Q.In a normal electrocardiogram (ECG), the QRS complex represents

The electrocardiogram (ECG) is a graphical record of the heart's own electrical activity, detected non-invasively by electrodes on the body surface. A normal trace for one cardiac cycle shows a P wave (atrial depolarisation, triggering atrial contraction), followed by the QRS complex, a sharp spike (ventricular depolarisation, triggering ventricular contraction — the atria repolarise around this time too, but that signal is masked by the larger QRS spike), and finally the T wave (ventricular repolarisation, as the ventricles relax). Beca …