Interesting Trigeminy – ECG Challenge – Discussion

Interesting Trigeminy – ECG Challenge – Discussion

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The rhythm strip shows ventricular ectopic trigeminy. The beat marked as VPC is a ventricular ectopic beat because:

1. It is not preceded by a P wave
2. Has a wide bizarre QRS complex
3. Secondary ST depression and T wave inversion
4. Followed by a compensatory pause

The next beat marked as a fusion beat:

1. Has a P wave partly hidden by the QRS (marked by red stepped arrow)
2. Width and morphology intermediate between the VPC and the next sinus beat (with preceding P wave and narrow QRS).
3. Occurs just before the next expected sinus beat

The ventricular ectopic beat which has fused with the next sinus beat is a late diastolic ectopic as it has occurred after the P wave of the next cycle. In a fusion beat, ventricular activation is partly contributed by the ectopic beat and partly by the conducted sinus beat. The occurrence of fusion beats in ventricular tachycardia has been called Dressler beat after the person who described it [1].

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Reference

1. William Dressler, Hugo Roesler. The occurrence in paroxysmal ventricular tachycardia of ventricular complexes transitional in shape to sinoauricular beats; a diagnostic aid. Am Heart J. 1952 Oct;44(4):485-93.