Differentials

Question 1

DDx for new right axis differentiation (give 10)

Answer 1

• Pulmonary Hypertension
• Na⁺ Channel blocker toxicity
• Hyperkalemia
• Old lateral MI (Q-waves)
• RVH
• LPFB
• Ventricular ectopy
• Misplaced leads
• Situs Inversus
• Newborns/infants

Question 2

DDx for new left axis differentiation (give 8)

Answer 2

• LBBB
• Paced rhythm
• Pre-excitation (WPW)
• Prior inferior MI (Q-waves)
• LAFB
• LVH
• Hyperkalemia
• Elderly/obese patients

Question 3

DDx for ST elevation (16)

Answer 3

• Acute myocardial injury (trauma, ACO/MI)
• Global Ischemia (Dissection, GI bleed)
• Early repolarization
• Myo/Pericarditis
• Vasospasm
• Ventricular aneurysm
• LBBB/Pacemaker
• Pulmonary Embolism
• High Voltage (LVH, Athlete’s heart, WPW, etc.)
• Na⁺ Channelopathies (TCA, Na-blockers, Brugada, hyperK)
• Hypothermia
• Takotsubo
• Intracranial abnmls
• “Spiked Helmet” sign
• Hypercalcemia

Question 4

Key acute causes of diffuse STE with differential indicators

Answer 4

• STEMI
  
  • Often with reciprocal STD, sometimes Q-waves
• Pericarditis
  
  • Often with PR depression and concave upwards STE, no Qs
• Myocarditis
  
  • Similar to STEMI, no Qs
• BER
  
  • No reciprocal changes, concave upwards STE, no Qs
• Ventricular aneurysm
  
  • Large Q-waves with no reciprocal depression

Question 5

DDx for poor R-wave progression (r<3mm in V3) (the 6 Ls)

Answer 5

• LAFB
• LBBB
• LVH
• Low voltage
• Lead Misplacement
• Prior AS MI

Question 6

Criteria for “pathologic” Q-waves

Answer 6

• >40ms (>1 small square)
• >2mm deep
• >25% depth of QRS
  
  • especially for inferior leads, where 2mm may be normal
• any q-waves in v1-v3

Question 7

Signs of hypokalemia

Answer 7

• U-waves (“camel-hump” T’s)
  
  • Especially in precordial leads
• QTc prolongation
• Flattened/inverted Ts with sagging or depressed ST-segments
• “reverse Wellen’s” biphasic T-waves
• STE in aVR
• PVCs and pseudo-ischemic patterns

Mimic for aVR MI! Look for biphasic precordial Ts and grossly prolonged QTc

Question 8

Describe Ashman phenomenon

Answer 8

• intermittent abberant conduction during AFib with RVR
• usually follows a “long-short” cycle of AFib
• aberrant conduction mimics short runs of VTach
• Usually mimics RBBB morphology

Question 9

What are normal HR and QRSD for VTach?

Answer 9

• HR >120-130
• QRSD<200ms
  
  • Unusually slow/wide VTach may indicate severe hyperkalemia!

Question 10

ECG features of Na⁺-channel blockade (TCA OD, Class I antiarrhythmic OD)

Answer 10

• Interventricular conduction delay >100ms in II
• RAD with terminal R deflection >3mm or R/S ratio >0.7 in aVR
• Sinus tachycardia due to antimuscarinic effects in TCA OD

Question 11

Criteria for differentiating between acute pericarditis and STEMI

Answer 11

Suggests STEMI:

• STD in ANY lead except for aVR or V1 (definitive)
• STE in III > II (definitive)
• Horizontal or convex upwards STE (definitive)
• Known NEW Q-waves

Suggests AP:

• Friction Rub
• PR depression in multiple leads

STEMI findings trump AP findings!

Question 12

Universal criteria for STEMI

Answer 12

• STE at J-point in 2 contiguous leads
• Men >=40: 2mm in V2/3, 1mm in all other leads
• Men <40: 2.5mm in V2/V3, 1mm in all other leads
• Women: 1.5mm in V2/V3, 1mm in all other leads
• Posterior STEMI
  
  • tall R-waves, STD, and upright Ts in V1/2/3

Question 13

Indicators for BER

Answer 13

• Widespread, concave-up STE most prevalent in V2-5
• Notching or slurring at the J-point
• STE is <25% the amplitude of the T
• Prominent, assymetrical T-waves
• No other signs of STEMI (reciprocal changes, TWIs, pathological Qs, etc.)
• ST changes are stable over time