Cardiovascular 4 Flashcards
Mastery
3 factors regulate stroke volume:
- Preload
- Contractility
- Afterload
Stroke Volume
Depends on
3 factors regulate stroke volume:
- Preload - the amount of myocardial stretching (the greater the preload the greater the SV)
- Contractility – the amount of force produced during a contraction at a given preload (the greater the force of contraction the greater the SV)
- Afterload – the tension required for the left ventricle to force open the aortic semilunar valve
(as afterload increases, SV decreases)
Stroke Volume
Depends on Preload (Venous Return),
Afterload, Contractility
Cardiac Remodeling
Pathological remodeling
Physiological remodeling
Pathological remodeling
Consequence of disease
* High BP, heart failure,
infarct
Physiological remodeling
Consequence of
training or pregnancy, improves function
Ischemia
time? damage? symptoms occur when? symptoms ease when? technical term
Infarct
time? damage? symptoms occur when? technical term? pain where?
Treatments:
Transient. BLOCKED CORONARY ARTERY
No permanent damage to heart muscle
Symptoms occur when cardiac demand increases beyond what the heart can match
Symptoms ease when demand does down
“Angina”
INFARCT
Permanent blockage of CORONARY ARTERY
Muscle cells are permanently damaged
Symptoms remain and worsen
“Heart Attack”
Symptoms:
Chest pain
* diaphoresis (sweating)
* Nausea, “indigestion”
* Referred pain - neck, arm, jaw
Treatment:
* Coronary artery bypass graft (CABG)
* Vasodilators
* Angioplasty
* Reduce risk factors
⬧ Diet
⬧ Exercise
⬧ Smoking
Factors affecting Heart Rate (HR)
Sympathetic NS
Parasympathetic NS
Hormones (E/NE…. Ach….)
Age (older people → )
Gender (females)
Physical fitness (low fitness → )
Body temperature (increased Tb → )
Sympathetic NS increases HR
Parasympathetic NS decreases HR
Hormones (E/NE increase HR; Ach decreases HR)
Age (older people → higher HR)
Gender (females have faster HR than males)
Physical fitness (low fitness → increased HR)
Body temperature (increased Tb → increased HR)
Inotropic Effect
Role of Epinephrine or Norepinephrine
The effect of increased sympathetic stimulation on contractility of the heart
Increases both contractility and heart rate
* Harder and faster contractions
Cardiac Output
Calculated as
Depends on
Cardiac Output
Calculated as heart rate times stroke volume. HR xSV
Depends on venous return and sympathetic tone
Variables That Influence Heart Rate, cell level
Thyroid hormone
*
Caffeine
*
Nicotine
*
Cocaine
*
*
Variables That Influence Heart Rate
Thyroid hormone
* ↑ number of β1-adrenergic
receptors on SA node cells
Caffeine
* Inhibits breakdown of cAMP
Nicotine
* ↑ release of norepinephrine
Cocaine
* Inhibits reuptake of
norepinephrine
* remains in cleft longer – longer
response
Stroke Volume (SV) =
SV equation
Average Stroke Volume =
EDV =
ESV =
Stroke Volume (SV) = amount of blood
pumped in 1 beat
SV=EDV-ESV
Average Stroke Volume = 70 mL
EDV = end-diastolic volume (after filling)
ESV = end-systolic volume (after ejection)
Contractility affected by
Contractility affected by
Sympathetic tone
Length of muscle fibre
Long-term Benefits of Exercise and Fitness
Stroke Volume
Resting Heart rate
Coronary artery diameter
blood flow
Collateral Blood vessels
ischemia
Long-term Benefits of Exercise
and Fitness
Bigger Heart
Bigger Stroke Volume
Resting Heart rate can bigger
Greater Coronary artery diameter
Greater blood flow
Greater Collateral Blood vessels
lower ischemia
Ischemia and Infarct
Blocked coronary artery
Decreased…
due to…
Poor muscle function
Stroke Volume
Cardiac Output
XX% of one-week survivors experience late complications (heart failure, arrhythmias, etc.) that can result in death.
10-year survival rate for heart attack survivors is about XX%, with long-term complications playing a major role in mortality.
Blocked coronary artery
Decreased blood flow and oxygen to heart muscle
Due to plaque or clot
Poor muscle function
lower Stroke Volume
lower Cardiac Output
40% of one-week survivors experience late complications (heart failure, arrhythmias, etc.) that can result in death.
10-year survival rate for heart attack survivors is about 25%, with long-term complications playing a major role in mortality.
Coronary circulation:
* During exercise
- heart rate is…
- filling time (diastole) is…
- heart still gets…. blood supply
- due to dilation of…..
⬧ via….
Coronary circulation:
* During exercise
* heart rate is ↑
* filling time (diastole) is ↓
* heart still gets adequate blood supply
* due to dilation of
coronary arteries
⬧ via adenosine production
by cardiac muscle
Heart Muscle Metabolism:
*Heart muscle is…
*abundant…
*Gets oxygen from…
Heart Muscle Metabolism:
*Heart muscle is highly oxidative
*abundant mitochondria and myoglobin
*Gets oxygen from coronary circulation
In Exercise
Higher demand for O2 and blood flow
Increases…
leading to….
Both of these increase…
Casual athletes – increase by up to
Elite athletes increased to
Increase epinephrine
Higher contractility and stroke volume
Faster heart rate
Increased venous return
Both of these increase cardiac output
Casual athletes – increase by up to 5X
* ~25 L/min
Elite athletes increased to 35 or 40L/min
Frank-Starling Law of the Heart
*Preload –
an increase in EDV…
Frank-Starling Law of the Heart
*Preload – filling of the heart
Greater filling or preload means greater stretch of the myocardium and then a greater force of contraction
causes SV to increase
Cardiac Myopathies
Damage of the heart muscle
name and why?
Fibrosis
Necrosis
Acute myocardial infarction (heart attack)
Myocardial ischemia (aka heart attack)
* Inadequate delivery of oxygenated blood to heart tissue
Fibrosis
buildup of scar tissue
Necrosis
* Death of heart muscle cells
Acute myocardial infarction (heart attack)
* Occurs when a blood vessel supplying an area of the heart becomes blocked or ruptured. permanent damage
Venous return – what is it and affected by
End diastolic volume – affected by…
End systolic volume – what is it and affected by
Venous return – amount of blood entering heart (greatly increases with exercise)
Venous return is affected by
Skeletal muscle pump
Respiratory pump
Sympathetic innervation
End diastolic volume – affected by venous return and filling time (ie, duration of diastole)
End systolic volume – the amount of blood still in the chamber after a contraction; is influenced by contractility (force of contraction) and afterload
Arterial Hypertension
Causes include :
Increased…
LV pressure must…
Shorter ejection time
Stroke Volume
Cardiac Output
AFTER
Hypertension
Treatments
Medications
Arterial Hypertension
Causes include :
* Smoking
* Stress
* Diet
* Age / genetics
Increased Arterial pressure
LV pressure must exceed this to open aortic valve and eject blood
Shorter ejection time
lower Stroke Volume
lower Cardiac Output
AFTER
Hypertension
Higher risk of heart failure, haemorrhage, and stroke
Treatments
Exercise
Diet – reduced caffeine and salt
Medications
* ACE inhibitors
* Beta blockers
* Ca channel blockers
Heart Failure
Compromised Heart
- 3 things
Stroke Volume
Heart compensates with heart rate
heart rate means :
filling times - stroke volume
Faster fatigue of heart muscle
contraction and stroke volume
Eventually:
Muscle is so …. it barely contracts
stroke volume
Blood volume
Excess blood backs up into …. – called a
Heart Failure
Compromised Heart
- Aortic Valve stenosis
- Ischemia or Infarct
- Hypertension
LOWER Stroke Volume
Heart compensates with GREATER heart rate
GREATER heart rate means :
SHORTER filling times - LOWER stroke volume
Faster fatigue of heart muscle
LOWER contraction and LOWER stroke volume
Eventually:
Muscle is so fatigued it barely contracts
LOWER stroke volume
HIGHER Blood volume
Excess blood backs up into
lungs – Pulmonary edema
Effect of Afterload
Afterload –
Afterload increases with… 2 things
With higher afterload…
SV?
In heart failure
…
tension required to force open aortic valve
Afterload – force heart works against
to eject blood
Afterload increases with high blood pressure
valve stenosis
With higher afterload,
stroke volume decreases
In heart failure
Harder to eject
Congestive Heart Failure
CHF
Symptoms:
*
* Right-sided
⬧
* Left-sided
⬧
Heart Failure Treatments
Reduce…
Digitalis or similar drugs to….
Diet and exercise – to…
Heart transplants
Average post-transplant
survival:
Temporary
Artificial heart
Congestive Heart Failure
CHF
Symptoms:
* Gradual dyspnea and tachypnea
* Tachycardia
* Neck vein distention
* Edema in ankles and lower legs
* Right-sided
⬧ congestion of liver and spleen
* Left-sided
⬧ congestion of lungs
Heart Failure Treatments
Reduce fluids - diuretics
Digitalis or similar drugs
to increase contraction strength
Diet and exercise – to strengthen muscle
Heart transplants
Expensive
Average post-transplant
survival: 15 years
Temporary
Artificial heart
Pulmonary Hypertension
LV Pr ?????? RV Pr
Eg.
Septum…
Myocardial….
coronary blood flow
Pulmonary Hypertension
RV Pr > LV Pr
Eg. Pulmonary stenosis
Septum inverts
Myocardial compression
lower coronary blood flow
Cardiac Aneurysm
Bulge of …
Muscle….
From…
Cardiac Aneurysm
Bulge of ventricular wall
Muscle weakness
Congenital or from infarct
Cardiac Testing
Cardiac Testing
ECG
Blood pressure / pulse
Catheterization
Blood work - Enzymes
Ausculation - valves
X-Ray
Echocardiography
Stress Testing
MRI
