Electrocardiography: Why is the ECG termed as "PQRST" and not (for example) ABCDE?

ECG stands for electrocardiography, an important medical diagnostic tool used to detect irregularities in the electrical activity of the heart.

The components that make up an electrocardiogram are referred to by their initial letters: P, Q, R, S and T. Each component stands for a corresponding stage of cardiac electrical cycle known as 'the cardiac rhythm'. The P-wave corresponds with atrial depolarization; the Q-wave represents depolarization leading to ventricular contraction; the R-wave suggests ventricular systolic excitation; and finally, the S-T segment invites repolarization.

Therefore ECG is termed as ‘PQRST’ and not (for example) ABCDE as these five letters represent distinct stages of cardiac electrical cycle in sequence. This sequence is integral diagnostically in order to accurately examine a patient's heart rhythm or any pathological abnormalities related it.