Ch 4 Hemodynamics Flashcards
The cardiac cycle is divided into how many phases hemodynamically?
7
List the 7 cardiac phases?
-Atrial systole
-IVCT
-Rapid ejection
-Reduced ejection
-IVRT
-Rapid filling
-Reduced filling
What happens in phase 1 atrial systole?
-P wave represents atrial depolarization, atrial contraction occurs shortly after
-Atria pressure increases (causes valves to open, a wave on graph)
-Blood moves through AV valves + into ventricles
-LV pressure rises due to increased volume
-Onset of QRS representing ventricular depolarization
What valves are open in phase 1 atrial systole?
AV valves open, semilunars closed
Does a mechanical function occur before or after the electrical stimulation?
After, always need electrical stimulation first before a mechanical function can occur
Where blood flows, what happens to pressure?
Pressure increases where blood goes
Are valves open or closed in phase 2 IVCT?
All closed
What happens in phase 2 IVCT?
-Beginning of systole (aka end diastole) represented with QRS, ventricular depolarization
-LV pressure keeps rising as muscle tension + contraction intensifies
-Isovolumetric b/c no change in ventricular volume (MV + AV closed)
-LA pressure increases as MV bulges into LA + continues pulmonary venous return (c wave on graph)
-Hear S1 due to MV closure
Which valves are open in phase 3 rapid ejection?
Semilunar valves, AV remain closed
What happens in phase 3 rapid ejection?
-LV pressure exceeds aortic pressure causing AoV to open + begin rapid ejection of blood from LV into AO
-LV volume rapidly decreases
-Peak systolic pressure reached in this phase (120 systolic BP # for systemic circulation)
-Atrial pressure remains stabilized
If we see mmHg in a question, what should we think right away?
Know it is a pressure gradient question
(mmHg = mm of mercury)
What valves are open in phase 4 reduced ejection?
Semilunar valves still open, AV still closed
What happens in phase 4 reduced ejection?
-LV still contracting but at slower rate until T wave occurs (ventricular repolarization)
-Ventricular pressure drops below AO pressure
-AO pressure goes down as well
-Outward flow still occurs due to kinetic energy of blood from LV propelling blood into AO still
-AoV closes, ending ventricular systole
-LA pressure slowly starting to increase
(think ventricles live high + atria live low)
Are valves open or closed in phase 5 IVRT?
All closed (causing equal pressure)
What happens in phase 5 IVRT?
-Onset of diastole (aka end systole) seen at end of T wave
-LV pressure falls rapidly due to relaxation, ventricular repolarization (T wave)
-Ventricular volumes remain constant due to all valves being closed
-LA pressure increases (v wave on graph) due to increasing volume of blood from pulmonary veins
-S2 sound occurs from AoV closure
What valves are open in phase 6 rapid filling?
AV valves open, semilunars closed
What happens in phase 6 rapid filling?
-LV pressure falls below LA, causing MV to open + allow rapid passive filling to occur
-Rapid filling of LV is due to the LA already being maximally filled when that MV opens
-Ongoing relaxation of LV causing a suction effect
-LA pressure decreases once MV opens, then levels off due to continuous flow from pulmonary veins
On m-mode of MV, what do each peaks represent?
1st E peak: 80% of blood from LA that passively fills LV (phase 6/7)
2nd A peak: 20% of blood from atrial kick as LA contracts
(phase 1)
(MV wants to close, but the atrial kick keeps it open a little longer which produces that second peak)
Phase 6 rapid filling correlates to which letter on m-mode of the MV?
E
What valves are open in phase 7 reduced filling?
AV valves still open, semilunars still closed
What happens in phase 7 reduced filling?
-Passive ventricular filling almost completed
-Referred to as period of ventricular diastasis (diastole)
-Ventricles continue to fill with blood + expand
-Ventricles become less compliant causing intraventricular pressure to rise
What happens after phase 7?
Cycle repeats again
Why is it important to know the normal pressure values in the heart?
To diagnose certain types of cardiac disease + dysfunction
List the pressure values for each chamber, the PA + AO?
RA: 4
RV: 25/4
PA: 25/10
LA: 8
LV: 120/8
AO: 120/80
(atria + ventricles must have similar diastolic values so that the atria can overcome the pressure in the ventricles in order to open the valve to allow blood to flow into the ventricles)