Cardiac Function Flashcards
hooks law
the more you stretch the more tension you develop (up until the plastic point)
isometric
states the same length
isotonic
same rate, tone, afterload
how do you” make muscle work better”
1.) Increase preload 2.) Change contractility (ionotropic state)
relationship between ionotropy and velocity
increased ionotropy results in increased velocity due to more calcium availibility
Vmax (muscle) definition
velocity of shortening without weight
relationship between Vmax and prelaod
Vmax is independent of preload - Vmax depends on how much Ca is available
Relationshop between afterload and velocity of shortening
as afterload is decreased the velocity of shortening increases. When afterload is 0 the velocity of shortening is Vmax
Relationship between Velocity and ionotropic state
Vmax increases with increasing velocity (even when preload is unchanged)
Vmax is a measure of what
contractility
End diastolic volume
correlate of muscle fiber stretch prior to contraction ( preload)
afterload
pressure the heart must work agianst during shortening (ventricular pressure during systolic ejection)
what relates end diastolic pressure to end diastolic volume
compliance
Laplaces Law
Hypertrophy can thickin wall and narrow chamber
Concentric Hypertrophy is due to
Pressure overload
Eccentric Hypertrophy is due to
volume overload
Cardiac Pump function
ability of the heart to do something. Can be defined in terms of many differnent parameters ( CO, stroke volume, ect)
Myocardial performance is dependent on what 4 factors
1.) Prelaod 2.) Contractility 3.) Afterload 4.) Heart rate
Starlings Law of the Heart
the more you strech the more contractile tension on excitation thereby increasing stroke volume
list factors that change contractility
increase - neural influences (sympathetic discharge, circulating NE) Decrease- hypoxia, hypercapnia, ischemia, and acidosis
Afterlaod effect
stroke volume decreases with increased afterload (decreased ejection fraction and rise in end systolic volume)
what compensations can occur for increased afterload
1.) Starlings Law (blood left behind will result in increased preload when the new blood comes in) 2.) Anrep Effect
Anrep Effect
contractility is increased by increased coronary artery perfusion pressure
How does heart rate affect heart performance
INDIRECTLY. Increases contractility (more Ca) and decreases preload due to less diastolic filling time - net result is more or less a wash
Treppe (Bowdich Effect)
Staircase effect - as rate is increased over range of 20 bmp to 200 bpm the force of cardiac contraction increases
rest potentiation
if there is an extended interval between beats then the subsequent beat shows increased force of contraction
Post-extrasystolic potentiation
premature ventricular depolarization results in weak contraction but the subseqent beat shows increased force of contraction
Ecjection Fraction
ratio of blood ejected (SV) to the total blood contained in the ventricle at the end of diastole
Stroke volume
End Diastolic volume - End Systolic Volume
relationship between afterload and stroke volume and ejection fraction
increase in afterload decreases stroke volume and decreases ejection fraction
which way does increased contractility move the end systolic volume line
up and to the left
relationship between contractility and stroke volume and ejection fraction
increased stroke volume and increased ejection fraction
what are we measuring when we look at dp/dt max
contractility
where in the cardiac cycle is Vmax
opening of aortic and pulmonary valves
