Endothelial dysfunction in patients with polycythaemia vera

Patients with polycythaemia vera (PV) are at increased risk of developing a rterial and venous thromboembolic complications. We investigated whether en dothelium-dependent. flow-mediated vasodilatation (FMD) is impaired in PV p atients without clinical evidence of artery disease as observed in patients with conventional cardiovascular risk factors. FMD and endothelium-indepen dent, nitroglycerine-induced vasodilatation (NMD) were assessed using high- resolution ultrasound in the brachial artery of 20 patients with PV and 20 sex- and age-matched control subjects (CTL). FMD was markedly impaired in P V patients compared with CTL (7.6 +/-2.91% versus 11.6 +/-5.7%. P=0.009) wh ereas NMD was similar in both study groups. The impairment of FMD was indep endently related to the presence of PV (r=-0.434, P=0.009) and vessel size (r=-0.107. P=0.038) but was not related to haematocrit values and platelet counts. The results demonstrate that PV is associated with endothelial dysf unction in the pre-clinical phase of arterial disease. However, the precise mechanisms by which PV leads to this altered vascular reactivity remain un clear.