PubMed2005
Thromboembolism is considered the inciting cause of many vascular disorders including acute coronary syndrome (ACS), ischemic stroke, pulmonary embolism (PE), deep vein thrombosis (DVT), and mesenteric ischemia. Adrenergia and inflammation are known to accompany these conditions, particularly among arterial thromboembolic disorders, but the teleologic basis of these associations remains poorly understood. We argue that thromboembolism may sometimes be the result, rather than the cause, of acute vascular events, and may be precipitated by underlying adrenergia. Thromboembolic events are most prone to occur during parts of the circadian, seasonal, lifespan, and reproductive cycles with sympathetic dominance, as well as during behavioral, exertional, physiologic, and iatrogenic activation of sympathetic stress. Molecular evidence suggests that adrenergia and inflammation can promote coagulation and lead to co-activation of the pathways. Acute vascular events that occur without angiographic evidence of occlusion suggest that some infarcts may be attributable to adrenergia alone. "Embolic" disorders may represent asynchronous systemic phenomena rather than clot migration. During acute thromboembolism, downstream tissue hypoxia can activate maladaptive self-propelling cycles of sympathetic bias, inflammation, and coagulation. The counterproductive co-activation of these pathways may reflect a maladaptive interlink forged during the primordial evolution of trauma physiology. Their rapid co-mobilization enables rapid control of hemorrhage, microbial defense, and perfusion maintenance during trauma, but the pathways may behave maladaptively in the setting of modern diseases where endothelial injury may be more often precipitated by smoking, diabetes, dyslipidemia, or hypertension. Sympathetic blockade is already employed in ACS, and beta-blockers are used as antihypertensives to prevent stroke. Our hypothesis suggests that the benefits of beta-blockers in stroke may be independent of antihypertensive effects, and that adrenergia may represent a target for managing all thromboembolic disorders, independent of anti-coagulative and thrombolytic therapies. Perhaps reducing adrenergia, rather than maintaining high cerebral perfusion pressure, may represent a counterintuitive strategy for treating stroke and for reducing reperfusion injury. Plausible mechanisms by which autonomic dysfunction may induce venous thrombosis are discussed, especially in those with baroreceptor dysfunction, immobilization, or dehydration. Unexplained hypercoagulability of cancer may also operate through tumor-induced adrenergia and inflammation.