MCC Block 2 Practice Test

In atrial fibrillation, the atria beat extremely rapidly and irregularly, but the ventricular rate depends on how the AV node conducts those impulses. The AV node acts as a gatekeeper, so the ventricular response is faster than normal but not unbounded. Without rate-control therapy, the typical ventricular rate tends to be around 100 to 175 beats per minute, with occasional spikes toward higher values under stress or sympathetic stimulation but rarely staying above about 180 bpm on a regular basis. That’s why the range around 100–175 bpm best matches the usual upper limit seen in clinical practice.

The other options describe rates that are either too slow for atrial fibrillation without rate-control (60–75 or 40–60) or describe an upper limit that’s less representative of the common non–rate-controlled AF range (180–200).