What characteristic defines a 2nd degree AV block type 2?

A 2nd degree AV block type 2 is characterized by the consistent presence of dropped QRS complexes. In this type of block, the PR intervals are constant, making the rhythm more predictable compared to type 1 AV block (Wenckebach). This consistency is crucial in understanding the nature of the block.

The dropped QRS complexes indicate that while the atrial impulses are generated normally, not all of them are conducted through the AV node to the ventricles, leading to a 'blocking' phenomenon. This can result in some beats being missed entirely, which can impact the overall heart rhythm and function.

In contrast, variability in the PR interval is a hallmark of 2nd degree AV block type 1, where the PR interval progressively lengthens until a QRS complex is dropped. The heart rate typically does not exceed 100 bpm in 2nd degree AV block type 2; rather, it is often slower due to the conduction abnormality. Additionally, while QRS duration can vary, it does not necessarily exceed .12 seconds in this type of block unless there is an underlying bundle branch block. Thus, the defining characteristic of this arrhythmia is indeed the occurrence of dropped QRS complexes without changes in the