Cardiology 2 Flashcards
how does atrial fibrillation appear on venous pressure wave?
- -A-wave = LOST
- -C-wave = Prominent
split S2 sound physiologic explanation?
-deep breath in; decreases intrathoracic pressure. sucking more blood back to R side of heart; filling R side more than L side. So Right sided pulmonic valve closes later in systolic bc R side has more blood to eject.
what’s a gallop?
all four sounds together
In aortic pressure tracing, what is representative of aortic valve closing? what PHASE does this occur in?
- dicrotic notch
- Phase 4 of cardiac cycle
what heart sound correlates with dicrotic notch?
S2 (it’s when aortic valve closes)
measure CO clinically with what principle?
FICK
what is Fick principle?
can know what the FLOW is, if you measure something being carried along with the FLOW, that can be extracted/added along with the flow.
what things are needed for Fick principle calc?
- entrance to lung blood measure
- sample blood on arterial side
- rate of oxygen useage
what other methods/products can be used to implement the Fick Principle?
-indicator dye
(measure concentration at later point)
-thermodilution
(bolus of saline at different temp, measure temp at later point in circuit to back-calculate the flow)
normal CO?
3-5 L/min
how calculate cardiac index?
normal range?
CI = CO/BSA
2.5-4.2
L/min/m^2
muscle fiber length prior to contraction, which affects SV, is known as?
PRELOAD
-how much blood before
tension against which the muscle must contract?
AFTERLOAD
-how much pressure pushing against
intrinsic property of cardiac muscle that adjusts SV?
Contractility
Which Law addresses PRELOAD?
Laplace
what is the equation for law of laplace?
(for spherical chamber); tension in the wall is equal to pressure times the radius of the chamber; divided by 2*wall thickness
T=Pxr/2h
T = LVEDP*LVEDR/2h
what indicators (however unreliable) have been used to estimate SV?
PCWP and CVP
further from ventricle, more unknown things intervene
other methods?
- PPV (pulse pressure variation)
- echo
Preload equals what?
TENSION
what factors affect PRELOAD?
(same as in law)
- pressure
- radius
- wall thickness
Preload INVERSELY proportional to which variable
(2 x) the Wall thickness
End Diastolic filling pressure affected by
- how much blood came back to fill
- compliance of heart chamber
- venous compliance
- atrial contraction
end diastolic radius affected by what issue?
-dilated cardiomyopathy (decompensated)
tension developed in ventricle during PEAK systolic contraction
AFTERLOAD (what ventricle pushes against)
normal SVR?
900-1500 dynscm^-5
SVR formula?
SVR = 80*(MAP-CVP/CO)
what things affecet ventricular systolic pressure?
aka - output impedence
-SVR; Total periph resistance; total blood volume
normal PVR
50-150 dynscm^-5
PULMONARY
PVR formula?
80*(PAP-LAP/CO)
for PULMONARY
intrinsic ability of myocardium to generate force
contra
what is basic element that affects length-tension relationship in isometric contraction?
actin-myosin overlap
optimized
according to force velocity curve, if you INCREASE preload only, for same afterload (force generated), what happens to speed of shortening?
(see page 16 of Cardiology worksheet - Pass Machine)
- -increase shortening velocity
- -essentially ALL reach same max velocity
[ if you are stronger, you will lift things at a faster rate ]
if you increase INOTROPY, for same afterload (force), what happens to speed of shortening?
increases proportionately
how measure contractility?
rate change in time trace; SLOPE of curve. (dP/dT)
-covaries with rate, preload and afterload, however
what’s MAIN graph used to estimate contractility now?
Pressure-volume loop
what affects Pressure volume loop?
HEART RATE!
sympathetic stimulation of myocardial musc, what happens?
- phosphorylate G-proteins, etc
- ALSO facilitate Calcium mobilization overall, so get greater RATE and FORCE of contraction.
contractility decreased by what things? (3 min)
1) anoxia
2) acidosis
3) catecholamines
what does increased contractility mean, based on same volume?
for given volume, can generate MORE pressure
what measure of the systolic function curve represents CONTRACTILITY?
slope of the systolic function curve (STEEPER SLOPE = increased contractility
diastolic function curve’s change in position represents what?
COMPLIANCE
more compliance can hold more vol and pressure not increase as much
which measurement represents total work/energy by cardiac muscles during cycle?
PVA = PE +SW
(pressure volume area)
PE=potential energy d/t stretch remaining in wall at end of systole
SW=stroke work (d/t contraction); work Ventricle is doing thru contraction and relaxation
measure of work is represented by WHAT graphical representation on PV loop?
Work = PxV (area)
- -STROKE WORK is normal shaded area btwn curves between isovolumetric lines and filling/ejection lines
- -TOTAL work , is total area between two curves (under right side of loop)
what other marker can be generally measured based on PVA (pressure volume area)?
MVO2
- myocardial oxygen consumption
- potential energy and stroke work
how calculate ejection fraction?
EF = (EDV-ESV)/EDV
at constant contractility, how do preload and afterload affect SV?
- INCREASE preload INCREASE SV
- INCREASE afterload DECREASE SV
ECG changes d/t Calcium are because?
secondary to altered trans-membrane potentials that affect conduction times
Hypercalcemia on EKG?
- MC finding = shortened QT interval 2ndary to shortened ST
- widened or flattened T-wave
- SIGNIFICANT HYPERCALCEMIA - can mimic acute MI
Hypocalcemia on EKG?
-arrhythmias possible?
Intermittent QT prolongation (or QTc)
- Torsades de pointes
- VT
- complete heart block
what’s E/A ratio?
-extent to which heart fills normally
E = early diastolic filling A = Atrial filling
SHOULD be faster E than A in normal heart
what’s normal E/A?
0.8-1.2
What are limitations of E/A ratio to diagnose diastolic dysfunction of heart?
-if A-fib, don’t have A-wave, cuz no atrial contraction
what’s the PRIMARY determinant of myocardial oxygen demand?
HEART RATE
heart rate is only way to increase amount of oxygen since maximally extract already
what is equation for pressure as it relates to Force and resistance?
(delta pressure) = FxR
name of pressure equation for BP?
ohm’s law
flow version
what happens to pressure that expended by ventricle once gets to greater cross-sect area?
pressure drops
what component of the vascular tree accounts for the steady flow of pressure that travels to organs?
arterioles
what substance do arterioles NOT have?
no elastic
which blood vessels DON’T have any direct sympathetic innervation?
capillaries
resistance equation for blood?
R = (8nL)/(pi x r^4)
L = vessel length n = viscosity of blood
alpha mediators do what to peripheral vessels?
vasoconstriction
beta2 receptors mediate which action at peripheral?
vasodilation
viscosity is measure of?
slipperiness between 2 layers of fluid
blood viscosity is affected by what THREE things?
1) hematocrit (less hct decr viscos)
2) temp (more cool = more visc)
3) vessel radius
viscosity in LARGE vessels relates to resistance how?
viscosity INDEPENDENT of Resist in LARGE vessels?
viscosity in small vessels relates to resistance how?
viscosity decreases in very small vessels (???)
laminar flow = ?
columns of fluid slide across each other without interaction; EFFICIENT
turbulent flow?
disorganized flow; have NO linear relationship between driving pressure and FLOW
how predict turbulence of fluid?
Reynold’s number
Reynold’s equation?
Re = 2rv*p/n
r-radius
v-velocity
p-density
n-viscosity
how is reynold’s number translated?
INVERSELY proportional to viscosity
more viscous you are, more likely you are to behave in laminar manner
what NUMBER Reynold’s value correlates to laminar flow?
Re
what percentage of blood is in PULMONARY circulation at any given time?
9%
how much of circulation is in VENOUS system?
65% !!!!
unstressed vs stressed volume in your body?
unstressed (venous blood; big compliance)
stressed (arterial blood under pressure)
increased venous return how?
- muscle pumping forces blood upward
- respiratory pump (increased inhalation)
- trendelenburg
hydrostatic pressure vs osmotic pressure?
- hydrostatic pressure (push out of vessel)
- oncotic pressure (pull into vessel)
which pressure (oncotic vs hydrostatic) is greater at arterial end?
hydrostatic
which vessel pressure is higher at VENOUS end?
oncotic
lymphatic drainage/pump does what?
pick up extra fluid that was extravasated during blood travels
how does permeability of capillaries affect flow?
(SEPSIS) increased permeability allows greater extravasation of fluid
HOW calculate MAP?
(diast press + pulse press) /3
PP=SBP-DBP
what law relates calculation of BP?
Ohm’s law
Ohm’s law?
P=QR
what three things control autonomics CENTRALLY?
- hypothal
- pons
- medulla
peripheral baroreceptors?
- carotid baroreceptors
- aortic baroreceptors
where aortic baroreceptors?
-in arch of aorta
where are carotid baroreceptors?
at bifurcation of carotids
how is afferent information carried about BP? (aortic)
Vagus nn
how is afferent information carried about BP? (carotid)
Hering’s nerve (CN9)
Inhalational that has LEAST depressant effect on baroreceptor response?
isoflurane
what other function in Carotid and Aortic bodies also present?
-CHEMOreceptors
pH, Co2, O2
what regulatory control centers are the signals ultimately sent to?
cardioregulatory and vasomotor control centers (IN MEDULLA OBLONGATA)
initial controller/regulator of RAS?
kidney
(renin….which converts angiotensinogen [from liver] to angiotensin I
angiotensin II does what things?
1) stimulates the release of aldosterone from ADRENALs (stim na reabsorption in distal tubules of kidney)
2) vasoconstrictor
uncomplicated post-pregnancy reflex?
Bainbridge reflex (autotransfusion from uterus)
Bezold-Jarisch Reflex is from what?
response to noxious stimuli to ventricle
ex: ischemia
what happens in Bezold-Jarisch reflex?
TRIAD:
- hypotension
- bradycardia
- coronary artery dilation
(these all PROTECT the heart!!)
Bainbridge reflex?
R atrium sense sudden INCREASE in VOL; inputs into medullary reg center to INCREASE HR
oculo cardiac reflex?
pushing on your eye INCREASES PARASYMPATHETIC tone and BRADY
how occulo-cardiac reflex travel?
ciliary nn —> ophthalmic division of TRIGEM –> gasserian ganglion
gasserion ganglion from where? to where?
FROM - ophthalmic division of trigeminal
TO - parasympathetic centers
tx of occulocardiac reflex?
-antimuscurinic (atropine or glycopyrrolate)
