ICL 1.5: Principles of Cardiac Physiology I: The Cardiac Cycle & Normal Heart Sounds Flashcards
what is the normal heart rate for adults?
60-100
what is a hypertensive crisis?
180/120 and above
elevated BP is 120-129
HTN stage 1 is 130-139
HTN stage 2 140+
what are the normal intracardiac pressures in the atria?
RA = 2-8 but usually around 4
LA = 2-10 but usually around 8
LA pressure is almost always higher than the RA pressure to protect against right-left shunting and possible stroke
what are the normal intracardiac pressures in the ventricles?
RV = 15-30 systole/2-8 diastole
LV = 100-140 systole/3-12 diastole
so if the RA pressure is 4 then the RV pressure MUST be lower than it because blood goes from high to low pressure
what are the normal intracardiac pressures in the pulmonary artery?
15-30 systolic
4-12 diastolic
it needs to be around 10 diastolic so that it’s higher than the right ventricle diastolic pressure
what is wedge pressure?
the pressure in the left atrium
why is it so important that the left atrium has higher pressure than the right?
clots!
you constantly throw clots to your lungs and your lungs usually have no problem handling that – what doesn’t handle it fine is your brain!!
so it’s really important that all the clots coming from the IVC have to go to the RV and out the pulmonary artery – if they shunt to the left atrium from the right atrium like if you have a PFO then you are at a huge risk of a paradoxical stroke so it’s important that the LA pressure is higher to keep that blood from the right side from entering
so right to left shunting or higher pressure on the right side puts you at risk for having a stroke
what is compliance?
LV has higher pressure than RV because what determines atrial pressure is compliance
compliance is the ability for the ventricle to relax; how well can it relax to accommodate blood?
the LV is a thicker ventricle so it doesn’t relax as well and isn’t as compliant
what determines systolic blood pressure?
the systolic BP in the left ventricle!!
what determines the diastolic blood pressure?
the elasticity of the arteries, specifically the aorta
you stretch it out during systole and it wants to go back to its normal shape during diastole so the pressure of the artery trying to go back to its normal shape is the diastolic pressure
what’s the oxygen saturation of the blood in the IVC and SVC?
75%
so 25% of your oxygen is extracted if you have normal cardiac output
if you have 60% saturation in the SVC that tells you that the cardiac output is low because the blood is going slower through the body and there’s been more time to extract more oxygen (provided your lungs are working well and there’s no shunts)
so there should only be a 25% discrepancy between the left and right side in oxygen saturation
SVC = 68% IVC = 74% RA = 86% RV = 86% LV = 95%
what’s the likely diagnosis?
left to right atrial level shunt
LV is 95% and SVC is 68% so there’s a 27% discrepancy which is fine
but the RA has much higher saturation than it should; it’s 86% when the SVC and IVC are 68% and 74% so that means there has to be a significant left to right atrial shunt!
what’s the formula for pulse pressure?
SBP-DBP
what is the formula for mean arterial pressure?
MAP = 1/3SBP + 2/3DBP
this is the normal amount of time you spend during the cardiac cycle in each phase if you have a normal heart rate
diastole shortens if you increase your heart rate
what is the formula for stroke volume?
end diastolic volume (EDV) - end systolic volume (ESV)
what is the formula for ejection fraction?
[end diastolic volume (EDV) - end systolic volume (ESV)]/EDV x 100
= (EDV-ESV)/EDV x 100
should get about 55% of your blood out of the ventricles with each squeeze
what is the formula for cardiac output?
stroke volume x HR
= (EDV-ESV) X HR
what is the formula for cardiac index?
cardiac output/body surface area
what is the formula for systemic vascular resistance?
(MAP - mean right atrial pressure)/cardiac output
= [(1/3SBP + 2/3DBP)- mean right atrial pressure]/ [(EDV-ESV) X HR)]
what is the formula for pulmonary vascular resistance?
(mean pulmonary artery pressure - mean pulmonary capillary wedge pressure)/cardiac output)
= (mean pulmonary artery pressure - LA pressure)/[(EDV-ESV) X HR)]
which substances decrease pulmonary vascular resistance?
- prostacyclin (prostaglandin I2)
- NO
- endothelian antagonist
these are all vasodilators!
the pulmonary vascular system acts the opposite of the systemic resistance
what is pulse pressure?
wide pulse pressure = “bounding pulses”
pulse pressure = SBP - DBP
having a high pulse pressure is almost always due to a low DBP, not a high SBP
what can cause a wide pulse pressure?
- arteriosclerosis
- aortic regurgitation
- PDA
- fever
- anaemia
what can cause a narrow pulse pressure?
- low cardiac output (i.e. cardiogenic shock, ventricular dysfunction)
- cardiac tamponade
- aortic valve stenosis
- pericardial disease
seymour butts has a BP of 150-90, HR 60, RR 30, EDV 120 mL, ESV 50 mL
what’s his:
- pulse pressure
- MAP
- cardiac output
- ejection fraction
PP = SBP-DBP = 60
MAP = 1/3SBP + 2/3DBP = 50 + 60 = 110
CO = (EDV-ESV) x HR = (120-50) x 60 = 4,200
EF = (EDV-ESV)/EDV x 100 = (120-50)/120 x 100 = 58.3%
what are the 2 phases of systole?
- isovolumetric ventricular contraction
AV valves are closed and you start to squeeze your ventricles
- ventricular ejection
when you squeeze hard enough to get enough pressure to pop open the pulmonary and aortic valves
when you’ve lost enough blood and pressure has dropped lower than the pressure in the semilunar valves, they’ll close
what are the phases of diastole?
- isovolumetric ventricular relaxation
ventricles are done squeezing, semilunar valves are closed and the ventricles are relaxing so that they can lower their pressure lower than the right atria so that the AV valves can open again during diastole
ventricular filing
2. rapid filing phase
- passive venous filling
accounts for 90% of diastolic filling
- active venous filling
when the atria squeeze to get that last bit of blood into the ventricle = atrial kick
really important slide 18
go look at it
page 287 in first aide
35 minutes into the lecture, seriously go listen
what does the P wave represent?
diastole
what does the QRS wave represent?
systole
what is S1?
closure of the AV valves
mitral and tricuspid valves
what is S2?
closure of the semi-lunar valves
aorta and pulmonary valves
what is physiological splitting of S2?
when you breath in a decrease your intrathoracic pressure even more, it encourages venous return
so the right side of the blood will get some extra blood and the P2 component will lag behind since the pulmonary valve will take just a little longer to close than the aortic valve since it has to pump out extra blood from the right ventricle
there are other things that cause increased blood flow and will cause a fixed splitting that you hear all the time because it’s a pathological problem – can be from a shunt or leaky valve like pulmonic stenosis, right bundle branch block or atrial septal defect
what 3 things can cause pathological fixed S2 splitting?
- valvar narrowing issue = pulmonic stenosis
- conduction delay = right bundle branch block
- volume issue = atrial septal defect
when does S3 happen?
right after S2 during diastole
can be normal like in athletes and pregnant woman
may also be a sign of ventricular or systolic dysfunction –> if your ventricle doesn’t squeeze well, as soon as diastole starts you get extra sound
when does S4 happen?
right before S1 during the end of diastole
tend to be pathological and suggest a stiff ventricle or diastolic diastolic dysfunction
A previously healthy 18 yo male presents to your office with a one week history of URI symptoms. Over the last day he has had worsening fatigue, malaise and SOB. His vitals are T 101.4F, P 120, RR 30, BP 85/45. Which of the following is the most likely cardiac finding?
A. Systolic ejection murmur louder with standing
B. Diastolic murmur loudest at the apex
C. Fixed split S2
D. S3 gallop rhythm
E. S4 gallop rhythm
S3 gallop rhythm
BP is low, fever, high respiration
you should be worried about myocarditis which causes ventricular dysfunction!
what is a pressure-volume loop?
slide 22
page 287 first aide
minute 52 lecture
what happens if you increase heart contractility?
you increase the stroke volume which is how much blood the heart is pumping out with every pump and you will decrease the end systolic volume ESV since you’re squeezing more blood out
it also increases the ejection fraction since ESV is decreased
EF = (EDV-ESV)/EDV x 100
things that increase contractility and make your heart squeeze better are things like epinephrine and norepinephrine
what happens if you increase the preload of the heart?
this is like if you give someone a fluid bolus!
so you will increase the end diastolic volume since you’ve filled the heart with more fluid since you gave them extra venous return
provided you don’t have any problems, you’ll squeeze out all the blood plus the extra blood from the bolus which will result in an increased stroke volume
there isn’t any increased contractility because your heart is just pumping to get back to its baseline ESV that it’s used to
what happens if you increase the after load of the heart?
so what if you increase the BP or cause aortic stenosis; something that would make it harder to get blood out of the left ventricle then your left ventricle will have a harder time getting blood out
if you drive up the systemic vascular pressure for whatever reason, during the isovolumic contraction your left ventricle will have to build up a lot more pressure to get the aortic valve to open
this will cause your stroke volume to decrease because you’re spending so much time building up pressure to get the aortic valve to open that you don’t get as much blood out which also means your end systolic volume ESV will be increased since there’s more blood left
so severe HTN or aortic stenosis will increase your afterload and make it harder to get blood out –> HTN means that the ventricle has to build up more pressure to get to a higher pressure than the aorta so that the aortic valve will actually open since blood goes from high to low pressure
squatting does which of the following?
A. Increases preload
B. Lowers pulmonary vascular resistance
C. Decrease systemic venous return
D. Decreases afterload
E. Increases contractility
A. increases preload
as you squat and squeeze on the blood vessels on your legs it’ll encourage blood to go back AND you’re driving up your afterload because you’re increasing your BP
so squatting increases preload AND afterload!
