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CARDIOVASCULAR SYSTEM CARDIAC CYCLEHEART SOUNDS
LECTURE – 4DR. ZAHOOR ALI SHAIKH
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HEART SOUNDS
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• There are four heart sounds SI, S2, S3 & S4.
• Two heart sound are audible with stethoscope S1 & S2 (Lub - Dub).
• S3 & S4 are not audible with stethoscope Under normal conditions because they are low frequency sounds.
• Ventricular Systole is between First and second Heart sound.
• Ventricular diastole is between Second and First heart sounds.
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First heart sound (S1)
• It is produced due to the closure of Atrioventricular valves (Mitral & Tricuspid)
• It occurs at the beginning of the systole and sounds like LUB
• Frequency:50-60 Hz
• Time: 0.15 sec
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Second heart sound (S2)
• It is produced due to the closure of Semilunar valves (Aortic & Pulmonary)
• It occurs at the end of the systole and sounds like DUB
• Frequency:80-90 Hz [ High pitch ]
• Time: 0.12 sec
• It is short and sharp
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HEART SOUNDS
Important
• Sounds are caused by vibrations set within the wall of the ventricles and major arteries during valve closure .
• Opening of the valve does not cause sound.
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Third heart sound (S3)• It occurs at the beginning of middle third
of Diastole
• Cause of third heart sound – Rush of blood from Atria to Ventricle during rapid filling phase of Cardiac Cycle. It causes vibration in the blood
• Frequency:20-30 Htz
• Time: 0.1 sec
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Fourth heart sound (S4)or Atrial Sound
• It occurs at the last one third of Diastole
(just before S1)• Cause of Fourth heart sound – Due to Atrial
contraction which causes rapid flow of blood from Atria to noncompliant Ventricle and vibration in the blood.
• Frequency: < 20 Htz
Note:• Third and Fourth heart sound are low pitched sounds
therefore not audible normally with stethoscope• S3 may be heard in children and young adults but
usually pathological in old age 9
AD AS
VS VD
EVENTS
HEART SOUNDS
0.7 Sec. 0.1 sec.
0.3Sec. 0.5 sec.
1 st Heart Sound 2 nd Heart Sound 3 rd Heart Sound 4 th Heart Sound
AS – Atrial Systole; AD – Atrial Diastole ; VS – Ventricular systole; VD – Ventricular diastole 10
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Heart Murmurs
• Murmurs are abnormal sounds produced due to abnormal flow of blood [turbulent blood flow] through abnormal heart valves e.g.. stenosis or incompetence.
• Stenosis means narrow or stiff, valve that does not open completely.
• Incompetent means valve which does not close properly and remains open.
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Heat Murmurs
• When blood is forced through stenotic valve, it produces an abnormal whistling sound.
• When blood flows backward through incompetent valve, it produces swishing or gurgling murmur sound.
• Most common cause of stenosis and incompetent valve is Rheumatic fever, an auto immune disease triggered by Streptococcus bacterial infection.
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Heat Murmurs• Systolic murmur are produced during the
systole of the ventricle, between 1st and 2nd heart sound (Lub – Murmer – Dup).
• Diastolic murmur are produced during the diastole of the ventricle, between 2nd and 1st heart sound (Lub – Dup – Murmer – Lub).
• During aortic stenosis and mitral incompetence – systolic murmur.
• Aortic incompetence and Mitral Stenosis – diastolic murmur.
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We will discuss
1. PRESSURE VOLUME LOOP
2. EVENTS OF CARDIAC CYCLE
Relationship between Lt. ventricular volume & pressure changes
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Events of cardiac cycle for Lt. ventricular function showing changes in Lt. atrial pressure, Lt. ventricular pressure, aortic pressure, ventricular volume, ECG &
phonocardiogram 19
THANK YOU
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