Clinical/electrophysiologic characteristics of infranodal Wenckebach in patients with indication for permanent ventricular pacing: A prospective study

BACKGROUND

Infranodal Wenckebach is rare and not well characterized.

OBJECTIVE

We prospectively studied clinical and electrophysiologic characteristics of patients with atrioventricular (AV) Wenckebach with an indication for permanent ventricular pacing.

METHODS

During a 2-year period, all patients with an indication for permanent ventricular pacing underwent targeted preimplantation electrophysiologic study. Clinical and electrophysiologic characteristics at presentation and ventricular pacing percentage at 6-month follow-up were evaluated.

RESULTS

A total of 163 patients (median age, 68 [interquartile range, 60-74] years; male, 59%; median QRS duration, 110 [90-130] ms; complete AV block in 123 [75.5%]) were included. AV Wenckebach was noted in 22 (13.4%) patients (median age, 70 [63-76.5] years; male, 54%; median QRS duration, 120 [110-140] ms) and classified as infranodal (12/163 [7.3%]) vs AV nodal (10/163 [6.1%]). Patients with infranodal Wenckebach (infrahisian in all), compared with AV nodal Wenckebach, demonstrated higher frequency with left ventricular ejection fraction ≤40% (41.7% vs 0%; P = .04), longer median HV interval (90 vs 49 ms; P = .005), lower frequency of isolated first-degree AV block (8.3% vs 60%; P = .02), higher frequency of right bundle branch block with left anterior fascicular block (75% vs 10%; P = .003), lesser PR increment at onset of AV Wenckebach (20.5 vs 80 ms; P = .002), and onset of 2:1 AV block at longer cycle lengths (91.7% vs 20%; P = .002).

CONCLUSION

Of patients referred for pacemaker implantation, infranodal Wenckebach was present in 27.5% (11/40) without complete AV block. It was as frequent as AV nodal Wenckebach and associated with characteristic electrophysiologic findings.

Review of His-Purkinje System Abnormality with Case Studies

A single beat arising as extra systole within the His-Purkinje system or from ventricle or even atrium based on conduction timing can invoke delayed conduction or block within intra-Hisian or infra-Hisian sites. This may be either manifested in the form of premature atrial or ventricular complexes or concealed as with His extra systoles. It appears commonly there is disease within the His-Purkinje system.

Infra-Hisian block as cause of Wenckebach's phenomenon in an asymptomatic middle-aged man

We report the case of a 60-year-old man with asymptomatic sinus bradycardia and Holter recording showing episodes of Wenckebach block alternating with episodes of 2:1 block. Electrophysiological testing revealed Infra-Hisian block with progressive prolongation of the H-V interval resulting in block after H potential. This produced typical Wenckebach-type block on surface electrocardiogram resembling the clinical one. The patient was successfully treated with permanent dual-chamber pacemaker implantation.