cardiac-cycle-by-dr-roomi
DESCRIPTION
Amna inayat medical college UHS uploaded by class representative,TRANSCRIPT
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BY
DR. MUDASSAR ALI ROOMI (MBBS, M. PHIL)
CARDIAC CYCLE
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• Period between start of one beat to start of next.
• It consists of one complete heart beat.
• It consists of one systole & one diastole.
DEFINITION OF CARDIAC CYCLE:
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• Initiated by Cardiac Impulse, which originates from SA node.
INITIATION OF CARDIAC CYCLE:
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• Pressure Changes.
• Volume Changes.
• Production of Heart Sounds.
• Closure & Opening of Cardiac Valves.
• Electric Changes (ECG recording).
EVENTS THAT OCCUR IN THE
CARDIAC CHAMBERS DURING CARDIAC CYCLE
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VENTRICULAR SYSTOLE 0.31 sec(Peak of R wave of QRS complex to the end of T wave)
ISO-VOLUMETRIC CONTRACTION
0.06 sec
MAXIMUM EJECTION (2/3) 0.11 sec
REDUCED EJECTION (1/3) 0.14 sec
VENTRICULAR DIASTOLE 0.52 sec(End of T wave to the peak of R wave of QRS complex)
PROTODIASTOLE 0.04 sec
ISO-VOLUMETRIC RELAXATION 0.06 sec
RAPID INFLOW 0.11 sec
SLOW INFLOW / DIASTASIS 0.2 sec
ATRIAL SYSTOLE (after P wave) 0.11 sec
8 Phases of CARDIAC CYCLE 0.8 sec
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A) Pressure changes in left ventricle during cardiac cycle.
B) Pressure changes in right ventricle during cardiac cycle.
C) Pressure changes in atria.
PRESSURE CHANGES:
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‘Phase 1’ of cardiac cycle / Iso-volumetric contraction of ventricle:
At the start of ventricular systole L.V is full of blood (received from left atrium during previous diastole).
Pressure in L.V at the start = 1-3 mm Hg. Now L.V begins to contract I.V.P (Intra-
ventricular pressure) begins to rise closure of mitral valve / Left AV Valve 1st phase starts: Isometric Contraction Phase Or Isovolumetric Contraction Phase.
PRESSURE CHANGES IN LEFT VENTRICLE (L.V) DURING CARDIAC CYCLE:
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• Phase 1’ of cardiac cycle / Iso-volumetric contraction of ventricle (CONT…)
• With closure of mitral valve ventricle is a closed chamber no change in blood volume ISO-VOLUMETRIC, as both valves are closed ISO-METRIC CONTRACTION (no change in length of muscle but rapid increase in I.V.P).
• When IVP rises just above 80 mm Hg opening of Aortic or Semi-lunar valve.
• Duration of I.V.C of Ventricle = 0.06 sec.
• With opening of Aortic valve, 2nd phase starts: MAXIMAL EJECTION PHASE.
PRESSURE CHANGES IN LEFT VENTRICLE (L.V) DURING CARDIAC CYCLE:
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‘Phase 2’ of cardiac cycle / Maximal Ejection Phase (M.E.P) / Rapid Ejection Phase (R.E.P):
Ventricle muscle is contracting powerfully with opening of Aortic valve.
Blood is ejected from ventricle (2/3 of stroke volume) Aorta (at maximum rate). 70% EMPTYING occurs in first 1/3 of ejection phase.
In this phase: I.V.P maximum = 120 mm Hg.
Duration of M.E.P = 0.11 sec.
PRESSURE CHANGES IN LEFT VENTRICLE (L.V) DURING CARDIAC CYCLE:
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‘Phase 3’ of cardiac cycle / Reduced Ejection Phase (R.E.P):
• Blood ejection (remaining 1/3 of stroke volume, 30% EMPTYING occurs in last 2/3 of ejection phase) from L.V Aorta, continues but at a reduced rate.
• I.V.P falls from maximum.
• This phase ends when I.V.P becomes equal to OR
slightly less than AORTIC PRESSURE.
• Duration of R.E.P = 0.14 sec.
PRESSURE CHANGES IN LEFT VENTRICLE (L.V) DURING CARDIAC CYCLE:
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DURATION OF VENTRICULAR SYSTOLE (3 PHASES):1. Isovolumetric contraction = 0.06 sec
2. Maximum Ejection Phase = 0.11 sec
3. Reduced Ejection Phase = 0.14 sec
So, Ventricular Systole = 0.31 sec
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• ‘Phase 4’ of cardiac cycle / Protodiastole:
• duration = 0.04 sec.
• At the junction of systole & diastole, but included in diastole.
• At this stage, I.V.P = Aortic Pressure or
I.V.P is slightly less than Aortic pressure, BUT SMALL AMOUNT OF BLOOD CONTINUES TO OOZE, because of momentum.
• In protodiastole: THIS MOMENTUM IS OVERCOME due to further fall in I.V.P & there is some retrograde flow of Aortic blood in 1st part of Aorta closure of Aortic valve end of Protodiastole.
PRESSURE CHANGES IN LEFT VENTRICLE (L.V) DURING CARDIAC CYCLE:
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• ‘Phase 5’ of cardiac cycle / Isovolumetric Relaxation Phase (I.V.R):
• Starts with closure of Aortic valve.
• Why it is called ISOVOLUMETRIC RELAXATION?
PRESSURE CHANGES IN LEFT VENTRICLE (L.V) DURING CARDIAC CYCLE:
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ANSWER• Ventricle relaxation without change in volume, because: BOTH VALVES ARE
CLOSED no change in blood volume Rapid fall in I.V.P because of relaxation.
When
(left ventricular pressure) < (left atrial pressure) Opening of left AV valve / mitral valve end of I.V.R phase.
• Duration of I.V.R = 0.06 sec.
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• ‘Phase 6’ of cardiac cycle / Rapid Inflow Phase (R.I.P) / Rapid filling phase (R.F.P):
• Starts with opening of mitral valve.
• Blood from Left Atrium rapidly flows into Left Ventricle.
• 2/3 of ventricular filling occurs in this phase (during first 1/3 of ejection phase)
• Duration of R.I.P = 0.11 sec.
PRESSURE CHANGES IN LEFT VENTRICLE (L.V) DURING CARDIAC CYCLE
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• ‘Phase 7’ of cardiac cycle / Slow Inflow Phase / Diastasis:
It appears that: No blood is flowing from Lt. Atrium Lt. Ventricle because:
• During last phase (R.I.P), most of blood Lt. Vent.
• Mitral valve is open Lt. atrium & Lt. Ventricle = common chamber whatever blood that returns in small amount from pulmonary veins Lt. Atrium Lt. Ventricle (through open valve) so it appears that no blood is flowing.
• Only slight filling of Lt. Ventricle in this phase.
• Duration of diastasis / Slow Inflow Phase = 0.20 sec.
• THE LONGEST PHASE OF CARDIAC CYCLE.
PRESSURE CHANGES IN LEFT VENTRICLE (L.V) DURING CARDIAC CYCLE:
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• ‘Phase 8’ of cardiac cycle / Atrial Systole:
• Last phase of cardiac cycle
• Lt. Atrium contracts pushes the blood from its cavity Lt. Ventricle 20% ventricular filling by atrial contraction.
• Atria contract towards the end of ventricular diastole.
• With atrial contraction, ventricular filling is complete.
• Duration: 0.11 sec.
• AV nodal delay allows atria to contract before ventricles begin to contract, at the end of ventricular filling.
PRESSURE CHANGES IN LEFT VENTRICLE (L.V) DURING CARDIAC CYCLE:
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• Protodiastole = 0.04 sec
• Isovolumetric Relaxation = 0.06 sec
• Rapid Inflow Phase = 0.11 sec
• Slow Inflow Phase = 0.20 sec
• Atrial Systole = 0.11 sec
• Ventricular Diastole = 0.52 sec
DURATION OF VENTRICULAR DIASTOLE (5 PHASES):
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DURATION OF CARDIAC CYCLE (8 PHASES):= Duration of systole + diastole =
• (0.31) + (0.52) = [0.8 sec]
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PRESSURE CHANGES IN RIGHT VENTRICLE:• Same phases as for Lt. ventricle.
• Same duration as for Lt. ventricle.
• Only change in pressure levels & in names of valves.
• Aortic valve is replaced by pulmonary valve.
• Mitral valve is replaced by Tricuspid valve.
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PRESSURE CHANGES IN RIGHT VENTRICLE:
At the beginning of Rt. Vent. Systole:
• Pressure = 0-1 mm Hg.
• During I.V.C Pressure increases on the right side just exceeds 8 mmHg opening of pulmonary valve (above 80 mmHg, there was opening of Aortic valve).
• Maximum increase in pressure in Rt. Vent systole = 25 mmHg (it was120 mm Hg in Lt. vent.)
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PRESSURE CHANGES IN RIGHT VENTRICLE:• Right ventricle & Pulmonary artery is a low pressure system.
Pulmonary artery pressure variation:
• 8 – 25 mm Hg
Aortic pressure variation:
• 80 – 120 mm Hg
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DURATION OF CARDIAC CYCLE & HEART RATE:• Duration of cardiac cycle = 0.8 sec at heart rate = 70 beats / min.
• When heart rate increases duration of cardiac cycle decreases.
• Diastole is more affected as compared to systole with rapid heart rate.
• At heart rate = 180 / min, cardiac cycle duration = 0.33 sec: (systole = 0.18 sec, diastole = 0.15 sec).
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QUESTION• At a very rapid heart rate: Cardiac output decreases, Why???
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ANSWER• Because diastole becomes too short ventricular filling decreases decrease stroke volume &
decrease in cardiac output, in spite of increase in heart rate.
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CARDIAC OUTPUT:• Output of heart per unit time = 5 L / min in a resting supine man.
• Cardiac output = stroke volume x heart rate
= 70 ml x 72 beats / min
nearly equal to 5 L / min
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STROKE VOLUME (S.V):• Difference between End Diastolic Volume (EDV) & End Systolic Volume (ESV).
• S.V = EDV - ESV
• S.V = 120 – 50
• = 70 ml
• When ventricular contraction is forceful ESV decreases (10-20 ml only). Normal is 50 ml.
• When venous return increases up to 200 ml or more EDV increases (normal = 120 ml)
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EJECTION FRACTION:• Fraction of EDV that is ejected in one systole or one stroke = Ejection Fraction.
• Value of Ejection Fraction = 60% (usually).
• 65% in some books.
• In Myocardial disease / heart failure Ejection Fraction decreases.
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PRESSURE CHANGES IN ATRIA DURING THE CARDIAC CYCLE: • Atrial systole duration = 0.11 sec• Atrial diastole duration = 0.70 sec• Atrial systole + Atrial diastole = 0.8 sec = cardiac cycle.
• Atrial diastole > Atrial systole, because basic function of atria is to receive blood from large veins & it can receive blood only when it is relaxed.
3 waves can be recorded from atria which represent atrial pressure changes:
• a-wave, c-wave & v-wave (Seen as Jugular Venous Pulse, not a true pulse, but a reflection of pressure changes in right atrium.
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a-wave: Due to increase in atrial pressure during atrial systole.
PRESSURE CHANGES IN ATRIA DURING THE CARDIAC CYCLE:
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c-wave: Recorded at beginning of contraction of ventricle. During isovolumetric contraction, ventricular pressure increases Cusps of AV valves are pushed into atrial cavity pressure rises in atria ascent of c-wave.
PRESSURE CHANGES IN ATRIA DURING THE CARDIAC CYCLE:
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PRESSURE CHANGES IN ATRIA DURING THE CARDIAC CYCLE:
The top of c-wave coincides with opening of semi-lunar valves (Aortic & Pulmonary).
With opening of semi-lunar valves, 2nd phase starts, which is maximum ejection phase.
It is later on followed by iso-volumetric relaxation of ventricle muscle length increases now AV valve is pulled to ventricular cavity atrial cavity increases pressure falls in the atria descent of c-wave.
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• v-wave: Due to gradual increase in atrial pressure, resulting from venous filling of blood (from the venae cavae) into the atria, with closed AV valves ascent of v-wave.
• Top of v-wave coincides with opening of AV valves rapid inflow phase decrease pressure in atria descent of v-wave.
PRESSURE CHANGES IN ATRIA DURING THE CARDIAC CYCLE:
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RIGHT ATRIAL PRESSURE = CENTRAL VENOUS PRESSURE.
• During most of cardiac cycle, this pressure remains almost zero.
• During wave a, c & v pressure rises. Otherwise remains almost zero.
• 4-6 mm Hg Rt. Atrium (during a, c, v)
• 7-8 mm Hg Lt. Atrium (during a, c, v)
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• Normally arteriolar pulse ends in arterioles & in veins no pulsation.
• But we can record pulsation in jugular vein, which is not a true pulse.
• It is just backward transmission of pressure changes in Rt. Atrium (a, c. v waves) transmitted in neck veins.
JUGULAR VENOUS PULSE:(A, C, V WAVES)
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SIGNIFICANCE OF J.V.P:• ac interval coincides with PR interval of ECG.
• Ac interval increases in delayed av conduction
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• a waves are absent in: ATRIAL FIBRILLATION.
• (a wave) > (c wave) in COMPLETE AV BLOCK.
• ‘Giant a waves’ in TRICUSPID & PULMONARY STENOSIS.
• Pulsating Neck Veins in CCF (Congestive Cardiac Failure).
SIGNIFICANCE OF J.V.P:
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Beginning of ventricular systole: Ejection Phases: (Maximum Ejection Phase
& Reduced Ejection Phase)
Iso-volumic Relaxation Phase:
Rapid Inflow Phase:
Diastasis / Slow Inflow Phase:
Atrial Systole:
VOLUME CHANGES IN VENTRICLES DURING CARDIAC CYCLE:
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• Ventricle is full of blood (collected during previous diastole, EDV = 120 ml) at the onset of ventricular systole.
• This much volume is there at the start of ventricular systole.
• With this volume onset of Isovolumic / Isometric Contraction, with no change in blood volume.
BEGINNING OF VENTRICULAR SYSTOLE:
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Maximum Ejection Phase:
• 2/3 of Stroke Volume (total = 70 ml) is ejected out.
Reduced Ejection Phase:
• Remaining 1/3 is ejected out.
After ejection phases, the volume of blood left behind is ESV = 50 ml.
EJECTION PHASES: (MAXIMUM EJECTION PHASE & REDUCED EJECTION PHASE)
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ISO-VOLUMIC RELAXATION PHASE:
• No change in blood volume occurs.
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RAPID INFLOW PHASE:
• 2/3 of ventricular filling.
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DIASTASIS / SLOW INFLOW PHASE:
• Only slight filling occurs.
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ATRIAL SYSTOLE:
• Remaining 1/3 filling (30%). Now filling of ventricles is complete & EDV of 120 ml is left.
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• Fraction of EDV that is ejected in one systole or one stroke = Ejection Fraction.
• Value of Ejection Fraction = 60% (usually).
• 65% in some books.
• In Myocardial disease / heart failure Ejection Fraction decreases.
EJECTION FRACTION:
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• Right atrial systole begins earlier as compared to left atrial systole.
• Left ventricular systole begins earlier as compared to right ventricular systole.
• But blood ejection from right ventricle pulmonary artery, starts earlier as compared to ejection from left ventricle aorta, BECAUSE pressure in pulmonary artery < Aortic pressure.
SEQUENCE OF SYSTOLE IN CHAMBERS OF HEART:
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AV VALVES:• Are closed at the beginning of
Isovolumic contraction Phase.
• Are open at the beginning of Rapid Inflow phase.
• AV valve closure is slow & soft & does not require backward flow of blood.
• Cusps of AV valves are soft & thin because they are not subjected to increase in pressure & rapid blood flow.
CLOSURE & OPENING OF HEART VALVES:
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• SEMILUNAR VALVES:• Are closed at the beginning of
Isovolumic relaxation phase.
• Cusps of these valves are thick & heavier (as they are subjected to increased pressure & rapid blood flow).
• Their closure is rapid & requires backward flow of blood (incisura in case of Aortic valve).
CLOSURE & OPENING OF HEART VALVES:
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• Forward pressure gradient opening.
• Backward pressure gradient closure.
• AV valves prevent, leakage of blood from ventricle atria, during ventricular systole (when pressure rises in ventricle).
• Semilunar valves prevent leakage of blood from large arteries ventricles, during ventricular diastole (when pressure falls in ventricle)
CLOSURE & OPENING OF BOTH AV & SEMILUNAR HEART VALVES:
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• During each cardiac cycle, 4 heart sounds are produced.
• These can be recorded in phonocardiogram.
• By auscultation we can hear / auscultate, 1st & 2nd heart sounds & sometimes 3rd as well.
• But 4th is Atrial heart sound, which is never auscultated normally.
• 1st & 2nd heart sounds are called as CLASSICAL HEART SOUNDS (as they are usually auscultated in normal subjects).
HEART SOUNDS:
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4 AUSCULTATORY AREAS:• Pulmonary Area: Left 2nd intercostal
space, sternal border.
• Aortic Area: Right 2nd intercostal
space, sternal border.
• Mitral Area: Apex.
• Tricuspid Area: 4th intercostal space.
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4 BASIC FACTORS AFFECTING HEART SOUNDS:• Acceleration of blood: Sudden flow.
• Deceleration: Sudden stoppage of blood flow.
• Turbulance.
• Thickness of chest wall effects.
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Characteristics:
• Long, soft, low pitched. (heard as LUBB)
• Frequency: 30 – 50 cycles / sec.
• Duration: 0.14 sec
1ST HEART SOUND:
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CAUSES:
• Vibrations due to closure of AV valves, at the beginning of ventricular systole.
• Vibrations in ventricles & large vessels when ventricular muscle contracts.
• Vibrations when blood starts ejecting into large artery.
1ST HEART SOUND:
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Mechanism:
• Tricuspid valve may close earlier than mitral.
PHYSIOLOGICAL SPLITTING OF 1ST HEART SOUND:
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Depends on:
• Force of ventricular systole.
• Rate of increase in ventricular pressure, during isovolumic contraction phase.
INTENSITY OF 1ST HEART SOUND:
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Characteristics:
• Short, sharp, high pitched. (heard as DUBB)
• Frequency: 50 – 200 cycles / sec.
• Duration: 0.11 sec
2ND HEART SOUND:
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Minor causes:
• When blood flows from ventricle to large arteries, there may be turbulance.
2ND HEART SOUND:
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• PHYSIOLOGICAL
• Increases or Widens during inspiration (0.5 sec) & decreases during expiration (0.02 sec or disappear).
Cause of splitting:
• During inspiration venous return increases more blood returns to right atrium right ventricle more ejection delayed closure of pulmonary valve.
• Reverse occurs in expiration.
• PATHOLOGICAL
• In bundle branch block, mainly right bundle branch block.
• Intensity of pulmonary component of 2nd heart sound is increased in pulmonary hypertension.
• Intensity of aortic component is increased in aortic hypertension
SPLITTING OF 2ND HEART SOUND:
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Prominent sometimes in children.
Can be made prominent by increasing venous return:
i) exercise.
ii) lying position.
• Low frequency sound.
• Duration: 0.04 sec.
• Best heard at: Apex of heart, in 5th intercostal space
(mid-clavicular line).
• Cause: Vibrations produced in ventricular wall during
Rapid Inflow Phase.
3RD HEART SOUND:
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• Not normally auscultated but recorded in phonocardiogram.
• Low frequency, low intensity sound.
• Produced just before 1st heart sound.
• Also called ATRIAL HEART SOUND.
Cause:• Vibrations of ventricular wall, due to impact
of blood pumped from the atrium ventricle, during Atrial Systole.
Diseases:• In CCF, 4th Heart Sound is auscultated.
4TH HEART SOUND:
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• Abnormal heart sounds.
Produced when:• Valvular stenosis.
• Valvular incompetence.
• Hyperdynamic circulation: Hyperthyroidism, severe
anemia (hemic murmurs)
MURMURS: