Cardiac Cycle: Major events with ECG, Valves, and heart sounds Flashcards
Atrial Systole
Major events, EKG, Valves, Heart sounds
Atrial contraction (P waves) final phase of ventricular filling (PR interval)
Mitral valve open
Fourth sound of the heart
Isovolumertric Ventricular Contraction
Major events, EKG, Valves, Heart sounds
Ventricles contract (QRS complex)
Ventricular pressure increases
Ventricular volume is isovolumetric
mitral valve closes
first heart sound
Rapid Ventricular Ejection
Major events, EKG, Valves, Heart sounds
Ventricles contract
Ventricular pressure reaches maximum
Blood is ejected from ventricle into pulmonary trunk
Ventricular volume decreases but AORTIC pressure increases and reaches maximum
ST segment
Aortic valves close!
no heart sound
Reduced Ventricular Ejection
Major events, EKG, Valves, Heart sounds
Slow rate of ventricular blood ejection in arteries
Ventricular volume reaches minimum
Aortic pressure starts to fall as blood runs off into arteries
T wave
no valve/heart sounds
Isovolumetric Ventricular relaxation
Major events, EKG, Valves, Heart sounds
Ventricles relaxed
Ventricular pressure decreases
Ventricular volume is constant
Aortic valves closes
second heart sound
Rapid Ventricular Filling
Major events, EKG, Valves, Heart sounds
Ventricles relaxed
Ventricles fill passively with blood from atria
Ventricular volume increases
Ventricular pressure low and constant
mitral valve opens, third heart sound
Reduced Ventricular Filling, or Diastasis
Major events, EKG, Valves, Heart sounds
Ventricles relaxed
Final phase of ventricular filling
What pressure does the L and R ventricle have to reach before valves will open?
Normal is 120/70
normal pulmonary a. is 25/15
ventricular pressure must exceed the diastolic pressure on each side to open the valve (above 70 and 15)
what happens when the aortic and pulmonic valve exceed the pressure in the ventricles?
their respective valves close
what is the second heart sound associated with?
the closing of the pulmonary and aortic valves when the blood “backflows” off the valves
where and what is the “diacrotic notch”
this is the point on the cardiac pressure cycle where the aortic valve closes, and aortic pressure curve diverges from the ventricular pressure curve. the left atrial pressure curve also wriggles here as well.
Where is the second heart sound?
at the diacrotic notch on the cardiac diagram
Isometric contraction/isometric relaxation
isometric contraction occurs when the mitral valves close and the aortic valves aren not yet thrust open
isometric relaxtion occurs when the the aortic valve subsequently closes and the valves are not yet thrust
open
What pressure does the L and R ventricle have to be at for the blood to enter from the atria?
atria both have 15/4 systole-diastole
R. Ven: 25/0 systole-diastole
L. Ven 120/0
ventricular pressures have to be lower than other pressure during diastole for blood to move from high to low pressure
third heart sound
occurs during the rapid filling period of the ventricles
may be heard in children but not adults
Peripheral Run Off
this is when the aortic pressure curve drops during the rapid filling phase in the ventricles. it occurs because blood from the aorta is pushed into peripheral tissues from the arteries
what determines peripheral run off
resistance to blood flow
a wave
jugular pressure
a wave is the pressure wave created by atrial contraction. because there is no valve between the atria and the great vessels, the pressure is reflected backward.
c wave
jugular pressure
is the pressure wave created by the periodic isovolumetric contraction in the ventricles- there is bulging of the wall back into the atria
v wave
jugular pressure
pressure wave created as blood returns back to the heart but cant enter the ventricle
4th heart sound
heard during atrial contraction
it is the result of the last little bit of blood being squeezed into the ventricle
like the third heart sound, heard in children but not adults
1st, 2nd, 3rd, and fourth heart sounds: where and what
1st: when blood rushes against closed AV valves
2nd: when blood rushes against closed aortic/pulmonic v
3rd: when blood is running into the ventricles
4th: atrial contraction
murmur is heard when either
blood is moving in a direction it shouldnt be moving or when blood is having a hard time moving in the right direction
A systolic murmur is heard when….
either blood is moving BACK into the atria causing by mitral regurgitation
OR
blood can’t get into the aorta or pulmonary a due to stenosis of the valve
A diastolic murmur is heard when….
blood is moving back into the aorta or pulmonary artery caused by aortic regurgitation
OR
blood cant get into the ventricle due to stenosis
PR interval depends on ___ and can be altered by
mainly how long AP takes to travel through AV node
can be altered by ischemia or infarction
structural defect
autonomic stimulation
drugs altering conduction
QRS Interval and Complex
what does the normal QRS signify and how is it altered
normal QRS indicates an AP traveling through the purkinje fibers and normal path through myocaridum
can be altered if signal doesn’t originate in the AV
ischemia or infarction
hypertrophy: thicker wall, dilated ventricle
QT INTERVAL
Dependent on phase 2 plateau
Can be altered by heart rate Drugs timed K channels function alteration Ca channel function alternation
ST is an “ “ line
isoelectric line
if it differs from the “baseline”, it’s actually the baseline which has been shifted making the ST appear depressed or elevated
Ischemia
an ischemic region of the heart will remain depolarized in phase 4
the extracellular tissue is less positive than on the other side of the heart
an electrode facing the ischemic ventricle will register a
negative potential voltage during phase 4
During the ST segment, the voltage an ischemic heart will appear
positive, interpreted as an elevated ST
A patient will have an -_______ - ST line during exercise
depressed
A patient will have an - ________ - ST line after a mycardial infarction
elevated
T wave is altered by
electrolyte disturbance, drugs, altered depolarization sequence
Sinus or Supraventricular Arrhythmia
depolarization initiated above ventricles
originating in SA, AV nodes, or atrial muscle
since it triggers AP through bundle of HIS, QRS is normal. may be short or longer than normal
Bradyarrhythmia
3rd degree AV block
slow AV nodal firing known as sick sinus syndrome if symptomatic
can be sometimes caused by atrial fibrillation or flutter
normal QRS
SSS
Slow SA nodal firing: sick sinus syndrome, 3rd degree bradyarrhythmia
can be sometimes caused by atrial fibrillation or flutter
normal QRS
a slower than normal phase 4 depolarization of SA node indicates
bradyarrythemia
after ischemia, an electrode will still pick up a negative signal during phase 4: why is that?
part of the ischemic tissue has not fully repolarized, so there will still be a differential
