What Is S1 Heart Sound 【2026 Release】

Because the left ventricle contracts slightly before the right ventricle (due to earlier electrical activation and faster pressure rise), the mitral valve closes before the tricuspid valve. This physiological asynchrony is normally too brief to be heard as a split S1. However, in conditions that —such as a right bundle branch block (RBBB), which delays right ventricular activation and thus tricuspid closure—the M1 and T1 become separated enough to be appreciated as a widely split S1 on auscultation, best heard at the left lower sternal border.

The S1 heart sound has several clinical applications: what is s1 heart sound

Located between the right atrium and right ventricle. Because the left ventricle contracts slightly before the

The intensity of S1 is highly variable and diagnostically valuable. It primarily depends on three factors: (1) the position of the AV valve leaflets at the onset of systole, (2) the structural integrity of the valve, and (3) the force of ventricular contraction. The S1 heart sound has several clinical applications:

The S1 heart sound is composed of two distinct components: