Estimates of repolarization and its dispersion from electrocardiographic measurements: Direct epicardial assessment in the canine heart

This study investigates a technique to estimate dispersion based on the roo t mean square (RMS) signal of multiple electrocardiographic leads. Activati on and recovery times were measured from 64 sites on the epicardium of cani ne hearts using acute in situ or Langendorff perfused isolated heart prepar ations. Repolarization and its dispersion were altered by varying cycle len gth, myocardial temperature, or ventricular pacing site. Mean and dispersio n of activation and recovery times, and activation-recovery interval (ARI) were calculated for each beat. The waveform was then calculated from all le ads. Estimates of mean and dispersion of activation and recovery limes and mean ARI were derived using only inflection points from the RMS waveform. Q T intervals were also measured and QT dispersion was determined. Estimates determined from the RMS waveform provided accurate estimates of repolarizat ion and were, in particular, a better measure of repolarization dispersion than QT dispersion.