2 - Cardiac Flashcards
Why does cardiac output decrease with age?
Indicative of decreased basal metabolic rate and decreased muscle mass
When the right atrium is stretched, it triggers which reflex?
Bainbridge
According to Ohm’s Law, what is the calculation for Cardiac Output?
Arterial Pressure/Total Peripheral Resistance
How does BerBeri effect cardiac output?
Massively increased
Interferes with cells’ ability to use nutrients, creating enormous vasodilation to try to get more nutrients to the cells
Decreased peripheral resistance –> increased CO
Would an AV shunt/fistula cause increased or decreased cardiac ouput?
Increased
More venous return
How does hyperthyroidims effect cardiac output?
Increases 40-80% above normal
Increased metabolic rate
How does anemia influence cardiac output?
Increases
Decreased O2 carrying capacity, triggers vasodilation in the periphery
What are 5 peripheral factors that lower cardiac ouput?
Decreased Blood volume
Acute venous dilation
Large Vein obstruction
Decreased tissue mass (skeletal esp)
Decreased metabolic rate
What is the mean systemic filling pressure?
The pressure at which all systemic flow in the periphery ceases, and both atrial and venous pressures reach equilibrium
Venous return increases as RA pressure decreases, but if RA pressure are less than 0, venous return plateaus even if the RA becomes more and more negative. Why?
Because the veins collapse
Negative pressure in the RA sucks the walls of the large veins entering the thorax together
What is the mean circulatory filling pressure?
Pressure that would be measured in the entire circulatory system if cardiac pumping stopped completely
A big increase in blood volume (bolus) only increases cardiac output for a couple of minutes. What three compensatory effects cause this?
- Increased cardiac output increase capillary pressure, creating diffusion out of the capillary
- stress-relaxation in veins causes them to distend in response to the increased volume
- Autoregulation increases peripheral vascular resistance, which decreases venous return
How does a Fick equation determine cardiac output?
Measures the rate of oxygen diffusion by comparing a mixed venous O2 levels with arterial levels
During exercise, why do capillaries dilate?
- Internal:
decreased o2 and presence of vasodilators (K, ATP, lactic acid, CO2, adenosine)
- External:
sympathetic stimulation
During exercise, while the capillaries are dilating, the major vessels are _________
contracting
increases flow
Most of the venous flow from the L ventricle returns to the heart via _______
Most of the venous return from the R ventricle returns via __________
coronary sinus
anterior cardiac veins
How does the heart get extra nutrients during exercise?
Partially through increased coronary flow, but that alone isn’t sufficient. The heart has to be more efficient and utilize energy optimally to make up the difference and provide the needed cardiac output.
Coronary arteries perfuse the heart during _______
Diastole
At a normal resting state, what is the % VO2 of cardiac muscle?
70%!
Constrictor receptors are called ________
Dilator receptors are called _________
Alpha Receptors
Beta Receptors
The epicardial coronary vessels have mostly ______ adrenergic receptors.
The intramuscular arteries have most ______ adrenergic receptors.
Alpha
Beta
What is the major driver of vasodilation and vasoconstriction in the coronary arteries?
Metabolic control
Very little sympathetic control
In all tissues, more than 95% of the energy liberated ffrom foods is used to ________
form ATP in the mitochondria
What is the role of adenosine in capillaries?
When ATP is broken down and not resynthesized, adenosine is floating freely in the cell. If it escapes into the vasculature, that’s a sign to the body that the tissue needs more oxygen/nutrient delivery, and the capillary dilates
Why is adenosine loss one of the major causes of cellular death?
It’s crucial for ATP formation, and once it escapes into the vasculature it takes hours if not days to be replaced. This makes recovery of the tissue (even when oxygen delivery is restored) extremely unlikely.
Why do infarcted areas turn bluish-brown?
The tissue uses all of the remaining oxygen in the blood that lays stagnant at the infarcted site.
Where does infarction occur first: the epicardium or the subendocardium?
The subendocardium
Has a higher oxygen consumption and is more easily compressed during systole, much less resilient to decreased O2
What are the four ways an MI leads to death:
- Decreased CO
- Pulmonary edema from blood stuck in the lungs
- Fibrillation of the heart
- Rupture of the heart
Why do patiens who are recovering nicely from a heart attack develop pulmonary edema two days out?
Kidney failure for decreased flow at the time of infarct
When does rupture after an MI usually occur?
Not immediately. Several days later.
After an infarct, dead fibers are replaced with ______
fibrous scars
Why does the heart often return to normal function after an MI, even though a portion of it is now fibrous?
Healthy areas of the heart hypertrophy to compensate
What is a normal cardiac reserve?
What reserve is required to function as long as no strenuous exercise is performed?
300-400% capacity
100% capacity
Why do patients who have a heart attack often faint, then regain consciousness?
During MI there is a massive decrease in CO and therefore venous return, which initially leads to fainting
Within 30 seconds the sympathetic system is stimulated and makes the healthy heart parts beat harder and causes veins to constrict, increasing blood return to the heart
What happens initially in the kidney following a heart attack?
Initially, moderate fluid retention that increases blood volume and helps compensate for decreased pumping
In severe or prolonged cardiac failure, what happens in the kidneys?
When blood flow to the kidney drops low enough it can’t excrete urine and sodium, fluid retention is excessive and worsens cardiac failure
How long does it take for the heart to acheive most of its final recovery?
5-7 weeks
What drug is digitalis?
How does it increase cardiac function?
cardiotonic glycoside
Depresses the sodium-calcium exchange pump, which increases calcium ion concentration in muscle fibers and makes contraction easier
What are 5 known causes of reduced renal output during cardiac failure?
- Decreased GFR
- R-A-A activation
- Increased Aldosterone
- Increased ADH
- SNS activation
In cardiac failure Aldosterone is obviously increased due to R-A-A activation, but what else increases it?
Increased potassium d/t renal failure
If ANP is the hormone released by the RA during distention, why do we use BNP instead of ANP when assessing for CHF?
The half life of BNP is much longer and much more easily detected in the blood
Where is ANP released?
BNP?
Atria
Ventricles
What is the best means of diagnosing low cardiac reserve?
Exercise Stress Test
Heart failure associated with impaired contractility is reffered to as ________ or __________
systolic HF
HFrEF
What is a normal EF?
50-70%
When is heart failure associated with normal EF?
concentric hypertrophy
decreases filling
Diastolic failure
HFpEF
What kind of heart failure is associated with cardiometabolic syndrome?
diastolic
What are two examples of high output cardiac failure?
AV Fistula
BeriBeri
A valve opening does/does not normally produce a sound
Does not
The first heart sound is the closing of the _______
A-V valves
Tricuspid
Mitral
The second heart sound is the closing of the _______
Semilunar Valves
Aortic and Pulmonic
What patient position can extra heart sounds be heard best?
Apex while laying in L Lat Decub
An S3 is caused by ______
Volume overload in the ventricle
An S4 is caused by ________
Pressure Overload
Another name for S3
S4
Ventricular Gallop
Atrial Gallop
Any time the ventricular is hypterophied you get decreased flow to ______
the coronary arteries
hypertrophied muscle blocks flow during systole (somewhat normal) but also during diastole d/t increased ventricular mass
Once left atrial pressure reaches _______ you get pulmonary edema
25-40
Disease in which valve is associated with atrial fibrillation? Why?
Mitral
L atrial stretch elongates the pathway between the SA node and the atria, and excitatory spots can develop leading to Afib
What is the ductus arteriosis?
Connects the pulmonary artery and the aorta in the fetus
In patent ductus arteriosis, blood passes through ______ multiple times before reaching _______
lungs
systemic circulation
A PDA causes a ___ to ___ shunt
left to right
Tetralogy of Fallot causes a ____ to _____ shunt
right to left
Four abnormalites in Tet of Fallot
- Aorta comes off the RV instead of the LV
- Pulmonary artery is stenosed
- The septum is open between the ventricles
- Enlarged RV (d/t increased workload)
Average cardiac weight
200-350 g
Functions of the pericardial sac (3)
- prevents displacement during accel/decel
- physical barrier from infection and inflammation
- pain and mechanoreceptors that can alter BP and HR
How much pericardial fluid is in the sac?
20 ml
What is the outermost layer of the heart?
Epicardium
Function of the epicardium
provides smooth layer to minimize friction with pericardium
What is the thickest layer of the heart wall?
Myocardium
Myocardium function
composed of cardiomyocytes
responsible for contraction
Innermost layer of the cardiac muscle wall
Endocardium
Endocardium function
connective tissue and squamous cells
Continuous with the endothelium that lines all the arteries, veins, capillaries that supply the heart
What is the normal thickness of the RV?
LV?
4-5mm
12-15mm
Annuli Fibrosi Cordis
Four rings of fibrous tissue that hold the structures of the heart in place
The tricuspid has ______ cusps. The mitral has ______.
3
2
Mitral and tricuspid complex
The Tricuspid, mitral, both atria, chordae tendenae, and annuli fibrosi are all interconnected by tissue and function as one unit.
When something happens to one, the others will have altered function
Which valves have chordae tendinae?
What do chordae tindinae prevent?
The AV valves
Prolapse of the valves into their respective atria
Which muscles attach the chordae tendinae to the myocardium?
Papillary muscles
There are _____ pulmonary arteries and ______ pulmonary veins
2
4
Which muscle separates the outflow tract from the inflow tract?
Crista Supraventricularis
Strands of _____ mix blood in the ventricles
trabeculae carnae
The only bicuspid valve in the heart is the ______
mitral
What is arteriogenesis?
Angiogenesis?
New artery growth/branching from preexisting artery
Growth of new capillaries within a tissue
What (3) things stimulate collateral flow growth in the myocardium?
- Shear stress (increased blood flow through a stenosis, narrowing)
- Production of growth factors
Why does diabetes impede collateral formation?
Increased production of endostatin and angiostatin
At rest what is the VO2 of cardiac muscle?
70-80%
How do capillaries adjust for increased muscle mass in hypertrophy?
They don’t.
The capillary network doesn’t expand, so the same number of capillaries have to perfuse a larger area
The visceral pericardium is another word for _____
Epicardium
Resting membrane potentials:
Myocardial
SA Node
AV Node
- 80 to -90
- 50 to -60
- 60 to -70
What is automaticity?
property of generating spontaneous depolarization
Rhythmicity
regularity of generation of an action potential by the heart’s conduction system
Name three vasodilators released when MVO2 is elevated
adenosine
nitric oxide
prostaglandins
What are the three calcium channel blockers?
Nifedipine
Verapamil
Diltiazem
How do calcium channel blockers work?
Block L-type long lasting calcium channels, leading to decreased contractility
How does LaPlace’s law apply to the ventricle?
Wall stress = (P x r)/2(wall thickness)
When there is increased pressure, the heart will increase its thickness and decreased its radius to reduce wall tension and prevent rupture
What are the three layers of blood vessel walls?
- Tunica Intima (innermost)
- Tunica Media (middle)
- Tunica externa/adventitia (external)
How are the cells that comprise large vessels nourished?
Vasa Vasorum
Located in tunica externa
How is vasculogenesis different rom angiogenesis or arteriogenesis?
refers to the growth of vessels from progenitor or stemlike cells that originate in the bone marrow and other tissues
What are elastic arteries?
Very thick tunica media
Have higher proportion elastic fibers to muscle cells
Aorta and major branches
pulmonary trunk
What are muscular arteries
Medium and small sized arteries
few elastic fibers, more mm fibers
Distribute blood to arterioles
When does an artery become an arteriole?
lumen less than 0.4mm
A given vein is ______than its corresponding artery
larger
Which are more numerous: veins or arteries?
Veins
