Women's chances of surviving cardiac arrest are half those of men, study says. Here's why

The window to shock a woman's heart back into a stable rhythm after cardiac arrest seems to close faster than in men.

Women less likely to be resuscitated by bystanders and fade faster, even with use of defibrillator

Just one in 10 patients survives an out-of-hospital cardiac arrest. Acting fast to get an automatic external defibrillator is one of the keys to saving more lives. (Derek Hooper/CBC)

Women fall sick faster from cardiac arrest than men, have a worse chance of receiving care from a bystander and experience diminished odds of survival, say cardiologists.

They hope greater awareness of the symptoms of heart problems in women and of the need to shock the heart into restarting again will bring improvements.

Cardiac arrest occurs when the electrical impulses the heart needs to keep beating go into an irregular, chaotic rhythm and the heart stops pumping. It differs from a heart attack or myocardial infarction caused by a blocked coronary artery.

Just one in 10 patients survives an out-of-hospital cardiac arrest (OHCA), making it a major public health issue, according to Ontario's Institute for Clinical Evaluative Sciences, which studies health outcomes across the province.

Medical researchers are learning more about differences in symptoms and cardiac function between men and women.

Window to help shorter for women

Now a study published in Wednesday's issue of the European Heart Journal suggests that the window to shock the hearts of women into restarting closes sooner than in men. The chances of surviving among women were about half those of men.

If a woman drops down, it's not necessarily that she has fainted.- Dr. Hanno Tan

"I think a policy solution lies in increasing awareness among citizens," said Dr. Hanno Tan, a cardiologist at Amsterdam University Medical Centre. "If a woman drops down, it's not necessarily that she has fainted. It could also be sudden cardiac arrest. I think this is a very important message."

A woman in cardiac arrest will collapse suddenly, and in that period, there will be no breathing or movement. 

Tan and his co-authors analyzed records and hospital charts from more than 5,700 out-of-hospital cardiac arrests treated by emergency medical services in the city of Amsterdam and surrounding rural areas between 2006 and 2012.

They said women were shocked by a bystander using a defibrillator less often than men (68 per cent versus 73 per cent). And when a bystander attempted a resuscitation, women had lower survival rates at every stage of healthcare.

Defibrillator needed?

A low rate of recognition by bystanders could also contribute to slower care in women, Tan said.

When someone with cardiac arrest is connected to an automated external defibrillator or AED, the device looks for shockable initial rhythm or SIR, an abnormal electrical rhythm that is associated with cardiac arrest. 

If a heart with SIR isn't shocked within about 10 minutes, the damage becomes too severe and the person flatlines, meaning all electrical activity stops. At that point, shocking no longer helps.

Overall, the researchers found the shockable initial rhythm in women disappears faster than in men (appearing in 33 per cent of women versus 52 per cent of men.)

Gender issues and biological issues go hand in hand to explain why women show poorer survival rates after cardiac arrest, said Dr. Paula Harvey. (Derek Hooper/CBC)

Even after taking factors like pre-existing disease and how long it took for paramedics to arrive into account, women were still half as likely to have shockable initial rhythm as men.

Not the Hollywood heart attack

As for why, Tan said women themselves may not recognize the urgency of their symptoms.

Heart attack occurs in about a quarter of those who present with cardiac arrest. But heart attack symptoms in women may be harder to recognize than the classic "Hollywood heart attack" of clutching the chest and starting to sweat that men often experience, cardiologists say.

In women, those chest symptoms of a heart attack may occur, or there could be profound nausea and vomiting with palpitations, lightheadedness, extreme fatigue or discomfort in the neck, jaw, shoulder, arms or back.

It's also possible that fewer women with cardiac arrest receive attention from a bystander, to call 911 for instance, because more elderly women live on their own than elderly men.

Melissa Dunlay is thankful a defibrillator was on-site at her dental office. (Roger Cosman/CBC)

Besides education campaigns to raise awareness, the study's authors suggested quicker access to resuscitation care for elderly women living alone. Providing more AEDs in long-term care homes could help.

Pregnancy, menopause and hormonal changes also affect the heart.

The Dutch findings likely apply in Canada, said Dr. Paula Harvey, chief of medicine and cardiology division head at Women's College Hospital in Toronto.

Women more likely to live alone

The reasons for the survival differences between women and men also depend on multiple social factors. For instance, women who are living on their own could be encouraged to wear a device around the neck to send an alarm if she starts to experience symptoms, Harvey said.

"The gender issues and then the biological issues go hand in hand," Harvey said. 

Earlier this month, researchers at the Institute for Clinical Evaluative Sciences published their findings on adults' use of emergency departments before out-of-hospital cardiac arrest in Ontario from 2007 to 2018.

Conventional wisdom holds that out-of-hospital cardiac arrest occurs without previous contact with the health-care system. But the Ontario study found that more than one in four patients were assessed in the emergency department in the 90 days before their cardiac arrest.

"That study was a really important study," Harvey said, because those symptoms are a warning signal for future prevention strategies. "These people clearly are developing a severe heart problem that is putting them at risk of sudden death." 

It's also important to train the general public to recognize when someone is unconscious, not breathing and there's no circulation, she said.

"Just by doing chest compressions you increase significantly the chance of survival. And of course if there is an automatic external defibrillator that can be used," Harvey said.

Melissa Dunlay of Saint John, N.B., is extremely grateful that staff at her dental office used an AED on her when she experienced cardiac arrest in January.

"They noticed I wasn't breathing,  they got out the AED machine and started CPR," Dunlay recalled. "I was shocked five times at the office and four more in the ambulance."

Dunlay, 42, described herself as physically active. She said she doesn't smoke or drink and doesn't have a heart condition, underscoring the importance of more awareness of how cardiac arrest can occur in anyone. 

Explaining the increased heart attack risks for women

4 years ago
Duration 2:16
Men are more likely to suffer a heart attack than women but women are more likely to die from one, and new research explains why.



With files from CBC's Vik Adhopia


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