Ventricular Function

CO =

HR x SV

CI (cardiac index) =

CO / BSA

what are the four determinants of cardiac performance?

preload, afterload, contractility, heart rate

__ is muscle stretch / end-diastolic wall stress

preload

__ is the forces opposing ejection of blood

afterload

__ involves intrinsic strength of cardiac muscle

contracility

if increase preload then ___ length and ___ passive force

increase, increase

in isolated muscle, ___ is the passive force needed to stretch the sarcomere to its resting length before contraction

preload

preload ___ with increasing length

rises exponentially

in ventricle, ___ is the passive force in the ventricle at its End Diastolic Volume (EDV)

preload

when sarcomere stimulated to contract, ___ develops

active force

sarcomere length before contraction is set by __

preload

increased preload (length) → ___ active tension (force)

increased

preload sets the ___ of the sarcomere, which affects the ___ developed when muscle stimulated to contract

resting length, active tension

preload = ___ of muscle or intact heart = end-diastolic wall stress

initial stretch

preload is estimated by the ___ or ___

EDP (pressure filling the ventricle, EDV (end-diastolic volume)

Frank-Starling or Starlings Law shows that when there is increased End-diastolic stretch of the ventricle (increased EDV or EDP), there is ___

increased SV and increased CO

based on effects on Starlings Law: RV are ___ while effects on LV are ___

immediate, delayed

length-dependent activation shows that stretching cardiac muscle causes ___ force than predicted from only changes in ___

greater, overlap of thick and thin filaments

with longer sarcomere length (more stretch) there is a ___ between myosin and actin filaments

narrow space

with shorter sarcomere length (less stretch) there is a ___ between myosin and actin filaments

wider space

___ brings actin and myosin closer together, which causes ___ filament lattice spacing → ___ number of crossbridges

Titin, decreased, increased

increased sarcomere length → ___ filament lattice spacing → ___ probability and cooperativity of actin-myosin cross-bridge formation

decreased, increased

increased sarcomere length → ___ Ca++ binding affinity by cardiac TnC → ___ exposure of myosin binding site on actin → ___ actin-myosin cross-bridge formation

increased, increased, increased

mechanisms forming basis of Starlings Law include

changes in overlap of thick and thin filaments

length-dependent activation also contributes

potential mechanisms for length-dependent activation

altered filament lattice spacing

changes in Ca++ sensitivity

cardiac muscle ___ increase tension by summation of contractions

cannot

__ is systolic wall stress produced by ventricular properties with additional properties of the vasculature, during systole

afterload

afterload can be defined by ___ or ___

aortic pressure (for LV), pulmonary artery pressure (for RV) during the interval that the aortic valve or pulmonic valve is open

as afterload increases, SV ___

decreases

increased BP → ___ pressure opposing LV ejection → ___ SV

increased, decreased

Law of Laplace describes that as radius decreases, pressure directed into the LV cavity (inward pressure) ___

increases

with increased r, inward pressure is ___ (end-____)

reduced, diastole

with decreased r, inward pressure is ___ (end-____)

increased, systole

__ is the intrisic force-generating capacity of the cardiac myocyte and heart with fixed __

contractility, preload and afterload

__ is the passive force stretching the sarcomere to its resting length or filling the ventricle to its EDV

preload

stroke work =

SV x MAP

dP/dt =

change in pressure/change

EDP decreases as contractility ___

increases

what common therapy can change Ca++ homeostasis to enhance contractility?

increases phosphorylation of LTCCs (CICR)

how can we physiologically change Ca++ homeostasis to enhance relaxation?

increases phosphorylation of phospholamban → decreases inhibition of SERCA → increased Ca++ reuptake

dP/dtmax is a measure of ___

contractility

more NE and EPI causes ___ contractility

inreased

angiotensin causes ___ contractility

increased

hypoxia and associated acidosis (decreased pH) causes ___ contractility

decreased

hyperkalemia causes ___ contractility

hyperkalemia

sympathetic stimulation → ___ contractility and ___ relaxation

increased, increased

immediate consequence of increased contractility is ___ EDP (EDV) due to ___ SV

decreased, increased

heart rate influences cardiac performance by altering ___ and ___

time for ventricular filling, myocardial O2 supply demand balance by altering time for adequate coronary blood flow/O2 supply

preload: if increase stretch (___ diastolic filling) → ___ SV (systole)

increase, increase

where is preload represented on a pressure-volume loop?

end diastole/begin systole (EDV/EDP), DPVR

how does preload affect the PV loops?

SV

an increase in preload causes ___ in SV

increase

a decrease in preload causes ___ in SV

decrease

how does afterload impact the PV loop?

preload affects ___ while afterload affects ___

preload → SV

afterload → SV and BP

an increase in afterload causes ___ SV and ___ BP

decreased, increased (this is because afterload is how much resistance the heart has to pump against to pump blood out of the LV during systole)

a decrease in afterload causes ___ SV and ___ BP

increased, decreased

contractility is found on the pressure-volume loop by the ___

ESPVR (end-systolic pressure volume relationship)

how does contractility/inotropy affect the PV loop?

an increase in inotropy would ___ SV and ___ ESPVR

increase, increase (greater slope)

a decrease in inotropy would ___ SV and ___ ESPVR

decrease, decrease (smaller slope)

in aortic stenosis, the pressure in the aorta a lot ___ than in the LV

less (because of narrowed valve)

describe a PV loop for aortic stenosis

for aortic stenosis, afterload is ___

increased (because increased ventricular pressure)

for aortic stenosis, SV is ___

decreased

for aortic stenosis, ESV is ___

increased

for aortic stenosis, EDV is ___

increased

for aortic stenosis, preload is ___

increased

for aortic stenosis, contractility is ___

increased