“When will my clot and pain go away?” is a question commonly asked following diagnosis of deep vein thrombosis (DVT) or pulmonary embolism (PE).
Blood-thinners themselves do not dissolve the clot. The body naturally absorbs a blood clot over the course of several weeks to months and the symptoms which accompanied the blood clot gradually improve and often eventually disappear.
Most patients with DVT or PE recover within several weeks to months without significant complications or long-term effects.
In some patients, the clot never goes away completely: about half of the patients with DVT will have left-over (residual) clot if a follow-up Doppler ultrasound is done 6 months after the acute clot. This is not a clot that can break off, but rather scar tissue within the blood vessel. Because other blood vessels take over and bypass the narrowed or damaged veins, patients are often without symptoms, even if they do have left-over damage at the area where the DVT was.
The risk of clot breaking off and forming a PE is mostly present in the first few days, up to approximately 4 weeks, while the clot is still fresh and fragile and not scarred. Some people have chronic (long-term) problems after a clot due to damage done when the clot formed and partly due to the chronic obstruction from left-over clot, i.e. scar tissue.
Post-thrombotic syndrome is one complication from a blood clot in the leg which results in long-term swelling and pain. PTS occurs in approximately 40% of persons with DVT and varies from person-to-person in its severity. Post-thrombotic syndrome is discussed in detail, here.
Blood clots in the lung can sometimes cause left-over symptoms of shortness of breath, decreased exercise ability, or chest discomfort, but most people recover completely. However, in a few patients, clots do not completely dissolve and significant chronic damage to the lung results, called pulmonary hypertension. Pulmonary hypertension is discussed in detail, here.
It is not helpful to obtain regular follow-up Doppler ultrasounds of the legs to see whether the clot is gone or still there. Finding left-over clot or scar tissue does not change management. The only time a follow-up Doppler ultrasound is really helpful is once a patient comes off blood thinners. A new ultrasound at that time provides a new baseline, so that it is easier to tell in the future, if new symptoms occur, whether a new clot is present or whether the changes seen are old. Follow-up CT scans are also typically not helpful. Because of the radiation exposure, even though relatively low, a routine CT of the chest is typically not obtained as a new baseline when a patient stops the blood thinner.