Heart Sounds and Heart Murmurs, Animation.

Heart Sounds and Heart Murmurs, Animation.

November 13, 2019 100 By Bernardo Ryan


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. 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, called SYSTOLE. The interval between S2 and the NEXT S1 is
when the ventricles relax and are filled with blood, called DIASTOLE. Diastole is longer than systole, hence the
lub-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
the aortic, pulmonic, tricuspid, and mitral valves, respectively. This is how SIMILAR defects associated with
DIFFERENT 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 common
systolic 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. Because the valve closure in mitral regurgitation
is INcomplete, S1 is often quieter. 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 end
of 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 direction
of 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 systolic
murmurs include ventricular septal defect and mitral valve prolapse. An example of diastolic murmurs is aortic
valve regurgitation. This is when the aortic valve does NOT CLOSE
properly, resulting in blood flowing back to the left ventricle during diastole- the
filling 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. Other common diastolic murmurs are associated
with pulmonic regurgitation, mitral stenosis and tricuspid stenosis.