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The Heart Attack You Didn't See Coming
"MINOCA" cases are rising, especially in women.
By Joe Kita
Feb. 16, 2023
Rita Conrad was saying goodbye to friends in the parking lot of a Mexican restaurant when she started feeling fatigued and uncomfortable. It was 10:30 on a Thursday night, so she assumed it was the late hour or maybe the enchiladas. But when she got home, she started to feel discomfort in her back, shoulders, and chest.
"It wasn't a sharp stabbing pain," she recalls. "It was more of an uncomfortable squeezing."
Then the squeezing got worse and she started dry heaving. Her husband wanted to take her to the ER. She insisted it was fatigue, took an aspirin, and lay down. Her symptoms eventually stopped, and she fell asleep.
Although Conrad, 51 at the time and in good health, didn't know it then, she was having an unusual type of heart attack called MINOCA that puzzles doctors and affects women more often than men.
A Heart Attack With Open Arteries
MINOCA stands for myocardial infarction with non-obstructive coronary arteries. As its name suggests, it's a type of heart attack without any blockages (obstructions) in the main coronary arteries. A related condition, called INOCA (ischemia with non-obstructed coronary arteries), has many of the same symptoms but without the actual heart attack.
When diagnosing a heart attack, doctors typically look for blockages in the main coronary arteries. If any are found, they use various methods (such as bypass surgery, angioplasty, or stents) to restore blood flow. Then they prescribe medication, dietary changes, exercise, and other lifestyle changes to prevent more arterial plaque and clots from forming.
Conrad, who lives in Yucaipa, CA, already had a healthy lifestyle. She was a vegetarian with normal blood pressure and cholesterol, and no family history of heart disease. In fact, she'd finished a 5K the weekend before her symptoms started.
The morning after, her primary care doctor told her she'd probably had a heart attack and should get to the ER. A blood test showing elevated levels of a protein called troponin later confirmed that. She was admitted to the hospital and given an angiogram (imaging of the inside of blood vessels — in this case, in the heart).
There was no sign of plaque in her main coronary arteries.
"I'll never forget it," she says. "One of the techs in the room said, 'Your arteries are perfectly clear. You should celebrate with some McDonald's french fries.'"
Conrad says that before she was discharged, she wasn't given any explanation for her heart attack, no prescription for medication, not even a referral to a cardiologist. "My husband and I were driving home, and we were like, 'OK, what now?'"
MINOCA may account for up to 25% to 30% of all heart attacks in women (and less than 10% in men), according to C. Noel Bairey Merz, MD, director of the Barbra Streisand Women's Heart Center at Cedars-Sinai Medical Center in Los Angeles. The symptoms of MINOCA are the same as those of a classic heart attack that happens in someone with coronary artery disease. But because no blockages are found in the main coronary arteries, patients often leave the hospital unsure about what caused their MINOCA heart attack and how to prevent another one.
During the next 3 years, Conrad estimates she had 20 more episodes. None were as severe as the first one and, as far as she knows, none were heart attacks. She visited the ER three more times, but after being sent home as before, she stopped going.
Conrad consulted a cardiologist, who suspected spasms in the coronary artery wall and prescribed nitroglycerin for her chest pain (angina). She eventually quit her job as a local government finance director because she worried the stress might be contributing to her condition. "I thought, 'Well, this is something I'm just going to have to live with,'" she says.
Searching for a Cause
As with Conrad, MINOCA or INOCA can seriously affect a person's life.
Consider the findings of a survey published in January 2023, based on 297 people in an international INOCA patient support group:
What Happens in the Heart
Cardiologist Harmony Reynolds, MD, of NYU Langone Health and colleagues recently studied the blood vessels of 301 women who had had heart attacks. In their study, published in 2021, they took a different approach. Instead of using the typical angiogram to look for arterial plaque, they used various forms of imaging with higher resolutions. This allowed them to look beyond the main coronary arteries and search for trouble elsewhere. With 85% of MINOCA patients in the study, they were able to attribute the women's heart attacks to small plaques and clots in these smaller blood vessels.
"Your arterial system is a lot like a tree," Reynolds says. "It has large trunks and smaller and smaller branches. If a clot forms in the trunk, it can get carried into a smaller branch. If the clot is big enough, it can knock out the entire branch and kill a small part of the heart muscle. That's what we think happens in some MINOCA patients."
Heart attack patients with open arteries are often told, "You didn't have a heart attack," Reynolds notes. "Our study shows that's not correct most of the time." Misdiagnoses can be life-threatening. In the 4 years after someone has a MINOCA event, they have a 13% chance of dying of any cause and a 7% chance of having another heart attack, according to Reynolds.
Why Are MINOCA Cases Rising?
What we now call MINOCA was first described decades ago. Writing in the Archives of Internal Medicine in 1939, two New York doctors noted reports of autopsies of heart attack patients with minimal to no coronary artery disease. There are two main reasons why it's being discussed more now.
First, new technologies such as high-sensitivity troponin tests are much better at detecting small heart attacks. But the imaging systems available in most hospitals haven't caught up. That can leave doctors puzzling over high troponin levels that indicate a heart attack and angiograms that show clear coronary arteries.
Second, long-standing stereotypes about who gets heart disease have shifted. We now know it's the leading cause of death for men and women. Not long ago, heart attacks were incorrectly considered a male thing, and women seeking medical care for similar symptoms were often dismissed. They were told it was nerves and prescribed rest. Doctors and advocacy groups have been working to correct these misconceptions. And as more women get the message, more are coming to ERs at the sign of a possible heart attack, as health experts advise.
"When a woman comes into an ER today complaining of chest pain, she's more likely than 20 years ago to get an EKG and a blood troponin test," says Cedar-Sinai's Bairey Merz.
Researchers aren't sure why MINOCA and INOCA are more common in women than men. Reynolds and Bairey Merz suspect it could be due to hormones, hormone therapy, or the simple fact that women are physically smaller, on average, than men. Women's hearts and blood vessels are typically smaller, so arterial blockages and clots that may not show up on conventional imaging can do more damage.
But not all MINOCA and INOCA is caused by plaque buildup and rupture in the heart's small arteries.
Everyone has some plaque. When it exists in small arteries, it takes up more of the available space. There are other potential causes. For example, the interior of an artery wall can tear and cause a blockage that feels like a classic heart attack. This is known as spontaneous coronary artery dissection, or SCAD.
Other times, blood vessels can spasm, which interrupts normal blood flow and produces heart attack-like symptoms. Still, other potential causes include myocarditis (an inflammation of the heart muscle) and stress cardiomyopathy (a reaction to a surge of adrenaline). Reynolds and Bairey Merz encourage doctors to consider all these possibilities when a patient of any gender with open arteries has a heart attack or chronic chest pain.
How to Protect Yourself
After years of being unable to get her condition diagnosed, Rita Conrad was watching a TV news interview with Purvi Parwani, MD, director of the Women's Heart Health Clinic at Loma Linda University Health in California.
"She described my symptoms exactly," Conrad says. She quickly made an appointment to see Parwani, who diagnosed her with MINOCA caused by vasospastic angina (an artery spasm) and prescribed medication (ranolazine) to manage it.
Conrad says she's reached "a much better place" with her heart health. Her MINOCA episodes are down dramatically. She's working again and traveling with her husband. "I have my life back. I'm not scared anymore."