Just about everything we know about heart disease in women was learned in the early 1990’s. This is when the National Institutes of Health began requiring that women be included in the studies it funds. Up until then, most medical research was conducted on men: male patients, male rats, male monkeys and male cells. Like most gender gaps, this one is closing slowly. We are seeing differences between men and women in the development of heart disease and starting to take note.

In arteriosclerosis, men and older women are likely to have a blockage in one or more of their coronary arteries from localized plaque. But new research is showing that younger women are more likely to have diffuse plaque that lines and narrows the entire artery. Even though this leaves the heart muscle with a lack of oxygen and blood supply, no specific blockage is detected on tests. Even though a woman may have symptoms of blocked vessels, such as chest pain or shortness of breath, testing with repeated angiograms would show open arteries and no blockage. The woman is told that she is “free of heart disease” even though she is at high risk of a fatal heart attack.

Fortunately more doctors are now recognizing that despite having open arteries, half of women with this pattern have ischemia…poor blood flow through the heart. This condition is now called, ischemia and no obstructive coronary artery disease (INOCA). It comprises 25-30% of ischemic heart disease in women and 10% in men. You wonder why and how the heart can be starved for blood if its main arteries are not blocked. The answer is that women have smaller capillaries and arterioles that deliver oxygen and nutrients to the heart muscle. The walls of these vessels become dysfunctional where they fail to contract and dilate as they should.

Why women are so much more susceptible is unknown. The typical suspects are smoking, diabetes, high blood pressure and high cholesterol. But a history of problems during pregnancy, such as elevated blood pressure, pre-eclampsia and diabetes, as well as depression and autoimmune diseases, which are more common in women, may also contribute.

Effective treatment is badly needed. The first large trial comparing an intensive drug regimen got underway in 2018 and we should have results by 2022 which should help set treatment standards for women with INOCA. Women with microvascular dysfunction often go on to develop heart failure. Women have a different type of heart failure than men but both types are rising in the U.S. because our population is getting older, heavier and more diabetic. Even if you have had a heart attack and survived, you have a higher risk of dying of heart failure down the road.

Heart disease is the number one killer of U.S. women, far exceeding deaths from all cancers put together including breast cancer. Younger women, in particular, often go undiagnosed because physicians do not consider the possibility of cardiac disease. Hopefully that will soon change as more research continues to emerge describing these gender differences.

Reference: Wallis, C. “What Ails a Woman’s Heart”. The Science of Health. Scientific America, January 2019.