Let’s look at an ECG, or electrocardiogram (EKG if you’re in a country that spells “cardio” with a K). This is a reading of the electrical impulses of the heart – taken by a series of electrodes placed on the body. It lets you “see” what is being signaled, and therefore, what actions are probably taking place.
P wave – An electrical impulse from the sinus triggers the right atrium, then left.
PR segment – The Bundle of His and Purkinje fibers activate!
QRS complex – The septum, then ventricular muscles do their very powerful push! Especially the left. (It has to pump blood way up high and over the aortic arch.)
T wave – Repolarization, or a reset, occurs so the sinus impulse can start again strong.
An arrhythmia might be a skipped beat where the SA node failed, for example.
You really tug on my heartstrings. -CNx