Ischemic ST-Segment counterpoise: One mechanism of false electrocardiographic response to exercise stress testing

The concept of cancellation of electromotive Forces has been employed in explaining the vagaries of electrocardiographic (EGG) appearances in patients With multiple myocardial infarctions. This interpretive approach attributes the modification of QRS complexes resulting from infarctions to areas of myocardial necrosis opposite to each other. The underlying vectorial ECG analysis can be extended to the interpretation of false negative ECG results in the setting of exercise stress testing. The authors present a case of a patient who developed exercise-induced myocardial ischemia involving two planes of his heart, opposite each other. Thallium-201 myocardial scintigraphy showed evidence of severe reversible myocardial ischemia, while the ECG did not reveal such changes. The authors expounded on the importance of ischemic ST-segment counterpoise in explaining some of these false ECG responses to exercise stress testing.