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The Second Heart Sound (S2)
Chapter 8
Are G. Talking, MD, FACC
Instructor
Patricia L. Thomas, MBA, RCIS
Components of S2
• Second heart sound
• The end of ventricular systole & has two
high frequency components A2 & P2
• Rapid vibrations of the valves resulting
from sudden decrease of blood
• 4 factors to determine frequency & intensity
of vibrations & affect the production of the
aortic and pulmonic components
Components of S2 cont…
• The pressure & its rate of development
across the closed semilunar valves
– The greater the rate of development of the
pressure gradient (rapid ventricular relaxation),
the more rapid the velocity of valve vibration
and the louder the sound produced
Components of S2 cont…
• Pliability or stiffness of the value leaflets
– Normal or slightly stiff valve leaflets vibrate
easily and produce distinct sounds
– When heavily calcified reduced mobility as
seen in aortic or pulmonic stenosis, they do not
vibrate & are associated with decreased or
absent A2 & P2
Components of S2 cont…
• Valve Radius
– Dilatation of the aorta or the pulmonary artery
increases their respective valve radius and the
intensity of these closing sounds
Components of S2 cont…
• Blood Viscosity
– Decreased viscosity (anemia) increases the
amplitude of these sounds
Where to Listen
• To hear splitting of S2
– Listen with the diaphragm
– Listen with the bell
– Second or Third intercostal space, left sternal
border
– Sitting position, breathing should be quiet,
never forced
Physiological Splitting of S2
• Expiration
– A2 & P2 are heard as one because of small interval
• Inspiration
–
–
–
–
–
The splitting of the two sounds is evident
Occurs because increases blood return to the right heart
Increases vascular capacitance of the pulmonary bed
Decreases the blood return to the left heart
Occur in normal children, most young adults, elderly
individuals
“Hangout” Interval
• Three major intervals of right ventricular
contractions are the
– Isometric contraction period
– Ejection period
– “Hangout” interval (a very brief interval at the
end of the ejection period & the measure of the
impedance of the pulmonary bed)
– When impedance is low, the inertia of the blood
leaving the right ventricle carries the blood
forward even after the force of right ventricular
ejection has dissipated
Abnormal Splitting
• Wide Splitting of S2
– Audibility of the two components
• Paradoxical
– Reversed splitting
– Reversed in timing (pulmonic closure before
aortic closure)
Delay of the Pulmonary Component
• Pulmonic Stenosis
– Mild Stenosis is a loud sound
– Moderate Severe Stenosis unable to hear
Differential Diagnosis
•
•
•
•
Opening Snap (OS)
Pericardial Knock (PK)
Third Heart Sound (S3)
Late Systolic Click (LSC)
Opening Snap of Mitral Stenosis
• Stand patient up to decrease venous return
• Any maneuver that decreases LA pressure
tend to delay opening snap
• Heard in the aortic area
Pericardial Knock
• Loud/Sharp and best heard along the lower
left sternal border
• Constrictive Pericarditis
Paradoxical (Reversed) Splitting of S2
Absence of P2
• Severe pulmonary stenosis
• Single truncal valve
• Transposition of the great arteries in
children
Pathological Alteration of S2
• Pulmonary Hypertension
– P2 louder because of congestive heart failure, mitral
stenosis or congenital heart disease
• Valve and Vessel Pathology
– Diameter and thickening (lacks ability to vibrate in
marked thickening and calcification)
• Ventricular Dysfunction
– Isovolumic relaxation is delayed, the rate of
development of pressure across the aortic valve is
decreased, produced a diminished A2
THE END
OF
CHAPTER 8
Tilkian, Ara MD Understanding Heart Sounds and Murmurs,
Fourth Edition, W.B. Sunders Company. 2002, pp. 72-92.