Diversity of atrioventricular conduction in a female teenager

Abstract

A 13‐year‐old girl was admitted to the Cardiology Clinic of West China Hospital with complains of recurrent palpitations for 1 year, dizziness, and chest tightness. Her ECG intercepted at different time periods in the Holter exhibited complex electrophysiological phenomena, such as sinus arrhythmia, dominant PJB, interpolated PJB, concealed PJB, isolated forward block, insularly retrograde block, reciprocal beat, junctional escape beat, interference atrioventricular dissociation, pseudo‐I°AVB, and pseudo‐II°AVB, which occurred simultaneously. This condition is extremely rare in clinical practice. The patient was prescribed an antiarrhythmic drug (propafenone 50 mg tid). After treatment, the PJB gradually decreased, and the pseudo‐AVB disappeared. Pseudo AVB is generally a benign phenomenon and proper recognition may avoid erroneously permanent pacemaker implantation.

The long lead II strips intercepted at different time periods in the Holter indicate sinus rhythm, sinus arrhythmia, and diversity of atrioventricular conduction.

1. CASE

A 13‐year‐old girl was admitted to the cardiology department of West China Hospital of Sichuan University with complaints of recurrent palpitations, dizziness, and chest tightness for 1 year. She had an irregular pulse, with a pulse rate of 104 beats/min and a blood pressure of 132/84 mmHg on admission. Other physical examination findings were unremarkable. A 24‐h Holter monitor revealed sinus rhythm, sinus arrhythmia, frequent premature beats, and diversified conduction in the atrioventricular junction (Figure 1). The size of each cardiac chamber, determined using echocardiography, was normal, and the measured value of left ventricular systolic function was normal, with a left ventricular ejection fraction (LVEF) of 70%.

FIGURE 1.

Lead II strips excerpted from the 24‐h Holter

On the basis of the findings in Figure 1, what are the ECG diagnoses? what is the mechanism of the considerable diversity in the pattern of atrioventricular conduction?

Interpretation and clinical course (Figure 2).

FIGURE 2.

Diagrammatic representation of the postulated mechanism of diversity of atrioventricular conduction

Strip A indicates sinus rhythm with a P–P interval of 1020 ms and a PR interval of 120 ms. Premature beats (R4 and R8) followed by inverted P' waves (P'4, P'8) can be seen, the shape of which is slightly different from the sinus QRS complex. In addition, the P3–P'4 interval was the same as the P7–P'8 interval, both with a duration of 760 ms, and the compensatory interval was complete, so premature atrial beats can be ruled out. A diagnosis of atrioventricular junction (AVJ) beats with aberrant intraventricular conduction was considered. However, premature ventricular beats (PVBs) were not completely discharged (Figure 2a). Strip B shows an interpolated premature beat (R5, R10, and R13), which is similar in shape to the premature beat in strip A, followed by sinus P waves, suggesting that conduction of impulses from an ectopic focus backward to the atrium is being blocked. Moreover, the subsequent sinus PR interval was significantly prolonged (P5‐R, P9‐R, and P11‐R, with a range of between 200 ms and 280 ms), which is presumed to be due to concealed conduction within the AVJ by premature beats upon the subsequent sinus impulse, resulting in a pseudo‐I° atrioventricular block (AVB, asterisks in Figure 2b). Strip C indicates inverted P' waves (P'6, P'14) without a QRS complex are seen and the durations of the P5–P'6 and P13–P'14 intervals are still equal, both of which are 760 ms, which is consistent with the P–P' interval produced by the dominant premature beat in strip A. Logically, it is assumed that P'6 and P'14 are from the same ectopic focal impulses (J3 and J8) retrograde conduction to the atrium, but at the same time, forward conduction to the ventricle is blocked. This can furtherly rule out PVB, and PJBs from the AVJ were substantiated. Otherwise, the PR interval (240–280 ms) is intermittently prolonged, a phenomenon similar to that in the strip B, which is speculated to result from concealed conduction by the PJB (J1, J2, J4, J6, J7, and J9) in the AVJ area, where a new relative refractory period is generated, causing a pseudo‐I°AVB (asterisks in Figure 2c). Forward conduction of P10 and P17 to the ventricle is blocked, which is considered to be related to the newly generated effective refractory period by the concealed PJB in the ABJ area, causing a pseudo‐II°AVB. Strip D suggests a 2: 1 model of atrioventricular conduction (P1‐P10), which is similar to what is seen in P10 and P17 in strip C.

To confirm the speculations, we performed an electrophysiological study (EPS) on the patient. The His bundle recordings documented frequent premature His spikes with intermittently antegraded and retrograded nonconduction following the premature His deflections, substantiating the existence of His bundle extrasystoles.

2. DISCUSSION

The diversity of conduction in the AVJ caused by concealed PJB was first discovered by Langendorf (Langendorf & Mehlman, 1947) in 1947 and subsequently confirmed by Narula (Narula, 1975) using His bundle electrograms in 1975. The concealed conduction (Jazayeri, 2019) by PJB can generate a new refractory period in the AVJ area and affect the conduction of the subsequent sinus impulse. Due to the longitudinal heterogeneity and anisotropy of the AVJ tissue, PJB in this area is prone to form retrograde block, forward block, and both retrograde and forward blocks at the same time, resulting in some special electrophysiological phenomena (Higuchi et al., 2021; Morgan et al., ²⁰²²).

Distinguishing between true and pseudo‐AVBs is critical and may influence clinical decision‐making. Pseudo‐AVB is generally a benign phenomenon and proper recognition of it may avoid erroneously permanent pacemaker implantation (Kawji & Glancy, 2018). In this patient, complex electrophysiological phenomena, such as sinus arrhythmia, dominant PJB, interpolated PJB, concealed PJB, isolated forward block, insularly retrograde block, pseudo‐I°AVB, and pseudo‐II°AVB, occurred simultaneously. This condition is extremely rare in clinical practice.

The patient was prescribed an antiarrhythmic drug (propafenone 50 mg tid). After treatment, the PJB gradually decreased, and the pseudo‐AVB disappeared.

AUTHOR CONTRIBUTIONS

Xianchao Jing contributed significantly to data collection and manuscript preparation. Qingyong Chen reviewed the whole manuscript. All the authors agree on the order in which their names will be listed in the manuscript.

CONFLICT OF INTEREST

None.

ETHICAL APPROVAL

All procedures performed in this study were in accordance with the ethical standards of the Ethics Committee of West China Hospital of Sichuan University and written consent has been obtained from the patient.

Chen, Q. , & Jing, X. (2023). Diversity of atrioventricular conduction in a female teenager. Annals of Noninvasive Electrocardiology, 28, e13023. 10.1111/anec.13023

DATA AVAILABILITY STATEMENT

All data generated or analyzed during this study are included in this published article.