Key result
Intravenous injection of isoproterenol under hypercalcemic conditions produced a giant negative T wave associated with QT prolongation and marked prolongation of the phase 2 action potential in dogs.
The combination of isoproterenol and hypercalcemia in a canine model produces giant negative T waves and QT prolongation, suggesting a role for calcium movement in these ECG abnormalities.
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Supports hypothesis of calcium involvement in repolarization abnormalities; leaves open clinical translation from this canine model.
Changes of the surface ECG and monophasic action potential induced by isoproterenol injection were investigated under normo- and hypercalcemic conditions in dogs. (1) Biphasic time course of T wave changes, initially inverted and subsequently uprightly tall, was observed after intravenous injection of isoproterenol in doses of more than 2 microgram. (2) Initial prolongation and subsequent shortening of the phase 2 of action potential were observed on the ventricular surface in accordance with the biphasic time course of the T wave changes on the surface ECG after isoproterenol injection. (3) Giant T wave inversion associated with QT prolongation was obtained by isoproterenol injection under hypercalcemia. (4) Marked prolongation of total duration as well as phase 2 of action potential was observed in accordance with the giant negative T wave on the surface ECG. Although the mechanism of this experimental model of giant negative T wave is not clear, this model could have important suggestions on the unknown mechanism of giant negative T wave observed in various clinical status.
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Murayama et al. (1981) studied Giant negative T wave (experimental model) (n=15). Isoproterenol and hypercalcemia vs. Baseline (normocalcemia) was evaluated on Changes in surface ECG (T wave and QT interval) and monophasic action potential duration. Intravenous injection of isoproterenol under hypercalcemic conditions produced a giant negative T wave associated with QT prolongation and marked prolongation of the phase 2 action potential in dogs.
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