Her doctors also told her that the only thing she could do to avoid SCAD in the future was to never get pregnant again. But seeking to learn more about the disease that had almost taken her life, she went online and started to find other women with similar symptoms around the world.

In 2009, Ms. Leon went to the WomenHeart Science and Leadership Symposium at the Mayo Clinic, where she met Dr. Sharonne N. Hayes, a professor of cardiovascular medicine at Mayo. At that time, the largest study on SCAD included 43 patients. “I walked up to Dr. Hayes and told her we had 70 people, and we wanted research,” Ms. Leon recalled. “She was like, ‘Wow.’”

“Everything I learned about SCAD in my medical training was wrong,” Dr. Hayes said.

By 2010, with the help of Dr. Hayes, and subsequently SCAD Research Inc., an organization founded by Bob Alico, who lost his wife to SCAD, Dr. Hayes devised an innovative way to do research, using online networks of far-flung patients and analyzing genetic and clinical data. “We never imagined there would be 1,000 female patients in our virtual registry,” Dr. Hayes said.

That fortuitous meeting between Ms. Leon and Dr. Hayes has helped transform SCAD from being an unknown, unrecognized condition to something all physicians are taught about during medical school and in later training. SCAD is now recognized as the most common cause of heart attacks in women under 40.

Why did it take so long for physicians and researchers to recognize SCAD? The most important reason might have been that the condition predominantly affects women. “We listen less well to women,” said Dr. Hayes. “We are much more likely to associate their symptoms with psychological causes.” A heart attack is more likely to be fatal in a young woman than a young man, perhaps because women’s cardiac symptoms are more often misattributed to anxiety or depression than men’s.

The bias that many women feel they face in the clinic or the emergency room has led some, like Ms. Leon, to take action and advocate for themselves and others. “People are activated by injustice, by unanswered questions,” said Dr. Hayes

She offers this advice: “Don’t walk out of a doctor’s office without answers. Find a doctor who is committed to listening to you and does not think they know everything about anything.”

The story of SCAD underscores how much we doctors still don’t understand, including about heart disease in women. Too often those in the medical profession downplay women’s complaints, telling them nothing is wrong. Women are often expected to take care of others but too often neglect themselves. Indeed, women take much longer to seek medical care for a heart attack than men. As we embrace new technologies to peer ever deeper inside the human body to find answers, perhaps the better route might be simply to attend to the patient in front of us. Often what we need to do is listen.