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Heart attacks with no blockage
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Through the 1970s, 80s, and 90s, cardiologists pictured a coronary artery as a tube. If a clog stopped the blood from passing, that was a heart attack. Then women began arriving with chest pain, abnormal stress tests, and abnormal EKGs. Angiograms, which thread a catheter into the heart, showed no blockage, so the women were told they had no heart disease and were offered an antacid or a Valium.
Damage without blockage
Those women kept coming back to the hospital, and when researchers looked at their lifespans, they were shortened. That made it clear the problem was real. Microvascular disease can cause all the damage of a heart attack without a blockage: a blood vessel can spasm, or react differently to stress hormones like the ones behind fight or flight. A heart attack with no obstructive coronary disease has its own name, MINOCA.
Tests and unknowns
Tests came afterward, some invasive with catheters and others special cardiac imaging studies. Microvascular disease and spontaneous coronary artery dissection are the two heart conditions unique to women. How common they are remains unknown, because so many women were sent away over the decades without a diagnosis.
Why can the heart suffer without a blockage?
Heart muscle gets oxygen from the large coronary arteries and from a web of far smaller vessels branching off them. If those small vessels squeeze shut or fail to widen when the heart works harder, part of the muscle runs short of oxygen even though the large arteries are open. A coronary artery can also clamp down in spasm and briefly cut off flow. Blood tests for troponin, a protein released by injured heart muscle, can show damage in these cases just as they do in blockage-driven attacks.
How can an artery tear without any plaque?
In spontaneous coronary artery dissection, the layers of an artery wall separate and blood seeps between them. The pooled blood forms a bulge called an intramural hematoma that narrows the channel the blood needs. It is a recognized cause of heart attacks in younger women, including some that happen during or after pregnancy. Because the artery holds no plaque, an angiogram can look close to normal.
Why can't an angiogram see the smallest vessels?
Angiography works by injecting contrast dye and taking X-ray images of the dye filling the arteries. It outlines the main coronary arteries and their larger branches well. Vessels of the microcirculation are well under a half millimeter across, which is below what the images resolve. A scan can therefore show open large arteries while the smallest vessels stay out of view.
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