Question

Which of the following correcty explains a phase/event in cardiac cycle in a standard electrocardiograph?

• A. QRS complex indicates atrial contraction
• B. QRS complex indicates ventricular contraction
• C. T-wave represents the return of the atria
• D. P-wave indicates beginning of ventricular contraction

Answer 1

The correct option is B QRS complex indicates ventricular contraction


The P-wave represents the electrical excitation (or depolarisation) of the atria, which leads to the contraction of both the atria.

The QRS complex represents the depolarisation of the ventricles, which initiates the ventricular contraction. The contraction starts shortly after Q and marks the beginning of the systole.

The T-wave represents the return of the ventricles from excited to normal state (repolarisation). The end of the T-wave marks the end of systole.