TREATMENT OF ORTHOSTATIC TACHYCARDIA WITH ERYTHROPOIETIN

PURPOSE: TO determine whether increasing red blood cell volume with er ythropoietin reverses the hemodynamic response to standing in patients with orthostatic tachycardia. PATIENTS AND METHODS: Eight patients (2 men, 6 women) with orthostatic tachycardia were administered erythrop oietin (50 U/kg body weight 3 times a week for 6 to 12 weeks) in order to reverse their red blood cell volume deficit. Six of the patients a lso received fludrocortisone (0.1 mg/d). Plasma and red blood cell vol umes as well as the hemodynamic response to orthostatic stress were me asured before and after erythropoietin therapy. RESULTS: Erythropoieti n therapy increased the mean +/- hematocrit from 37.6 +/- 1.0 to 46.4 +/- 1.4 (+/- standard error) (P <0.01) and increased the red blood cel l volume from 17.7 +/- 1.1 to 24.6 +/- 2.0 mL/kg (P <0.01). Treatment increased supine mean blood pressure (from 87 +/- 4 to 93 +/- 5 mm Hg, P <0.025) and standing mean blood pressure (from 87 +/- 4 to 94 +/- 5 mm Hg, P <0.025). Erythropoietin therapy, however, failed to reverse orthostatic tachycardia. Following treatment, the mean heart rate afte r 5 minutes standing was 129 +/- 7 bpm, not significantly different fr om the pretreatment standing heart rate (134 +/- 5 bpm). CONCLUSIONS: Although patients with the orthostatic tachycardia syndrome have a def icit in red blood cell volume, this is not the cause of their abnormal hemodynamic response to standing. Erythropoietin therapy fails to rev erse orthostatic tachycardia.