Digitalis is a drug that can be used during coronary insufficiency to increase the strength of cardiac muscle contraction. But when overdosages of digitalis are given, depolarization duration in one part of the ventricles may be increased out of proportion to that of other parts. As a result, nonspecific changes, such as T wave inversion or biphasic T waves, may occur in one or more of the electrocardiographic leads. A biphasic T wave caused by excessive administration of digitalis is shown in Figure.
Therefore, changes in the T wave during digitalis administration are often the earliest signs of digitalis toxicity.
I was reading about it in Guyton and Hall Physiology (volume 1, heart , chapter 12) and there was nothing about this that answers my questions.
And my questions are:
- Why is T wave more affected by digitalis toxicity?
- Why does it cause Biphasic T wave?