QRS Complex of ECG

QRS complex of ECG represents-

Correct Answer: Ventricular depolarization

The QRS complex represents ventricular depolarization — the electrical event triggering ventricular contraction (systole). It is the most prominent wave on the ECG.

ECG Waves and Their Meaning

• P-wave: Atrial depolarization (SA node fires → atria contract)
• QRS complex: Ventricular depolarization (atrial repolarization is hidden/masked within QRS)
• T-wave: Ventricular repolarization (ventricles relax — diastole begins)

Einthoven's Triangle

• Einthoven's triangle is used in ECG recording; formed by standard limb leads (right arm, left arm, left leg)
• It is related to Electrocardiography (ECG)

Cardiac Conduction Speeds

• Purkinje fibers: 4 m/sec (fastest)
• AV node: 0.05 m/sec (slowest — creates delay to allow ventricular filling)
• Internodal fibers: 1 m/sec; Ventricular muscle: 0.5 m/sec

Heart Sounds Reminder

• 1st heart sound (lub/systolic): Closure of AV valves (at start of ventricular contraction)
• 2nd heart sound (dub/diastolic): Closure of semilunar valves (at end of ventricular contraction)