heart function curves Flashcards
what is the relationship between cardiac output and venous return
venous return is equal to cardiac output
what compartments make up the venous system
central (great veins of the thorax and right heart) and peripheral venous compartments(peripheral veins of the body)
what is the venous return
the rate at which blood return to the right atrium of the heart from the body
what is CO
the rate at which blood s ejected from the left ventricle and moves through the aorta and systemic circulation
what is the central venous compartment
- volume of blood enclosed by the right atrium and the great veins of the thorax
how can the volume of blood in the central venous compartment be measured clinally
- as the right ventrical preload
- right atrial pressure(preload)
- and central venous pressure
cardiac and vascular function curve:
- what does the cardiac function curve ( cardiac output curve) demonstrate
- what law is this
When does it plateau
- demonstrates the direct relationship between central venous pressure (right atrial pressure) on cardiac output
- as central venous pressure increases up to 4mmhg CO increases but beyond 4mmhg CO reaches a steady state because the heart has reached its limit
- Frank Starling law of the heart
cardiac and vascular function curve:
- what does the vascular function curve demonstrate ( venous return curve).
- demonstrates the inverse (negative effect) of central venous pressure on venous return
- as central venous pressure increases venous return decreases
what is the mean systemic (circulatory) pressure
- the volume of blood in the total systemic circuit, when the heart is in cardiac arrest and no blood is flowing through the system
what is the equilibrium point
is the point which cardiac output and venous return are always equal and stabalized
what does the venous return back to the heart depend on
- a pressure gradient between the central and peripheral venous compartment
what happens to venous return as the right atrial pressure falls below 0
the intrathorasic pressure is higher, which will cause a collapse of the veins and a plateu of the venous return
what may decreases in peripheral venous pressure result from
- blood loss by hemorrhage
- loss of body fluid through severe sweating, diarrhea or vomiting
- venodialation ( decrease sympathetic stimulation)
what may increased peripheral venous pressure be a result from
- blood transfusion
- fluid retention in the kidneys
- increases in circulating blood volume
- venoconstriction ( increased sympathetic stimulations)
- venous compressions
- exercise
- wearing elastic stockings
what may mean systemic pressure be affected by
can be affected by changes in circulating Blood volume, venous reserve, and venous tone ( venous constriction or dilation)
what deoes a positve and negative inotropic drug do to the cardiac function curve
( increasing and decreasing contractility)
- postive: decreases atrial pressure and increases cardiac output and venous return( equib pt is also higher
- negative: increases right atrial pressure because reduced contractile force and decreased CO and venous return
what happens to the vascular function curve when you increase and decrease BV
- increase BV: increase in right atrial pressure and increase in CO and venous returnBV: decrease right atrial pressure and decrease CO and venous return
what happens to mean systemic pressure when you increase and decrease BV
- when you increase BV mean systemic pressure increases and when you decrease BV it
what does it mean when you increase TPR
- youre increases resistiance to flow via vasoconstriction
what happens to the cardaic function and venous return curves when you increases and decrease TPR
and why
- when you increases TPR venous return and cardiac output decreases but right atrial pressure stays the same (because rate of blood flow is descreassinf)
- when you decrease TPR venous return and CO increases and right atrial pressure stay the same ( bc rate of blood flow is increasesing- vasodilation)
what happens to mean systemic pressure when you increases and decrease TPR and why
- it stay the same because blood volume isn’t changing
what do work (solid and fluid) equal ?
work(solid)= force (F) x distance
work (liquid)= volume x pressure
what is the the work being performed during a normal HR and what is the definsiton
- the worked being performed is called stroke work
- and it is the work of the ventricles oto eject blood out of the aorta
via which formula can stroke work be calculated
what is stroke work performed by init time called
power
what is the power of the heart known as? and how can it be calculated
-
into what components can stroke work and cardiac minute work be divided into
- pressure work (aortic pressure)
- volume work ( CO anf stroke volume)
how does pressure work diffir from volume work
pressure work consumes more energy
what is the enrgy consumed by the heart known as
myocardial oxygen consumption (MVO2) ans is the amount of oxygen consumed by the heart per minute
what is the relationship between myocardial ocygen consumption and stroke work and cardiac minute work
directly proprotional
what is mechanical efficency
the ratio between work of the heart and oxygen consumption
what is the mechanical efficency eqn
= external worked performed/ O2 consumption
what happens with pressures and SV with an increased afterload?
- what happens to oxygen consumptions and mechanical efficenty
- with an increased afterload ( hypertension or aortic stenosis) high pressures are required to eject SV
- o2 consumption increases and mechanical efficiency decreases
how does strenous exercise effect CO
increases CO
how oxygen consumptionduring exercise compare to the Mechancial efficiency during elevated afterload
- although oxygen consumption increaes it is a smaller change when compared to the reduction in mechanical efficiency with an elevated afterload
- thus mechanical efficiency is reduced but to a lesser extent
how does left ventricular presure work comapre to the right
- how does pressure work effect ventricular thickenss
- left ventricular pressure work is greater and pressure work increases ventricular wall thickness thus the left is thicker than the right
how does the work of the right heart compare to the left and why (numerical)
- work done by the righ heart is 1/6 of the rok of the left heart because the mean pulmonary pressure is 1/6 of the aortic
what happens to tension as pressure and volume work increase
- wall stress/tension increases
what is the law of laplace
- the tension of the wall is the product of the pressure and the radius of the chamber and the tension is inverselt related to the thickness of the wall
what is thw eqn for the law of laplace
what happens to the heart moprpholgy as you increase pressure or volume
- with increased pressure or volume load, the heart will undergi hypertrophy to reduce wall stress
what is the effect of excessive preload on heart morphology
eccentric hypertorphy
what is the effct of excessive afterload on heart morphology
