Mechanisms of the spatial distribution of QT intervals on the epicardial and body surfaces

Spatial Distribution of the QT Interval. Introduction: The role of QT dispe rsion as a predictor of arrhythmia vulnerability has not been consistently confirmed in the literature. Therefore, it is important to identify the ele ctrophysiologic mechanisms that affect QT duration and distribution. We com pared the spatial distributions of QT intervals (QTI) with potential distri butions on cardiac and body surfaces and with recovery times on the cardiac surface. We hypothesized that the measure of QTI is affected by the presen ce of the zero potential line in the potential distribution, as well as the sequence of recovery. We also investigated use of the STT area as a possib le indicator of recovery times on the cardiac surface. Methods and Results: High-resolution spatial distributions of QTI and poten tials were determined on the body surface of human subjects and on the surf ace of a torso-shaped tank containing an isolated canine heart, Additionall y, spatial distributions of QTI, recovery times, and STT areas were determi ned on the surface of exposed canine hearts. Unipolar electrograms were rec orded during atrial and ventricular pacing for normal hearts and cases of m yocardial infarction, Regions of shortest QTI always coincided with the loc ation of the zero potential line on the cardiac and body surfaces, On the c ardiac surface, in regions away from the zero line, similarities were obser ved between the patterns of QTI and the sequence of recovery, STT areas and recovery times were highly correlated on the cardiac surface, Conclusion: QTI is not a robust index of local recovery time on the cardiac surface. QTI distributions were affected by the position of the zero poten tial line, which is unrelated to local recovery times. However, similaritie s in the patterns of QTI and recovery times in some regions may help explai n the frequently reported predictive value of QT dispersion. Preliminary re sults indicate STT area may be a better index of recovery time and recovery time dispersion on the epicardium than QTI.