SA Blocks Flashcards
Where is the SA node located?
in sinus venarum region of Right Atrium near the superior vena cava
What are the two cells present within the SA node?
‘P’ Pace maker cells
‘T’ Transitional cells
What is the main role of P cells?
produce sinus impulse
What is the main role of T cells?
transmit impulse to right atrium
What prevents role of P cells?
lack of impulses
What prevents role of T cells?
impulse produced but blocked
What are some examples of sinus dysfunction?
SA block
SA arrest
Sinus bradycardia
Chronotropic incompetence
Tachy-Brady syndrome
SANRT
IST
What are some atrial arrythmias caused by abnormalities of SA node?
Asystole
Atrial tachycardia
Atrial escape rhythm
Atrial Fibrillation
Atrial flutter
Tachy-Brady syndrome
What is first degree AV block?
Delay between impulse generation and transmission to atrium
not detectable on ECG
What is second degree AV block Type 1
WENCHEBACH
Gradual prolongation of PR interval
(lengthening duration of impulse generation and transmission)
lengthens over a few cycles until an atrial impulse is completely blocked and there is a P wave not followed by QRS complex
Second degree AV block Type 2
MOBITZ
Atrial impulses blocked at irregular intervals. Dropping intermittent P waves with no pattern. Constant interval
Intermittent dropped P waves with a constant interval between impulse generation and atrial depolarisation.
Third degree AV block
none of sinus impulses are conducted to right atrium
Complete absence of P waves
early onset may produce sinus pauses/ sinus arrest which may lead to asystole
rhythm may be maintained by atrial junctional escape rhythm
What is chronotropic incompetence?
inappropriate increase in HR in response to changing metabolic needs during activity
inability to achieve at least 80% of maximum predicted HR (220-age) during exercise
What is sinus arrest?
pause greater than 3 seconds
no electrical activity of heart is seen
becomes asystole when there is an absence of spontaneous sinus or escape rhythm
What is tachy-brady syndrome?
Abnormal automatic conduction within atrial tissue
presents as sinus pause/ arrest however, is saved by a escape rhythm atrial/junctional/ventricular
Failure to resume sinus rhythm after cardioversion, manifesting as a prolonged sinus pause.
AF with slow V response in the absence of AV node blocking agents
This is likely due to the simultaneous degeneration in the AV node
