Qrs complex

QRS Complex

The QRS complex is a significant component of the electrocardiogram (ECG), which is a graphical representation of the electrical activity of the heart. The QRS complex represents the electrical depolarization of the ventricles (the heart's lower chambers), which leads to the contraction of the ventricles and the main pumping action of the heart.

Overview

The QRS complex is named for the three deflections seen on a typical ECG. The first downward deflection is the Q wave, the subsequent upward deflection is the R wave, and the final downward deflection is the S wave. Not all three waves are necessarily present in every ECG lead.

Measurement

The duration, amplitude, and morphology of the QRS complex are important aspects of the ECG interpretation. The duration of the QRS complex is usually between 0.06 and 0.10 seconds. A prolonged QRS duration can indicate a bundle branch block, hyperkalemia, or ventricular hypertrophy.

Clinical Significance

Abnormalities in the QRS complex can indicate various cardiac conditions. For example, a missing or inverted R wave can suggest a myocardial infarction. A wide QRS complex can indicate a ventricular rhythm, such as ventricular tachycardia.

See Also

• Electrocardiography
• P wave (electrocardiography)
• T wave
• U wave