The incidences of most cardiovascular and thromboembolic events were similar in the two baseline-Hb groups except for a slightly increased incidence of arrhythmias in patients in the ≥10 g/dL baseline-Hb group who received QW darbepoetin alfa; there was also a slightly higher incidence of embolism/thrombosis events in the ≥10 g/dL baseline-Hb group compared with the < 10 g/dL baseline-Hb group. This evidence concerns the gene GSTM1 and cardiac arrhythmia.