Recent Advances in Thrombosis and Hemostasis - Part I.

The burden of thrombotic diseases is heavy on the world population. It is widely known that coronary artery disease is amajor cause of death but many laymen do not know that the mortality is mediated by thrombosis on a ruptured plaque. It is also lesswell-known that stroke is commonly the result of a thrombus that might have embolized from the heart or the carotid artery or was sometimes generated in situ. Together, ischemic heart disease and stroke account for 25% of the deaths worldwide.1 Still, deaths related to venous thromboembolism are often hidden in the statistics. With the drastically decreasing rate of autopsies performed, an increasing number of cases with fatal pulmonary embolism are misclassified. For the survivors of venous thromboembolism there is a high risk of long-term sequelae, mainly as postthrombotic syndrome and, for a smaller proportion of those with pulmonary embolism, the development of chronic pulmonary hypertension is a feared complication. Furthermore, approximately 50% of those with unprovoked venous thromboembolism will have one or several recurrent events during their remaining lifewith or without hospitalizations andwith accumulating risk of sequelae. Venous thromboembolism is therefore associatedwith significantmorbidity andmortality. Despite substantial advances in the diagnosis, treatment and prophylaxis of venous thromboembolism during the past decades there is still room for improvement. It is our pleasure to provide the readers of Seminars in Thrombosis & Haemostasis with an update on several of these aspects in the current and a forthcoming issue of the journal. The topics were formulated by a group of leading scientists in the field, as facilitated by a gathering in Stockholm, Sweden, in November 2016, as hosted by the Swedish Society of Medicine in cooperation with Karolinska Institutet. There seems to be an ever-expanding list of risk factors for venous thromboembolism, and they can be classified as environmental or genetic. The genome-wide association studies have verified much of what we already knew about components in the coagulation cascade and the ABO blood groups and their influence on risk. Interestingly, also some single nucleotide polymorphisms in genes without apparent relation to these systems have been identified as susceptibility loci. This may teach us more about mechanisms involved in thrombus formation. Crous-Bou et al review all these risk factors and some of their interactions in the first paper of this issue.2 Familial aggregation or family history of venous thromboembolism encompasses both genetic and environmental components and thus demonstrates the characteristics of a complex trait. Zöller et al have carefully analyzed whether familial aggregation can be considered a causal risk factor for venous thromboembolism by examining each of the nine Hill’s criteria for causation.3 There are good reasons why family history always should be evaluated in the work-up of patients with venous thromboembolism. The diagnosis of deep vein thrombosis is now almost exclusively performed with ultrasonography. Similarly, computed tomography of pulmonary arteries (CTPA) has become standard for diagnosis of pulmonary embolism because of the around the clock availability at most emergency departments. It is also perceived as a simplification, being a single exam, compared with the combined ventilation–perfusion lung scan. The latter has, however, improved its performance with the use of three-dimensional single photon emission computed tomography, abbreviated as V/Q SPECT. This method is now outperforming the CTPA in some aspects. It can also be combined with a low radiation CTPA. Hess et al present here a systematic review and meta-analysis of the performance of current diagnostic imaging methods for pulmonary embolism.4 Subsequently, they develop a thorough discussionwith a review of eachmethod as well as their role in specific patient populations. Patients with deep vein thrombosis and to a larger extent those with pulmonary embolism are still treated in the