Clinical electrophysiology

• what is the axis in an ECG?

  direction of the impulse TO the electrode, this is shown as a positive impulse
• which directions are the axis in in comparison to the heart?

  impulses that travel to the direction of the electrode/lead are positive

  
• why is the aVR lead the only one with an inverted/negative QRS complex?

  because normally impulses travel to the left hand side like the green arrow but in the aVR they are traveling away from the electrode

  movement to the direction of the leads is positive

  
• what is the isoelectric line and what does it signify?

  it is the baseline of ECGs and denotes the resting membrane potential

  
• •Electricity moving towards an electrode is POSITIVE

  •Electricity moving away from an electrode is NEGATIVE

  if leads I and II are positive the axis is normal
• what do the different areas/leads on an ECG represent?


  the rhythm strip is normally lead II

  
• how do the leads on an ECG correspond to the areas of the heart?

  here are the different areas of the heart

  
• how many seconds is one big box with 5 small boxes? how many of these boxes are needed to make 1s? how many seconds/how long is a normal rhythm strip?

  1. 200ms or 0.2s
  2. 1 second
  3. 10sec
• how long is a normal PR interval and what is it suggestive of if it is longer?

  norally 3-5 small boxes (120-200ms) and if it is >200ms it is suggestive of 1st degree heart block
• what should you look out for with QRS complex? what is its normal duration and what does it imply if it is longer than this?

  look for the width and hight

  normally 3 small boxes/ 120ms

  longer than 120ms is indicative of a bundle branch block
• ST elevation can be seen in MIs
• what should you look for when looking at T waves?

  size and direction/ inverted?
• which leads is the T wave normally inverted in? what can cause inversion of the T wave? what happens to the T wave when there is high and low K+?


  V1 and AVR

  inversion - ischaemia, heart abnormality

  high K+ - see a peak T wave, may be early MI

  low K+ - T wave will be flat and prolonged
• how long is the QT interval in males vs females?

  350 - 440 ms males

  350 - 460 ms females
• how to approach an ECG

  1. rhythm - regular irregular?
  2. HR
  3. is the axis in lead I and II positive to check these are normal
  4. check there is one p-wave next to each wave
  5. is there ST elevation?
  6. check the lengths of the intervals (PR, QRS, QT)
• what is the range of normal heart rate? what is classed as bradycardia? what HR is tachycardia

  normal = 60-100bpm

  bradycardia = less than 60 bpm

  tachycardia = more than 100 bpm
• what is the this rhythm strip showing?

  • Regular rhythm, rate approx 75bpm

  • P waves present

  • Ratio: 1 p-wave to 1 QRS

  • Normal PR interval

  = Normal sinus rhythm

  
• what should you check if you think it is normal sinus rhythm

  –Normal looking P wave

  –Always followed by a QRS

  –In a regular fashion
• what is the HR and rhythm? what is the Dx?

  Atrial fibrillation:

  • no p-waves
  • irregularly irregular QRS complexes

  the rhythm's irregularity has no pattern and does what it wants

  Atrial fibrillation can cause the formation of clots and strokes

  
• what can be seen here?

  Atrial fibrillation

  • irregularly irregular
  • no clear p-waves

  
• what is normally seen in atrial flutter?


  • saw-tooth shaped
  • REGULAR distances between the shapes
• Atrial flutters are broken down into grades called blocks because when blocks in the conduction system happen can affect the ECG. What are the different types of blocks and how would you know which is which?

  2:1 block - two p-waves to one QRS

  3:1 block - three p-waves to one QRS

  variable block - number of p-waves per QRS keeps changing/ irregular

  complete (third degree) AV block - regular QRS complexes but irregular P-waves, more p waves than QRS complex
• what does this ECG show and what causes it?

  paroxysmal atrial tachycardia

  caused by the making of a shorter circuit in the in the artia which causes sudden rapid HR which suddenly stops

  
• what does this ECG show?

  Narrow QRS complex < 120ms

  
• what does this ECG show?

  Broad QRS complex >120ms

  
• ventricular ectopics in ISOLATION can be regular in sinus rhythm, when are they not considered normal?


  when they are seen in 4 or more clusters

  
• how would you check if the patient had a LBBB?

  pnemonic WiLiaM (L - check for W shape in lead V1 and M shape in V6):

  • W: complexes in V1 resemble the letter W: deep downward deflection (dominant S wave), which may be notched
  • M: complexes in V6 resemble the letter M: broad, notched or ‘M’ shaped R wave in V6

  
  

  more information:

  • Broad QRS complex: >120 ms (3 small squares)
  • Dominant S wave in V1
  • Broad, monophasic R wave in lateral leads: I, aVL, V5-V6
  • Absence of Q waves in lateral leads
  • Prolonged R wave >60ms in leads V5-V6

  
• How would you know a patient had RBBB?

  MaRroW

  • V1 shows M shaped waves
  • V6 shows W shaped waves
• How would you know a patient had RBBB?

  MaRroW

  • M: complexes in V1 resemble the letter M: initial small upward deflection (r wave), a larger downward deflection (S wave), then another large upward deflection (second R wave)
  • W: complexes in V6 resemble a W: initial small downward deflection (Q wave), then a larger upward deflection (R wave), and then a wide downward deflection (S wave)

  
• what is the most common broad complex tachycardia?

  ventricular tachycardia - looks like you gave a child a crayon to scribble
• what would you see on an ECG of a patient with ventricular tachycardia (a broad complex tachycardia)?


  •  Fast (120-250 bpm)

  •  Regular

  •  Broad QRS

  •  No P waves

  •  Potentially life-threatening – need to think about schocking

  •  Usually associated with structural heart disease

  
• what is an ST depression? which conditions can you see this in?

  when there is a downwards shift of the ST segment

  can be seen in:

  • hypokalemia
  • cardiac ischemia, (sx of chest pain or angina)
  • medications like digitalis

  
• what is ST elevation? which conditions can you see this in?

  when there is an upwards shift in the ST segment

  can be seen in a myocardial infarction, myocarditis, pericarditis

  
• what is the difference between a STEMI and an NSTEMI?

  STEMI  - ST elevation MI

  NSTEMI  - Non ST elevation MI (not a full thickness MI)

  
• how should you tx someone who has came in with chest pain and discomfort until the cardiac cause is excluded? what diagnostic tests should you do?

  With symptoms of chest discomfort/pain treat as an acute coronary syndrome (ACS) until cardiac cause is excluded.

  Use Diagnostic tests and risk;

  1. ECG
  2. Trop T markers
  3. Risk factors
  4. Previous Cardiac history
• simple rhythm guide