ECG Tutorials Flashcards
Why do you get Q waves?
Because the “electrical hole” created by the infarcted tissue means the lead will pick up the R waves on the opposite ventricular wave.
How do pacemakers work?
Set a HR cut off below which the pacemaker will kick in and set the rate
What is the pathophysiology of MI?
Rupture of artherosclerotic plaque causing local thrombus formation and occlusion. The plaque can be any size
How does the QRS appear in SVT?
Narrow
What does the QRS represent physiologically?
The onset of conduction of action potential
Why do you get ST elevation?
A current traveling from the endo to the epicardium, when the endocardium is infarcted it doesn’t transmit a full action potential
What happens in atrial flutter?
Impulse travels around the tricuspid annulus and hits the AV node. Impulses are transmitted depending on the AV node refractory period
How does R axis deviation appear?
Negative QRS in I
In which condition do you get a delta wave?
Wolf-Parkinson’s-White syndrome
What determines the HR in AF?
The length of the refractory period of the AV node - as random impulses are occasionally sent from the atria when the AV node is not refractory
What do you call two ventricular ectopic beats together?
Cuplets
Why might you have a wide QRS?
Bundle branch block
Ventricular origin beat (cell to cell conduction)
Pacemaker
Alternate pathway
What is sinus arrhythmia?
When rate changes according to inspiration (faster) and expiration (slower)
How do ECG changes progress with time in a AMI
First few hours - ST elevation and reciprical depression
T wave inversion after
Q waves can come anytime
Three reasons why beats aren’t propagated through the His-Purkinje system after traveling through the AV node?
Third degree heart block causing a ventricular origin beat
Right or left bundle branch block
Pace maker (it’s place in the RV and signals are conducted to LV cell-to-cell
What drugs are used in AF?
Beta blockers
Calcium channel blockers (non-hydropyridines)
Digoxin
Amiodarone
Adenosine
How does L axis deviation appear?
Negative in II
Is aVR usually positive or negative?
Negative
How do you tell a pacemaker from a defib on xray?
The defib lead is much thicker
Describe ECG findings for AF?
Irregularly irregular
No P waves
What is the criteria for diagnosis of LVH on ECG?
Positive R wave in V6
+
Negative S wave in the V1
= > 7 large squares
What is the most common reason for the absence of p-waves?
AF
Is aVL usually positive or negative?
Positive
What are some complications of the accessory pathway in WPW?
SVT with narrow QRS (normal AV node pathway is used and signal travels back around through the accessory pathway)
Wide QRS SVT (signal travels through the accessory pathway then back through the AV node)
AF with wide and narrow QRS’ (AF sending signals through both AV node and accessory pathway)
What controls the rate in AF?
The AV node - varies between people so it can be fast or slow
A wide QRS means what?
Slowed conduction through the ventricles therefore not going through the His-Purkinje system
What do you use to revert an SVT?
Adenosine
What do Q waves respresent?
Old infarcts
Describe the journey of the action potential in Left BBB?
Down the right bundle (fast) then across to left via cell to cell (slow)`
What is bigeminy?
Normal beat followed by ectopic ventricular beat
Where do you look on an ECG for right bundle branch block?
Positive in V1
How do you tell a R from L BBB?
The wide QRS
“I can be positive about the side of the block”
LBBB: Positive in V6
RBBB: Positive in V1
William - W pattern = left or Marrow
What is your first thought with a wide QRS, regular, and tachycardic ECG?
VT
Which drugs slow the AV node
Calcium calcium blockers - verapamil and diltiazam
Digoxin
Beta-blockers
Amiodarone
How do people with bigeminy often present (vitals)?
Sinus bradycardia
Does everyone with sinus disassociation have third degree heart block?
No, can be sinus bradycardia with escape beats
What does a prolonged PR interval mean?
1st degree heart block
How do you tell an ectopic is ventricular?
The QRS and T wave are abnormal
ST elevation in anterior leads, what will you see in the reciprical leads?
Depression
What is the most likely cause of a L axis deviation?
A conduction problem
How wide is a normal QRS?
150ms
Where is the pathology in Mobitz type II heart block?
His-purkinje system
Where is the pathology in Mobitz type I heart block?
AV node
