ECG of the Week - 12th June 2017 - Interpretation

The following ECG is from an 81yr old female who presented complaining of dizziness, nausea and fatigue. She has a history of pulmonary hypertension and paroxysmal atrial fibrillation.

  

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Rate:

• Ventricular rate ~36 bpm
• Atrial rate ~72 bpm

Rhythm:

• Regular ventricular complexes
• Regular atrial complexes
• 2:1 AV Block

Axis:

• Right axis deviation

Intervals:

• PR - Normal (~160-180ms)
• In conducted complexes
• QRS - Prolonged (120ms)

Additional:

• RBBB Morphology
• Not entirely classic appearance
• ST Depression II, III, aVF, V2-4
• ST Elevation lead aVL
• Only 1 full complex captured which has 1mm STE
• Partially captured ST segment shows less ST elevation
• ? Artefact
• Biphasic T wave leads V2-3

Interpretation:

• 2:1 AV block
• QRS Prolongation favours Mobitz II / Infra-nodal block
• Abnormal QRS morphology and ST/T wave changes

The ST and T wave changes on the ECG are interesting and raise the question of potential causes for the conduction abnormality. Differentials for these features include:

• Ischaemia / ACS
• Electrolyte Abnormality
• Drug effect especially digoxin
• Cardiomyopathy
• Myocarditis
• Hypothermia
• Hypothyroid / Hyperthyroid

Interestingly in our case there was no discernible or reversible cause identified for her conduction abnormality.

What happened ?

The patient was commenced on iv isoprenaline infusion due to symtomatic nature of the bradyarrhythmia. Medication review relieved no culprit mediation and her electrolytes and cardiac biomarkers were normal. She underwent an uncomplicated dual chamber PPM insertion, settings DDD-CLS 60-130 bpm, and was discharged following a brief in-patient stay. The DDD code refers to pacing and sensing of both atria and ventricles with potential response of either inhibition or triggering of pacing. The CLS is a Biotronik proprietary Closed-Loop Simulation algorithm (explained here) 

References / Further Reading

 

Life in the Fast Lane

• Pacemaker Function
• 2:1 AV Block
• 2nd Degree AV Block Mobitz II

Textbook

• Chan TC, Brady WJ, Harrigan RA, Ornato JP, Rosen P. ECG in Emergency Medicine and Acute Care. Elsevier Mosby 2005.