Cardiology Day Flashcards
(126 cards)
heart formation is completed by ? gestation
8 weeks
in fetal circulation, ventricles work in ?
where does RV supply and percentage of blood volume?
where does LV supply and % of blood volume?
work in parallel
RV: 66% blood volume. lower body, placenta
LV: 34% heart brain, upper body.
56% cross PDA
which side heart has higher oxygen saturation in utero.
oxygen in DV and IVC
Left side (65%) - preductal higher, this is due to DV directly shunt cross PFO to LA.
R side (55%): this is due to mixing from IVC
DV 70% oxygen
IVC 45%
SVC 40%
fetal compensation for hypoxic environment
high fetal epo/HCT
high affinity for oxygen by fetal hemoglobin
minimal oxygen consumption (minimal respiratory effort, maternal thermoregulation, minimal GI digestion and absorption, decrease renal tubular reabsorption
fetus can only regular Cardiac output (CO) via what?
increase HR.
CO = SV x HR
hypoxemia vs hypoxia
hypoxemia: decrease amount of o2 in blood (pulse oximeter)
hypoxia: decrease o2 to tissues.
Fetal O2 delivery can be reduced by 50% without significant effect on O2 uptake.
with hypoxia, where does blood shunt in fetal circulation?
how does fetal response to chronic placentla insufficiency.
heart, brain, adrenal gland
DV dilate. shunt blood away from portal circulation –> decrease liver growth, decreased abdominal circumference.
closure of PDA due to (3 reasons)
low amount of PGE (no placenta supply, increase PBF (pulmonary blood flow), increased metabolization of PGE in the lungs)
bradykinin (produced by lung) > constrict PDA
higher oxygen concentration within ductal tissues.
oxygen effect on umbilical artery, PDA and pulmonary vein
oxygen: constrict umbilical artery, PDA,
dilate pulmonary vein.
cardiac output (2 equations)
CO = Systemic blood pressure/ Total peripheral vascular resistance
–>
P = Q (flow) x R
CO = SV x HR
Afterload depend on what?
SVR
ventricular wall thickness and ventricle radius
( ventricular wall stress = ventricular P x ventricular radius / wall thickness)
Frank-Starling: where does curve move?
bad: move down (increase after load)
good: move up (decrease afterload) .
x-axis: preload (LV end-diastolic volume)
y-axis: contractility. (stroke volume)
cardiac filament
actin (thin)
myosin (thick)
increase preload and increase stretch, there’s optimal overlap between thin and thick muscle filaments of sarcomeres
BP formula
BP = CO x SVR
Three types of Shock
Hypovolemic
Cardiogenic
Distributive (sepsis, vasodilator, adrenal insufficiency, anaphylactic)
Compensation Mechanism for Shock
baroreceptors: decrease stimulation of baroreceptros in aortic arch and carotid sinus –> vasoconstriction
Brain chemoreceptors: cellular acidosis -> vasoconstriction, and respiraotry stimulation.
Renin-angiotensin system
humoral response (catecholamines)
autotransfusion: reabosrotpions of interstial fluid
Receptors, their Effects, and mechanism of action
Alpha -1
Alpha-2
Beta-1
Beta-2
Alpha-1
Increase SVR, increase contractility
- signal phospholipase C
Alpha-2
decrease SVR
- inhibit adenylyl cyclase
Beta-1
Increases contractility (mostly ventricles) Increases HR (SA and AV nodes) Increases conduction velocity (higher risk for arrhythmias)
- cAMP
Beta-2
Decreases SVR , Note: also bronchodilation
-cAMP
Dopamine vs. Dobutamine
compound, receptor, dose-dependent, HR, contractile, SVR effect, BP effect
Dopamine:
endogenous
precuorsor to epi and nor-epi
Receptors: beta-1 and alpha-1
low dose: renal, medium: beta-1, high: alpha-1
clinical example: use in “warm shock”
Dobutamine:
synthetic
Receptors: beta-1, some beta-2
not dosing dependent
clinical example: use in cardiogenic shock
Epinephrine:
dose effect
effect on HR, contractility, SVR, BP
low dose: Beta-1 and Beta-2 (similar to dobut)
^ HR, ^ contractility, v SVR, BP: depends -
high dose: alpha-1 and beta-1 (similar to dopa)
decrease HR because ^ vagal tone on SA and AV nodes ( beta receptor in vagal nerve).
^ contractility, ^ SVR (alpha-1), ^ BP
norepinephrine:
receptor, HR effect, contractility, SVR, BP
Beta-1 and Alpha-1. some Beta-2 (similar to high-dose epi)
DECREASE HR because increase in Vagal tone on SA and AV nodes.
^ contractility, ^ SVR, ^ BP
Milrinone
phosophdesterase type 3 receptor
(PDE 3)
increase cAMP (stop PDE III from breaking down cAMP to AMP. cAMP convert to ATP via adenylyl cyclase)
vasodilation (decrease SVR, decrease coronary artery perfusion)
Hydrocortisone Effect on treating volume-resistant and pressure resistant shock
- block breakdown of catecholamines
- up-regulate cardiovascular adrenergic receptors (sustain response to adrenergic agents)
- hormone replacement if adrenal insufficient
smooth wall, which ventricle
not smooth wall, which ventricle
left ventricle.
R ventricle, (not smooth)
Qp/QS in L to R shunt
Qp/Qs > 1