Final answer:
In second-degree AV block, the behavior of the heart and changes to the ECG depend on the type of block. Type 1 block is characterized by a gradual prolongation of the PR interval and a missing QRS complex, while Type 2 block results in occasional dropped QRS complexes without progressive prolongation. In Type 1 block, the ventricles fail to depolarize and contract, while in Type 2, only some ventricular contractions are missed.
Step-by-step explanation:
Second-degree AV block is a condition where the AV node fails to conduct some of the signals to the ventricles. In Type 1 second-degree AV block, also known as Wenckebach block, the P wave will be present, but there will be a gradual prolongation of the PR interval until a QRS complex is dropped. This results in a missing QRS complex. In Type 2 second-degree AV block, there will be occasional dropped QRS complexes without any progressive prolongation of the PR interval. In this case, the QRS complex and T wave will be missing for the dropped signal.
Behavior of the heart in second-degree AV block depends on the type. In Type 1, the ventricles will fail to depolarize and contract for the dropped QRS complex. In Type 2, only some of the ventricular contractions will be missed, so the overall contraction of the ventricles will be reduced but not completely absent.
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