ECG of the Week - 25th March 2013 - Interpretation

This ECG is from a 40 yr old male who presented following a large overdose of an anti-spasmodic agent.

Click to enlarge

Rate:

• 66

Rhythm:

• Sinus Arrhythmia

Axis:

• Inferior (+90 deg)

Intervals:

• PR - Normal (~120ms)
• QRS - Normal (~80ms)
• QT - 560-600ms (QTc Bazette ~ 610-630 ms)
• Note absolute QT interval greater than 1/2 of R-R interval

Segments:

• Up-stroked ST segment I, V2-4

Additional:

• T Wave Inversion aVL, aVR

Interpretation:

• Marked QT Prolongation
• Secondary to toxic ingestion
• Using QT-RR Nomogram as described by Chan et al. this patient is 'at risk' of developing Torsades de Pointes

Check out the links below for more examples of toxicological QT prolongation from Life in the Fast Lane, and a link to the Chan et al. article describing a QT nomogram for TdP risk stratification in drug-induced QT prolongation.

References / Further Reading

Life in the Fast Lane Blog

• The QT Interval here
• Drugs Causing QT Prolongation here
• Clinical cases of drug-induced QT prolongation
• Quetiapine here
• Citalopram here
• Polymorphic VT & TdP here

The Blunt Dissection Blog

• ECG & Case of toxicological QT prolongation here

Article

• Chan A, Isbister GK, Kirkpatrick CMJ, Duffu SB. Drug-induced QT prolongation and torsades de pointes: evaluation of a QT nomogram. QJM 2007 100(10):609-615 PMID: 17881416 Full text here

Textbook

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