Accessory atrioventricular muscle bundles of the developing human heart

Truex, Raymond C.; Bishof, J. K.; Hoffman, E

doi:10.1002/ar.1091310105

Cited by 84 publications

(14 citation statements)

References 16 publications

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“…7 However, numerous accessory AV myocardial connections can be identified until the end of the second trimester of pregnancy. Comparable to other studies, 16 these accessory AV myocardial connections were observed at the subendocardial aspect …”

Section: Discussionsupporting

confidence: 75%

“…Previous studies have demonstrated the presence of accessory myocardial AV connections between atrial and ventricular myocardium during normal embryological and fetal heart development in humans 16,31,32 and other mammals. 9,10 However, the present study for the first time systematically describes the presence and specific locations of gradually disappearing accessory AV myocardial connections that cross the developing annulus fibrosus in human embryonic, fetal, and neonatal hearts.…”

Section: Discussionmentioning

confidence: 99%

“…AVRT in this age group has been speculated to originate from the transient presence of conducting APs during the normal process of maturation of the annulus fibrosus. 8,16 The development of this isolating structure involves several processes in which the endocardial cushions that line the luminal side of the primitive AV canal, together with the inward migration of the epicardially located AV sulcus tissue, play an important role. [17][18][19] Recently, it has been shown in more detail that a combination of bone morphogenetic protein signaling, 20,21 periostin (an osteoblast-specific factor), 22 and epicardiumderived cells that enter the heart at the AV sulcus play a key role in this process.…”

Section: Discussionmentioning

confidence: 99%

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Accessory Atrioventricular Myocardial Connections in the Developing Human Heart

et al. 2008

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Background-Fetal and neonatal atrioventricular (AV) reentrant tachycardias can be life-threatening but resolve in most cases during the first year of life. The transient presence of accessory AV myocardial connections during annulus fibrosus development may explain this phenomenon. Methods and Results-A total of 45 human embryonic, fetal, and neonatal sectioned hearts (4 to 36 weeks of development)were studied immunohistochemically. Accessory myocardial AV connections were quantified and categorized according to their specific location, and 3D reconstructions were made. Between 4 and 6 weeks of development, the atrial and ventricular myocardium was continuous at the primitive AV canal. At 6 to 10 weeks, numerous accessory myocardial AV connections were identified in the left (45%), right (35%), and septal (20%) regions of the AV junction. Most right-sided accessory connections comprised distinct myocardial strands, whereas left-sided connections consisted of larger myocardial continuities. At 10 to 20 weeks, all accessory AV connections comprised discrete myocardial strands and gradually decreased in number. The majority of accessory connections were located in the right AV junction (67%), predominantly in the lateral aspect (45%). Seventeen percent of the accessory connections were observed in the left AV junction, and 16% were observed in the septal region. 3D reconstructions of the developing AV nodal area at these stages demonstrated multiple AV node-related accessory connections. From 20 weeks until birth, and in neonatal hearts, no further accessory myocardial AV connections were observed. Conclusions-Isolation of the AV junction is a gradual and ongoing process, and right lateral accessory myocardial AV connections in particular are commonly found at later stages of normal human cardiac development. These transitory accessory connections may act as substrate for AV reentrant tachycardias in fetuses or neonates. (Circulation. 2008;117: 2850-2858.)

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Section: Discussionsupporting

confidence: 75%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Accessory Atrioventricular Myocardial Connections in the Developing Human Heart

et al. 2008

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“…Pacing of the His bundle was performed in an additional three 35,52,6 The association of Ebstein's anomaly and additional accessory atrioventricular pathways has been reported. 34 Review of the literature uncovered six well-studied case reports.…”

Section: Studies During Observed Arrhythmiasmentioning

confidence: 99%

Role of Mahaim fibers in cardiac arrhythmias in man.

Gallagher¹,

Smith²,

Kasell³

et al. 1981

Circulation

273

128

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SUMMARY Twelve patients with evidence of Mahaim fibers are reported, six with nodoventricular (NV) fibers and six with fasciculoventricular (FV) fibers. All patients with NV fibers had left bundle branch block morphology, and a sustained reentrant tachycardia with this morphology was proved in each case. In three of the six, ventriculoatrial dissociation occurred during tachycardia. We postulate that the mechanism of this tachycardia is a macroreentry circuit using the NV fiber for the antegrade limb and the His-Purkinje system with a portion of the atrioventricular node for the retrograde limb. ECGs of patients with FV fibers were varied, suggesting a functional relation to the right or left side of the septum. No direct relationship of FV fibers to observed arrhythmias could be found.THE ROLE of Mahaim fibers in the genesis of cardiac arrhythmias in man has been controversial since they were first described.' The initial report was limited to fibers connecting the His bundle to the septum, but this was soon broadened to include fibers connecting the atrioventricular (AV) Received March 25, 1980; revision accepted November 14, 1980. Circulation 64, No. 1, 1981. All patients were admitted to the hospital and placed on continuous telemetry; all cardioactive medications were discontinued. Before cardiac catheterization, all had history and physical examination, routine blood work, ECG, chest x-ray, and twodimensional echocardiography using a microcavitation technique. All patients gave informed consent before catheterization. Electrophysiologic StudyAll patients were studied in the postabsorptive, nonsedated state using techniques previously described.15' 60, 58, '9 Multiple electrode catheters were used to record and pace from the right atrium, the left atrium via the coronary sinus, and the right ventricle. Observations were made during overdrive pacing and refractory period determination from all three locations, during tachycardia and after deliberate induction of atrial fibrillation. TerminologyRecently, Anderson et al.'5 suggested that there are two main anatomic types of Mahaim fibers -nodoventricular (NV) fibers, which arise from the AV node, and fasciculoventricular (FV) fibers, which arise from the His bundle and bundle branches. Because the functional consequences are significant, we have found it useful to consider the two groups separately according to an anatomic and functional classification ( fig. 1). Anderson et al. proposed two varieties of NV fibers -those which arise from the transitional zone of the AV junction and those which arise from the deep, compact nodal portion of the AV junction. NV fibers, depending on level of takeoff relative to the area of physiologic delay, can be associated with either a short or normal PR interval. Ventricular activation in this case results from fusion of impulse propagation via the NV fiber and the normal conduction system, resulting in QRS complexes with varying degrees of anomalous conduction. The PR interval should be normal with isolated FV fibers...

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“…It has been suggested that APs involved in these tachycardias are remnants of the primary AV canal myocardium, which disappear during development and maturation of the annulus fibrosus before and after birth (12,18). Although presence of APs has been demonstrated during normal cardiac development in human fetuses and neonates, their etiology and conducting properties as well as their causative role in AVRT are largely unrevealed (17)(18)(19)(20). It is known that APs can be associated with congenital heart disease specifically with abnormal tricuspid valve development like in Morbus Ebstein (21).…”

Section: Discussionmentioning

confidence: 99%

Accessory Atrioventricular Myocardial Pathways in Mouse Heart Development: Substrate for Supraventricular Tachycardias

et al. 2011

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Atrioventricular reentry tachycardia (AVRT) requiring an accessory atrioventricular pathway (AP) is the most common type of arrhythmia in the perinatal period. The etiology of these arrhythmias is not fully understood as well as their capability to dissipate spontaneously in the first year of life. Temporary presence of APs during annulus fibrosus development might cause this specific type of arrhythmias. To study the presence of APs, electrophysiological recordings of ventricular activation patterns and immunohistochemical analyses with antibodies specifically against atrial myosin light chain 2 (MLC-2a), Periostin, Nkx2.5, and Connexin-43 were performed in embryonic mouse hearts ranging from 11.5 to 18.5 days post-conception (dpc). The electrophysiological recordings revealed the presence of functional APs in early (13.5-15.5 dpc) and late (16.5-18.5 dpc) postseptated stages of mouse heart development. These APs stained positive for MLC-2a and Nkx2.5 and negative for Periostin and Connexin-43. Longitudinal analyses showed that APs gradually decreased in number (p ϭ 0.003) and size (p ϭ 0.035) at subsequent developmental stages (13.5-18.5 dpc). Expression of periostin was observed in the developing annulus fibrosus, adjacent to APs and other locations where formation of fibrous tissue is essential. We conclude that functional APs are present during normal mouse heart development. These APs can serve as transient substrate for AVRTs in the perinatal period of development. (Pediatr Res 70: 37-43, 2011)

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Accessory atrioventricular muscle bundles of the developing human heart

Cited by 84 publications

References 16 publications

Accessory Atrioventricular Myocardial Connections in the Developing Human Heart

Accessory Atrioventricular Myocardial Connections in the Developing Human Heart

Role of Mahaim fibers in cardiac arrhythmias in man.

Accessory Atrioventricular Myocardial Pathways in Mouse Heart Development: Substrate for Supraventricular Tachycardias

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