Third Degree Heart Block | Reference Guide.
EKG Features
Rate: Characterized by Atrial rate usually normal and faster than ventricular rateRhythm: Regular, but atrial and ventricular rhythms are independent
P Wave: Normal shape and size, may appear within QRS complexes
PR Interval: Absent: the atria and ventricles beat independently.
QRS: Normal, but wide if junctional escape focus
In third degree heart block, none of the SA node impulses reach the ventricles. The ventricles will typically compensate by their own pacemaking, known as an escape rhythm. Thus the atria and ventricles will beat independently and this can be observed on the ECG. The P waves (atrial beating) and QRS complex (ventricles) are unrelated in time. The PR interval will be variable.
External Source:
