The Cardiac Cycle Flashcards
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
Why is IJV preferred over ext. jugular for measuring venous P?
- IJV anatomically closer to R atrium while ext. doesn’t drain directly into SVC
- IJV valveless so pulsations can be seen whereas EJV not
- vasoconstriction 2ndary to hypotension (as in congestive heart failure) can make EJV small + barely visible
- EJV superficial + prone to kinking
How does JVP differ waves differ in tricuspid stenosis?
- valve narrow + inc R
- a wave enhanced - working harder to get blood through valve as a result so RA P inc during contraction
- v wave diminished as vent P wave tends not to be so effectively transmitted back through stenotic inflexible tricuspid valve
How does JVP differ waves differ in tricuspid regurgitation?
- a wave diminished as atria not as effective so P doesn’t inc much
- v wave enhanced as vent contraction ejects blood through incompetent tricuspid valve back into atria
- JVP inc in this stage
How does damping change shape of arterial P wave?
- stretch aorta - lots of energy in ejection goes into stretching aorta
How does reflection change shape of arterial P wave?
- elastic aorta means some stretch given back as reflected wave
- reflected waves can interfere with forward compression wave so pulse wave is altered
- if interference summative, pulse P can actually inc in magnitude but if its out of phase can depress forward P wave
List primary heart sounds
- S1: initiation of vent systole + closure of AV valves (low freq)
- S2: Closure of SL valves (higher freq, shorter)
List extra heart sounds
- S3: opening of AV valves + rapid refilling
- S4: atrial systole (rarely heard unless EDP raised)
When can S3 + S4 be heard?
- when EDP raised (usually during heart failure)
- heard as gallop rhythm
What causes heart murmurs?
- turbulence in blood
- not always pathological, occur in young + in exercise
What are causes of heart murmurs?
- valve stenosis (too narrow)
- valve regurgitation (incompetent)
What causes diastolic murmurs?
- mitral stenosis as vent fills + occurs after S2
- aortic incompetence leads to early murmur with softening + prolongation of 2nd sound
What causes systolic murmurs?
- aortic stenosis (high P)
- mitral incompetence leads to pan-systolic lush
- occurs after S1
