Background: Patients with chronic heart failure (CHF)
have a markedly increased incidence of malignant ventricular
arrhythmias. QT dispersion (QTd), defined as the difference
between maximal and minimal QT intervals, reflects the regional
inhomogeneity of ventricular repolarization dispersion and may
mark the presence of malignant ventricular arrhythmias.
Purpose: To determine the effects of exercise training on
QTd in patients with CHF.
Patients: Fifteen patients
with CHF and ejection fractions < 40% (mean, 28 ± 9%) who
were on a stable medical regimen.
intervention: Standardized 12-lead surface ECGs were obtained at
the beginning and end of the exercise training program, and QT and JT
intervals were measured manually and corrected for heart rate by
using Bazett’s formula. QTd, heart rate-corrected QTd (QTc-d),
JT dispersion (JTd), and heart rate-corrected JTd (JTc-d) were measured
in at least eight ECG leads in each patient.
Following the cardiac rehabilitation and exercise training programs,
patients with CHF had only slight improvements in exercise capacity
(results were not significant). However, these patients had
marked improvements in QTd (71 ± 11 to 59 ± 17 ms; p < 0.02),
QTc-d (82 ± 28 to 63 ± 17 ms; p < 0.01), JTd
(76 ± 19 to 57 ± 18 ms; p < 0.002), and JTc-d (84 ± 23 to
61 ± 18 ms; p < 0.001) following the exercise training
Conclusion: These data indicate that aerobic
exercise training significantly reduces the indices of ventricular
repolarization dispersion in patients with CHF. Further studies are
needed to evaluate how effectively this reduction in ventricular
repolarization dispersion decreases the risk of malignant ventricular
arrhythmias and sudden death in patients with