When a healthy heart beats, it makes a “lub-dub” sound.
The first heart sound “ lub ”, also known as S1,
is caused by the closing of the AV valves
after the atria have pumped blood into the ventricles.
第二个心音 嗒嗒声 称为S2
The second heart sound “ dub ”, or S2,
originates from the closing of the aortic and pulmonary valves,
right after the ventricles have ejected the blood.
The time interval between S1 and S2 is when the ventricles contract,
The interval between S2 and the next S1
is when the ventricles relax and are filled with blood,
Diastole is longer than systole, hence thelub-dub, lub-dub, lub-dub…
Heart sounds are auscultated at 4 different sites
on the chest wall which correspond to
the location of blood flow as it passes through
分别为主动脉瓣区 肺动脉瓣区 三尖瓣区和二尖瓣区几个听诊区
the aortic, pulmonic, tricuspid, and mitral valves, respectively
This is how similar defects associated withdifferent valves are differentiated.
Heart murmurs are whooshing sounds produced by turbulent flow of blood.
Murmurs are diagnosed based on the time they occur in the cardiac cycle,
their changes in intensity over time, and the auscultation site where they are best heard.
Examples of conditions associated with commonsystolic murmurs include:
– mitral valve regurgitation,
when the mitral valve does not close properly and blood surges
back to the left atrium during systole.
The murmur starts at S1, when the AV valves close,
and maintains the same intensity for the entire duration of systole.
This holosystolic murmur is best heard at the mitral region-the apex,
with radiation to the left axilla.
On the other side of the heart,
a tricuspid valve regurgitation has similar timing and shape,
but it is loudest
in the tricuspid area and the sound radiates up,
along the left sternal border.
– aortic valve stenosis,
when the aortic valve does not open properly and blood is forced
through a narrow opening.
The blood flow starts small,
rises to a maximum in mid-systole at the peak of ventricular contraction,
then attenuates toward the endof systole.
This results in a crescendo-decrescendo,
or a diamond-shaped, murmur which starts a short moment after S1.
It is often preceded by an ejection click caused by the opening of the stenotic valve.
Aortic stenosis murmur is loudest
in the aortic area and the sound radiates to the carotid
arteries in the neck following the directionof blood flow.
Again, on the other side of the heart,
a pulmonic stenosis has the same characteristics but
is best heard in the pulmonic area and does not radiate to the neck.
Other conditions that cause audible systolicmurmurs include ventricular septal defect
and mitral valve prolapse.
An example of diastolic murmurs is aorticvalve regurgitation.
This is when the aortic valve does not close properly,
resulting in blood flowing back
to the left ventricle during diastole- thefilling phase.
As the blood flows in the reverse direction,
the murmur is best heard not in the aortic area,
but rather along the left sternal border.
It peaks at the beginning of diastole when the pressure difference is highest,
then rapidly decreases as the equilibrium is reached.
其他常见的舒张期杂音 均与肺动脉瓣返流 和二尖瓣狭窄
Other common diastolic murmurs are associatedwith pulmonic regurgitation, mitral stenosis
mitral stenosis and tricuspid stenosis.