Link between von Willebrand factor multimers, relapses and coronary microcirculation in patients with thrombotic thrombocytopenic purpura in remission

Abstract

Introduction: ADAMTS13 deficiency results in unusually large von Willebrand factor (ULVWF) multimers in the circulation and a higher risk of microthrombi due to high shear stress. In patients treated for acquired thrombotic thrombocytopenic purpura (TTP), a persistently severe ADAMTS13 deficiency (<10%) in remission is associated with more relapses. A reduced plasma ADAMTS13 activity and increased VWF levels are associated with a higher risk of myocardial infarction. Assessing coronary flow reserve (CFR) enables a better cardiovascular risk stratification: a lower CFR correlates inversely with cardiovascular risk. The aim of the study was to establish whether patients with TTP in remission have an impaired coronary microcirculation, in terms of a lower CFR, and whether there is any correlation between ADAMTS13 activity, the presence of ULVWF multimers, and the occurrence of relapses.

Methods: The clinical information and hemostatic parameters of 24 patients with TTP in remission managed at our center were analyzed. The CFR was assessed in a subgroup of the TTP patients and compared with a control group consisting of 50 healthy volunteers.

Results: The CFR was statistically lower in patients in remission of TTP than in controls, but there were no differences between TTP patients with normal and lower CFR. The occurrence of relapses correlated with the presence of ULVWF multimers and with a residual ADAMTS13 activity.

Conclusions: When compared with healthy controls, TTP patients in remission have an impaired coronary microcirculation and the occurrence of relapses in the former reveal the presence of ULVWF multimers.

Keywords: ADAMTS13; Thrombotic thrombocytopenic purpura (TTP); von Willebrand factor.