QRS complex

QRS complex is a series of deflections on an electrocardiogram (ECG) that represents the electrical activity of the heart during ventricular depolarization. The QRS complex is normally the most noticeable feature on the ECG.

Overview

The QRS complex is a result of the simultaneous activation of the right and left ventricles. Although it is usually more prominent than the other waves, it is not always the largest wave of the ECG. The size of the QRS complex can be influenced by various factors such as the distance between the heart and the electrodes, the mass of the ventricles, and the direction and velocity of the ventricular activation wave.

Components

The QRS complex consists of three individual waves: the Q wave, the R wave, and the S wave. The Q wave represents the initial negative deflection, the R wave is the initial positive deflection, and the S wave is the subsequent negative deflection. However, not all QRS complexes contain all three waves. The configuration of the QRS complex can vary widely among individuals, and it can also be influenced by the heart rate and the direction of the heart's electrical axis.

Clinical significance

The duration, amplitude, and morphology of the QRS complex are important indicators of many cardiac conditions. For example, a prolonged QRS duration can indicate a bundle branch block or ventricular tachycardia. A low-amplitude QRS complex can suggest a pericardial effusion or cardiomyopathy. Abnormal QRS morphology can be a sign of a previous myocardial infarction or a ventricular hypertrophy.

See also

• Electrocardiography
• P wave
• T wave
• U wave

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