Cardiovascular Flashcards
What causes the plateau in the AP of the myocardium?
Calcium channels open in response to the depolarisation slower than the Na+ channels prolonging the depolarisation–> plateau
What is the resting potential of the myocardium?
-90mV
What is the mechanism for the cardiac AP?
Na+ channels open 1st from depolarisation = Na+ influx –> rapid depolarisation
Ca2+ channels then open in response to the depolarisation but slower than the Na+ channels –> plateau
K+ channel conductance decreases following depolarisation allowing the Ca2+ to maintain the depolarisation.
After 200ms K+ conductance increases = replarisation
Where is the sinus rhythm generated?
Pacemaker cells –> Sino atrial node
What stops the AP being transmitted from the atria to the ventricles?
Fibrous rings (anulus fibrosus cordis) direct the AP to the AV node
What does the P-wave on an ECG show?
depolarisation across the atria
What does the QRS complex show on an ECG?
Spread of the depolarisation across the ventricles
What does the T- waves on an ECG show?
Repolarisation of the ventricles
Why is the T- wave a positive inflection on an ECG?
It is a -ve -ve, which shows up as positive.
I.e. The polarisation is moving away from the ecg node.
How is HR calculated on an ECG?
Distance between R waves:
300 / No. Large squares in the R-R interval
What do bifid p-waves indicate?
Mitral stenosis
What will right axis deviation show up as on an ECG?
The average direction move clockwise –> Lead 1 becomes predominantly -ve.
What does left axis deviation show up as on an ECG?
leads 2 and 3 become predominantly -ve.
What do tall, tented t-waves on an ECG indicate?
Hyperkalaemia
How does right bundle branch block appear on an ECG?
MaRroW- QRS has M and W shapes
How does left bundle branch block show up on an ECG?
WilliaM- QRS has W and M shapes
What is 1st degree heart block and how does it appear on an ECG?
A delay at the AVN/ bundle of his.
PR interval is >0.2s
What is 2nd degree- Mobitz type 1 heart block?
Progressively longer PR interval until there’s a ‘dropped beat’.
Described as Wenkebach P:QRS
What is 2nd degree mobitz type 2 heart block?
Normal PR interval with QRS dropped at random.
Due to a block at the bundle of His
What is 3rd degree heart block?
Complete dissociation between the atria and the ventricles.
What is syncope?
Transient loss of consciousness due to global cerebral hypoperfusion.
What are the types of syncope?
Reflex, orthostatic hypotension, cardiac syncope
What is acute coronary syndrome?
A range of disorders such as MI, unstable angina
All caused by the underlying problem of sudden decrease in blood flow to part of the myocardium.
What is the initial management of ACS?
MONA:- Morphine Oxygen Nitrates Aspirin
