Which ecg characteristic indicates myocardial ischemia

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Long PR intervals are seen in first degree AV block. Long QRS intervals represent bundle branch block, ventricular preexcitation, ventricular pacing, or ventricular tachycardia. Step 5: P wave — the P wave may vary in morphology, amplitude and duration. If the P wave has an amplitude of more than 0. Wide QRS complexes denote bundle branch block or pre-excitation. Are there T wave inversions? These abnormalities denote myocardial ischemia or infarction. Step 8: Overall interpretation — This is a collation of all the information gathered from steps 1 to step 8.

In the normal patient, the ST segment is isoelectric with a measurement of relatively zero millivolts. At this point, all of the myocardial cells are in the plateau phase of the action potential Figure 1. Therefore, the diagnosis of acute myocardial infarction should be made circumspectively in the presence of pre-existing LBBB. Acute myocardial infarction MI affects both ventricular depolarization appearance of pathological Q waves and repolarization ST-T wave changes.

Specific manifestations depend on whether the lesion is subendocardial or transmural in location. Depression is reversible if ischemia is only transient but depression persists if ischemia is severe enough to produce infarction. In transmural MI, ischemia in the subendocardium spreads to the epicardium and involves full thickness of the myocardium.