ECGs Flashcards
Which leads show anterior pathology?
V1-V4 = Left Anterior Descending (LAD) V1&V2 = Septal
Which leads show lateral pathology?
V5, V6, I, aVL = Circumflex
Which leads show inferior pathology?
II, III, aVF = Right Coronary Artery (RCA)
What is shown with a normal axis?
leads I, II, and III positive (II most positive)
What is shown with right axis deviation?
QRS is positive (dominant R wave) in leads III and aVF
QRS is negative (dominant S wave) in leads I and aVL
Causes:
Left posterior fascicular block
Lateral MI
Right ventricular hypertrophy
Acute Lung Disease (PE)
Chronic Lung Disease (COPD)
Ventricular Ectopy
WPW Syndrome
Hyperkalaemia
Horizontally positioned heart
Septal Defects
What is shown with left axis deviation?
QRS is positive (dominant R wave) in leads I and aVL
QRS is negative (dominant S wave) in leads II and aVF
Causes:
Left anterior fascicular block
LBBB
Left ventricular hypertrophy
Inferior MI
Ventricular ectopy
Pacing
WPW syndrome
What is the regular PR interval?
Normal 120-200ms
3-5 small squares
Prolongation suggests heart block, hypokalaemia, acute rheumatic fever
Shortening with upsweeping Q wave indicative of WPW
What is the regular QRS complex width?
<120ms
3 small squares
Wide suggests ventricular origin
Narrow suggests supraventricular origin
Reporting an ECG
Patient Name
Date of ECG
Rate (# of beats)
Rhythm (regular/irregular)
Axis
P wave (presence, amplitude)
PR interval (normal, shortened, widened)
QRS complex (presence, size)
ST segment
T waves (presence, inversion)
QT interval (elongated)
Other: LBBB, RBBB, pacing, ectopics, Q waves
Sinus Rhythm
each QRS complex is preceded by a P wave
Bradycardia vs Tachycardia
<60 = brady
>100 = tachy
Escape Rates
Atrial: 60-80bpm
Junctional: 40-60bpm
Ventricular: 20-40bpm
First Degree Heart Block
PR interval widened (P waves may be burried in T wave)
Right Bundle Branch Block
MaRRoW (M in V1, W in V2)
Broad QRS > 120ms
Typical RSR’ pattern in V1-3
Wide slurred S wave in I, aVL, V5-6
NB: Delayed activation of the right ventricle also gives rise to secondary repolarization abnormalities, with ST depression and T wave inversion in the right precordial leads.
Left Bundle Branch Block
WiLLiaM (W in V1, M in V2)
QRS duration > 120ms
Dominant S wave in V1
Broad monophasic R wave in I, aVL, V5-6
Absence of Q waves in lateral leads
LBBB can mask ECG signs of MI
Second Degree Heart Block (Mobitz I)
Progressive prolongation of PR interval culminating in non-conducted P wave
Second Degree Heart Block (Mobitz II)
Intermittent non-conducted P waves without progressive prolongation of the PR interval
Third Degree Heart Block
Atrial rate is approximately 100bpm
Ventricular rate is approximately 40bpm
Perfusing rhythm is maintained by Junctional or Ventricular escape rhythm
Atrial Flutter
Serrated / saw-toothed P waves
May show alternating pattern of 2:1, 3:1, 4:1 conduction ratios
250-350bpm
Atrial Fibrillation
Irregularly irregular rhythm
no P waves
no isoelectric basline
>350bpm
Wolff-Parkinson White
Delta waves - slurring slow rise of initial portion of QRS
Ventricular Fibrillation
Chaotic irregular deflections of varying amplitude
No P waves, QRS complexes, or T waves identifiable
Fatal if not cardioverted
Ventricular Ectopic Beats (Premature Ventricular Complex)
Premature broad QRS complex with abnormal morphology
ST segment discordant to QRS
bigeminy = frequent PVCs coupled with sinus rhythm
Atrial Ectopic Beats (Premature Atrial Complex)
Abnormal P wave followed by normal QRS (P wave may be hidden in T wave)
AV nodal (junctional) rhythm
Junctional rhythms are narrow complex, regular rhythms arising from the AV node.
P waves are either absent or abnormal (e.g. inverted) with a short PR interval (=retrograde P waves).
Hyperkalaemia
Peaked/ Tall T waves
Loss of P wave
Widening QRS (approaching sine wave)
Ventricular Tachycarida
Wide QRS
May degenerate to VF (fatal)
Pulmonary Embolism
S1Q3T3
- prominent S wave in lead I
- abnormal Q wave in lead III
- T wave inversion in lead III
Past MI
Q waves seen in leads V1-3
Inferior Q waves (II, III, aVF)
May have T wave inversion
Supraventricular Tachycardia
Similar to VT but has narrow QRS and possible evidence of P waves (although not sinus rhythm)
Causes of Regular Rhythm Bradycardia
Physiological (athletes, during sleep: due to increased vagal tone)
Drugs (e.g. beta-blockers, digoxin, amiodarone)
Hypothyroidism (decreased sympathetic activity secondary to thyroid hormone deficiency)
Hypothermia
Raised intracranial pressure (due to an effect on central sympathetic outflow)—a late sign
Third-degree atrioventricular (AV) block, or second-degree (type 2) AV block
Myocardial infarction
Paroxysmal bradycardia: vasovagal syncope
Jaundice (in severe cases only, due to deposition of bilirubin in the conducting system)
Causes of Irregular Rhythm Bradycardia
Irregularly irregular
Atrial fibrillation (in combination with conduction system disease or AV nodal blocking drugs) due to:
● alcohol, post-thoracotomy, idiopathic
● mitral valve disease or any cause of left atrial enlargement
Frequent ectopic beats
Regularly irregular rhythm
Sinus arrhythmia (normal slowing of the pulse with expiration)
Second-degree AV block (type 1)
Apparent
Pulse deficit* (atrial fibrillation, ventricular or atrial bigeminy)
Causes of Regular Rhythm Tachycardia
Hyperdynamic circulation, due to:
● exercise or emotion (e.g. anxiety)
● fever (allow 15–20 beats per minute per °C above normal)
● pregnancy
● thyrotoxicosis
● anaemia
● arteriovenous fistula (e.g. Paget’s disease or hepatic failure)
● beri-beri (thiamine deficiency)
Congestive cardiac failure
Constrictive pericarditis
Drugs (e.g. salbutamol and other sympathomimetics, atropine)
Normal variant
Denervated heart, e.g. diabetes (resting rate of 106–120 beats per minute)
Hypovolaemic shock
Supraventricular tachycardia (usually >150)
Atrial flutter with regular 2:1 AV block (usually 150)
Ventricular tachycardia (often >150)
Sinus tachycardia, due to:
● thyrotoxicosis
● pulmonary embolism
● myocarditis
● myocardial ischaemia
● fever, acute hypoxia or hypercapnia (paroxysmal)
Multifocal atrial tachycardia
Atrial flutter with variable block
Causes of Irregular Rhythm Tachycardia
Atrial fibrillation, due to:
● myocardial ischaemia
● mitral valve disease or any cause of left atrial enlargement
● thyrotoxicosis
● hypertensive heart disease
● sick sinus syndrome
● pulmonary embolism
● myocarditis
● fever, acute hypoxia or hypercapnia (paroxysmal)
● other: alcohol, post-thoracotomy, idiopathic
Multifocal atrial tachycardia
Atrial flutter with variable block
What is the normal QT interval?
The QT interval should be aproxametly less than half the cardiac cycle
A lengthened QT interval is a marker for the potential of ventricular tachyarrhythmias like torsades de pointes and a risk factor for sudden death.
What is a delta wave
Early ventricular depolarisation typically due to Bundle of Kent activation pathway
Seen in Wolff Parkinson White Syndrome
CHADS2
Assessment Scale for Atrial Fibrillation and need for anticoagulants
