Cardiac Flashcards
What are the layers of the blood vessel wall and what are they made of?
Tunica externa - collagen fibres
Tunica media - external elastic lamina & smooth muscle
Tunica intima - internal elastic lamina & basement membrane
Endothelium
What makes up capillary walls?
Basement Membrane
Endothelial Cells
What is diastole?
Relaxation phase - when heart is filling with blood
Typical 80mmHg
What is systole?
Contraction
Typical 120mmHg
Describe the cardiac cycle
Atrial Systole: A contracts. V relaxes. AV valve opens. SL valve closed
Early Ventricular Systole: A relaxes, V contracts, all valves closed
Late Ventricular Systole: A relaxed, V contracts, AV closed, SL opens
Early Ventricular Diastole: A relaxed. V relaxes. All valves closed. A passively filling.
Late Ventricular Diastole: A and V relaxed. AV opens. SL closed. A still filling passively.
What do heart sounds ‘Lub dub’ correspond to?
Lub = AV valve closing Dub = SL valve closing
What is isovolumetric contraction?
Valves closed as ventricular depolarisation occurs and ventricles contract.
Build up of pressure as the valves are closed.
At about 80mmHg, there is enough pressure that the SL valve will open. This is when QRS finished.
How is cardiac output calculated?
Heart Rate x Stroke Volume
bpm x ml/beat = ml/min
What is cardiac output?
How much blood ejected by heart in 1 minute
Name 4 factors for cardiac output
- heart rate
- preload
- afterload
- contractility
How does heart rate affect cardiac output
chronotropic factors
positive =
sympathetic stimulation eg. adrenaline
drugs e.g atropine
negative=
parasympathetic eg acetlcholine
drugs eg adenosine
What is preload with regards to cardiac output?
amount of blood entering ventricles in diastole
aka end diastolic volume
influenced by: venous return
blood volume
atrial contraction
What is after load?
Afterload is in systole when ventricles contract?
It’s the resistance the ventricles must overcome in order to circulate blood
How does contractility affect heart rate?
Ionotropic factors
How hard the myocardium is contracting for given preload.
Positive:
Sympathetic system - noradrenaline
drugs - dobutamine
Negative:
Parasympathetic - acetlycholineD
Drugs - beta blockers
what can affect contractility of heart?
Increase:
High blood calcium
Glucagon
Thyroid hormone
Decrease:
Hypoxia
Hyperkalaemia (K+>5.2)
What can affect the after load?
increase: hypertension atherosclerosis vasoconstriction SL valve damage
they all increase resistance therefore increase after load
What can lower preload?
decrease thyroid hormone decrease calcium decrease body temp hypoxia abnormal pH
What are 3 types of ASD?
- Central defect (secundum type defect) - most common
- Low defects of atrial wall (primum ASD) - alongside mitral valve deformity
- High defects (sinus venous ASD) - commonly seen with abnormal R upper Lum vein position
What are 3 functional categories of congenital heart disease?
- R to L shunt
2 L to R shunt
- Obstruction to flow.
Describe R to L shunt
Blood shunted away from pulmonary circulation
Give examples of R to L shunt
pulmonary atresia
trunks arteriosus
tricuspid atresia
HLHS
What is treatment for R to L shunt?
Initially to maintain foetal circulation with prostin or create septal defect
Describe L to R shunt?
High peripheral vascular resistance initially. Then 6-8 weeks this reduces and then get mixing. Hence it presents as late cyanosis.
Get increased pulmonary flow and therefore decreased systematic flow.
What is Eisenmenger’s syndrome?
Start with L to R shunt but then as lung damage increases the shunt reverses and becomes R to L
Give 3 examples of obstruction to flow
- Co-arctation of the aorta
Aortic Valvular stenosis
Pulmonary stenosis
What are two types of heart failure in children (and describe)
- Diastolic
Overloaded blood = increased myocardium
Heart becomes an ineffective pump
- Systolic
Heart muscle fails to work properly
Causes cardiomyopathy
Includes trauma, drug reaction, conduction issues
What are signs of heart failure?
- Cool peripheries
- Weak pedal pulses
- Poor feeding/weight gain
- Tachypnoea/Tachycardia
- Cardiomegaly/Hepatomegaly
What are 2 ways that the heart adapts to preserve contractile state?
- Intracardiac
If ventricles thicken then increased contractions = increased mitochondria = myocyte exhaustion = myocytic death = heart failure
- Extracardiac
Hormones eg sympathetic system
Renin angiotensin aldoterterone system
Naturetic peptides
What are 3 types of natriuretic peptides?
Atrial
Brain
C-type
Where are ANP and BNP produced?
Secreted by myocardial cells in atrium in response to increased stretch
What are natriuretic peptides marker of?
They are used as marker of treatment of heart failure.
