Session P94.2

QT Dispersion Induced by Local Temperature Variations

A Guill, I Trapero, E Roses, J Millet*, A Tormos,
F Pelechano, L Such-Miquel, L Such, FJ Chorro

Universitat Politècnica de València
València, Spain

Abnormally long and short QT intervals (QTi) have been shown to be associated with an increased risk for life-threatening ventricular arrhythmias and sudden cardiac death. Because of its electrophysiological effects temperature can influence this parameter. Therefore hypothermia or/and hyperthermia can be used for modulate QTi in studies with experimental models. In this work, a novel electrode-device to perform epicardial mapping and simultaneous thermal modifications is presented, as well as its first application to the study of the QTi dispersion induced by local temperature variations. The electrode-device contains 128 unipolar electrodes 1 mm spaced. Its surface is adapted to the curvature of the epicardium, and is equipped with a thermoelectric cooler and sensors for acute temperature adjustment. In ten preparations of isolated rabbit hearts (Langendorff-perfused) changes in QTi was analyzed in two different left ventricular areas (MA and NMA). The MA temperature (TMA) was modified through the developed device. TMA was regulated in 5ºC steps from 37 ºC to 22 ºC (hypothermia) and to 42 ºC (hyperthermia). The NMA temperature remained at basal value, using in this case a conventional electrode for acquiring signals. QT intervals measured from QRS onset to the end of T (QTf) and to the peak of T (QTp) were obtained by averaging the determinations from five electrodes. The differences between the two areas under study were analyzed. The results showed that the differences in QTf between MA and NMA were not significant at basal temperature (37 ºC). During hypothermia the differences increased and reached statistical significance, mainly due to the prolongation of the QTf in MA. Hyperthermia had the opposite effect, that’s a shortening of QTf in MA versus NMA. Localized hypothermia induces heterogeneity in the QTi by prolongation of this parameter in the modified area, and the magnitude of this variation depends directly on the degree of the temperature decrease. Hyperthermia increases the QT dispersion shortening the interval in the altered area.

(Abstract Control Number: 90)