Session 2- heart anatomy and CO Flashcards
Which system needs the most blood at rest?
Gastrointestinal system
Cardiac muscle functions as a _____. The cardiac myocytes communicate through ___ _____?
Syncytium
gap junctions
What can the jugular vein pulse tell you?
Approximate right heart function
On a Wiggers diagram, why does the pressure in the ventricles fall more steeply (quicker) than the aortic pressure?
The aorta (and pulmonary artery) is elastic
Length of systole and diastole?
systole 0.35s
diastole 0.55s
What holds the atrioventricular valves closed?
What does this stop?
chordae tendinae and papillary muscles in the ventricles
Atrial regurgitation during ventricular contraction
Pressure in the atrium and ventricles?
Right heart
A- 0-4 mmHg
V- 25* / 4’ mmHg
Left heart
A 8-10mmHg
V 120 / 10 mmHg
*systole ‘diastole
Pressure in the arteries leaving the heart?
Pulmonary artery
25*/ 10’ mmHg
Aorta
120/ 80 mmHg
*systole ‘diastole
How long is the cardiac action potential?
How long is the AVN delay?
280 ms
120ms
The pacemaker cells are muscular/ neuronal in origin?
Conduction through the ventricles spreads in what direction?
muscular- specialised cardiac myocytes
endocardial to epicardial face
inner to outer surface
Describe an atrial pressure curve
Hint; there are 3 waves and 2 descents
A wave- Atrial contraction/ kick
C wave- mitral valve closes so atrial volume reduces and pressure transiently increases
X descent- base of atria is pulled downwards in ventricular contraction so volume increases and pressure falls
V wave - venous return
Y descent - mitral valve opens
When does the mitral valve open?
When does the aortic valve close?
When ventricular pressure falls below atrial
When ventricular pressure falls below aortic
What is the atrial kick?
How does the majority of ventricular filling occur?
Atrial contraction which forces the final 10% of blood volume into the ventricles
90% full due to passive filling
What are the 7 stages of the cardiac cycle?
SYSTOLE
1) Atrial contraction
2) Isovolumetric contraction
3) Rapid ejection
DIASTOLE
4) reduced ejection
5) isovolumetric relaxation
6) rapid filling
7) reduced filling
Why does the rate of ventricular emptying reduce?
Why does the rate of ventricular filling reduce?
What is this stage called?
Ejection rate reduces because repolarisation (T wave) reduces tension in the ventricles
Filling rate reduces because it approaches its inherent relaxed volume (90% full); passive filling has ceased
- diastasis
What is the dichrotic notch on a Wigger’s diagram?
Brief increase in aortic pressure due to closure of the aortic valve
(as ventricular pressure falls below pressure in the aorta)
The aortic volume reduces so pressure rises transiently
Normal EDV and ESV values?
EDV - 120ml
ESV- 50ml
(SV 70ml)
When are the two heart sounds heard in the cardiac cycle?
When would you hear S3 in the cycle and what does it signal?
Who is more likely to have an S3 sound?
S1 - isovolumetric contraction
S2- isovolumetric relaxation
S3- phase 6/ rapid filling
It signals turbulent flow during filling
Common in children
pathological in adults
The S2 sound is 2 sounds very close together. Explain.
Closure of the aortic valve minutely precedes that of the pulmonary valve due to higher pressure gradients on the Left side
How long does a cardiac cycle last?
How do you label the axes of a wiggers diagram?
0.9 s
X axis- time/ seconds
Y- Pressure/ mmHg
Volume/ ml
What is the jugular venous pulse used for?
Where is it measured?
What does the JVP waveform look like?
Indicates right atrial pressure
(because there’s a direct column of blood from the atria to the internal jugular vein)
Right internal jugular vein
Biphasic pulse (2 peaks per cardiac cycle); exactly the same as the atrial pressure curve
How do you measure the jugular venous pressure?
Two methods;
- measure height of the pulse behind the sternocleidomastoid muscle (normal; 5-8 cm H20)
- Insert a central line into the internal jugular vein to see the waveform
What’s the normal height of the jugular venous pulse?
Where is it seen?
5-8cm H20
Behind the sternocleidomastoid muscle
What could increase the JVP?
- Impaired filling
- Impaired ejection of R side
- Volume overload with IV infusion
