Cardio Physiology Flashcards
What causes hs1 and 2?
1- closure of the AV valves
2- closure of the SL valves
Why does HS2 have a physiological split
Pulmonary valve always closes slightly after the aortic
Exaggerated in inspiration as increased blood to the RA
What causes a fixed split S2
ASD
What causes a widened split S2 and why?
Delayed pulmonary valve closure
RBBB
HOCM
Pulm stenosis
What causes a pathological split S2
Aortic closing after the pulmonary
LBBB
Aortic stenosis
What causes a single S2
Pulm HTN
Truncus, pulm or aortic atresia
TOF, TGA, univentricular circ
What are the normal sats and pressures of the right heart-
RA
RV
Pulm a
RA-75% 5mmhg
RV- 75% 25/0mmhg
PA- 75%- 25/10
How do you calculate mixed venous sats
3xsvc+1xivc/4
What are the normal sats and pressure values for the L heart
LA-97% 5-10mmhg
LV-100/10 97%
Aorta- 97% 100/70
How do you calculate qp and Qs
What does Qs equate to
120/(pulm v- pulm a sats) hb x1.36
120/(aorta-Mv sats) x hb x1.36
Cardiac output
What is normal qp:Qs
What will it be in a right to left shunt
What will
It be in a left to right shunt
1
<1
>1
How do you calculate pulmonary vascular resistance
What is the normal value
Pa-la sats over qp
2, high is >6
What level is the shunt in ASD
is it volume or pressure related? Why?
What controls the degree and magnitude of the shunt
Arterial
Volume- occurs in diastole
Ventricular elasticity (compliance)
What level is the shunt in VSD
Is it volume or pressure related?
What controls the degree and magnitude of the shunt in a small or large lesion
Ventricular
Pressure related- increased left pressures
Small- pressure gradient
Large- pulmonary and systemic compliance
Left to right shunts- what is eisenmengers syndrome and why does it occur
Reversal to a right to left shunt over time- increased pulm pressure to the point where right heart pressure higher than left
Give 5 right to left shunts
What is the cardinal feature
Cyanosis
Truncus, TGA, tricuspid atresia, TOF, TAPVD
What are 2 physiological mechanisms behind cyanosis
Reduced oxygenation
Increased tissue usage
What are the 5 phases of the cardiac cycle
In which stages are the heart sounds
In which phase is the p wave, QRS complex and t wave
Isovolumetric ventricular contraction Rapid ejection Reduced ejection Isovolumetric ventricular relaxation Ventricular filling
Isovolumetric contraction- HS1 Isovolumetric relaxation- HS2 P wave- ventricular filling QRS- isovolumetric contraction T wave- reduces ejection
At what developmental point can the fetal heart circulate blood?
When do AV valves form?
3 weeks
6 weeks
Outline the anatomy of the fetal circulation
Placenta sends oxygenated blood to the umbilical vein.
Shunts through the liver via the porta hepatis to the hepatic vein which attaches to the ivc
1/3 goes across the PFO (right to left shunt)
2/3 goes to the pulm artery
Highest oxygenated blood to the brain and coronaries
90% of blood across pda
Only 15%through the lungs
What happens after birth to alter fetal back to normal circulation
Placenta is removed so systemic vascular resistance is raised. Porta hepatis closes
Take a breath, pulm vascular resistance falls, reversal of shunt and closure of PFO
o2 is sensed In the aorta and prostaglandin is released which causes the PDA to constrict
Why does the PDA not close in premature babies ( 2 reasons)
Smooth muscle hasn’t learned to constrict with increased o2 levels
High levels of PGE2
Why are premature babies more likely to have heart failure with a PDA
Smooth muscle isn’t developed as well
Sharp fall in PVR
large L to right shunt
Timing of PDA closure:
Physiological
Anatomical
10-15 hrs
2-3 weeks
Outline the pattern of electrolyte movement in the cardiac action potential
Resting potential -90 Na rushes in- rapid increase to positive K starts to leave- becomes more negative Calcium enters- plateaus- slow channels K leaves again and ca channels close- returns to negative
How do you calculate cardiac output
HR x SV
How do you calculate stroke volume?
End systolic volume- end diastolic
How do you calculate blood pressure
Cardiac output x SVR
How do you calculate pulse pressure
Systolic BP- diastolic BP
How do you calculate MAP
Diastolic + 1/3 pulse pressure
What does Bernoulli’s equation calculate?
Change in pressure across a shunt or valve
What is the equation used in a simple Bernoulli calculation
Change in pressure=4(distal velocity squared)
What is the difference between ejection fraction and fractional shortening?
Ejection fraction=percentage pumped out with each contraction of systole
Fractional shortening=how much systole cuts into the end diastolic volume
How do you calculate ejection fraction?
What is the normal value?
ESV-EDV/ESV
60%
How do you calculate fractional shortening?
What is the normal value?
EDD-ESV/EDD
30%
What is seen on ECG with right atrial and left atrial hypertrophy
Right- tall tented p waves
Left-bifid p waves (p mitrale)
When are t waves upright
First week of life. After adolescence
Axis
What is the mnemonic to remember a right and left axis deviation
What will a superior axis look like
Look at leads 1 and AVF
Right- right for each other- pointing towards
Left- left each other- pointing away
Superior- both point down
What is the easy criteria for RVH
RAD
Upright t waves in v1
Tall R in v1
Deep S in v6
What is the easy criteria for LVH
Tall r in v6, deep S in v1
What do you seen in biventricular hypertrophy
Both and right criteria positive
Bibentricular forces v3-6
ECG and electrolytes What do you see in: Hyperkalaemia Hypokalaemia Hypercalcaemia Hypocalcaemia Hypomagnesaemia
Hypothermia?
HyperK- tall tented t waves and widened QRS HypoK- u waves HyperCa- short QT HypoCa- long QT HypoMG- long QT
Long QT
What is the main cause of systole in pacemaker cells
Rapid ca influx- stored in the sarcoplasmic reticulum
Which embryonic structure is the heart made from
When do the 2 tubes fuse
When does looping begin
Mesoderm
20 days
28 days
What makes the left and right ventricles
When does looping occur
When do the 4 chambers form?
When do the valves form?
Left- primative ventricle Right- bulbous cordis 24 days 28 days 8 weeks
