Pseudo Atrioventricular Block Research Articles

PC-577-01 FASCICULAR ECTOPY FROM THE RIGHT CORONARY SINUS OF VALSALVA

Fascicular ectopic complexes (FEC) can cause symptoms and pseudo atrio-ventricular block (AVB). Ablation is a viable option but carries a risk of AVB. Successful far-field ablation of left anterior fascicular beats from right aortic sinus of Valsalva (RASoV) has been reported. We present a case of FEC with earliest HPS signal and successful ablation from the RASoV. N/A A 60-year-old woman had palpitations and blocked P waves. ECG revealed frequent FEC and occasional blocked P waves (fig. 1a). We postulated this to be due to concealed FEC (pseudo AVB). She failed flecainide and presented for ablation. A decapolar catheter was placed across the right His-Purkinje system (HPS). She had frequent FECs with early activation of the HPS. We observed FECs with complete antegrade block within the HPS but retrograde penetration into the atrium proving this as the mechanism for pseudo AVB (fig. 1b). Activation mapping of the right and left (retroaortic) HPS was performed with the earliest HPS potential on the decapolar catheter as the fiducial reference. Activation progressed retrograde to the proximal His and antegrade to the RBB, both being later than the distal His. Similarly, the left bundle branch and both fascicles were late. Mapping in the RASoV identified a His-like signal in sinus rhythm that was the earliest site in FEC, 7 ms ahead of reference (fig 1c & d). Focal radiofrequency ablation immediately abolished FECs. Monitoring overnight revealed no further FECs or blocked P waves, and patient reported relief of symptoms. Mapping of FEC should include the RASoV. The anatomic basis for such fascicular potential in the RASoV may be the dead-end tract of the conduction axis reported by Kurosawa and Becker.

Second-degree atrioventricular block revisited

Type I second-degree atrioventricular (AV) block describes visible, differing, and generally decremental AV conduction. The literature contains numerous differing definitions of second-degree AV block, especially Mobitz type II second-degree AV block. The widespread use of numerous disparate definitions of type II block appears primarily responsible for many of the diagnostic problems surrounding second-degree AV block. Adherence to the correct definitions provides a logical and simple framework for clinical evaluation. Type II second-degree AV block describes what appears to be an all-or-none conduction without visible changes in the AV conduction time before and after the blocked impulse. Although the diagnosis of type II block requires a stable sinus rate, absence of sinus slowing is an important criterion of type II block because a vagal surge (generally a benign condition) can cause simultaneous sinus slowing and AV nodal block, which can superficially resemble type II block. Furthermore, type II block has not yet been reported in inferior myocardial infarction (MI) and in young athletes where type I block may be misinterpreted as type II block. The diagnosis of type II block cannot be established if the first postblock P wave is followed by a shortened PR interval or the P wave is not discernible. A narrow QRS type I block is almost always AV nodal, whereas a type I block with bundle branch block barring acute MI is infranodal in 60-70% of cases. A 2:1 AV block cannot be classified in terms of type I or type II block, but it can be nodal or infranodal. A pattern resembling a narrow QRS type II block in association with an obvious type I structure in the same recording (e.g., Holter) effectively rules out type II block because the coexistence of both types of narrow QRS block is exceedingly rare. Concealed (nonpropagated) His bundle or ventricular extrasystoles may mimic both type I and/or type II block (pseudo AV block). All correctly defined type II blocks are infranodal. Infranodal block presenting with either type I or II manifestations requires pacing regardless of QRS duration or symptoms.

Atrial lead threshold testing failure: are we seeing double?

An atrial pacing threshold is shown ( Figure 1A ). Modality of pacing is AAI at 90 bpm. The first paced beat is followed by two consecutive ventricular depolarizations. The second atrial paced beat is not followed by any ventricular-related sensed beat. The third is normally conduced to the ventricles. The electrocardiographic behaviour observed concomitantly to the first two atrial paced beats is explained with a double response ( Figure 1B ) (antegrade conduction over both the fast and the slow AV-nodal pathway) followed by a pseudo-atrioventricular block due to collision of the following antegrade impulse generated by atrial …

Pseudoatrioventricular Block

The diagnosis of Mobitz II (second-degree, atrioventricular [AV]) heart block implies a primary disorder of conduction localized to the His-Purkinje system and the potential for sudden progression to complete heart block.¹However, an ectopic focus located in the His bundle or a bundle branch may, with proper timing, partially penetrate the conduction system and collide with normal sinus impulses, causing either slowing or complete blockage of the sinus impulse. This phenomenon, a manifestation of concealed conduction, may mimic first- or second-degree AV block, including a Mobitz II pattern, resulting in what has been termed<i>pseudoatrioventricular block</i>.²Pseudoatrioventricular and true AV blocks have different therapeutic and prognostic implications. Therefore, identification of pseudoatrioventricular block is clinically important. <h3>REPORT OF A CASE</h3> A 29-year-old woman was admitted to the hospital for elective repair of an ostium primum atrial septal defect. Her admission ECG disclosed normal sinus rhythm, a left-axis deviation, and

Pseudo atrioventricular block

Pseudo first- and second-degree atrioventricular (AV) block can occur due to depressive effects of concealed junctional discharges on AV conduction of sinus impulses. Pseudo AV block is not indicative of a primary impairment of AV conduction and is reversible by interventions that suppress ectopy.

Pseudo Atrioventricular Block

Pseudo first- and second-degree atrioventricular (AV) block can occur due to depressive effects of concealed junctional discharges on AV conduction of sinus impulses. Pseudo AV block is not indicative of a primary impairment of AV conduction and is reversible by interventions that suppress ectopy.

Occurrence of Pseudoatrioventricular Block and Atrioventricular Block in the Same Patient

The term, “pseudoatrioventricular block,” describes an arrhythmia characterized by blocked P waves on the surface electrocardiogram, which reflects the occurrence of concealed junctional premature depolarizations. 1 Langendorf R Mehlman JS Blocked (nonconducted) A-V nodal premature systoles imitating first and second degree A-V block. Am Heart J. 1947; 34: 500-506 Abstract Full Text PDF PubMed Scopus (62) Google Scholar , 2 Rosen KM Rahimtoola SH Gunnar RM Pseudo A-V block secondary to premature nonpropagated His bundle depolarizations: Documentation by His bundle electrocardiography. Circulation. 1970; 42: 367-373 Crossref PubMed Scopus (99) Google Scholar These depolarizations are concealed because of retrograde refractoriness, with resulting absence of premature retrograde P waves, and because of anterograde refractoriness, with resulting absence of premature junctional QRS complexes; however, the concealed junctional premature activation does penetrate the atrioventricular node, so that the subsequent sinus P wave is blocked. This arrhythmia is termed “pseudoatrioventricular block,” since the blocked P wave reflects no intrinsic abnormality of conduction. The phenomenon of pseudoatrioventricular block is thus a compensatory pause seen on the surface ECG, in which the initiating premature beat is electrocardiographically silent.

Pseudo bundle branch block produced by premature impulses arising in the bundle branches

Pseudo bundle branch block, a previously unreported arrhythmia produced by concealed premature impulses arising in the bundle branches, was seen in two patients with sick sinus node syndrome. Although concealed conduction was not apparent in either the surface or intracardiac leads, the latter were essential in localizing the site of manifest impulse formation. Patient 1, with left bundle branch extrasystoles, had pseudo bundle branch block and pseudo atrioventricular block that depended on the timing and extent of concealment of premature depolarization. Because of the coexisting sinus bradycardia in this patient, electrical stimulation and the recording of the right ventricular apical electrograms gave additional information that helped corroborate the postulated mechanisms. Patient 2 had right bundle branch extrasystoles with sinus beats that showed a right bundle branch block pattern possibly caused by pseudo bundle branch block. In this case the possibility that both the automaticity and the conduction disturbance had a mechanical origin could not be excluded.

Unexpected Total Preexcitation Possibly Secondary to Pseudoblock

The term, atrioventricular (AV) block, has been used to characterize a phenomenon in which blocked P waves reflect the occurrence of concealed junctional or fascicular extrasystoles.14 The mechanism of pseudo AV block is concealed conduction of the electrocardiographically silent extrasystole to the AV node, resulting in block of the subsequent P wave. In the present report, we describe a patient with preexcitation who manifested fusion complexes of normal and anomalous pathway conduction during sinus rhythm, and also sporadic QRS complexes with unexpected total preexcitation. The occurrence of junctional extrasystoles in this patient suggested that pseudoblock of the normal AV pathway produced the unexpected beats with total preexcitation.