In a junctional rhythm viewed in lead II, where is the location of the P wave on the ECG if ventricular depolarization precedes atrial depolarization?
A) Before the QRS complex
B) During the QRS complex
C) After the QRS complex

Question

Quizplus · Accepted Answer

If the AV junction paces the heart, the electrical impulse must travel in a backward (retrograde) direction to activate the atria. If the atria depolarize before the ventricles, an inverted P wave will be seen before the QRS complex and the PR interval will usually measure 0.12 second or less. The PR interval is shorter than usual because an impulse that begins in the AV junction does not have to travel as far to stimulate the ventricles. If the atria and ventricles depolarize at the same time, a P wave will not be visible because it will be hidden in the QRS complex. When the atria are depolarized after the ventricles, the P wave typically distorts the end of the QRS complex and an inverted P wave will appear after the QRS.

In a Junctional Rhythm Viewed in Lead II, Where Is