AnneMarie Hess, a 40-year-old mother with a newborn, was taking a shower when she felt an unusual pain in her chest. She stopped the shower and sat down. The pain abated.

Later, while driving her other children to a violin lesson, the chest pain returned: this time it didn't subside.

A concerned neighbor took her straight to the emergency department. There, the medical staff worked quickly, taking EKGs and pumping her with IV fluids. The tests revealed a heart attack.

“It’s really a blur, I just remember being given a little cup with maybe 30 baby aspirin,” says Hess of the heart attack which occurred in 2008. “I just kept saying to the nurse, I have to be okay, I have this 17-day-old baby.”

An angiogram found nothing; her arteries were clear. She began exercising more regularly and even started weightlifting.

But six years later, during a Fourth of July trip in Wisconsin, it happened again. Only this time it was a full cardiac arrest.

“I didn’t have pulse,” says Hess. “I had about 45 minutes of CPR and I was shocked about 10 times before they could get me back into a normal rhythm.”

Related: 5 Things to Know About Sudden Heart Attacks

After Hess’s second heart attack, it became clear that this was not a postpartum complication — she was diagnosed with spontaneous coronary artery dissection, or SCAD.

“I didn’t have pulse,” says Hess. “I had about 45 minutes of CPR and I was shocked about 10 times before they could get me back into a normal rhythm.”

“SCAD is a type of heart attack, but completely different than the one we normally think of,” says cardiologist Dr. Sharonne Hayes of the Mayo Clinic, Rochester, Minnesota. “It's caused by a split or tear in an otherwise healthy artery that leads to a drop in blood flow to the heart leading to a heart attack.”

Researchers are discovering that SCAD heart attacks occur more frequently than once thought.

The most vulnerable are younger women who are otherwise healthy, with normal blood pressure and no risk factors for heart disease. The average age of those affected is 42-years-old, with roughly 10 to 20 percent being new mothers or pregnant. The condition can also affect men.

SCAD is often misdiagnosed, says Hayes. It is relatively uncommon, but in women under 50, it may be the cause of up to 45 percent of heart attacks.

“We haven't really found anything specific that will prevent SCAD,” says Dr. Hayes.

Related: Cardiac arrest killing too many

Patients with SCAD are advised to avoid pregnancy, as well as competitive sports or heavy weightlifting.

Signs of a heart attack

SCAD has no special warning signs, so doctors advise women to know the signs of a heart attack:

chest discomfort

pain in the arm, back, or even the jaw

cold sweats

light-headedness

fatigue

shortness of breath

Hess now takes medications, including blood thinners, to try to prevent another attack. The mother of five has decided she won't have more children and avoids strenuous exercise. By raising awareness of SCAD, she hopes women with vague symptoms won't feel foolish about going to the ER.

“A lot of women are told they have anxiety and then they later find out later that it was SCAD,” says Hess.