ECG Flashcards
Normal ECG paper output speed?
25 mm per second = 5 large squares = 25 small squares
ECG: 1 small square?
1 mm = 0.04 seconds
ECG: 1 large square?
5 small squares = 5 mm = 0.2 seconds
ECG: 1mV amplitude?
10 mm = 10 small blocks
How calculate rate on ECG
Number of R waves on rhythm strip (bottom) x 6
7 step approach to ECG rhythm analysis?
Rate Rhythm I Am pqrst
- Rate
- rhythm: relationship between P waves and QRS - P before every QRS, AV association/ disassociation., Pr interval
- Ischaemia /infarction? St, t wave changes.
- Axis
- P waves present / absent!!
- Pattern of QRS complexes: regular/irregular , QRS morphology: narrow/ wide, qt interval
- Individual qrst: q waves present? Poor r wave progression v1-v6?
Interpretation of Narrow complex QRS on ECG? (3)
Origin is:
- sinus
- atrial
- junctional
Interpretation of wide complex QRS on ECG? (2)
Origin is :
- ventricular or
- supraventricular with aberrant conduction
Differential diagnosis narrow complex tachycardia? (11)
= supraventricular origin
Atrial + regular rhythm
- sinus tachycardia
- atrial tachycardia
- atrial flutter
- inappropriate sinus tachycardia
- sinus node re-entrant tachycardia
Atrial + irregular
- Afib
- atrial flutter with variable block
- multi focal atrial tachycardia
Atrioventricular
- AV re-entry tachycardia (AVRT)
- AV nodal re-entry tachycardia (AVNRT)
- automatic junctional tachycardia
Differential diagnosis broad complex tachycardia (BCT)? (8)
Regular rhythm BCT
- Vtach (all VT until proven otherwise)!
- antidromic AV re-entry tachycardia (AVRT)
- any regular supraventricular tachycardia with aberrant conduction eg due to BBB, rate related aberrancy
Irregular
- Vfib
- polymorphic VT
- torsades de pointes
- AF with Wolff Parkinson White syndrome
- any irregular supraventricular tachy with aberrant conduction
Differential bradycardia with P wave present and every P followed by a QRS (3)
= sinus node dysfunction
- sinus bradycardia
- sinus node exit block
- sinus pause/arrest
Differential bradycardia with P wave present and every P not followed by a QRS (2)
= AV node dysfunction
- AV block second degree
- AV block third degree (complete heart block)
Differential bradycardia with P wave absent (2)
Narrow complex = junctional escape rhythm
Broad complex = ventricular escape rhythm
Normal cardiac axis on ECG
QRS axis between -30 and +90 (down and slightly left)
Define left axis deviation
QRS axis less than -30
(Less than -90 to 180 = extreme axis deviation)
Define right axis deviation
QRS axis more than +90
(More than 180 to -90 = extreme axis deviation)
How estimate cardiac axis on ECG (4)
Normal axis = 0 - 90 = lead 1 positive (R>S) and lead aVF positive
Left axis deviation = 0 - -90 = lead 1 positive and lead aVF negative (S>R)
Right axis deviation = 90 - 180 = lead 1 negative and aVF positive
Extreme axis deviation = -90 - 180 = lead 1 negative and aVF negative
ECG rule of 4s?
- 4 initial features: history , rate, rhythm, axis
- 4 waves: P wave, QRS complex, T waves, U waves
- 4 intervals: PR interval, QRS width, ST segment , QT interval
Which leads should be mirror images on ECG?
aVL and aVR (limb leads)
Normal PR interval?
3-5 small blocks = 0.12 - 0.2 seconds
Cause prolonged/lengthening PR interval?
Heart block
Cause shortened PR interval? (2)
- WPW syndrome
- junctional rhythm
Normal QRS width?
Less than 3 small squares = 0.12 sec
Widened QRS meaning?
Conduction defect
Name 6 types different STEMI patterns on ECG
- septal (V1 V2)
- anterior (V3-4)
- lateral (I + aVL, V5-V6)
- inferior (II,III, aVF)
- right ventricular (V1, V4R)
- posterior (V7-9)
SALI RP
Normal P wave duration
Less than 3 blocks (0.12s)
= atrial depolarization
Define sinus P wave (4)
Morphology = monophasic in lead 2, biphasic in V1
Axis = upright in leads 1 and 2, inverted in aVR
Duration = less than 3 blocks (0.12 sec)
Amplitude = less than 2.5 mm (0.25mV) in limb leads; less than 1.5 (0.15) in precordial leads
How does right atrial enlargement appear on ECG?
Lead 2:
Tall P wave > 2.5 mm
Width unchanged (<120 ms)
Lead V1:
Increase height > 1.5 mm in the initial positive portion of the biphasic P wave
P pulmonale ( peaked P)
How does left atrial enlargement appear on ECG?
Lead 2:
Long duration > 120 ms (3 blocks)
Height unchanged
May have P mitrale (notch)
Lead V1:
Wide > 40ms and deep > 1mm in the terminal negative portion of the biphasic P wave
Cause P wave inversion?
Ectopic atrial and junctional rhythms
Name 6 ECG changes in hyperkalaemia
- peaked T waves (early sign - 5.5-6.5)
- p wave widening/flattening, PR prolongation (K 6.5-7)
- bradyarrythmias: sinus bradycardia, high grade AV block with slow junctional and ventricular escape rhythms, slow AF (7-9)
- conduction blocks: BBB, fascicular blocks (late)
- QRS widening with bizarre QRS morphology
- severe >9: sine wave appearance (pre-terminal rhythm), Vfib, PEA (pulse less electrical activity) with bizarre wide complex rhythm, asystole
Name 6 ECG features of hypokalaemia
- increased P wave amplitude
- prolonged PR interval
- widespread ST depression and T wave flattening/inversion
- prominent U waves (best seen V2 V3)
- apparent long QT intervals due to fusion T and U waves (actually long QU interval)
Severe <2.4: frequent supraventricular and ventricular ectopics , supraventricular tachyarrythmias, potential V arrhythmias
Define a pathological Q wave
- > 40 ms (1mm) wide
- > 2 mm deep
- > 25% depth of the QRS complex
- seen in leads V1-3 (should be absent in these)
What does pathological Q wave indicate
Current or prior MI
ECG features left ventricular hypertrophy?
Tall and thin complexes!
- R wave in V6 > 25 mm (5 big blocks) or
- S wave in v1 + r wave in V6 > 35 mm
ECG features left BBB?
Wide QRs! > 0,12s (3 small blocks)
Also:
- m pattern of QRs in v5
- no septal q waves
- inverted T waves lead 1, avL, V5 - V6
Name 4 causes lbbb
- IHD
- Ht
- cardiomyopathy
- idiopathic fibrosis
ECG finding pulmonary embolism? (4)
- Sinus tachycardia
- Rbbb
- R ventricular strain: inverted T in v1 to V4
- classical S1 Q3 T3 pattern = rare (deep S wave in lead 1, Q in lead 2, t ware inversion lead 3)
ECG findings first degree heart block?
Prolonged Pr interval
ECG findings second degree heart block?
Dropped beats - P wave not followed by QRs
Mobitz 1: Pr interval lengthens with each beat until dropped beat
Mobitz 2: Pr intervals lengthened consistently until beat drop
ECG findings third degree heart block?
No correlation P and QRs
ECG features unstable angina? (3)
- May or may not have St segment depression
- transient St elevation
- new t wave inversion
