Pulmonary embolism (PE) is regarded as perhaps the most dire complication of deep venous thrombosis (DVT), but a new study indicates that venous blood clots may also pose a strong risk of heart attack or stroke within a year’s time (Lancet. 2007;370:1773-1779).
Although arterial blood clots have been a well-known cause of MI and stroke, venous clots were not thought to have the same consequences. Some studies had made the link, but other research has revealed no such relationship. A large, long-term evaluation of DVT patients in Denmark may help settle the question.
Using their nation’s medical databases, the Danish researchers evaluated the risk of MI and stroke over a 20-year period in 25,199 patients hospitalized with DVT as well as 16,925 patients admitted for PE. None of the patients had known cardiovascular disease.
Compared with 163,566 population controls, the DVT patients were 60% more likely to have a heart attack and 119% more likely to suffer a stroke during the first year after the thrombotic event.
Patients with PE were 2.6 times more likely to have an MI and nearly three times more likely to have a stroke in that same time frame. The researchers said DVT was comparable to smoking, diabetes, and other conventional risk factors for arterial cardiovascular events.
Over the full 20 years of follow-up, the risks for heart attack and stroke were 20%-40% higher for the two groups of patients—weaker than the first year after hospital admission for DVT but still significant.
“It is not plausible that venous thromboembolism in itself causes MI and stroke,” noted the investigators in their report. “Rather, the association we find must be due to shared risk factors or etiologic pathways, or both.”