Myocardial infarction and other arterial occlusions are considered to be rare in hemophilia A. However, a systematic study of the subject has never been attempted. All case reports of myocardial infarction or other arterial occlusions have been now gathered and properly evaluated from a cardiological point of view. Thirty-six patients with myocardial infarction and 6 patients with documented cerebrovascular event were retrieved from the literature. The age of the patients varied between 7 and 79 years, with a mean of 44 years. In 16 cases, the arterial occlusion occurred in men <40 years of age. The majority of myocardial infarctions (MIs) were anterolateral (12 cases). Posterior-inferior MI was present in 6 cases whereas it was of the non-Q type in 4 patients. It was multiple in 6 cases, and in the remaining patients the type of infarction could not be determined. In 26 cases, the thrombotic event (22 myocardial infarctions and 4 ischemic cerebrovascular accidents) occurred during or after the infusion of factor VIII concentrates and, more frequently, after prothrombin complex concentrates (activated or non-activated ones) or recombinant factor VIIa preparations. In 3 cases, the vascular complication occurred after intravenous desmopressin administration. MI was fatal in 7 instances. After the event, signs and symptoms of heart failure were seen as sequels in 7 patients. One patient had to undergo cardiac transplant 5 months after the MI. No death occurred after ischemic cerebrovascular accidents. Since not all hemophilia patients develop inhibitors and therefore are not usually treated with activated concentrates, this series of patients is somewhat biased and does not allow general conclusions. The high prevalence of MI and other arterial complications which occurred after transfusion therapy, usually in patients with inhibitors, clearly indicates the need for a careful evaluation of the appropriate therapeutic approach in each single patient.

Vitamin K-dependent clotting factors are commonly divided into prohemorrhagic (FII, FVII, FIX, and FX) and antithrombotic (protein C and protein S). Furthermore, another protein (protein Z) does not seem strictly correlated with blood clotting. As a consequence of this assumption, vitamin K-dependent defects were considered as hemorrhagic or thrombotic disorders. Recent clinical observations, and especially, recent advances in molecular biology investigations, have demonstrated that this was incorrect. In 2009, it was demonstrated that the mutation Arg338Leu in exon 8 of FIX was associated with the appearance of a thrombophilic state and venous thrombosis. The defect was characterized by a 10-fold increased activity in FIX activity, while FIX antigen was only slightly increased (FIX Padua). On the other hand, it was noted on clinical grounds that the thrombosis, mainly venous, was present in about 2% to 3% of patients with FVII deficiency. It was subsequently demonstrated that 2 mutations in FVII, namely, Arg304Gln and Ala294Val, were particularly affected. Both these mutations are type 2 defects, namely, they show low activity but normal or near-normal FVII antigen. More recently, in 2011-2012, it was noted that prothrombin defects due to mutations of Arg596 to Leu, Gln, or Trp in exon 15 cause the appearance of a dysprothrombinemia that shows no bleeding tendency but instead a prothrombotic state with venous thrombosis. On the contrary, no abnormality of protein C or protein S has been shown to be associated with bleeding rather than with thrombosis. These studies have considerably widened the spectrum and significance of blood coagulation studies.

The congenital deficiency of prekallikrein (PK) is a rare condition in which there is a peculiar discrepancy between a severe in vitro defect and absence of bleeding. The gene controlling PK synthesis is located on chromosome 4 and consists of 14 exons and 15 introns. Only approximately 80 cases of PK deficiency have been described in the literature. Owing to the lack of bleeding, most cases go undetected or, if detected, go unreported. Occasional bleeding or thrombosis have been reported in a few patients but this was only due to the presence of associated risk factors. It is certain that the defect does not protect from thrombosis. Diagnosis is based on the presence of a great prolongation of partial thromboplastin time and normal prothrombin time and thrombin time. The long partial thromboplastin time is fully corrected by the addition of normal plasma or normal serum and presents the unusual feature of shortening on long incubation times. Platelet and vascular tests are normal. Immunological studies allow differentiation into two types, namely cases of true deficiency, which are approximately 70% of the total, and cases with abnormal forms. PK is a glycoprotein synthesized in the liver as a single-chain peptide of 88000 Da. It mostly circulates (∼75%) as a complex with high-molecular-weight kininogen. It is cleaved by FXIIa into a heavy chain and a light chain (catalytic domain), held together by disulfide bonds. Molecular biology techniques have so far only been applied to eleven families, and these studies do not yet allow definite phenotype/genotype conclusions. The exons involved are 5, 8, 11, 14 and 15. The noncoagulative effects of PK, mainly based on the effect of kallikrein, have been studied less, since they appear to be the result of the involvement of other components of the contact phase. Kallikrein can mainly affect the formation of bradykinin from high-molecular-weight kininogen and the activation of pro-urokinase to urokinase. Bradykinin causes inflammation, vasodilatation and an increase in vessel permeability. The activation of pro-urokinase results in enhanced fibrinolysis. However, fibrinolysis has been reported to be normal or defective in these patients.