I read with interest the case report by Ho and colleagues.
1
I would like to present arguments suggesting alternative diagnoses.The tracing recorded during ambulatory electrocardiogram was interpreted as “Mobitz II AV [atrioventricular] block” because “the P-P and PR intervals are constant before and after the blocked P wave.” However, I found a progressive increase in the 4 first P-P cycle lengths before a decrease in the last 2 (980/1060/1180/1240/1160/1100 ms). The blocked P wave is preceded by the longest P-P interval (1240 ms). In addition, the PR following the blocked P is shorter by ≈20 ms than the previous PR interval. Therefore, this block should be called “atypical Mobitz-type II AV block,”
2
which is vagally mediated and located at the AV node.2
Exercise usually abolishes this type of block and fast rates with 1:1 AV conduction are possible so that pacemaker implantation is not required.The tracing recorded during treadmill exercise stress test was interpreted as suggesting “a His extrasystole likely blocked antegrade in the His-Purkinje system with…retrograde atrial activation…(pseudo-AV block).” I would rather suggest we are dealing with short-coupled (≈320 ms) pleomorphic extrasystoles originating from the left ventricular Purkinje system.
3
Thus the retrograde P wave originates from a concealed Purkinje extrasystole that fails to depolarize the ventricle.4
A left ventricular origin of the Purkinje ectopy has been frequently observed in women.5
Only electrophysiologic study after discontinuation of flecainide will enable to confirm or infirm my presumed diagnosis. This may be a difficult task, since there is no certitude that the Purkinje ectopic beats will recur. Use of provocative tests may be necessary.
6
Funding Sources
The author has no funding sources to disclose.
Disclosures
The author has no conflicts of interest to disclose.
References
- Concealed His extrasystoles: a masquerader of atrioventricular block.HeartRhythm Case Rep. 2022; 8: 727-729
- Vagally mediated atrioventricular block: pathophysiology and diagnosis.Heart. 2013; 99: 904-908
- Short-coupled idiopathic ventricular fibrillation: a literature review with extended follow-up.JACC Clin Electrophysiol. 2022; 8: 918-936
- Short-coupled ventricular fibrillation.J Cardiovasc Electrophysiol. 2016; 27: 1236-1237
- Sex differences in the origin of Purkinje ectopy-initiated idiopathic ventricular fibrillation.Heart Rhythm. 2021; 18: 1647-1654
- Idiopathic ventricular fibrillation: role of Purkinje system and microstructural myocardial abnormalities.JACC Clin Electrophysiol. 2020; 6: 591-608
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Published online: October 21, 2022
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- Concealed His extrasystoles: A masquerader of atrioventricular blockHeartRhythm Case ReportsVol. 8Issue 11
- PreviewConcealed His extrasystoles are a well-known masquerader of atrioventricular (AV) block. It is therefore necessary to consider pseudo-AV block in patients who develop unexpected AV block without a clear etiology. In this report, we present a case of a 46-year-old female patient who was found to have pseudo–Mobitz II AV block secondary to His extrasystoles diagnosed on surface electrocardiogram (ECG) without requiring invasive electrophysiology study. We also demonstrated in this patient that flecainide can be an effective treatment for His extrasystoles.
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