Chapter 11: THE RESTING ELECTROCARDIOGRAM RECIPROCAL ST-SEGMENT CHANGES
In an inferior MI with abnormal ST-segment elevation limited to this wall, the reciprocal ST-segment changes will occur in diametrically opposed leads located in the same plane. For example, "indicative" ST-segment elevation in leads III and aVF,which record the electrical activity of the inferior (posteroinferior or diaphragmatic) wall, yields "reciprocal" ST-segment depression in leads I and aVL because they face the superior (anterolateral) wall11'56'57 (see Fig. 11-3). ST-segment depression in lead V2 may reflect injury in the anterior subendocardial wall as well as injury in the posterobasal (or true) posterior wall.!0 The ECG by itself cannot distinguish with absolute certainty between these two possibilities.!0 The differential diagnosis perhaps can best be made by performing cardiac catheterization or radionuclear studies in the acute phase of the MI, when the ST-segment changes are still present. Another way is by analyzing ST-segment changes occurring during percutaneous transluminal coronary angioplasty in patients with proven single-vessel disease.58,59 This has shown that reciprocal ST-segment depression in leads V2 and V3 can occur during balloon occlusions of dominant right, as well as of dominant left, coronary arteries.-50
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.