Syncope Flashcards
What is syncope?
TLOC due to global cerebral hyopoperfusion.
What does the P wave represent?
Atrial depolarisation
What does the QRS complex represent?
Ventricular depolarisation
What does the T wave represent?
repolarisation of the myocardium of the ventricles.
Why is the T wave in the same direction as the QRS complex if one is repolarisation and one is depolarisation?
The depolarisation occurs from the inside to the outside of the ventricles - positive, travelling towards the lead. Repolarisation is negative, and travels away from the lead (net effect is the same).
What is the normal length of a PR interval?
120-200ms
What is Wolff-Parkinson-White syndrome?
propagation from atria to ventricles is not controlled through the AVN, instead, it passed through the muscle fibres.
Sinus rhythm, but the R wave has a delta wave at its base
Wolff-Parkinson-White syndrome.
What is the normal length of the QRS complex?
120ms - this is described as a narrow complex
If the QRS complex is wide, what might the pathology be?
Activity is starting in the ventricles, OR
Bundle of His is not working properly, causing the ventricles to depolarise at different times.
From where do sensory cardiac fibres arise (and therefore susceptible to referred pain)?
C8-T4.
Sinus rhythm, QRS complex follows every P wave, PR interval is greater than 220ms.
1s degree AV block.
Progressive PR interval prolongation until P wave fails to conduct.
2nd degree AV block - Mobitz 1
Regular P waves but QRS complexes within the P wave pattern are regularly dropped. A ratio of P:QRS can be determined.
2nd degree block - Mobitz 2
What is the cause of 2nd degree block Mobitz type 2?
His-purkinje conduction problem.
What is the cause of 2nd degree block Mobitz type 1?
AVN problem.
What are the symptoms of Stoke-Adams?
Syncope,
often no warning,
slow/absent pulse,
After a few seconds, regains colour and consciousness.
May convulse if O2 level in brain drops too low.
What is the pathology of vasovagal syncope?
peripheral vasodilation, venous bood pooling, little/no return to heart, responsive vigorous contraction, starch receptors - 'too much stretch' reduction in ventricular stretch (vigour) i.e. vasodilation, reduction in BP syncope.
P waves, and QRS complexes, but no relationship between them.
Third degree/complete heart block - ventricular beats are escape beats - self generated.
What is an escape beat?
a ‘self generated’ depolarisation of the ventricles after having not had an appropriate P wave stimulation.
What is the sign for a RBBB?
Broad QRS
rsR wave
M in V1 and W in V6
What is the sign of a LBBB?
Broad QRS
W in V1 and M in V6
What is the sign of atrial flutter?
sawtooth waves
What is the cause of atrial flutter?
Recurrent depolarisation around the fossa ovalis. They can stimulate the bundles of His with every depolarisation, or often in a 2:1 ratio (about 150 BMP).
What does atrial fibrillation do to the heart?
AVN bombarded with multidirectional depolarisations, stimulating the bundle of His randomly.
What is pulse pressure?
Difference between systolic and diastolic pressures.
What is Darcy’s law of laminar flow?
Q = (P1 - P2) / R
Q - Flow
P - Pressure
R - Resistance.
What is compliance (wrt vessels?)
The amount the tube can stretch.
Arteries are about 20x more compliant than veins.
What is the Windkessel effect?
The elastic recoil properties of vessels enabling a more smooth change in BP throughout each cardiac stroke.
What is mean arterial pressure?
NOT just the median of diastolic and systolic. The arteries spend about 2/3rds of their time closer to diastolic and 1/3 closer to systolic.
What is the advantage of having some tissue perfused by parallel vascular circuits as opposed to series?
The tissue can regulate the amount of blood flow it receives by this method, rather then relying on the ‘standard’ output from the heart.
