Commonly, the first heart sound consists of two sounds separated by a very small interval (20-30 milliseconds). The mitral sound (M1) typically occurs before the tricuspid sound (T1). T1 and S1 splitting can be best heard at the tricuspid location. If M1 and T1 are separately distinguished, this is called an S1 split. S1 splitting is common in children. An S1 split can be associated with EKG-related abnormalities such as right bundle branch block, premature ventricular contractions, or ventricular tachycardia in adults.
A minimally split first heart sound is a normal variation of the first heart sound.
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The patient's position is supine.
