Cardiac Physiology V

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Cardiac Physiology(V)

• A. Rüçhan Akar
• Ankara University
• School of Medicine
• December- 2003

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Cardiac Cycle

• the left and right sides almost synchronous

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Cardiac Cycle

• LV filling
• rapid phase (f)
• slow phase (diastasis) (g)
• atrial systole or booster (a)
• LV contraction
• isovolumic contraction (b)
• maximal ejection (c)
• LV relaxation
• start of relaxation and reduced ejection (d)
• isovolumic relaxation (e)

70
20-30
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(No Transcript)
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Ventricular Filling duration 0.5 sec
Diastole

• arterial outlet valves closed
• III. isovolumetric relaxation LV/ RV pressures lt
  LA/ RA pressures
• inlet (atrioventricular) valves open
• IV. filling phase

AVC
MVO
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Filling phase
Diastole

• IVa. phase of early rapid filling
• may cause the physiological third heart sound
  (S3) especially with hyperkinetic circulation
• IVb. slow filling (diastasis)
• LA-LV pressures equalize
• LV filling partially stops
• IVc. atrial systole (left atrial
  booster)

AVC
MVO
MVC
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Ventricular Filling
Diastole

• End-diastolic volume stroke volume RV
  120-140 ml
• LVEDP 9 mmHg
• RVEDP 4 mmHg

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Contraction

• arrival of calcium ions at the contractile
  proteins
• actin-myosin interaction
• R wave (ECG)

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Systole

• 1st heart sound-lup
• LV pressure gt LA pressure (10-15 mmHg)
• mitral component of the first heart sound (M1)
• shortly thereafter,
• RV pressure gt RA pressure
• tricuspid component of the first heart sound
  (T1)
• I. Isovolumetric Contraction (0.05 sec)

AVC
AVO
MVC
MVO
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Systole

• pressure in the left ventricle exceeds the aortic
  diastolic pressure (80mmHg),
  aortic valve opens
• pressure in the right ventricle exceeds the
  pulmonary diastolic pressure (10mmHg),
  pulmonary valve opens
• II. Ejection (0.3 sec)

AVO
MVO
MVC
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II. Ejection

• IIa. phase of rapid ejection 2/3 of the
  ventricular blood is ejected
• IIb. phase of reduced ejection
• blood flow from the LV to the aorta rapidly
  diminishes but is maintained by aortic
  distensibility-
• the Windkessel effect

AVC
AVO
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• 2nd heart sound-dup
• aortic pressure exceeds the falling pressure in
  the LV
• aortic valve closes,
• the aortic component of the second sound, (A2)
• pulmonary artery pressure exceeds that in the
  right ventricle
• closure of the pulmonary valve (P2)
• III. Isovolumetric Relaxation (0.08 sec)

AVC
AVO
MVC
MVO
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Frank-Starling Relationship

• Preload
• depends volume of blood before contraction
  (LVEDV)
• physiologically determined by the venous return
• wall stress at the end of diastole
• LVEDP determines the LVEDV and hence the
  resting length of the ventricular muscle fibers

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• Afterload
• the load on the contracting myocardium
• wall stress during LV ejection

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afterload systolic wall stress
arterial blood pressure
arterial compliance
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• myocardial oxygen uptake reflects the rate of
  mitochondrial metabolism, ATP production
• factors increasing wall stress increase the
  oxygen uptake
• a practical index of the oxygen uptake

systolic blood pressure heart rate (the
double-product)
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Atrial Cycle
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Atrial Cycle and CVP

• resting RA pressure 0-4 mmHg
• resting LA pressure 4-6 mmHg
• atrial contraction 7-12 mmHg
• (a wave)

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a wave atrial contraction c wave closure of
tricuspid valve carotid artery expansion x
descent atrial diastole during ventricular
ejection, AV septum moves downwards increasing
the volume of atria v wave venous return during
ventricular systole Its height reflects the rate
of filling and the elasticity of the RA y
descent opening of tricuspid valve emptying
atrial contents into the ventricule
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x descent disappears as the degree of TR
increases jugular pulse wave is said to be
ventricularised a wave disappears during
atrial fibrillation
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An increase in the magnitude ofa wave

• Tricuspid stenosis
• Pulmonary stenosis
• Pulmonary hypertension

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Cannon a waves

• atrial systole against closed tricuspid valve
• junctional tachycardia
• complete AV block
• ventricular ectopics

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An increase in the magnitude ofv wave

• Tricuspid incompetence

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An increase in the magnitude ofa and v waves

• Constrictive pericarditis

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• Normal
• Anocrotic pulse with slow initial upstroke. LVOTO
• Pulses bisferiens. AR or ASAR
• Pulses bisferiens in hypertrophic obstructive
  cardiomyopathy
• Accentuated dicrotic wave (sepsis, heart failure,
  hypovolemic shock, cardiac tamponade, after AVR)