Loud S1 Causes _top_ Jun 2026

Normally, atrial contraction (the "A wave") just before ventricular systole helps approximate the mitral valve leaflets. When the PR interval is short, ventricular systole occurs while the mitral valve leaflets are still maximally separated from the atrial kick, causing them to snap shut vigorously.

Loud S1 heart sounds, also known as an accentuated first heart sound (S1), can be a sign of various underlying conditions. The S1 sound is primarily caused by the closure of the mitral and tricuspid valves at the beginning of systole. Several factors can lead to an abnormally loud S1:

Conditions that increase blood flow and heart contractility, such as: Exercise . Anemia . Pregnancy . Fever or Sepsis . Hyperthyroidism (Thyrotoxicosis) .