QT dispersion: An electrocardiographic derivative of QT prolongation

Background QT dispersion has been considered a surrogate for heterogeneity of repolarization, leading to ventricular arrhythmias. Methods High-resolution 12-lead electrocardiograms were obtained in 15 pati ents with a history of ventricular tachycardia or ventricular fibrillation, 15 patients with congestive heart failure, 17 patients with a history of p revious Q-wave myocardial infarction without heart failure, and 23 healthy control subjects. Results QTc dispersion was prolonged in all 3 patient groups compared with controls (71 +/- 22, 68 +/- 31, 61 +/- 27 vs 44 +/- 17 msec, P = .003), but no difference was seen between heart disease groups. QTc dispersion was st rongly correlated with the QTc max (r = 0.73, P < .0001) but did not correl ate with the QTc min (r = 0.04, P = .76). QTc dispersion also strongly corr elated with the JTc max (r = 0.54, P < .0001) but did not correlate with JT c min (r = -0.007, P = .95). QTc dispersion correlated inversely with T-wav e amplitude (r = -0.35, P = .003). When all 876 electrocardiographic signal s were considered, a significant negative correlation was present between Q Tc duration and T-wave amplitude (r = -0.133, P = .0002). Logistic regressi on analysis failed to demonstrate any independent risk factors that predict ed ventricular arrhythmias, including all measures of dispersion. Conclusions The measurement of QT dispersion is strongly influenced by the maximum QT inierval, as well as by changes in T-wave amplitude. QT "dispers ion" may represent a summary of these changes that reflect the underlying m yocardial process but does not represent an accurate quantitative measure o f heterogeneity of refractoriness.