The conduction system in tricuspid atresia with and without regular (d-) transposition

Introduction to the Congenital Heart Defects: Anatomy of the Conduction System

The position and course of the conduction system in congenital heart disease are intricately tied to the underlying congenital malformation. Although only subtle differences exist between the anatomy of the conduction axis for simple congenital heart lesions and normal anatomy, almost every patient with congenital heart disease harbors some important anatomic variation. This article summarizes the body of literature by retaining original classical concepts and by attempting to translate the available knowledge into useful points for the congenital heart disease specialist. This discussion spans the entire spectrum of simple to complex congenital heart disease.

Bradyarrhythmias in Congenital Heart Disease

Bradyarrhythmias in adults with congenital heart disease (CHD) comprise a complex group of arrhythmia disorders with congenital and acquired origins, highly variable long-term sequelae, and complicated treatment options. They can develop across the spectrum of CHD defects and can be encountered at all ages. Although permanent pacing is effective in treating bradyarrhythmias, it is associated with many complications and morbidity, where it is often used early in life. This section discusses the incidence and prevalence of bradyarrhythmias in the CHD population, their timing of occurrence with respect to specific disease entities and interventions, and their short- and long-term clinical sequelae.

Understanding the morphology of the specialized conduction tissues in congenitally malformed hearts

To repair congenital heart defects by means of open heart surgery, the surgeon needs guidance about the location and distribution of the specialized conduction tissues, in order to avoid their direct damage and consequent conduction disturbances. This review addresses the historical steps of the morphological study of the conduction system in different types of heart defects, providing updated information about the subject.

Arrhythmias in adult congenital heart disease

Recent advances in pediatric cardiology and cardiac surgery have allowed a rapidly expanding population of patients with congenital heart disease to thrive well into their adult years. Often after prolonged uneventful clinical courses as children and adolescents, arrhythmias may surface later in life. These arrhythmias are a major source of morbidity. In addition, sudden death is the leading cause of mortality in adult patients with congenital heart disease. This review highlights the various types of brady- and tachyarrhythmias encountered in the more common forms of adult congenital heart disease and explores prognostic implications and therapeutic options.

Ablation of Atrioventricular Nodal Reentrant Tachycardia in Tricuspid Atresia

A 31-year-old woman with tricuspid atresia and a palliative Waterston shunt presented with intractable poorly tolerated supraventricular tachycardia. Electrophysiologic evaluation was consistent with AV nodal reentrant tachycardia. The fast pathway region was mapped electroanatomically during tachycardia and with constant rate ventricular pacing. Successful radiofrequency ablation was achieved by placement of lesions in an area adjacent and inferior to the His-bundle electrogram on the left side of the septum.

Analysis of the hypoplastic right ventricle utilizing electrocardiographic body surface potential mapping (BSPM)

The authors present electrocardiographic body surface potential maps (BSPMs) of 11 patients with hypoplastic right ventricle (HRV) of three types: type I, HRV with pulmonary atresia; type II, HRV with tricuspid atresia; and type III, HRV with tricuspid artesia and transposition of the great arteries. The BSPMs of all 11 patients demonstrated evidence for epicardial right ventricular breakthrough, indicating conduction through an intact right bundle branch and Purkinje system. Nonetheless, the BSPMs strongly suggested profound morphological, probably embryological, differences among the right ventricles of the three groups. The four patients with type I HRV had no evidence for conduction abnormality. The five patients with type II, HRV however, had very marked conduction abnormality. In four of these five, the standard ECG and VCG had initial forces suggesting left lateral wall myocardial infarction. The BSPMs showed no evidence for infarction but demonstrated very complicated slow initial activation, explaining why the initial QRS vector was to the right and posterior before extending leftward. In addition, in all five the initial positive potentials were unusually inferior and the initial negative potentials unusually superior. After the evidence for epicardial right ventricular breakthrough, the positive and negative potentials rapidly changed positions so that the positive potentials were unusually superior and the negative potentials unusually inferior, consistent with the BSPM of endocardial cushion defects. In four of these five there was marked delay of total ventricular activation time. Of the two patients with type III HRV, one had an initial QRS similar to that of type II. Neither had rapid change of inferior and superior positive and negative potentials after right ventricular breakthrough, and both had intraventricular slowing, one with partial left bundle branch block.

Atrioventricular conduction tissues in univentricular hearts of left ventricular type with absent right atrioventricular connection ('tricuspid atresia')

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Atresia of the right atrioventricular orifice with atrioventricular concordance

Three hearts are described in which a fibrous membrane was interposed between the right atrium and a formed but hypoplastic right ventricle, which possessed recognisable inlet, trabecular, and infundibular components. In these hearts the distribution of the conducting tissue was as expected for concordant atrioventricular connections, and contrasts with that seen in the classical type of 'tricuspid atresia'. The distinctive morphological and histological features of these specimens lend further support to our view that the majority of cases of atresia of the right atrioventricular orifice should be regarded as coming within the designation of 'the univentricular heart'.

Electrophysiologic studies in tricuspid atresia

Five patients with tricuspid atresia underwent His bundle studies with the recording catheter placed close to the mitral valve ring. Right atrial pacing and measurement of the refractory periods were performed in three. The prolonged intraatrial conduction time found in all patients is thought to be caused by a hypertrophied and dilated right atrium with increased internodal distance due to stretching of internodal pathways. The A-H interval was normal in all; the H-V interval was short in three and normal in two. The pattern of left axis deviation in the group with a short H-V interval is thought to be due to early origin of the posterior branches of the left bundle branch from the bundle of His and early activation of the posteroinferior parts of the left ventricle. The pattern of left axis deviation in the group with a normal H-V interval may be related to the previously reported anomalous course of the left bundle. Atrial pacing produced a normal response. The refractory periods were within normal range, suggesting functional integrity of conduction through the atrioventricular node and bundle branches.

Morphological and topographical variations of the outlet chamber in complex congenital heart disease: an angiocardiographic study

The outlet chamber of the human heart can show considerable variations in its morphology and topography (relationship to main ventricular chamber), and such variations in anatomy and spacial relationship may be predictive of the associated intracardiac anatomy. Although there is considerable debate about whether the position of the outlet chamber is indicative of the type of bulboventricular loop (whether D- or L-), a right-sided and anterior outlet chamber has different implications than a left-sided, superior, and more posterior positioned one. The inflows into the outlet chamber can vary anatomically, and progressive changes in the calibers of these communications can adversely alter the natural history. One or both of the greak vessels, or neither, or a persistent truncus arteriosus can originate from the outlet chamber, and any significant morphological change in the outlet chamber may or may not adversely affect either the pulmonary or systemic blood supply, or both. Finally, any consideration of the outlet chamber raises important conceptual difference in terminologies. At present, there is not unanimity as to what constitutes either an outlet chamber (as compared to a "small right ventricle" in tricuspid atresia) or a single (primitive) ventricle. Any discussion of the morphological and topographical variations of the outlet chamber must be viewed with respect to the terminology employed.