ABSTRACT
Why do the fibroids die, while the uterus survives? Fibroids seem to be more vulnerable to uterine ischemia than a healthy myometrium, a mechanism that is not fully understood. Perfusion studies by MRI and computed tomography performed after fibroid embolization indicate that blood initially clots in the vessels of both myometrium and fibroids. After a period of time, the blood clots disappear inside the vessels of healthy myometrium, but not inside the fibroid vessels. The myometrium survives until the bloodflow is re-established, unlike the ischemic fibroids, which die due to their insufficient blood supply. It is hypothesized that the fibroid tissue is less able to lyse clots that form inside the vessels after ischemia and less able to recruit collateral flow. Normal myometrium have
higher activity of fibrinolytic enzymes compared to fibroids, a fact which supports this theory. The combination of a greater microvascular density and vessels with a larger mean surface in the myometrium may contribute to this. The fibrinolytic enzymes are concentrated in the endothelium of the vessels. Future genetic and molecular investigations might reveal further insight to these mechanisms.
