Cardiac Cycle Flashcards
What is ventricular systole?
Contraction of the ventricles
What three things are SV into the aorta determined by (strength and velocity)?
- myocardial contractility (EC coupling)
- preload (sarcomere length)
- afterload (magnitude)
What does the peak of the R-wave indicate?
onset of ventricular contraction and initial vibration of first heart sound
ventricular systole
*indicates the electrical event
When is the earliest rise in ventricular pressure during ventricular systole?
after atrial contraction
What is isovolumic contraction?
phase between the start of ventricular systole and the opening of the semilunar valves
- because ventricle volume is constant
How does the LV increase area to decrease pressure?
LV contracts during twist base is being pulled down -> stretching out ventricle = increased area to decrease the pressure
What indicates the onset of ejection?
opening of semilunar valves
What are the two phases of ejection?
rapid ejection - earlier and shorter
reduced ejection - later and longer
What 3 ways is rapid ejection different from reduced ejection?
- sharp rise in ventricular and aortic pressure that terminates at peak pressures
- abrupt decrease in ventricular volume
- greater aortic blood flow
What does the sharp decrease in the LA pressure curve at the onset of ejection result from?
the descent of the base of the heart to stretch the atria
Why does aortic pressure decline during reduced ejection?
blood flow from the aorta to the periphery exceeds ventricular output
What does blood returning to the atria produce throughout ventricular systole?
a progressive increase in atrial pressure
What is the relationship between LV and aortic pressure during the first third of the ejection period?
LV pressure slightly exceeds aortic pressure, and flow accelerates
What is the relationship between LV and aortic pressure during the last two-thirds of the ejection period?
aortic pressure slightly exceeds aortic pressure, and flow decelerates
What is the reversal of the AV pressure gradient during ejection a result of?
the potential energy in the stretch arterial walls, which produces a deceleration of blood flow into the aorta
What does the peak of the flow curve coincide with?
the point LV pressure curve intersects with the aortic pressure curve during ejection
- therefore, flow decelerates because the pressure gradient has been reversed
During RV ejection what is caused?
shortening of the free wall of the RV (descend of the tricuspid ring) = lateral compression of the chamber
During RV ejection what is the main cause of ejection?
there is very little shortening of the base to apex axis, ejection is accomplished by compression of the LV chamber
*decreasing circumference
In venous pulse, what is the a wave caused by?
atrial contraction
In venous pulse, what is the c wave caused by?
the impact of the adjacent common carotid artery and, to some extent, by the transmission of a pressure wave produced by the abrupt closure of the tricuspid valve in early ventricular systole
In venous pulse, what is the v wave caused by?
the pressure of blood from peripheral vessels and abrupt opening of the tricuspid valve
What does the P-wave indicate?
atrial repolarization
What does the T-wave indicate?
ventricular repolarization
What does the QRS complex indicate?
ventricular depolarization
What does the aortic valve closure produce?
the incisura on the descending limb of the aortic pressure curve and the second heart sound
What does the aortic valve closure mark?
the end of ventricular systole
What is isovolumic relaxation?
the phase between the closure of the semilunar valves and the opening of the AV valves
ventricular diastole
What is isovolumic relaxation characterized by?
a precipitous fall in ventricular pressure without a change in ventricular volume
When does rapid refilling occur?
immediately upon opening of AV vales
What indicates the onset of the rapid filling phase?
decrease in LV pressure (pressure gradient) below LA pressure -> opening of mitral valve
What does a rapid flow of blood from atria to relaxing ventricles produce?
a decrease in atrial and ventricular pressures and a sharp increase in ventricular volume
What is diastasis?
follows rapid filling, a phase of slow filling
blood returning from the periphery flows into RV, and blood from the lungs into LV
*a phase in diastole, not diastole itself
What is diastasis indicated by?
a small, slow addition to ventricular filling indicated by a gradual rise in atrial, ventricular, and venous pressures, as well as an increase in ventricular volume
How can diastasis function be measured?
by measuring the velocity of blood across the mitral valve (ultrasound)
What is the E/A ratio?
early to late filling
want a high ratio -> minimal reliance on the atrium to push blood
more blood during rapid filling (sucking blood) -> pressure gradient
What is the onset of atrial systole?
occurs soon after the beginning of the P-wave and transfer of blood from the atrium to the ventricle (ventricular filling)
What is atrial systole responsible for?
small increase in atrial, ventricular, and venous pressure, as well as ventricular volume
Why does the atrial pressure barely exceed ventricular pressure throughout diastole?
indicates a low resistance pathway across open AV valves
function as a singe chamber
Why can atrial contraction force blood in both directions?
because there are no valves at the junction of venae cavae and RA or at pulmonary veins and LA
- little blood is pumped back into venous tributaries during brief atrial contraction because of the inertia of inflowing blood
What two conditions show that atrial contraction is not essential for ventricular filling?
atrial fibrillation - multiple ectopic foci (unsynchronized contraction)
complete heart block - SA and Av nodes don’t function in synchrony
What is the contribution of atrial contraction governed by?
HR and structure of AV valves
How does slow HR affect atrial contraction contribution?
filling ceases toward the end of diastasis, atrial contraction contributed little to filling
How does tachycardia affect atrial contraction contribution?
diastasis is shortened, the atrial contribution can become substantial, especially immediately after rapid filling when AV pressure gradient is maximal (~10-20% EDV during exercise)
What happens if HR becomes so great diastasis begins to encroach on rapid filling?
atrial contraction becomes very important to propel blood forward to fill the ventricle
What can happen if the filling period is too brief?
cannot prevent inadequate filling -> syncope (fainting)
- Bp -> CO -> impaired squeeze of filling
What happens if atrial contraction becomes simultaneous with ventricular contraction?
no atrial contribution to ventricular filling
- won’t generate more pressure with atria than with ventricle
