CV Physiology Flashcards
What does CO equal (equation)? What is the Fick principle (equation)? What is MAP? What is MAP (equation)? What happens to CO during exercise? What happens to diastole timing with incr. HR?
CO=SVxHR
CO=rate of O2 consumption/ (arterial O2 content-venous O2 content)
MAP=COxTPR=2/3 diastolic pressure + 1/3 systolic
Early in exercise: HR and SV incr., but SV reaches a limit and only HR can increase
With incr. HR, diastole shortens, eventually leading to decr. CO
What is SV (equation)? What causes it to increase? When is it decreased?
SV=EDV=ESV
Incr. with incr. contractility, incr. preload, decr. afterload
A failing heart has decr. SV (diastolic or systolic dysfunction)
What things incr. contractility? Decr.
INCREASE
Catecholamines: incr. activity of Ca pump in SR
Incr. IC Calcium
Decr. EC Na (Na/Ca pump)
Digitalis: blocks Na/K pump leading to less EC Na
DECREASE
beta 1 blockade (decr. camp) HF with systolic dysfunction acidosis hypoxia/hypercapnia Non-dihydropyridine Ca channel blockers
What things incr. myocardial oxygen demand? According to laplaces law, what things incrase wall tension/decrease it?
Incr. contractility
Incr. afterload
Incr. heart rate
Incr. diameter (incr. wall tension)
wall tension is incr. by pressure and radius and decr. by wall thickness
How is preload approximated? What does it depend on? What medications decrease it? How is afterload approximated? How does the LV compensate for incr. afterload? Why? What decr. afterload? What decr. afterload and preload?
Ventricular EDV
Venous tone and circ. blood volume
Venodilators decr. preload
approx. by MAP
Incr. in afterload leads to incr. in pressure leads to incr. wall tension. To compensate for this incr. wall tension, the LV incr. wall thickness (hypertension to cardiac hypertrophy)
Vasodilators (hydralazine) decr. afterload
ACEI and ARBs decr. both preload and afterload
What is the ejection fraction (equation)? What does it tell you? What is a normal value? What are the values in diastolic and systolic HF?
EF=SV/EDV=(EDV-ESV)/EDV
Index of ventric. contract=55%=decr. in syst., normal in diastolic
What is the idea behind a starling curve? What increases a starling curve? Decreases?
Force of contraction proportion to end diastolic length of muscle fibers (preload)
Incr. with catecholamines, positive inotropes
Decr. with loss of myocardium, beta blockers, ca channel blockers, dilated cardiomyopathy
How are resistance pressure and flow related? What is Q related to (equation)? What incr./decr. resistance? How is the total resistance of a vessel in series calculated? In parallel? What does viscosity depend on? What else can increase it? Decrease it? What vessels account for most of TPR? What vessels store the most? What does organ removal result in? Which vessels ahve the highest total cross sectional area and lowest flow velocity?
delta P = Q x R
Q=flow velocity (v) x cross sectional area (A)
Capillaries have highest A and lowest v
viscosity and length incr. resistance while incr. radius decreases it.
TR=R1+R2 etc. (series)
1/TR=1/R1 +1/R2 (parallel)
Viscoisty depends on hematocrit
Can be increased in mult. myeloma, etc.
Decr. in anemia.
Explain the cardiac portion of a cardiac and vascular function curve. What increases/decreases it? What are the the increases/decreases like? Dependent/indep. variables? Same questions for a vascular function curve. What does the intersection of curves mean when they’re combined? What changes occur in exercise? In HF?
It has an upward slant then plateaus.
Y axis is cardiac output (dependent)
X axis is RA pressure or EDV (independent)
When RA pressure is held constant, an incr. in HR, contractility, or a decr. in afterload will incr. the slope and move the end CO value up. The opposites will decrease it.
It starts plateaued then curves down.
The point where it meets the x axis is the mean systemic pressure.
Y axis is venous return (indep); same x axis (depen)
When blood volume or venous tone increases, the curve shifts to the right, but the slope does not change, which changes the mean systemic pressure.
When SVR decreases, the slope becomes more negative (less flat).
Intersection of curves=operating point of heart (venous return and CO are equal).
In exercise, incr. inotropy and decr. SVR maximize CO (both curves move up so operating point is at a high CO)
In HF, inotropy incr. so fluid is retained which results in incr. preload. The CO point moves down but the venous return curve moves up so the operating point isn’t quite so low.
What are the phases of a pressure volume loop? How does incr. preload affect it? Incr. Afterload? Incr. contractility?
Isovolumetric contraction-mitral valve closing to aortic valve opening
Systolic ejection-aortic valve opening and closing
Isovolumetric relaxation-aortic valve closes and mitral valve opens
Rapid filling-soon after MV opens
Reduced filling-just before mitral valve closes.
Incr. preload-incrases stroke volume (EDV), moves right side of curve to right
Incr. afterload-raises the maximum up (incr. aortic pressure), moves ESV to the right (decr. SV)
Incr. contractility-moves ESV to the left (incr. EF and incr. SV)
What signifies S1? Where is it best heard? S2? S3? What is it associated with? When is it normal? S4? What is it associated with? Best heard?
S1-mitral and tricusp closure-At mitral area
S2-aortic and pulmonary valve closure-LUSB
S3-In early diastole, high pressure atrial state (mitral regurg, HF, dilated ventricles, rapid ventricular filling.
Normal in pregnant women and children
S4-In late diastole (atrial kick). Best heard at apex in LLD. High atrial pressure. Ventricular hypertrophy.
Explain the 5 waves of the jugular venous pulse.
a wave-atrial contraction. Absent in a-fib
c wave-RV contraction (tricuspid bulging into atrium)
x descent-atrial relaxation and downward displacement of closed tricup. during ventricular contraction. Absent in tricuspid regurg.
v wave-incr. right atrial pressure due to filling against closed tricusp. valve
y descent-RA emptying into RV.
Waht causes normal splitting? What is it like? What causes wide splitting? What is it like? Fixed splitting? Paradoxical splitting?
NORMAL
Inspiration-drop in intrathoracic pressure leads to incr. venous return leading to delayed closure of pulmonic valve.
It also leads to inccr. pulm. capacity of pulm. circ. which has the same effect.
Therefore, during inspiration, the pulmonic closure is later than the aortic closure leading to a split. During expiration, they occur at the same time.
WIDE SPLITTING
Seen in conditions that delay RV emptying (pulm. stenosis and RBBB) leading to a delayed sound during insp. and exp. but still more delayed during insp.
FIXED SPLITTING
Seen in ASD. Left to right shut leads to incr. RA and RV volumes leading to incr. flow through pulmonic vlave so that there is a great and equal delay of the pulmonic closure leading to a split that is the same in both insp. and exp.
PARADOXICAL SPLITTING
Delayed aortic valve closure (aortic stenosis, LBBB). Aortic valve closes much later. Therefore, during insp., when the pulmonic valve is delayed, there is no splitting, but during expiration, there is a split due to the delayed aortic closure.
What murmurs are best heard in the aortic area? Are they systolic, pancystolic, diastolic, or systolic ejection murmurs? LMSB? Pulmonic area? Left infraclavicular region? Tricuspid area? Mitral area?
AORTIC
Systolic: aortic stenosis, flow murmur, aortic valve sclerosis
LEFT MIDDLE STERNAL BORDER
diastolic: aortic regurgitation, pulmonic regurg
systolic: hypertrophic cardiomyop.
LEFT INFRACLAVIC.
Continuous murmur: PDA
PULMONIC
Systolic ejection murmur: pulmonic stenosis, flow murmur (physiologic or due to ASD)
TRICUSPID
Pansystolic: tricuspid regurg, VSD
Diastolic murmur: tricuspid stenosis, ASD
MITRAL
systolic: mitral regurg
diastolic: mitral stenosis
What effect do inspiration, hand grip, valsalva, standing up, and rapid squatting have on heart sounds and why?
INSPIRATION
Incr. venous return to right atrium
Incr. intensity of right heart sounds
HAND GRIP
Incr. afterload
Incr. intensity of MR, AR, VSD murmurs
VALSALVA, STANDING UP
Decr. preload
Decr. intensity of most murmurs (including AS)
Incr. intensity of hypertrophic cardiomyopathy murmur
MVP: earlier onset of click/murmur
RAPID SQUATTING Incr. venous return and incr. preload Decr. intensity of hypertrophic cardiomyopathy murmur incr. intensity of AS MVP: later onset of click/murmur
