Semeiotics of the heart and cardiac tone: the 4 cardiac tones and the added tones

By Cristiano Antonino On Jun 9, 2023

Cardiac tones are short, transient acoustic events, produced by the opening and closing of valves; they are divided into systolic and diastolic tones

First tone

The second tone corresponds to the closing of the aortic and pulmonary valves.

The sound is produced by the vibrations of the closed valves and rapid deceleration of the flow.

It consists of an aortic and a pulmonary component.

It marks the end of systole and the beginning of diastole.

It is best appreciated at the base or aortic and pulmonary areas.

Second tone

The second tone corresponds to the closing of the aortic and pulmonary valves.

The sound is produced by the vibrations of the closed valves and rapid deceleration of the flow.

It consists of an aortic and a pulmonary component.

It marks the end of systole and the beginning of diastole.

It is best appreciated at the base or aortic and pulmonary areas.

III tone

The third tone immediately following the II tone, corresponds to the end of rapid filling of the ventricle.

The ‘sound’ is produced by the vibration of the mitral and tricuspid valvular apparatus due to the abrupt deceleration of blood flow within the ventricles.

It is best appreciated at the tip or mesocardium with the patient in left lateral decubitus.

It is physiological in children and young adults (rare over 40 years).

Often present in pregnancy after the 13th week.

Fourth tone

The fourth tone also called atrial tone immediately precedes the first tone and corresponds to a strong atrial contraction.

The ‘sound’ is produced by the sudden tension of the valve leaflets, chords, papillary, mitral and tricuspid muscles due to the rapid and abnormal atrial contraction.

It is best appreciated at the tip and with the patient in left lateral decubitus.

It is never audible in the normal heart.

Added tones

Pericardial knock: occurs in protodiastole. It is heard in constrictive pericarditis and is due to vibrations of the ventricular walls constricted by the thickened pericardium as rapid filling occurs.

It is mainly appreciated at the tip or on the mesocardium.

Ejection tones (ejection clicks): these are dry, short, high-pitched added tones heard in protosystole.

They are pops of opening of the aortic (or pulmonary) semilunar, or sounds of distension of a dilated aorta (or pulmonary) that distends as blood from the underlying ventricle arrives.

Non ejection meso-telesystolic tones (non ejection systolic clicks): later than ejection tones, often multiple, they mainly result from sudden tensioning of mitral chordae tendineae of unequal length to the others functionally unequal to the others.