cardiovascular system cardiac cycle heart sounds

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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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