According to the sources, a standard electrocardiogram (ECG) identifies specific peaks with letters from P to T. The P-wave represents the electrical excitation, or depolarisation, of the atria, which leads to their contraction . The QRS complex represents the depolarisation of the ventricles, while the T-wave represents ventricular repolarisation (the return to a normal state) and marks the end of systole . Mastering these wave interpretations is a high-priority strategy for medical aspirants, as approximately 95% of NEET Biology questions are derived directly from the NCERT textbooks .