The Cardiac Cycle Flashcards
(36 cards)
What is the R of healthy valves + why is it important?
v. little R (flexible) so small P gradient across them nec for them to open + close
What opens + shuts valves in the heart?
- P diff
- only small P gradient nec to open valve
What are the structure of the AV valves + sig?
- floppy but anchored to walls of vent by papillary muscles + chordae tendineae so don’t blow back into atria when P in vent rises during systole
What does the AV valve cause?
- add atrial P wave that can be seen ext. as it causes pulse of blood into jugular vein that can be seen at neck
What is an echo?
- damage to anchoring structures e.g. after MI causes AV valve everting back into atrium so during systole some blood pumped backwards in wrong direction
What is stroke vol?
- diff between how much blood in vent when full (120ml) vs empty (50ml) + therefore amount of blood pumped out by vent each beat
~ 70ml
What is stroke work?
- area of P-V loop
- how much work heart is doing
What does jugular vein do?
brings blood from head to SVC + then to R atrium
What is JVP?
- biphasic
- low P bc its venous
- assessed by viewing dilation of jugular veins in neck
What is the a wave of JVP?
- R atrial contraction (systole)
- P inc in R atrium + contraction causes pulse in jugular vein
What is X descent of JVP?
atrial relaxation
What is the C wave of JVP?
- interruption of X descent caused by transmitted carotid pulse
- carotid artery close to jugular vein + pulse transmitted through tissue to cause carotid pulse in jugular
What is v wave of JVP?
- R atrial filling during vent systole
- when R atrium contracts, push tricuspid (closed) - goes up towards atria which gives pulse in atria
What is y descent of JVP?
- atrial emptying during vent diastole
- before atrial contraction
- tricuspid open
What affects shape + size of v wave?
bulging, regurgitation + stenosis of tricuspid
What is peripheral arterial pulse?
- largely monophasic
- high P
What influences peripheral arterial pulse?
- shape of peak + descending phase influenced by factors of vessels themselves such as:
- reflected waves,
- compliance,
- resonance,
- interference
- damping
- why shape + mag of pulse varies along arterial tree
How does venous + arterial P diff?
- absolute venous P (+ pulse P) low (4-8mmHg)
- arterial P (+ pulse P) high (80-120mmHg)
What happens to jugular vein 5cm above RA?
- collapse bc not enough P to keep it inflated + due to hydrostatic influences
How do veins few cm above heart differ to veins closer to heart?
- CVP low so due to gravity, veins few cms above heart collapse bc P inside them -ve + are flat
- as move towards heart, P hgih enough so veins are rounded so height of this point above heart is readout of CVP
Why is IJV sig?
- see point of collapse
- P waves in R atrium back up into IJV + so can discern changes in collapse point
- also changes in pulse of IJV visualise changes in P in RA with diff pathologies affecting tricuspid valve + in heart failure
How do you measure JVP?
- support patient at 45 degree angle - can now see point where IJV collapses
- JVP is height of collapse of IJV above manubriosternal angle (about 3cm in healthy person, should have 0cm H2O + go from slightly distended to completely flat)
At what point is JVP pathoglogical?
- > 3cm
- means CVP/RA P too high
Why does the patient need to be at an angle to measure JVP?
- if patient upright, point of collapse lower as jugular below level of clavicle + can’t be seen
- if person lying down, no point of collapse
