Hi Dr Cranquis -- in an earlier question about anesthesia and stroke, you said that perhaps the patient had developed DVT and the clot shot up to the brain.What is the mechanism for this to happen? My mother suffered a massive stroke a couple days after an (otherwise successful) knee surgery and the Doctors said the same thing -- likely a blood clot formed and reached her brain. At the time, I didn't even think to ask how it could have happened.How does a blood clot go from a vein to the brain? I thought all venous blood had to go through capillaries at the alveoli in the lungs for oxygenation, so a blood clot from DVT should result in pulmonary embolism rather than a stroke? Is there some "bypass" route that some blood can take to get around the lungs?
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Yes, it would be impossible for an embolus (traveling blood clot) originating from a DVT (located, by definition, in the Venous system) to travel into the arterial blood flow up to the brain without getting trapped in the capillaries in the lung… unless the patient had a pre-existing abnormal anatomic passageway providing a “bypass” around the pulmonary blood vessels. A patent foramen ovale could provide that bypass, leading to a “paradoxical embolus” which travels from the “right-sided” venous system into the “left-sided” arterial system. Not common, no, but possible. A cardiac ultrasound (echocardiogram) would help pick up that structural defect.
The more common sources for ischemic stroke emboli are from thrombi formed within the heart (heart attacks, atrial fibrillation, endocarditis, atrial myxoma) and the arteries (aneurysms), all located to the “left” of the pulmonary blood vessel system.
I’m sorry to hear about your mother’s stroke! Hopefully she’s recovering from it? :(
