Question

Define the relationship between the ECG and the pulse wave. Explain why the timing of the QRS complex in the ECG and the start of the pulse wave do not coincide.

Answer 1

ECG (Electrocardiogram) is actually graph of the electrical activity of the heart which is measured by placing the electrodes on skin. It measures the electrical activity and data is plotted in a graph of voltage vs time. The activity begins with the initial firing of the SA node present on the right atrium when it is filled with the blood. As soon as the electrical signal is fired from the SA node of the right atrium , it immediately travels to the left atrium via a specialized conductive fibers calles as Purkinje fibers.Then both the atrium simultaneously contracts and pushes the blood in both ventricles at once.So this electrical activity of atrial contraction represents P wave, immediately after that ventricular contraction happens ones the blood is filled in ventricles and that electrical activity can be denoted by QRS wave and T wave is the wave of the electrical reset which heart does for the next atrial contraction.

So from the above answer it is clear that ECG is the electrical activity while the pulse wave  is the preassure wave of the fluid blood which leaves the aortic valve after each systole. At this time the aortic preassure increases rapidly an then drops after it travels further away.

QRS and the strat of the pulse wave will never coincide because the QRS wave is the atribution of the systole and after systole only the blood can be pushes with extreme preassure in the aortic valve.