What type of block involves a saved P wave but a dropped QRS?

Second-degree heart block type II is characterized by a scenario where P waves are still present, but there are intermittent dropped QRS complexes. In this type of block, the communication between the atria and ventricles is disrupted, causing some P waves not to be followed by QRS complexes. This means that while some electrical impulses from the atria successfully reach the ventricles (resulting in an accompanying QRS), others fail to do so, resulting in a dropped QRS.

What differentiates type II from type I is that in type I (Mobitz type I or Wenckebach), there is progressive lengthening of the PR interval until a QRS is dropped. In contrast, in type II, the PR intervals remain constant before the dropped QRS, making it potentially more dangerous as there is a higher likelihood of sudden complete heart block.

Third-degree heart block, on the other hand, involves a complete dissociation between the atria and ventricles, leading to no relationship between P waves and QRS complexes, which does not match the scenario described. In first-degree heart block, all P waves are conducted with a prolonged PR interval, but there are no dropped QRS complexes.