ECGs

Question 1

LVH criteria & causes

Answer 1

Slokov-llyon criteria

• voltage: S wave in V1 plus R wave in V5/6 > 35 mm
• non-voltage criteria: LV strain, ST depression & TWI in lateral leads, delayed R wave peak time > 50 msec in V5/6

Other criteria include R in aVL > 11 mm

Causes: HTN, aortic stenosis/regurg, HCM, coarctation of aorta

Question 2

Left bundle branch block

Answer 2

QRS > 120 msec
S wave in V1
Broad monophasic R in lateral leads, absence of w waves (RSR)
Prolonged R wave peak time, > 60 msec in V5-6

Associated: LAD, poor r wave progression, appropriate discordance ST changes

Question 3

RBBB

Answer 3

QRS > 120 msec
RSR’ in V1-V3
Wide, slurred S wave in lateral leads (V5-6)

Question 4

Left axis deviation - identification and causes

Answer 4

Positive deflection in I, negative in II and III. Less than -30 degrees.  
Causes 
- LBBB 
- LAFB 
- LVH
- old inferior MI 
- WPW 
- Ventricular ectopy / pacing

Question 5

Right axis deviation - description and causes

Answer 5

Positive deflection III, negative deflection in lead I, II positive or negative. > 90 deg. (90 degrees to II) 
Caueses 
- Lateral MI 
- LPFB 
- RVH 
- Acute RV strain, PE 
- WPW 
- Hyperkalaemia 
- TCA poisoning (sodium channel blockade)
(Normal)

Question 6

Describe ECG in heart blocks

Answer 6

1st degree - prolonged PR, > 200 msec ( 5ss)
2nd degree
- mobitz 1: progressively lengthening PR, until dropped beat
- mobitz 2: fixed non-condition of P wave. Higher risk of progression
- high grade, 2:1: unable to identify nature of conduction delay
3rd degree - no association between p waves and QRS complexes (some p waves may still randomly be conducted)
- complete heart block - nothing conducted P to QRS, all escape rhythm

Question 7

Brugada syndrome - describe ECG and ix/management

Answer 7

Coved ST elevation in >1 lead, V1-V3 > 2 mm with negative t wave
Type 2: saddle shapped STE V1/2
Type 3: appearance of coved STE V1/2 but < 2 mm

Brugada syndrome

• ECG changes
• PLUS: episodes of collapse / near collapse, witnessed VT/VF, nocturnal agnoal respiration, inducible VT, FHx sudden cardiac death < 45, coved ECGs in family members

Type 1 & symptoms - mortality 10% / year - Admit! ICD.
Type 2/3 or asympt T1- outpatient Ix with EP studies,

Question 8

ECG changes in arrhythmogenic right ventricular dysplasia

Answer 8

Epislon wave - termination of QRS complex
T wave inversion in V1-3
Localised wide QRS in V1-3
Frequent PVCs with LBBB morphology —> Paroxysmal VT with LBBB morphology (RVOT tachycardia)

Question 9

ECG changes in wolf-parkinson-white & reason

Answer 9

Short PR interval (<120 msec)  
Delta wave (slurred upstroke of QRS) 
Prolonged QRS - > 110 msec 
Discordant ST/T chagnes (due to abnormal repolarisation)

Pre-excitation pathway leads to depolarization of ventricle prior to that caused by passage of normal conduction through the AV node. Leads to short PR and segment of ventricle contracting early - thus delta wave.

Question 10

Long QT, ECG findings and causes

Answer 10

QT inverval of > 480 msec in women, or 450 msec in men.

• adjusted via nomogram (for rate) in toxicology to determine risk of TdP
• adjusted via bazzetts formula, QT / sq root RR interval in msec if congential / other

Causes

• electrolyte - hypomagnesaemia, hypocalcaemia, hypokalaemia
• drugs - methadone, antipsychotics (halloperidol, quetiapine), antibiotics (azithromycin), antiemetic (ondansetron, droperidol), SSRI, amiodarone
• congential
• myocardial disease - AMI, rheumatic heart disease, cardiomyopathy

Question 11

STEMI - findings in RV infarct & changes to mx

Answer 11

Associated with inferior MI
ST elevation in III > II
ST elevation in V1 and ST depression V2, or marked ST depression V2.

Right sided ECG
Mx: no nitrates, IV fluid bolus for hypotension, anticipate CHB

Question 12

STEMI - findings in posterior MI, implications

Answer 12

Associated with Inferior or lateral MI 
V1-V3: 
- horizontal ST depression 
- Tall broad R waves (dominant R wave in V2)  
- upright T waves 
0.5 mm STE on posterior lead ECG 

Implications: very large infarct - high risk of LV dysfunction and death.

Question 13

STEMI equivalent ECGs

Answer 13

De Winters T waves - hyperacute T, narrow based, tall. anterior leads. LAD occlusion.
Wellens syndrome: proximal LAD stenosis (high risk of death with exercise testing)
- A: biphasic t-waves
- B: symmetrical deep TWI
Posterior MI - isolated ST depression in V1-V3 with large R waves, and positive T waves. Posterior ECG.
STE aVR & V1 with widespread STD - critical LMCA/LAD stenosis or severe tripple vessel disease
Scarbossa criteria in Paced rhythms or LBBB - concordant ST depression, or STE in anterior leads. Or excessively discordant ST chagnes > 25% of preceeding QRS.

Question 14

STEMI Mimic ECG

Answer 14

Benign early repolarization - ST elevation 3 mm anteriorly men < 40, 2 mm men > 40, 1.5 mm women. No chest pain / concerning sx.
Pericarditis. STE concave, diffuse (not territorial). PR depression.
LBBB.
Hyperkalaemia
LVH
LV aneurysm

Question 15

Describe ECG in torsades des points

Answer 15

Polymorphic ventricular tachycardia
Associated with long QT syndrome
Typical “twisting” pattern or increasing and decreasing amplitude of QRS complexes