Key result
Local application of acetylcholine shortened excitation duration and increased T-wave amplitude, while adrenalin lengthened excitation and decreased T-wave, confirming the T-wave originates from variable excitation duration and conduction lag.
Experimental evidence in frog hearts demonstrates that the ECG T wave is generated by regional differences in the duration of excitation and the sequence of conduction.
Answers are grounded in this paper and cite their sources.
Regional ventricular repolarization gradients in frog heart extend basic T-wave models; leaves open relevance to human ECG.
The frog heart which has automaticity was employed to study the origin of T wave by means of recording the action potentials from the ventricular muscle fiber.The following results were obtained.1) The duration of excitation was measured by the intracellular potential recording from various parts of the ventricle. The longest duration was observed at the apex, and the shortest in the right wall near the trancus arteriosus. The other parts showed the middle value.2) The conducting process of excitation was also observed in various parts of the ventricle. The part where showed the longest duration was conducted firstly, and the shortest was conducted finally.3) During the intracellular recording from the ventricle, acetylcholine or adrenalin was locally applied on the surface with a microinjector. Acetylcholine made the duration of excitation short, and adrenalin made it long.4) During the ECG-taking from ventro-dorsal lead of frog heart in situ, acetylcholine was applied to the ventricular wall. It increased T-wave and raised up ST segment remarkably.In the same experiment, adrenalin decreased T wave and changed it diphasic.5) Discussing these results, it was confirmed that T wave of ECG was caused by both variable duration of excitation and lag of conducting process.
No takes yet. Share an insight, caveat, or question.
Suda et al. (1973) studied Normal frog heart. Acetylcholine and Adrenalin vs. Baseline (pre-application) was evaluated on Changes in duration of excitation and T wave morphology. Local application of acetylcholine shortened excitation duration and increased T-wave amplitude, while adrenalin lengthened excitation and decreased T-wave, confirming the T-wave originates from variable excitation duration and conduction lag.
Synapse has enriched 10 related papers. Consider them for comparative context: