Cardiac Cycle and ECG Interpretation

The cardiac cycle is a rhythmic sequence of events that occur with each heartbeat, allowing the heart to circulate blood efficiently. It consists of systole (contraction) and diastole (relaxation) phases, primarily focusing on the ventricles. The cycle is divided into seven phases: atrial contraction, isovolumetric contraction, rapid ejection, reduced ejection, isovolumetric relaxation, rapid ventricular filling, and reduced ventricular filling. Each phase involves specific changes in pressure and volume within the heart chambers, which are reflected in the heart sounds and ECG waveforms. Understanding these phases helps in comprehending the heart's function and the electrical events that drive it.

What are the two main phases of the cardiac cycle?

• Ejection and Filling

• Atrial and Ventricular

• Contraction and Relaxation

• Systole and Diastole

What initiates the atrial contraction phase?

• Semilunar valve opening

• AV node impulse

• SA node impulse

• Ventricular contraction

During isovolumetric contraction, what happens to the blood volume in the ventricles?

• It increases

• It decreases

• It fluctuates

• It remains constant

What causes the semilunar valves to open during the cardiac cycle?

• Atrial pressure exceeds ventricular pressure

• Ventricular pressure falls below atrial pressure

• Ventricular pressure exceeds aortic and pulmonary artery pressure

• Aortic pressure exceeds ventricular pressure

What marks the beginning of ventricular diastole?

• AV valves opening

• Semilunar valves closing

• Atrial contraction

• Ventricular contraction

During which phase do the ventricles receive 90% of the blood they will pump out?

• Reduced ventricular filling

• Isovolumetric relaxation

• Rapid ventricular filling

• Atrial contraction

What does the P wave on an ECG represent?

• Atrial repolarization

• Atrial depolarization

• Ventricular repolarization

• Ventricular depolarization

What is the significance of the QRS complex on an ECG?

• It represents ventricular depolarization

• It indicates atrial contraction

• It shows ventricular relaxation

• It marks the end of the cardiac cycle

What does the T wave on an ECG signify?

• Atrial repolarization

• Atrial depolarization

• Ventricular depolarization

• Ventricular repolarization

What is the role of the TP segment on an ECG?

• It shows the end of the cardiac cycle

• It marks the start of ventricular systole

• It indicates the interval between ventricular repolarization and the next atrial depolarization

• It represents the time between atrial and ventricular activation