The wide complex tachycardia, shown again here, is an example of atrial fibrillation with a rapid ventricular response (150 beats per minute) and left bundle branch block that appears to be rate (or cycle length) dependent, becoming more pronounced at the faster rates (shorter cycle lengths. Note that the rhythm, although appearing quite regular, is actually irregular, with RR intervals that range from 0.30 to 0.50 seconds, and that the QRS durations associated with the longer RR intervals are less than those associated with the shorter RR intervals. The second and fifth QRS complexes are examples of this rate (or cycle length) dependency.