Adult Critical Care Specialty (ACCS) Practice Exam

Which description accurately represents a 2nd degree AV block?

1. P wave longer and skips a beat

2. No P waves

3. Regularly spaced P waves

4. Irregular R-R intervals

The correct answer is: P wave longer and skips a beat

A second-degree AV block is characterized by a situation where there is intermittent failure of conduction from the atria to the ventricles. This is typically observed as a pattern where some P waves are not followed by QRS complexes, indicating that the impulse from the atria is sometimes not being conducted to the ventricles. The correct description identifies the phenomenon of a longer P wave duration leading to a beat being skipped. In this scenario, one or more P waves are present but do not result in a QRS complex after a certain number of cycles, which leads to the perception of a 'dropped' beat. This failure to conduct the sinus impulse results in a characteristic rhythm where there appears to be a pattern of P waves with some being blocked at regular intervals. The other choices do not accurately reflect the characteristics of a second-degree AV block. For instance, the absence of P waves would suggest a situation closer to a complete heart block or another arrhythmia, rather than the partial block described in second-degree AV block. Regularly spaced P waves without disruption would not occur in this context, as the essence of the second-degree block is the intermittent failure of conduction that leads to missing QRS complexes. Irregular R-R intervals are more indicative of