Double-inlet single left ventricle: echocardiographic anatomy with emphasis on the morphology of the atrioventricular valves and ventricular septal defect

Imaging of Double Inlet Left Ventricle

Double inlet left ventricle (DILV) is a form of single ventricle heart disease where both atrioventricular valves enter a single left ventricle. Surgical intervention may be needed in the neonatal period secondary to systemic outflow tract obstruction or less commonly pulmonary obstruction. Two-dimensional echocardiography can adequately assess newborn anatomy and define the need for surgery. Beyond the newborn period, there is a renewed interest in septation of DILV using intracardiac baffles in a staged approach. Cross sectional imaging can aid in surgical planning. This article will review common anatomic features of DILV and imaging considerations for both single ventricle palliation and DILV septation.

Association of Bulboventricular Foramen Size and Need for Early Intervention in Infants with Tricuspid Atresia or Double-Inlet Left Ventricle with Normally Related Great Arteries

BACKGROUND

The association of bulboventricular foramen (BVF) size and systemic outflow adequacy has been studied in patients with tricuspid atresia (TA) or double-inlet left ventricle (DILV) with transposed great arteries. The aim of this study was to determine the relationship between initial BVF size and risk for progressive pulmonary outflow obstruction requiring intervention to increase pulmonary blood flow in patients with TA or DILV with normally related great arteries.

METHODS

Patients with TA or DILV with normally related great arteries were identified by retrospective chart review at a single center from 2005 to 2021. Patients were stratified by indexed BVF area (iBVFA) to determine the relationship of iBVFA size and the need for intervention before the Glenn operation to establish supplemental pulmonary blood flow with either a Blalock-Taussig-Thomas shunt (BTTS) or patent ductus arteriosus (PDA) stent. Patients were followed through the time of their Glenn operations. Logistic regression analysis was performed to determine optimal iBVFA cut points.

RESULTS

Thirty-seven patients with TA or DILV with normally related great arteries were included. Sixteen had iBVFA < 1 cm²/m², with all 16 (100%) requiring either a BTTS or PDA stent to increase pulmonary blood flow before the Glenn operation. Seventeen had iBVFAs of 1 to 2 cm²/m², with 10 (59%) requiring either a BTTS or PDA stent. Nine of those 10 demonstrated flow acceleration across the BVF and/or pulmonary outflow tract. Four had iBVFA > 2 cm²/m², with only one patient (25%) requiring a BTTS. Among our cohort, an iBVFA of <1.8 cm²/m² provided sensitivity of 96% with good positive and negative predictive values (81% and 80%, respectively) for requiring intervention with a BTTS or PDA stent before the Glenn operation.

CONCLUSIONS

An iBVFA of ≤1.8 cm²/m² on initial postnatal echocardiography is associated with the development of subpulmonary obstruction requiring intervention with a BTTS or PDA stent before the Glenn operation, with the highest risk noted in those with iBVFA of ≤1 cm²/m². Factors such as BVF flow acceleration or pulmonary outflow tract narrowing should also be considered in the decision to augment pulmonary blood flow.

Doppler echocardiographic description of double-inlet left ventricle in an Arabian horse

Univentricular atrioventricular (AV) connections are rare and complex congenital cardiac anomalies in which both AV valves communicate into a large, common (single) receiving chamber. The common chamber can be of left, right, or mixed ventricular morphology. Although well documented in people, reports of the double-inlet ventricle malformation are rare in the veterinary literature. This report provides description of an Arabian horse with a double-inlet univentricular connection of left ventricular type, a hypoplastic subpulmonary right ventricle, two muscular ventricular septal defects, and a stenotic mitral valve. Transthoracic Doppler echocardiography enabled antemortem diagnosis, and provided an assessment of intracardiac hemodynamics. The findings indicate that Doppler echocardiography is a useful, noninvasive tool for evaluating equine patients with congenital univentricular AV connections, such as a double-inlet left ventricle.

Univentricular Heart

As early as 1699, Chemineau described a heart composed of 2 auricles but only 1 ventricle. 1 The univentricular heart has since fascinated the medical community. Unique in its complexity and scope, the univentricular heart has sparked intense debates about embryology and nomenclature, challenged our understanding of cardiovascular physiology and hemodynamics, and inspired some of the most creative surgical and interventional approaches in human history. The present report provides an overview of the nomenclature and classification of the univentricular heart, epidemiology and pathological subtypes, genetic factors, physiology, clinical features, diagnostic assessment, therapy, and postoperative sequelae. Although the present report touches on issues applicable to neonates and children with univentricular hearts, the focus is on information of interest and relevance to the adult cardiologist.

The anatomy of hearts with double inlet ventricle

In the past, hearts with double inlet ventricle have been amongst the most contentious of congenital cardiac malformations. This is because, although most examples found with this particular atrioventricular connection have one big and one small chamber within the ventricular mass, for many years the variant most frequently encountered, with a dominant left ventricle, was usually described as exhibiting a single ventricle.1With the recognition that, in this particular variant, the small chamber is an incomplete right ventricle, and is never capable of supporting independently the pulmonary circulation, the anatomic situation has now been clarified, as explained in the previous review,2by recognising that the arrangement produces a functionally single ventricle, and that almost always patients with this lesion, if treated surgically, will be converted to the Fontan circulation. Even though, nonetheless, most patients with all variants of double inlet ventricle will likely end up with the Fontan circulation, it remains necessary to identify the functionally significant variants, namely those to be found in ventricular morphology, atrioventricular valvar morphology, ventriculo-arterial connections, and associated malformations.3

Anatomoechocardiographic correlation double inlet left ventricle

Double inlet left ventricle (LV) is a type of atrioventricular connection in which the morphologically LV receives more than 50% of the atrioventricular valves when they are separate, or more than 75% of a common atrioventricular valve. The aim of this study was to establish an anatomoechocardiographic correlation between the morphologic features of equivalent anatomic specimens and the echocardiographic images of patients to provide a means of interpreting the image correctly and a more precise diagnosis of the cardiac defect. Echocardiography was used to study 18 patients with LV double inlet who were seen in a congenital heart disease clinic. The morphology of 17 hearts with this malformation from the department of embryology was analyzed to compare the anatomic features with their echocardiographic images. Echocardiography proved to be a noninvasive diagnostic tool that allowed characterization of anatomic and functional aspects of double inlet LV.

Designing therapeutic strategies for patients with a dominant left ventricle, discordant ventriculo-arterial connections, and unobstructed flow of blood to the lungs

The palliation of the cyanotic child with a dominant morphologically left ventricle, discordant ventriculo-arterial connections, and obstruction to the pulmonary outflow tract has continued to evolve and mature. The evolution began in the early days of surgical palliation with the Blalock-Taussig shunt, extended to construction of cavopulmonary shunts, if required, and then to the Fontan procedure and its subsequent modifications. This journey took nearly 30 years to complete. There is increasing clinical data to document the beneficial effects of this approach, with ever-improving outcomes. Some aspects of the history of the cavopulmonary shunt have been previously reviewed in this journal and elsewhere, as have analysis of outcomes for some groups of patients considered for surgical completion of the Fontan circulation. While there has been some ongoing interest in ventricular septation since the early success of Sakakibara et al., this approach has largely been abandoned. Considerably more challenges and debate resonate in the surgical algorithms defined for patients whose hearts are characterized by a dominant left ventricle, discordant ventriculo-arterial connections, and unobstructed flow of blood to the lungs. This latter group will be the focus of this review, as will the aetiology of the myocardial hypertrophy that is particularly frequent in this group of patients, its clinical recognition, indeed its anticipation, and the multiple surgical strategies designed to prevent or treat it. All these manoeuvres are considered to optimise suitability for, and outcome from, creation of the Fontan circulation.

Outcome of patients with double-inlet left ventricle or tricuspid atresia with transposed great arteries

OBJECTIVES

We sought to determine the long-term outcomes and risk factors for mortality in patients with double-inlet left ventricle (DILV) or tricuspid atresia with transposed great arteries (TA-TGA).

BACKGROUND

Patients with DILV or TA-TGA are at risk of systemic outflow obstruction and a poor outcome. The impact of various management strategies on the long-term outcomes of these patients remains unknown.

METHODS

We reviewed the outcomes of 164 consecutive pediatric patients with DILV or TA-TGA who underwent surgical palliation between 1983 and 2002. Patients with a Holmes heart or heterotaxy syndrome or who were lost to follow-up (n = 24) were excluded. Risk factors for mortality or the need for orthotopic heart transplantation (OHT) were assessed by multivariate analysis.

RESULTS

There were 105 patients with DILV and 35 patients with TA-TGA. The overall mortality rate, including OHT, was 29%. Patients with DILV had a lower mortality rate than patients with TA-TGA (23% vs. 49%, p = 0.007). Multivariate analysis showed the presence of arrhythmia and pacemaker requirement as independent risk factors for mortality, whereas pulmonary atresia or stenosis and pulmonary artery banding were associated with decreased mortality. Gender, era of birth, aortic arch anomaly, and systemic outflow obstruction were not risk factors. The perioperative and overall mortality were similar between patients who underwent the Damus-Kaye-Stansel procedure beyond the neonatal period and those had subaortic resection.

CONCLUSIONS

The mortality of patients with DILV or TA-TGA remains high. The outcomes of these patients are influenced by restriction of pulmonary blood flow, arrhythmia, and pacemaker requirement. Surgical palliation to relieve systemic outflow obstruction is not associated with a poor outcome.

Outcome of staged surgical approach to neonates with single left ventricle and moderate size bulboventricular foramen

Neonates with double-inlet left ventricle or tricuspid atresia with transposed great arteries and a bulboventricular foramen (BVF) area <2 cm(2)/m(2) develop BVF obstruction. This study examined the outcome of neonates with BVF area between 1 and 2 cm(2)/m(2) whose BVF was bypassed after the neonatal period. We reviewed 29 neonates with double-inlet left ventricles (n = 18) or tricuspid atresia (n = 11) and transposed great arteries. The study group consisted of 9 patients with neonatal BVF areas of 1 to 2 cm(2)/m(2) who did not undergo repair of the BVF obstruction as a neonate. The comparison group consisted of 8 "ideal" patients without BVF obstruction. Precavopulmonary shunt data from cardiac catheterization and echocardiogram and outcomes of the cavopulmonary shunt were compared. Study group patients developed a mild BVF gradient (18 +/- 10 mm Hg by cardiac catheterization) by a mean of 7 months. Left ventricular wall thickness, however, remained in the normal range (4.2 +/- 0.3 mm) and was not statistically different from the comparison group (4.1 +/- 0.4 mm). No difference was found in the precavopulmonary mean pulmonary artery pressure (15 +/- 5 vs 15 +/- 6 mm Hg), transpulmonary gradient (8 +/- 4 vs 8 +/- 5 mm Hg), and left ventricular end-diastolic pressure (7 +/- 2 vs 8 +/- 3 mm Hg). One patient in the study group died from respiratory syncytial virus pneumonia while awaiting cavopulmonary shunt. Neither group had mortality from the cavopulmonary shunt. The lengths of hospital stay were comparable (8.3 +/- 3.7 vs 8.9 +/- 6.0 days). Thus, neonates with BVF area between 1 and 2 cm(2)/m(2) develop mild but hemodynamically insignificant BVF gradient by 7 months of age. This group of patients can be managed safely with relief of BVF obstruction later in infancy.

The pathology of subaortic obstruction

BACKGROUND

In hearts having the atriums connected only to a dominant left ventricle, typified by double-inlet left ventricle but seen also in lesions such as tricuspid atresia, subaortic obstruction, when it exists, is usually found at the level of the ventricular septal defect when the aorta is supported by the rudimentary right ventricle.

METHODS

Heart specimens were examined to determine the nature and position of the ventricular septal defect existing between dominant left and rudimentary right ventricles when the ventriculoarterial connections are discordant.

RESULTS

Most commonly, the ventricular septal defect is positioned between the muscular apical trabecular septum and the muscular outlet septum. This type of defect is found not only in double-inlet left ventricle, but also in hearts with absence of either the right or left atrioventricular connection when the other atrium is connected to a dominant left ventricle, irrespective of the position of the rudimentary and incomplete right ventricle. Obstructive lesions within the aortic arch are commonly associated with restriction at the site of the ventricular septal defect. The atrioventricular conduction bundle takes a constant course relative to the margin of the septal defect.

CONCLUSIONS

Because subaortic obstruction is almost always caused by a restrictive ventricular septal defect, relief of the obstruction can be achieved by surgical enlargement of the septal defect, bearing in mind the course of the atrioventricular conduction system.

Usefulness of banding of the pulmonary trunk with single ventricle physiology at risk for subaortic obstruction

This study addresses the effects of early banding of the pulmonary trunk and subsequent management of subaortic obstruction on the attainment of acceptable pre-Fontan hemodynamics in patients with a single left ventricle and aorta arising from an outflow chamber. We report our experience with 26 patients seen at our institution between January 1984 and December 1994 with a diagnosis of double-inlet left ventricle or tricuspid atresia and transposed great arteries, who were initially managed with pulmonary artery banding in the first 6 months of life. Pulmonary artery band placement was performed at an age of 2.1 +/- 1.8 months (mean +/- SD). Associated aortic arch abnormalities were present in 8 patients (31%). There were 19 patients (73%) who underwent treatment with a Damus-Kaye-Stansel procedure or ventricular septal defect (VSD) enlargement for a significant subaortic gradient or morphologically small VSD, alone or in conjunction with a Glenn or Fontan procedure. Eighteen of 26 patients (69%) underwent cardiac catheterization to assess their candidacy for the Fontan operation. Of this group, 16 were classified as low to moderate risk and 2 as high-risk Fontan candidates, based on hemodynamic criteria. The cumulative mortality for the entire cohort was 19%. Our results suggest that this high-risk group of patients can undergo effective pulmonary artery banding as an initial palliative step, with subsequent intervention for subaortic ob- struction when it is documented or highly suspected, and that acceptable pre-Fontan hemodynamic parameters can be achieved.

Cardiac anatomy in patients undergoing the Fontan procedure

BACKGROUND

Controversies in nomenclature, especially of hearts with "single ventricle," have clouded discussion and understanding of the anatomy. Many patients with such malformations are submitted to the Fontan procedure as definitive surgical palliation. The spectrum of anatomy among these patients is wide and deserves analysis in an effort to provide a simple framework for description and to eliminate confusion.

METHODS

We reviewed 138 successive patients undergoing the Fontan operation at one institution to demonstrate the variability in pathology.

RESULTS

Only 89 patients (65%) had a univentricular type of atrioventricular connection. All but 5 patients had two ventricular chambers. Among the 49 patients with biventricular atrioventricular connections, 43 had a hypoplastic ventricle that precluded a biventricular repair.

CONCLUSIONS

Full understanding of the malformations that may preclude a "biventricular" repair and hence necessitate a Fontan procedure requires knowledge of the different forms of univentricular atrioventricular connection that, although usually associated with two ventricular chambers, are seldom amenable to a "two-pump repair." Understanding of those types of "biventricular heart" that preclude a two-pump repair (eg, severe hypoplasia of the left ventricle or the right ventricle) or are associated with high risks (eg, straddling atrioventricular valve) is also important.

Early changes in ventricular septal defect size and ventricular geometry in the single left ventricle after volume-unloading surgery

OBJECTIVES

This study investigated the phenomenon of, and the relation between, alterations in ventricular geometry after acute surgical volume unloading of the ventricle and the development of subaortic stenosis in patients with a single ventricle and ventricular septal defect-dependent systemic flow.

BACKGROUND

Subaortic outflow obstruction has been observed to occur in patients with a single left ventricle after placement of a pulmonary artery band. The timing and etiology of this phenomenon are not well defined.

METHODS

The preoperative and postoperative echocardiograms of 18 patients 14.9 +/- 22.8 months old (mean +/- SD) with a diagnosis of single left ventricle who underwent pulmonary artery banding or cavopulmonary connection were reviewed. Postoperative studies were performed a mean of 7.0 +/- 6.5 days after operation. The ventricular septal defect diameter was measured in two orthogonal views and the area calculated using the formula for an ellipse. Interventricular septal and posterior wall thickness and left ventricular diameter and length were also measured.

RESULTS

Mean ventricular septal defect area indexed to body surface area diminished by 36 +/- 23% (3.1 +/- 2.7 to 2.0 +/- 1.8 cm2/m2, p < 0.01). Mean interventricular septal and posterior wall thickness increased significantly, and left ventricular diameter and length decreased significantly. A greater diminution in ventricular septal defect area was noted after cavopulmonary connection (41 +/- 19%, p < 0.01) than after pulmonary artery banding (25 +/- 28%, p = 0.22).

CONCLUSIONS

In the single left ventricle, diminution in ventricular septal defect size occurs early and is related to an acute alteration in ventricular geometry that accompanies the decrease in ventricular volume. Ventricular septal defect diminution was greater after volume unloading of the ventricle after cavopulmonary connection than after pulmonary artery banding.

Understanding cardiac anatomy: the prerequisite for optimal cardiac surgery

If advances in cardiac surgery are to continue into the twenty-first century, it will be necessary to concentrate on details of matters such as the anatomy of the heart. This will be achieved best when anatomy is described as it is observed. This approach is obscured when words are used in inappropriate fashion, or else assigned a function separate from their everyday meaning. Examples of how the congenitally malformed heart and the normal heart have been described in the past are examined within the framework of using words in their vernacular meaning. Suggestions are made to improve descriptions and understanding for the 21st century. Using the example of the "univentricular heart", it is shown how conventions debarring ventricular status to discrete chambers within the ventricular mass are, of necessity, artificial. Similar examples are used to distinguish septal from parietal structures within the heart and to elucidate the structure of some congenital malformations. For values, it is shown how proper description requires assessment of these structures in their closed as well as their open positions. Understanding of cardiac anatomy, truly a prerequisite for successful cardiac surgery, will be facilitated in future if words are used in their generally accepted sense, and if artificial conventions are avoided.

The surgical anatomy of ventricular septal defects with univentricular atrioventricular connection

Hearts that do not possess one-to-one connections at the segmental junctions almost always produce a univentricular atrioventricular connection. One ventricle is usually large and dominant and the other small, lacking one or two of its components. The ventricular septal deficiency forms part of the circulatory pathway. We take the stance that only hearts that possess a truly solitary ventricular chamber are univentricular. They cannot have a ventricular septal defect, and so are excluded from this study. This review, therefore, is concerned with the morphology of septal defects in hearts in which both atrioventricular junctions are connected exclusively to a dominant left or a dominant right ventricle, and those lacking one atrioventricular connection, where the remaining valve is connected to a dominant ventricle. This morphology in the absence of one atrioventricular connection can be modified when there is overriding of the solitary atrioventricular valve. The ventricular septal defects are analyzed and categorized for the various groups, and the position of the conduction axis is described for the well-recognized entities.

Mitral atresia with a large left ventricle and an underdeveloped or absent right ventricular sinus: clinical profile, anatomic data and surgical considerations

In mitral atresia with a large left ventricle, the tricuspid valve is either straddling and biventricular or entirely left ventricular. To learn how to assess the identity of the tricuspid valve in such cases 15 heart specimens were examined as well as the echocardiograms of 10 living patients. When the right ventricular sinus was underdeveloped (11 cases), a straddling tricuspid valve was present; when it was absent (14 cases), the tricuspid valve was entirely left ventricular. Regardless of biventricular or exclusively left ventricular attachments, the tricuspid valve was tricommissural (at postmortem examination or on echocardiography) in 22 cases (88%). Its chordal attachments showed considerable variations but were usually paraseptal or on the ventricular septal crest or conal septum. When biventricular, the tricuspid valve straddled through an inlet ventricular septal defect. Clinical or anatomic evidence, or both, of tricuspid regurgitation was present in 14 cases (56%). It is concluded that 1) the identity of the atrioventricular valves is reflected in their chordal attachments more accurately than in their leaflet morphology and depends primarily on the type of ventricular loop present; 2) as a rule, the tricuspid valve is right-sided in D-looped and left-sided in L-looped ventricles; 3) valve identity expressed as the number and position of the papillary muscle attachments is generally recognizable echocardiographically and can be used to diagnose the type of ventricular loop that is present; and 4) the presence and degree of tricuspid regurgitation deserve attention when choosing optimal palliative surgery.