|A.||Hyperacute T waves in the precordial leads|
ST-segment depression in leads III and aVF
Shortened QT interval
New right bundle branch block
· Early recognition of myocardial infarction (MI) is critical to take full advantage of emergent percutaneous revascularization or fibrinolytic therapy.
· The earliest electrocardiographic finding in acute ST-elevation MI is ST-segment elevation and hyperacute (tall, positive) T waves overlying the affected region of the myocardium.
· Reciprocal ST-segment depressions are often noted in leads overlying the opposite cardiac territories.
· In the absence of reperfusion therapy, T wave inversions become evident in the leads overlying the region of infarction over a matter of hours, accompanied by Q wave development.
· In the case of an anterior Q wave MI, the early ST-segment deflections become apparent in the anterior precordial leads, whereas ST-segment depressions are often present in the inferior leads.
· Acute infarction affecting portions of the conduction system may produce a new bundle branch block.
· In a patient with a convincing history of prolonged ischemic chest discomfort, a new LBBB is an acceptable criterion of acute infarction.
· A shortened QT interval is typical of hypercalcemia, not acute MI.