Exam #2: Cardiac Cycle Flashcards
Outline the shortcut to axis determination on ECG.
Normal= + in I & aVF
Left= + I & - aVF
Right= -I & + aVF
Extreme Right= -I & -aVF
What is normal R-wave progression?
Positive R-wave in V1
Negative R-wave in V6
What is abnormal R-wave progression an indication of?
Hypertrophy
What is the cardiac cycle?
Cycle of one heartbeat to the next & all the associated events taking place
How are heart rate & cardiac cycle related? What are the units for cardiac cycle & HR?
Heart rate varies inversely with duration of the cardiac cycle:
Increase HR= Decrease CC
Decrease HR= Increase CC
HR= bpm/ min (60 bpm) CC= sec/ beat (1.33 sec/beat)
With a change in HR, is the change in CC uniform?
No
When there is a change in HR, what part of the cardiac cycle is affected more? What are the consequences?
Effects diastole more than systole i.e. there is reduced filling time with a faster heart rate
When is the heart perfused?
Diastole
What are the seven phases of the cardiac cycle? How are they grouped?
Ventricular systole=
1) Isovolumic contraction
2) Rapid ejection
3) Reduced ejection
Ventricular diastole=
1) Isovolumic relaxation
2) Rapid filling
3) Reduced filling
4) Atrial systole
Draw the atrial pressure curve & correlated the pressure curve to the ECG tracing.
N/A
What is the a-wave & what does it correspond to?
A-wave= atrial systole; atrial contraction against the large blood volume in the atria, causes an increase in pressure
What causes mitral & tricuspid valve closing?
Atrial pressure dropping below ventricular pressure
What is the C-wave?
Ventricular contraction causes the leaflets of the mitral & tricuspid valves to push against the atria, measured as a rise in atrial pressure
What is the V-wave?
Slow filling of the atria as the ventricular myocytes contract, corresponding to a steady increase in atrial pressure
Next wave?
Atrial pressure exceeds ventricular pressure, leading to an opening of the mitral & tricuspid valves, leading to a drop in atrial pressure
What is right external JVD a sign of?
Conditions that increase right atrial pressure
Draw the ventricular pressure curve with the atrial pressure curve. Relate both to the ECG.
N/A
What is atrial kick?
A small expulsion of blood into the ventricle at the end of atrial systole
*Contributes roughly 15% of volume
Why does isovolumic pressure develop?
Cardiac valves are closed while ventricular myocytes contract= increased tension/ pressure without a change in volume
When does the aortic valve open?
Ventricular pressure is greater than aortic pressure
Does the aorta distend?
Yes, need distensible aorta to accomodate rapid ejection
What is reduced ejection?
Ventricles still in contracted state, but there has been a decrease in LV pressure & blood flows lower out
When does the end of reduced ejection occur? What does this correspond to on the ECG?
Aortic valve closing
T-wave
What is isovolumic relaxation?
LVP continues to fall due to relaxation of the ventricles (chambers are getting bigger)
When do the mitral and tricuspid valves open?
Once ventricular pressure is lower than atrial pressure
What is rapid filling?
Fast flow of blood from the atria into the ventricles, after the mitral & tricuspid valves have opened
How long does rapid filling last?
As long as there is no increase in pressure from distention of the ventricular walls
What is reduced filling?
Filling of the ventricles that “stretches” the walls of the ventricles, generating pressure in the ventricles, but keeping the differential such that the AV valves remain open
Draw the aortic pressure curve superimposed on the other pressure curves.
N/A
What are the two clinically relevant points of the aortic pressure curve?
Diastolic pressure= low pressure prior to opening of the aortic valve
Systolic pressure= just after the highest pressure in the LV (max pressure)
What causes aortic valve opening?
Ventricular pressure greater than aortic pressure
Aorta has to expand to accommodate the huge rush of ventricular outflow & elastic recoil serves to push blood to the periphery
After ventricular ejection, the pressure gradient favors closure of the aortic semilunar valve during reduced ejection. Why does it not close?
Kinetic energy from the forward momentum of blood. When the aortic semilunvar valve closes, reduced ejection ends & isovolumic relaxation begins.
What is the diaortic notch/ incisura?
A slight uptick in aortic pressure after the aortic valve closes, which is due to the backward wave returning from the periphery
Draw the pressure wave from the arota.
N/A
How is the aortic pressure wave influences by compliance?
Longer time= more compliance
Shorter time= less compliance & higher magnification
When does the opening of the AV valves occur?
Diastole
When do the AV valves occur?
Systole
When does opening of the semilunar valves occur?
Systole
When does the closure of the semilunar valves occur?
Diastole
Draw the ventricular volume curve for the cardiac cycle.
N/A
What is stroke volume? What is a normal stroke volume?
LVEDV (130mL)- LVESV (60 mL)
Thus a normal SV is 70 mL
What is the first heart sound?
- Closure of the AV valves, which happens at the beginning of isovolumic contraction
- “Lub”
What is the second heart sound?
Closure of the semilunar valves
- “Dub”
What is physiological splitting?
Splitting of S2 (Dub) that occurs during deep inspiration
- delayed closure of pulmonic valve
- early closure of aortic valve
BOTH= aortic before pulmonic
What is an opening snap?
Abnormal sound
Snap after S2 that may be due:
- mitral valve stenosis “groaning” from fibrosis or calcification
What is S3? Is this abnormal?
- Ventricular filling during the middle third of disatole?
Sometimes abnormal
What is S4?
Pathological sound of atrial sytole into a stiff (hypertrophic) ventricle
What is a Diastolic Murmur? What is a diastolic murmur and indication of?
A sound heard after S2 that may be due to mitral valve stenosis
What is a Systolic murmur?
A sound heard after S1 & before S2
E.g. mitral valve regurgitation
What is paradoxical splitting of S2?
The opposite of physiological splitting–splitting of S2 occurs during EXHALATION. This is due to changes in conductance e.g. LBBB
