Study objective: QT dispersion (QTd) and late potentials derived from signal-averaged ECG (SAECG) have been proposed as noninvasive predictors of cardiac arrhythmias that occur in patients with COPD. In this study, we aimed to investigate QTd and SAECG in patients with COPD.
Design: Cross-sectional study.
Setting: Teaching chest disease hospital and cardiology center in a university hospital.
Patients: Thirty patients with COPD (28 men and 2 women; mean +/- SD age, 60 +/- 9 years) and 31 age- and sex-matched control subjects (28 men and 3 women; mean age, 57 +/- 7 years) were included.
Measurements and results: Respiratory function tests, arterial blood gas analyses, echocardiographic examinations, rhythm Holter recordings, and heart rate variability (HRV) analyses were performed in addition to the measurements of QT intervals and SAECG. Patients with COPD had higher rate of ventricular premature beats (VPBs) as compared to control subjects (924 +/- 493 beats vs 35 +/- 23 beats, p = 0.009). Eight patients with COPD (27%) had nonsustained runs of ventricular tachycardia (VT). QTd rates were significantly increased in patients with COPD as compared to control subjects (57.7 +/- 9.9 ms vs 37.5 +/- 8.2 ms, p < 0.001). On comparing patients with COPD with and without runs of VT, patients with VT had longer QTd (67 +/- 10 ms vs 55 +/- 8 ms, p = 0.001). However no difference in any HRV and late potential parameters were found between patients with COPD with and without runs of VT. VPB rates were strongly correlated with QTd in patients with COPD (r = 0.61, p < 0.001). On SAECG analysis, patients with COPD had significantly increased total QRS duration as compared to control subjects. Nine of the 30 patients with COPD (30%) had positive late potentials. However, QTd and VPB rates were also similar between patients with COPD with and without late potentials.
Conclusions: The development of ventricular arrhythmia in patients with COPD was associated with increased QTd. Increased QTd may be associated with autonomic changes seen in patients with COPD.