A first-degree, or 1 st degree, AV block is indicated on the ECG by a prolonged PR interval, as seen below. Recall that the P wave indicates atrial depolarization, initiated by firing of the SA node.

The first ECG strip below shows a P wave with sinus morphology, thus normal sinus rhythm. If the P wave has a morphology different from the typical sinus morphology, it is termed ectopic ...

1 The majority of disorders associated with increased risk of sudden cardiac death (SCD), such as cardiomyopathies and primary electrical diseases, are suggested by abnormal findings present on an ECG ...