Seamless Transition Between Narrow- and Wide-QRS Tachycardia Revealing Double Tachycardia

Figures

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  Visual Summary. Supraventricular Tachycardia and Ventricular Tachycardia are Competing with Each Other Alternating narrow- and wide-QRS tachycardias with progressive fusion suggest double tachycardia rather than simple aberrant conduction. ECG = electrocardiogram; PSVT = paroxysmal supraventricular tachycardia; VT = ventricular tachycardia.

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  Figure 1. A Rhythm Strip in the Emergency Department Continuous rhythm strip obtained in the emergency department demonstrating repeated seamless transitions between wide- and narrow-QRS tachycardia with progressive fusion.

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  Figure 2. Initial 12-Lead Electrocardiogram Obtained in the Emergency Department Demonstrating Sustained Wide-QRS Tachycardia With a Left Bundle Branch Block Morphology A fusion beat (red arrows) and a capture beat (blue arrow) are observed.

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  Figure 3. Second 12-Lead Electrocardiogram Obtained in the Emergency Department Narrow-QRS tachycardia terminates, followed by wide-QRS tachycardia after several sinus rhythm complexes. Retrograde P waves (red arrows) are observed immediately after each QRS complex, and termination of the narrow-QRS tachycardia occurs following a retrograde P wave, suggesting PSVT. PSVT = paroxysmal supraventricular tachycardia.

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  Figure 4. Isoproterenol Infusion Induced Manifest Preexcitation The earliest ventricular activation (red arrow) is recorded at the coronary sinus 1 to 2 electrodes located at the lateral mitral annulus.

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  Figure 5. Induction of Orthodromic Atrioventricular Reentrant Tachycardia (AVRT) Double atrial extrastimulation (500/300/250 ms) induces orthodromic AVRT. The earliest atrial activation (red arrow) is recorded at the coronary sinus 1 to 2 electrodes located at the lateral mitral annulus. AVRT = atrioventricular reentrant tachycardia.

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  Figure 6. Acceleration of Orthodromic AVRT by Superimposed Ventricular Tachycardia (VT) The first 2 narrow-QRS complexes are preceded by His bundle potentials (red arrows), which disappear with the onset of accelerated VT. AVRT = atrioventricular reentrant tachycardia; VT = ventricular tachycardia.

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  Figure 7. Transition from VT to Orthodromic AVRT Spontaneous termination of VT results in seamless continuation of orthodromic AVRT with aberrant conduction (right bundle branch block morphology) via the left lateral accessory pathway. His bundle potentials (red arrows) precede each QRS complex. AVRT = atrioventricular re-entrant tachycardia; VT = ventricular tachycardia.

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  Figure 8. Atrioventricular Dissociation During VT After Accessory Pathway Ablation Following successful ablation of the left lateral accessory pathway, atrioventricular dissociation is observed during VT (red arrows). VT = ventricular tachycardia.