Which rhythm has a slow rate that can cause signs or symptoms of low cardiac output?

Which rhythm has a slow rate that can cause signs or symptoms of low cardiac output?

• A. First Degree Heart Block
• B. Second Degree Heart Block Type I
• C. Second Degree Heart Block Type II
• D. Junctional Escape Rhythm

Answer: (B)

The key idea is that a slow ventricular rate can reduce cardiac output enough to cause symptoms like dizziness, fatigue, or low blood pressure. In this rhythm, there is a pattern of progressively longer delay in conduction through the AV node followed by a dropped ventricular beat. The atrial impulses keep coming, but not every one gets to the ventricles, so the heart rate falls. When the downbeat pace is slow enough, the heart can’t pump effectively, leading to signs of reduced cardiac output.

This pattern tends to produce bradycardia due to intermittent ventricular contractions, and that drop pattern is what can make the patient symptomatic. Other rhythms either maintain conduction more consistently (still 1:1) or have different mechanisms of slowing the rate, but the described slowing with periodic dropped beats best explains why low output signs appear in this scenario.