job, most of the time. “It’s incredible — I mean really, absolutely incredible — how evolution has shaped the heart to be perfect for its niche,” she says.
That perfection goes right down to the cellular level. For example, it isn’t only the whole heart that beats — although it’s great at that, and will even keep beating when removed from a person’s chest during surgery. The heart’s individual cells also beat. Under a microscope, a tiny heart cell in a dish pulses just like the heart itself.
And those beating cells last a long time. Unlike your skin, say, which constantly renews itself, the heart holds onto its existing cells. “About half of those cells will be with you from the beginning of your life to the end,” Harding says.
Unfortunately, that low rate of turnover means the heart is slow to heal from damage, such as the death of cells from a heart attack.
Damage can also compound over time. After damage to the heart, the body sees the organ’s weak output as an emergency and responds with a flood of adrenaline.
This hormone can be useful in a true emergency. But when your body keeps cranking out adrenaline over months or years, it further harms the heart cells. “There’s a second wave of damage that happens,” Harding says.
An adrenaline surge can also result from ordinary life events, which helps explain the relationship between our emotions and our hearts.
“Extreme stress, and particularly emotional stress, can cause a disturbance in your heart,” Harding says. This disturbance can be fatal. People are statistically more likely to die, for instance, after the death of a loved one. The recent case of a husband’s death from a heart attack after his wife, a teacher, was killed in the Uvalde mass shooting was a “classic presentation,” Harding says.
Anniversaries of losses can also be dangerous for the heart, she says. Overwhelming excitement or happy occasions, such as watching sports or walking into a surprise birthday party, can trigger a cardiac event, too.
In other cases, intense emotions or stress can lead to a phenomenon called takotsubo syndrome. The condition is most common in postmenopausal women. It causes the heart to beat oddly, most often with the top chambers squeezed tightly while the bottom balloons out. (The condition gets its name from that shape, which resembles a Japanese pot for catching octopuses.) Although takotsubo sufferers may feel like they’re having a heart attack, most will recover.
In experiments with anesthetized rats, Harding and her colleagues found a way to trigger takotsubo syndrome with a high dose of adrenaline. They also found a molecular way to block the takotsubo response. But when they dosed the rats with adrenaline and prevented takotsubo, the animals died. This suggests that takotsubo syndrome is “a kind of protective mechanism,” Harding says. It seems to act by “shutting down the heart temporarily,” she says, “to stop it from being overwhelmed by this giant flood of adrenaline.”
Yet the heart isn’t only a victim of our feelings. The connection goes both ways.
In one study, for example, people had a stronger emotional response to frightening images that flashed during their heartbeats rather than between heartbeats. A racing heart can also intensify feelings of fear. Even hearing a recording of a speeded-up heartbeat can cause anxiety and trigger a panic attack. This suggests our emotions and our heart muscles can interact to create a vicious circle of fear, Harding says.
But we can also use this connection to our advantage, such as when we calm fear or anxiety by breathing deeply and slowing our hearts.
Harding wrote her book because she wants people to know that our blood-pumping organ and its impressive tricks deserve all our cartoon-heart emoji: “It’s actually amazing.”
Elizabeth Preston is a science journalist in the Boston area.