Amal Mattu’s ECG Case of the Week – October 28, 2019

Causes of ST-segment elevation

• Acute myocardial injury (ACO or trauma)
• Global ischemia (e.g. Epi, dissection, massive GI bleeding, etc.)
• Vasospasm
• Early Repolarization
• Myo/pericarditis
• Ventricular aneurysm
• LVH/high left ventricular voltage
• LBBB/pacemaker
• Pulmonary embolism
• Hyperkalemia
• Na⁺channelopathy (e.g. Brugada syndrome & mimics, TCA’s, etc.)
• Hypothermia
• Post-cardioversion (stunning)
• Takotsubo cardiomyopathy
• Intracranial abnormalities
• “Spiked Helmet” sign
• Hypercalcemia

ECG findings in Hyperkalemia

• Peaked T-waves (even when inverted)
• Widening of the QRS (often marked)
• Prolonged PR-interval
• Flattening and eventual loss of P-waves
• Bizarre tachydysrhythmias, pseudo ventricular tachycardia
• Bizarre bradydysrhythmias, advanced AV Blocks and sinus pauses
• Axis changes (especially RAD)
• Fascicular & Bundle Branch Blocks
• Pseudo ACS with ST-segment changes (can mimic STEMI)
• Pseudo Brugada syndrome pattern
• Sine wave morphology

Causes of Rightward Axis Deviation

• Ventricular ectopy
• Right ventricular hypertrophy
• Left posterior fascicular block
• Lateral MI (from Q-waves in lead I)
• Na⁺channel blocker toxicity
• Hyperkalemia
• Pulmonary HTN – Acute (PE) & chronic lung disease (COPD)
• Lead misplacement / Dextrocardia
• Normal variant in young kids & thin adults with horizontally positioned hearts

Causes of Rightward Axis + ST-segment elevation mimicking STEMI (which usually does not produce rightward axis)

• Hyperkalemia
• Na⁺channel blocker toxicity
• Pulmonary HTN – Acute (PE) & chronic lung disease (COPD)

Final take-home points:

• Beware hyperkalemia!!
  • Peaked T’s
  • Widening of QRS
  • Prolonged PR
  • Flattening and eventual loss of P’s
  • Tachycardias
  • Bradycardias, AV blocks and sinus pauses
  • Pseudo-ACS, new BBB’s, ST changes
  • Sine wave
• STE common in V1-V2, and aVR in hyperkalemia
• Large PE’s can often mimic STEMI with ST-segment elevation (especially in rightward leads)
• STEMI’s don’t tend to produce a rightward axis
• Rightward axis in apparent “STEMI”? Pay attention to the axis and consider large PE and hyperkalemia!