A client with a bundle branch block is on a cardiac monitor. The nurse should expect to observe:
A. Sagging ST segments.
B. Absence of P wave configurations.
C. Inverted T waves following each QRS complex.
D. Widening of QRS complexes to 0.12 second or greater.
Correct Answer: D. Widening of QRS complexes to 0.12 second or greater.
Bundle branch block interferes with the conduction of impulses from the AV node to the ventricle supplied by the affected bundle. Conduction through the ventricles is delayed, as evidenced by a widened QRS complex. Rhythm must be of supraventricular origin (EG: ventricular activation coming from atrial or AV nodal activation). Lead V1 should have either a QS or a small r wave with large S wave. Lead V6 should have a notched R wave and no Q wave.
Option A: ST depression occurs when the J point is displaced below baseline. Just like ST elevation, not all ST depression represents myocardial ischemia or an emergent condition. There are multiple conditions associated with ST depression. Some of these include hypokalemia, cardiac ischemia, and medications such as digitalis.
Option B: Absence of P waves suggests either no normal atrial depolarization, e.g., atrial fibrillation, atrial standstill; or the P waves are hidden within the QRS complexes, e.g., ventricular tachycardia, junctional tachycardia.
Option C: Inverted T waves are associated with myocardial ischemia. The inversion of a T wave is not specific for ischemia, and the inversion itself does not correlate with a specific prognosis. However, if the clinical history is suggestive of ischemia in the setting of inverted T waves, this is correlative.
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