Cardiac Cycle Flashcards
-Explain how a drug that slows conduction through the AV node could reduce ventricular response rate and increase cardiac output during atrial fibrillation. -Explain why tachyarrhythmias, such as atrial fibrillation with rapid ventricular response, often result in reduced cardiac output.
7 periods of cardiac cycle
1) atrial systole=atria contract
2) isovolumetric contraction=ventricular contraction
3) rapid ejection=ventricular contraction
4) reduced ejection=Still ventricles contracting?
5) isovolumetric relaxation= All relax
6) rapid ventricular filling= all relax
7) reduced ventricular filling = all relax
A-wave:
-reflects the increase in pressure of the atria as the contract. A-wave/contraction of atria begins just after the atria depolarize (P-wave on ECG).
C-wave
- rise in pressure of atria - due to A-V valve getting pushed up INTO the artium (bc the contraction of the septum which brings the apex closer toward the base and hence the A-V valve toward the base and into the artium)
- decrease in pressure of atria - due to the contraction of the ventricular walls from inside to outside which effectively elongates the heart (apex and base move downward) and this pulls the A-V valves OUT of the atria decreasing the inside
- OVERALL–> RESULTS FROM VENTRICULAR CONTRACTION
Reduced ejection- which # in cycle? valves doing what?
- # 4
- Aortic and Pulmonic valves REMAIN OPEN
- Mitral and tricuspid CLOSED
Rapid ejection- which # in cycle? valves doing what?
- # 3
- Aortic valves OPEN - due to “momentum” of blood (pressure gradient reversed but TOTAL energy of blood coming from ventricle is still higher than total energy of blood in aorta
- STAGE MARKED BY CLOSURE OF AORTIC AND PULMONIC VALVES
- Mitral and tricuspid valves CLOSED
isovolumetric contraction- which # in cycle? valves doing what?
- # 2
- ALL VALVES ARE CLOSED
atrial systole-which # in cycle? valves doing what?
- # 1
- A-V valves OPEN which contraction of atria
- Pulmonic-Aortic valves closed
isovolumetric relaxation- which # in cycle? valves doing what?
- # 5
- ALL VALVES ARE CLOSED AT FIRST
- When pressure in ventricules falls below atrial pressure–> AV valves OPEN and ventricular filling begins
V-wave
- increase in pressure of atria due to increased venous return coming into atria (while AV valves closed)
- decrease in pressure marked when the AV valves open due to pressure in atria being greater than pressure in ventricles
repid ventricular filling- which # in cycle? valves doing what?
-#6
-AV valves OPEN due to pressure (V-Wave)
-Pulmonic and Aortic CLOSED
-stage lasts until the VENTRICLES HAVE PASSIVELY EXPANDED TO THEIR MAX
(DUE TO NEGATIVE PRESSURE)
reduced ventricular filling-which # in cycle? valves doing what?
- # 7
- FILLING DUE TO POSITIVE PRESSURE FROM SVC and IVC
- OPEN AV-VALVES
- CLOSED pulmonic/aortic valves
increased heartrate which portions of cardiac cycle are most reduced?
MOST DECREASE SEEN IN VENTRICULAR DIASTOLE PERIODS
aortic pressure response slope: factors
risistnace of ciruclation - if the arteriolar diameter got larger the slope of aortic pressure reponse would get steeper downward
(alpha 1 stimulation = less steep)
arteriolar diameter controled by?
- local metabolic byproducts - CO2 for vasodialation
- autonomic innervation
SA node receptors, actions, response
M2 - decreased freq of depol –> dec HR
Beta1 - increase HR –> inc Cardiac output
Ventricular muscle receptors, actions, response
beta1 - increase force –> inc cardiac output
Arterioles receptors, actions, responses
- M3 - inc dialation –> decrease resistance
- Alpha1 - inc constriction in skin, kidney, mesentary –> inc resistance
- Beta2 - inc dialation —> dec resistance
Left Ventricular End Diastolic Volume
represents the maximum ventricular volume of the cardiac cycle.
stroke volume=
difference between LVEDV and LVESV
First heart sound=
LUB S1 = CLOSURE OF MITRAL AND TRICUSPID VALVES
Second heart sounds=
DUB S2 = end of cardiac ejection AND closure of aortic and pulmonic valves
does the aortic or pulmonic valve close first/
aortic is first
Opening Snap Heart Sound (OS):
- you hear the valve OPEN (abnormal)
- mitral stenosis - fibrous bridging across the valvular commisures w/ calcification = produces OS
Third heart sounds=
- S3- occurs at the transition between rapid ventricular filling and reduced ventricular filling.
- may or may not be normal
- S3 is normal in childrena nd young adults
- After ventricles have been passively expanded to their max (rapid ventricular filling) –> S3 results from the sudden tensing of the chordae tendinae and AV ring as the relaxing ventricle pulls these structures taut at the end of its rapid filling.
- may also be found when the ventricle is dilated or when ventricular filling is unusually large. Such conditions are frequently associated with congestive heart failure.
Fourth Heart Sound:
-abnormal S4
-occurs after the peak of the A wave (i.e. during atrial systole).
-This sound is produced in the ventricles
originates in the ventricles during the rise in ventricular pressure produced by atrial contraction.
-It is frequently near the limits of audibility but may become much louder if ventricular compliance is reduced - (i.e. the ventricle becomes stiffer than usual).
-Reduction in compliance is generally associated with infarction, cardiac dilatation and/or hypertrophy
Diastolic Murmurs:
- TURBULENT SOUND occurs after S2 (end of reduced ejection) but prior to S1 (begnning of isovolumetric contraction)
- isovolumic relaxation, rapid & reduced ventricular filling and atrial systole
- VENTRICLES ARE ALWAYS RELAXED
- can result from mitral valve stenosis(narrowed thickened mitral valve
Systolic Murmurs:
- Turbulent sound occurs after S1 but prior to S2
- Condition: mitral regurgitationn: mitral valve cusps do not close completely during ventricular systole. Therefore, leakage flow may occur back up into the left atrium.
- holosystolic - or lasting all of systole.
Splitting of S2
- due to: a delay in closure of the pulmonic valve, or, a earlier than usual closure of the aortic valve.
- inspiration allows flow for longer time AND increased venous return to R ventricle–> inc RVEDV–>need more time to expel blood from R ventricle=delays closing of pulmonic valve
Mechanism I for S2 split:
1) inhalatin = increased venous return bc thoracic cavitiy is expanded and this reduces the pressure in the cavity and allows the IVC and SVC empty more into
2) Volume of R ventricle increased
3) R ventricular end diastolic volume increased
4) need more time to expel that inc volume
5) = pulmonic valve open for a little longer
Mechanism II for S2 split:
1) some blood trapped in the lungs upon inhalation due to expansion of lung tissue which expands blood vessels which results in LESS venous return to LEFT side of heart
2) less volume on right side = less time needed to expel it out so aortic closes sooner
Left bundle branch block
- SPLIT SOUND HEARD ON EXHALATION
- a block in the conduction system of the left ventricle = appears as a prolonged QRS complex on the ECG since depolarization of the left ventricle will take longer.
- more time is required for left ventricular depolarization, an increase in time will also be required for left ventricular contraction, since the ventricle cannot contract until the electrical event is completed.
- RIGHT side of heart is functioning normal but LEFT side needs more time ==> pulmonic will close FIRST and aortic SECOND.
paradoxical splitting of the second heart sounds=
split heart sounds are heard during exhalation and single heart sounds are heard during inhalation
ECG: Left bundle branch block would have?
Wide QRS
ECG: Accessory path from atria to ventricles would have?
- Short PR interval bc go around AV node so we would transmit signal to ventricles quciker
- QRS might be a little wide
ECG: Right bundle branch block would have??
wide QRS
ECG: atrial depolarization originating in AV junction would have:
-P-wave in lead 2 would be negative
ECG: some impulses from atria conduction to ventricles and some not would have?
- each P-wave would NOT have a QRS
- Problem is found between the Atria and ventricles – probably the AV node
P wave starts in which phase?
reduced filling
C wave represents:
ventricular contraction (in the atria)
which valves open in rapid filling?
mitral and tricuspid
Right Sided Heart Failure (Right Heart Failure) -
-Distended External Jugular
-Perhaps Prominent A wave
-Liver Congestion & Poor GI Absorption: (Oral Drugs don’t reach target)
-Lower Extremity Edema
Causes: Left Heart Failure; COPD and pulmonary hypertension from smoking; Numerous other lung diseases
Left-sided Heart Failure (Left Heart Failure)
- Pulmonary Congestion (ranging from mild to life-threatening pulmonary edema)
- Dyspnea
- Orthopnea
- Paroxysmal Nocturnal Dyspnea
What are the ventricles doing while they are contracting?
Repolarizing
stiffening of the arterial system does what?
higher systolic pressure
highest colume of heartbeat?
LVEDV
lowest volume of heartbeat?
LVESV
perido that shortened the most with heartrate?
reduced ventricular filling
irregularly irregular heartbeat - most likely problem? How do you fix this?
- atrial fibrilation*
- random QRS complexes = slow conduction through AV node fewer QRS complexes will get through
- dec rate of conduction = give Digoxin = inc vagal tone, fewer contractions, more forceful contraction=inc cadiac output
marker for ventricular systole?
FIRST HEART SOUND LUB
marker for ventricular diastole?
SECOND HEART SOUND DUB
What sound would be heart between rapid and reduced ventr filling?
S3
If you DO hear S3 in older patient this means?
the walls of chambers are tense stiff and expanded
What abn sound would you hear during atrial systole?
S4
If you DO hear S4 what does this mean?
ventricles are stiff (hypertrophy or myocardial infarction or ischemia - dead tissue) and dont accept “atrial kick” well
Ischemic patient (who may have heart attach soon) what woul you hear?
S4 sounds
After S2 and before S1.. what kind of murmur?
Diastolic!
Due to narrowed, thickened mitral valve
opening snap (thickened valve)
turbulent flow resulting from narrowed valve during rapid filling
After S1 and before S2. what kind of murmur?
Systolic!
Due to mitral valve cusps not completely closed during ventricular systole
turbulent flow from ventricle to atria
LBBB effect on pulmonic aoritc shutting?
LONGER TO depolarize left ventricle so inc in left ventricluar contraction so aortic valve closes late in EXHALATION
-On inhalation Pulmonic valve will close later than aortic so it will sound more normal
