Heart sounds and
Cardiac output
CVS Physiology
,Heart sounds
• Closure of the heart valves is associated with audible sounds (no sounds occur
the vibration of blood, adjacent blood vessels, and heart chambers associated with
through heart valves.
• The loudness of the heart sounds is almost directly proportional to the rate of chan
Normally, there are four heart sounds. Two of them are normally heard by diaphr
(consists of microphone and electrical amplification circuit) during each cardiac cy
[1] The first is slightly prolonged (0.15 sec), low-pitched “lub” (first sound, or S1), ca
mitral and tricuspid valves at the start of ventricular systole (at isovolumertic ventri
[2] The second is a shorter (0.12 sec), high-pitched “dup” (second sound, or S2), cau
pulmonary valves just after the end of ventricular systole (at isovolumertic ventricu
pulmonary valve closure during inspiration is frequently long enough for the S2 to b
This is called physiological splitting of S2, because during inspiration the filling of th
pool in the pulmonary vein as a result, the aortic valve closes earlier than pulmona
expiration ventricular filling equalizes so the aortic and pulmonary valves close simu
, Inspiration: Cardiac Effects and Heart Sounds
Inspiration (Inhalation)
• Intrathoracic pressure: becomes more negative (-) as the
intrathoracic volume increased.
• Right heart effects:
Venous return to the right atrium and ventricle increases
Right ventricular preload ↑ → ventricle stretches more → stronger
contraction (Frank-Starling mechanism) so systole take more time
• Left heart effects:
Blood temporarily pools in pulmonary circulation → left ventricular
preload ↓ slightly so the systole take less time
• Heart sound effect (S2):
Pulmonary valve closure is delayed due to increased right
ventricular filling
Aortic valve closes first → physiological splitting of S2
• S2 can be heard as two sounds “dup…dup” close together
Cardiac output
CVS Physiology
,Heart sounds
• Closure of the heart valves is associated with audible sounds (no sounds occur
the vibration of blood, adjacent blood vessels, and heart chambers associated with
through heart valves.
• The loudness of the heart sounds is almost directly proportional to the rate of chan
Normally, there are four heart sounds. Two of them are normally heard by diaphr
(consists of microphone and electrical amplification circuit) during each cardiac cy
[1] The first is slightly prolonged (0.15 sec), low-pitched “lub” (first sound, or S1), ca
mitral and tricuspid valves at the start of ventricular systole (at isovolumertic ventri
[2] The second is a shorter (0.12 sec), high-pitched “dup” (second sound, or S2), cau
pulmonary valves just after the end of ventricular systole (at isovolumertic ventricu
pulmonary valve closure during inspiration is frequently long enough for the S2 to b
This is called physiological splitting of S2, because during inspiration the filling of th
pool in the pulmonary vein as a result, the aortic valve closes earlier than pulmona
expiration ventricular filling equalizes so the aortic and pulmonary valves close simu
, Inspiration: Cardiac Effects and Heart Sounds
Inspiration (Inhalation)
• Intrathoracic pressure: becomes more negative (-) as the
intrathoracic volume increased.
• Right heart effects:
Venous return to the right atrium and ventricle increases
Right ventricular preload ↑ → ventricle stretches more → stronger
contraction (Frank-Starling mechanism) so systole take more time
• Left heart effects:
Blood temporarily pools in pulmonary circulation → left ventricular
preload ↓ slightly so the systole take less time
• Heart sound effect (S2):
Pulmonary valve closure is delayed due to increased right
ventricular filling
Aortic valve closes first → physiological splitting of S2
• S2 can be heard as two sounds “dup…dup” close together
