113 - Syncope and heart block Flashcards
How long should a PR interval be?
120-200ms (3-5 small squares)
How long should the QT interval be?
<0.45s
Which bundle has a block in right axis deviation?
LBB - posterior fascicle
Which bundle has a block in left axis deviation?
LBB - anterior fascicle
What would you notice about the PR interval on an ECG of a 1st degree heart block?
- PR interval would be prolonged > 0.2s
- impulse from the atria and ventricles are slower
What is seen on an ECG showing Mobitz 1 (Wenkebach) heart block?
Gradual progressive PR interval prolongation and dropped QRS
What is meant by 2:1 Mobitz?
2 p waves for every QRS
What characterises type 2 2nd degree heart block?
Intermittent non-conductive P wave not preceded by a QRS complex
What is 3rd degree heart block?
Discordant contraction of the atria and ventricles i.e. no association between the p waves and the QRS complexes
In which leads would an inferior infarct be seen?
- L2
- L3
- aVF
In which leads would a lateral infarct be seen?
- L1
- aVL
- chest leads V1-V4
In which leads would an anterior infarct be visible?
Chest leads V1 –> V4
Which conduction structure is situated at the opening of the coronary sinus?
AV node
Define pulse pressure
The difference between systolic and diastolic pressure
Which part of the cardiac cycle is the longest?
Diastole (60%)
What is the purpous of the Windkessel effect?
To dampen down the effect of the pulsatile blood flow to the viscera
Which vessels hold 70% of the total blood volume?
Veins
How can veins and venules control CO?
By constricting - increase atrial pre-load to increase CO
Which vessels have the most resistance in the CVS?
Arterioles
How is mean arterial pressure calculated?
CO x TPR
(cardiac output x total peripheral resistance)
Where are the baroreflex cells found?
- arch of aorta
- carotid sinus
Which CNs are involved with taking the baroreflex signals to the nucleus of the solitary tract in the brainstem?
CN IX and X (glossopharyngeal and vagus)
Where are the vaso vasorum found?
In the walls of the larger arteries –> blood supply to the tunica adventitia
Name 3 types of capillaries
- continious
- fenestrated
- discontinuous
What is another name for discontinuous capillaries?
Sinusoids
Where are discontinuous capillaries found?
- liver
- spleen
- bone marrow
Large proteins are able to cross
What is the term given to the point where blood pressure is unaltered by tilting ?
(just below the transition from abdo to thorax)
Hydrostatic indifference point
