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The electrocardiogram (ECG) at admission showed a broad complex tachycardia of 138 bpm with superior axis, left bundle branch block (LBBB) morphology and a transition in lead V5. There was no apparent atrioventricular (AV) dissociation. His device for cardiac resynchronisation therapy with defibrillator function (CRT-D) was interrogated and showed a regular tachycardia with 1:1 AV relationship and a short ventriculoatrial (VA) time (<60 ms, not compatible with a concealed bypass) (Fig. 1a).
a Implantable cardioverter defibrillator tracing. b Unsuccessful overdrive pacing with relatively long post-pacing interval (A atrial lead electrogram, RV‑N right ventricular lead near-field electrogram, RV‑F right ventricular far-field electrogram, PPI post-pacing interval)
Ventricular overdrive pacing was performed from the right ventricular (RV) lead (located at the RV apex) at 94%, 88% and 84% of the tachycardia cycle length. With the RV bursts at 94% and 88% of the tachycardia cycle length, the tachycardia did not terminate but was entrained. Fig. 1b shows the response to entrainment with a ventricular-atrial-ventricular (V-A-V) response and a long post-pacing interval. At 84% of the cycle length, the arrhythmia was terminated (unlikely for atrial tachyarrhythmia).
An electrocardiogram without biventricular pacing (Fig. 2) showed sinus rhythm with a broad LBBB with identical QRS morphology as the tachycardia. In conclusion, there was a broad complex tachycardia without AV dissociation, a QRS morphology identical to non-paced conducted sinus rhythm, a short VA interval and a long post-pacing interval as a result of entrainment from the RV apex, all findings compatible with AV nodal re-entry tachycardia.
Electrocardiogram without pacing
The metoprolol dosage was increased and the patient was instructed to perform Valsalva manoeuvre in case of palpitations. Alternative treatment with a calcium channel blocker was less opportune regarding the negative inotropic effects, preferably avoided in this patient with non-ischaemic cardiomyopathy. In case of recurrence, ablation will be considered.
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M.V. Regeer, L.F. Tops and M. de Riva Silva declare that they have no competing interests.
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Regeer, M.V., Tops, L.F. & de Riva Silva, M. Broad complex tachycardia; never judge a book by its cover. Neth Heart J 29, 173–174 (2021). https://doi.org/10.1007/s12471-020-01496-w
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DOI: https://doi.org/10.1007/s12471-020-01496-w