Which dysrhythmia has an irregularly irregular ventricular response?

• A. Ventricular tachycardia
• B. Atrial fibrillation
• C. Atrial flutter
• D. Sinus arrhythmia

Answer: (B)

The irregularly irregular ventricular response is a hallmark of atrial fibrillation. In AF, atrial activity is chaotic and disorganized, so the impulses entering the AV node come through in an unpredictable way. That variability in conduction makes the time between consecutive QRS complexes jump around, producing an irregularly irregular rhythm. On ECG you’d also see the absence of distinct P waves, with irregularly spaced QRS complexes.

Ventricular tachycardia, by contrast, is usually a rapid but regular rhythm. Atrial flutter often shows a sawtooth pattern and tends to have a more regular ventricular response (depending on block). Sinus arrhythmia is a normal, breath-related variation with overall regular rhythm. So the unpredictable spacing of beats points to atrial fibrillation.