Compensatory “eryhtrocytosis” in cyanotic heart disease

Abstract

We read with great pleasure the work by Wu and Tseng [1]. Indeed, the clinical presentation of pulmonary embolism (PE) can mimic as hypercyanotic crisis or Tet spells in a patient with tetralogy of Fallot. Furthermore, the presence of telltale sign of Tet spells, that is, profound hypoxia and cyanosis in patients with tetralogy of Fallot, decreases the clinical suspicion of PE. The authors maintained a commendable degree of clinical suspicion; however, we would like to highlight an additional important consideration in this case. The authors use the term compensated polycythemia, referring to an outcome in patients with cyanotic congenital heart disease causing an increase in blood viscosity and thromboembolic events. “Polycythemia” refers to increase in more than 1 cell lines in bone marrow. As a matter of fact, hypoxia in cyanotic congenital heart disease is a trigger for “erythrocytosis,” that is, proliferation of red blood cell lines and thereby increased red cell mass [2,3]. Therefore, we recommend using the term compensatory erythrocytosis instead of compensated polycythemia. TheWells score is truly not validated in cyanotic heart disease. Nevertheless, onemust remember that these patients have a slightly higher risk than general population for the development of PE given their underlying hyperviscosity [4]. Thus, a clinical suspicion for PE is perhaps very reasonable if there is no clinical improvement with the conventional therapy for Tet spells.