Late potentials and QT dispersion after high‐dose chemotherapy in patients with non‐Hodgkin lymphoma

The most common cardiotoxic effects of high-dose cyclophosphamide (CY) are electrocardiographic changes and transient arrhythmias. Therefore, we prospectively assessed serial electrocardiogram (ECG) and signal-averaged electrocardiogram (SAECG) recordings in 30 adult patients with non-Hodgkin lymphoma (NHL) receiving high-dose CY as part of high-dose chemotherapy (HDT) regimen. All patients were treated with anthracyclines earlier. Heart-rate-corrected QT interval and QT dispersion (QTc and QTc dispersion) were measured from ECG. QRS duration and late potentials (LPs) were analysed from SAECG. Both ECG and SAECG were recorded 1 day (d) prior to HDT (d-7) at baseline, and 1 day (d-2), 7 days (d+7), 12 days (+12) and 3 months (m+3) after HDT. Stem cells were infused on day 0 (d0). Cardiac systolic and diastolic function were assessed on (d-7), (d+12) and (m+3) by radionuclide ventriculography. At baseline, four patients presented with LPs. Cardiac systolic function decreased significantly (53 +/- 2; 49 +/- 2%, P = 0.009 versus baseline), whilst no patient developed acute heart failure. QRS duration prolonged and RMS(40) reduced significantly versus baseline (104 +/- 3; 107 +/- 3 ms, P = 0.003; 41 +/- 4; 38 +/- 3 microV, P = 0.03), and six patients (21%) presented with LPs after CY treatment. Both QTc interval and QTc dispersion increased versus baseline (402 +/- 5; 423 +/- 5 ms, P<0.001; 32 +/- 2; 44 +/- 3 ms, P = 0.012), and six patients (20%) developed abnormal QT dispersion. In conclusion, high-dose CY causes subclinical and transient electrical instability reflected by occurrence of LPs as well as increased QTc interval and QT dispersion. Thus, longer follow-up is required to confirm the meaning of these adverse effects on cardiac function and quality of life.