Clinical Cardiovascular Anatomy

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Clinical Cardiovascular Anatomy
Physiology Concepts, Definitions, Principles
Slides developed in collaboration with Dr. John
Green, 2003.
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The Normal Heart - Coronary Artery Anatomy
Left Main CA
Layers of the Arterial Wall
Circumflex
Adventitia
Media
Intima
Right CA
Marginal Branch
Left Anterior Descending CA
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The Heart as a Pump Reference Berne and Levy,
Physiology
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Cardiac Muscle Differences

• Fibers organized into functional syncytium
• branching, interconnected fibers
• ends separated by intercalated disks fused to
  adjoining fibers by tight junctions low
  resistance
• all-or-none law applies to entire myocardium
• Cannot be tetanized
• due to phase 2 (plateau) of action potential

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Left Ventricular Volumes - Definitions
End Diastolic Volume (EDV)
Volume at the end of diastole (end of
ventricular filling) End Systolic Volume
(ESV) Volume at the end of systole (end of
ventricular contraction) Stroke Volume (SV)
EDV - ESV Ejection Fraction (EF) SV EDV
Ejection Fraction is the best indicator of heart
performance and disease prognosis
Left ventricular norm 62
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Definitions

• Cardiac Output (Q) HR X SV
• Cardiac Index Q / body surface area
• Preload diastolic filling volume of the left
  ventricle (EDV reflects
  stretch of the cardiac muscle cells)
• Afterload resistance to ventricular emptying
  during systole (the amount of pressure the left
  ventricle must generate to squeeze blood into
  the aorta
• Frank Starling Law of the Heart - the heart
  will contract with greater force when preload
  (EDV) is increased
• Myocardial Contractility - the squeezing
  contractile force that the heart can develop at
  a given preload
• regulated by
• sympathetic nerve activity (most influential)
• catecholamines (epinephrine norepinephrine)
• amount of contractile mass
• drugs

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Starlings Law of the Heart and Contractility
? contractility
SV left ventricular performance
normal contractility
? contractility (heart failure)
preload (venous return)
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Using Ventricular Pressure Curves as Indices of
Contractility Cardiac Function
dP/dt change in pressure per unit of time
dP/dt
dP/dt
Normal Heart Failure
120
Note elevation in end diastolic pressure
0
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Contractility

• - a change in developed tension at a given
  resting fiber length OR an increase in Vmax
• increase max dP/dt from LV pressure curve
• Positive and negative inotropic effects
• Ejection fraction (EF SV/EDV) used in clinical
  practice
• increase contractility assumed with increase EF
• ? with Ca, NE, digitalis, exercise? with Ko,
  Nao

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Influences on Myocardial Contractility
? Contractility related to beta-sympathetic
adrenergic nerves catecholamines
epinephrine norepinephrine drugs
digitalis sympathomimetics ?
Contractility related to loss of contractile
mass - myocardial Infarction myocardial muscle
disease - cardiomyopathy drugs anesthetics,
barbiturates
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Definitions

• Arteriovenous Oxygen Difference (AVO2D) the
  difference in oxygen content between arterial
  and venous blood
• measured in ml - ml O2 / 100 ml blood
• Oxygen Consumption (VO2) - the rate at which
  oxygen can be used in energy production and
  metabolism
• absolute measures L / min , ml / min
• relative measures ml / kg body wt. / min
• Fick equation VO2 Q X AVO2D
• Maximum Oxygen Consumption (VO2max) maximum rate
  at which a person can take in and utilize oxygen
  to create usable energy
• defined as plateau of consumption rate increase
• often estimated with VO2peak
• Myocardial Oxygen Consumption VO2 of the heart
  muscle (myocardium)
• "estimated" by RPP HR X SBP
• Functional Aerobic Impairment

mild 27 - 40 moderate 41 -
54 marked 55 - 68 severe gt 69
predicted VO2max - attained VO2max
predicted VO2max
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Definitions

• Systolic Blood Pressure (SBP) pressure measured
  in brachial artery during systole (ventricular
  emptying and ventricular contraction period)
• Diastolic Blood Pressure (DBP) pressure measured
  in brachial artery during diastole (ventricular
  filling and ventricular relaxation)
• Mean Arterial Pressure (MAP) "average" pressure
  throughout the cardiac cycle against the walls
  of the proximal systemic arteries (aorta)
• estimated as .33(SBP - DBP) DBP
• Total Peripheral Resistance (TPR) - the sum of
  all forces that oppose blood flow
• length of vasculature (L)
• blood viscosity (V)
• hydrostatic pressure (P)
• vessel radius (r)

TPR ( 8 ) ( V ) ( L ) (?) ( r 4 )
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Cardiovascular Hemodynamic Basics
Pressure (MAP) P aorta P
vena cava Resistance (TPR)
(8) (V) (L)
(?) (r 4)
Flow (Q)
Flow (Q)
(?) (Pa Pv) (r 4) (8) (V) (L)
Normally Resting Q is about 5 - 6 liters / minute
V viscosity of fluid (blood) flowing through
the pipe L length of pipe (blood vessel) r
radius of the pipe (blood vessel) Pa aortic
pressure Pv venous pressure
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Brain
The Systemic Circulation
Lungs
Arteries (Stiff Inflexible Pipes)
Veins (Flexible Compliant Pipes)
Precapillary Sphincters
Liver
Stomach
Pancreas
Intestines
Kidneys
Arterioles
Skin
Muscle
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Microcirculatory Anatomy
Arteriole
Smooth Muscle
Precapillary Sphincter
Anastomosis (Shunt)
True Capillary With Single Layer of Endothelium
Metarteriole
Venule
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Effects of an Increase in Preload on Left
Ventricular Pressure Volume Loop
? Ejection Pressure
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Left Ventricular Pressure (mmHg)
? SV
? EDV ? EDP
6
40
140
Volume (ml)
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Effects of an Increase in Afterload on Left
Ventricular Pressure Volume Loop
? ESV ? ESP
120
Left Ventricular Pressure (mmHg)
? SV
6
40
140
Volume (ml)
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Mechanism of Control of Cardiovascular and
Respiratory Systems
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Sites of Cardiorespiratory Control
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Cardiorespiratory Control

• Stroke Volume regulated by Frank Starling
  mechanism
• ? venous return ? ? EDV ? ? stroke volume
• Cardiac Output (Q) main determinant body O2
  needs
• Autoregulated by intrinsic changes in preload,
  SV
• ? afterload ? initial ? in Q ? ? EDV ? ? SV back
  to normal
• ? venous return ? ? preload ? ? SV
• Autoregulated by extrinsic hormonal influences
• Norepinephrine release ? ? HR and SV

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Cardiorespiratory Control

• Exercise Systemic Blood Flow Autonomic
  influences
• Sympathetic outflow circulating catecholamines
• a activation ? vasoconstriction in non -
  exercising tissue
• Approximate redistribution of blood flow during
  maximal exercise
• NC in brain blood flow 500 ml/min ? to heart
• 11,300 ml/min ? to muscle 400 ml/min ? to skin
• 500 ml/min ? to kidneys 800 ml/min ? to viscera
• 200 ml/min ? to various other parts of the body

Rest
Max Exercise
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Acute Cardiorespiratory Responses to Endurance
Exercise
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Acute Responses to Aerobic Exercise

• Heart Rate
• ? up to 3 times resting value at peak exercise
  (? time spent in diastole)
• Oxygen Consumption (VO2)
• Expressed in both relative and absolute terms
• Relative ml O2/kg/min Absolute ml/min or
  L/min
• average VO2max for 40 year old male 37 ml/kg/min
• Resting metabolic equivalent 1 MET 3.5
  ml/kg/min
• Oxygen consumption linked to caloric
  expenditure (1 liter of O2 consumed 5 kcal)

180 160 140 100
Heart Rate
HR VO2 relationship is linear until about 90
VO2max
1.0 2.0 3.0
Oxygen Uptake (L / min)
50 150 250
Workloads (Watts)
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• Cardiac Output (Q)
• ? up to 4 times resting value at peak exercise
  (? is rapid at onset, then levels off)
• ? Q ? ? venous return
• Venous return mediated by and related to
• sympathetic venoconstriction
• muscle pump
• ? inspiration ? ? thoracic pressure
• blood flows to an area of reduced pressure
• ? inspiration ? ? abdominal pressure
• contraction of abdominal muscles
• squeezing of abdominal veins
• Stroke Volume
• ? up to 1.5 resting value at peak exercise
• increase levels off at 40 - 50 VO2 max
• ? in venous return ? ? EDV (Starling mechanism)
• ? ESV eluding to an ? in myocardial
  contractility
• ? ejection fraction rest 58 max
  exercise 83

Acute Responses to Aerobic Exercise
120 110 70
Stroke Volume (ml/beat
25 50 75
Percentage of VO2 max
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• Arteriovenous oxygen difference
• Difference in O2 between arterial and mixed
  venous blood
• Illustrated by the oxyhemoglobin desaturation
  curve
• ? approximately 3 fold from rest to max exercise
• at rest, about 25 of arterial O2 is extracted
• at peak exercise 85 of arterial O2 is
  extracted
• Blood Pressures and Resistance to Flow
• SBP ? - failure to ? signifies heart failure
• DBP slight ? or slight ? or NC
• MAP slight ?
• TPR ? - mainly due to vasodilation in
  exercising muscle
• Coronary (Myocardial) Blood Flow
• 4.5 of Q goes to myocardium at rest and at peak
  exercise
• this increase is due to ? MAP and CA
  vasodilation
• Blood Flow to the Skin
• ? as exercise duration ? to allow for heat
  dissipation

Acute Responses to Aerobic Exercise
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Acute Responses to Aerobic Exercise

• Minute Ventilation
• resting average 6 Liters/min
• peak exercise average 175 Liters/min
• respiratory rate resting 12-18 peak
  exercise 45-60
• tidal volume resting .5 liters peak
  exercise 2.25 Liters
• Plasma Volume
• blood plasma ? in the interstitum of exercising
  muscle
• fluid shift results in a 5 ? in the
  hemoconcentration
• blood viscosity increases

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Oxygen Debt and Deficit
Oxygen DEBT Oxygen DEFICIT
Oxygen Deficit
Oxygen Debt (EPEOC)
Steady State VO2
VO2
Untrained or people with
certain cardiorespiratory
diseases will have larger
DEBTS and DEFICITS
Rest
EXERCISE TIME
Onset
Termination

• Oxygen Deficit due to
• delay in time for aerobic ATP production to
  supply energy
• Oxygen Debt due to
• resynthesis of high energy phosphates (CP, ATP)
• replace oxygen stores
• lactate conversion to glucose (gluconeogenesis)
• ? HR, respiration, catecholamines, body
  temperature

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OBLA
Respiratory Compensation (hyperventilation)
No Change in VE VCO2
Ventilatory and Metabolic Changes During Exercise
Increasing workload
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Training Adaptations to Chronic Endurance Exercise
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Resting NC ? NC
VO2 HR x SV x
AVO2diff due to due to
? time in diastole
? preload ? afterload ? ventricle
size ? blood volume Submax Workload
(measured at same pre-training workload) NC
NC VO2 HR x SV x
AVO2diff note a ? in afterload (mentioned
above) accompanied by a ? in HR
response translates into a ? myocardial VO2 at
rest or at any workload Max Workload (measured
at peak exercise) NC VO2 HR
x SV x AVO2diff some studies
show a slight
decrease
?
?
Effects of Exercise Training on the Components of
the Fick Relationship
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• Mean Arterial Pressure
• NC at rest or during exercise
• Systolic and Diastolic Blood Pressure
• usually NC at rest or during exercise
• possible ? at submaximal workload
• may ? at rest in borderline hypertensives
• some studies report a mean ? of about 9 mmHg
• Total Peripheral Resistance and Afterload
• ? capillarization (more parallel circuits) ? ?
  TPR
• ? TPR ? ? Afterload (slight not of major
  significance)
• Respiratory Variables
• Respiratory Rate
• Rest NC
• Submax exercise d
• Max exercise slight ?
• Tidal Volume
• Rest NC
• Submax exercise NC or slight ?
• Max exercise slight ?

Training Adaptations
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• Mitochondria
• ? number, size and membrane surface area
• Aerobic Enzymes in Exercising Muscle
• ? Krebs cycle enzymes (succinate dehydrogenase)
• ? b oxidation enzymes (carnitine
  acyltransferase)
• ? electron transport enzymes (cytochrome
  oxidase)
• Fatty Acid Glycogen Utilization
• ? utilization of b oxidative pathways to produce
  ATP
• Called the glycogen sparring effect
• ? RER for any given submaximal workload
• ? muscle glycogen stores (with high carbohydrate
  diet)
• ? Platelet Aggregation
• ? Fibrinolytic Activity
• ? Circulating Catecholamines
• ? vagal tone ? ? risk of arrhythmia
• No Appreciable Change in Resting Metabolic Rate
• Exception training induced ? in lean muscle
  mass
• Resistance to Pathological Events
• smaller infarct size and quicker recovery

Training Adaptations
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"Average" Values for Sedentary and Trained
Individuals
Heart Rate ( beats / minute )
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"Average" Values for Sedentary and Trained
Individuals
Stroke Volume ( ml / beat )
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"Average" Values for Sedentary and Trained
Individuals
Cardiac Output ( liters / minute)
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"Average" Values for Sedentary and Trained
Individuals
A-V O2 Difference ( ml)
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"Average" Values for Sedentary and Trained
Individuals
Oxygen Consumption ( liters / minute)
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"Average" Values for Sedentary and Trained
Individuals
Oxygen Consumption ( ml / kg / minute)
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"Average" Values for Sedentary and Trained
Individuals
Systolic Blood Pressure ( mm Hg)
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"Average" Values for Sedentary and Trained
Individuals
Diastolic Blood Pressure ( mm Hg)
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"Average" Values for Sedentary and Trained
Individuals
Minute Ventilation ( liters / minute)
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