Pathologic substrates for 1 1/2 ventricular repair

The so-called "one-and-a-half" ventricular repair: where are we after 40 years?

OBJECTIVES

The indications, timing, and results of the so-called "one-and-a-half ventricle repair", as a surgical alternative to the creation of the Fontan circulation, or high-risk biventricular repair, currently remain nebulous. We aimed to clarify these issues.

METHODS

We reviewed a total of 201 investigations, assessing selection of candidates, the need for atrial septal fenestration, the fate of an unligated azygos vein and free pulmonary regurgitation, the concerns regarding reverse pulsatile flow in the superior caval vein, the growth potential and function of the subpulmonary ventricle, and the role of the superior cavopulmonary connections as an interstage procedure prior to biventricular repair, or as a salvage procedure. We also assessed subsequent eligibility for conversion to biventricular repair and long-term functional results.

RESULTS

Reported operative mortalities ranged from 3% to 20%, depending on the era of surgical repair with 7% risk of complications due to a pulsatile superior caval vein, up to one-third incidence of supraventricular arrhythmias, and a small risk of anastomotic takedown of the superior cavopulmonary connection. Actuarial survival was between 80% and 90% at 10 years, with two-thirds of patients in good shape after 20 years. We found no reported instances of plastic bronchitis, protein-losing enteropathy, or hepatic cirrhosis.

CONCLUSIONS

The so-called "one-and-a-half ventricular repair", which is better described as production of one-and-a-half circulations can be performed as a definitive palliative procedure with an acceptable risk similar to that of conversion to the Fontan circulation. The operation reduces the surgical risk for biventricular repair and reverses the Fontan paradox.

Long-term experience with the one-and-a-half ventricle repair for simple and complex congenital heart defects

OBJECTIVES

The one-and-a-half ventricle repair (1.5VR) is a surgical alternative to Fontan circulation or high-risk biventricular repair in patients with complex congenital heart disease (CHD) with a hypoplastic right ventricle (RV). We report our 25 years of experience to evaluate whether the degree of anatomical complexity of the CHD can affect long-term outcomes.

METHODS

This is a retrospective study including patients undergoing 1.5VR between 1994 and 2018. Clinical records and operative reports were reviewed. Follow-up data were collected from all survivors at the last evaluation or by phone contact.

RESULTS

Twenty-nine patients underwent 1.5VR [median age: 3.5 years, interquartile range (IQR) 0.8-7.8]. Fifteen patients had 'simple' (i.e. confined to right heart lesions) anatomical characteristics (48.3%); the median tricuspid valve annulus z-score was -3.5 (IQR -6.2 to +3.6). There were no operative deaths. The median hospital stay was 21 days (IQR 10-33), with postoperative complications in 21 patients (75.8%). At a median follow-up of 13.2 years (IQR 3.2-25.6 years; completeness 96.6%), there were 3 late deaths. There was no significant difference in survival and in freedom from adverse events between simple and complex anatomy groups. However, stress test findings showed a tendency towards a higher maximum oxygen uptake in the simple group (P = 0.055).

CONCLUSIONS

The 1.5VR strategy is an effective low-risk surgical option for patients with CHD with hypoplastic RV. When it is planned from birth, late outcomes can be satisfactory. In our experience, the presence of associated major cardiac anomalies was not associated with either worse early or long-term outcomes and functional status.

One and half ventricle repair: rationale, indications, and results

Surgical strategies in patients with functionally or anatomically borderline right ventricles include a high-risk biventricular repair, a Fontan procedure, or a one and half ventricle repair (also referred to as the partial biventricular repair). One and half ventricle repair (1.5VR) circumvents the high early mortality of a biventricular repair and also the late morbidity of the Fontan. The two most common indications for a 1.5VR are a small pulmonary ventricle and a dilated poorly functioning pulmonary ventricle. Extension of 1.5VR to patients undergoing anatomical repair for congenitally corrected transposition of great arteries, straddling tricuspid valves, and severe Ebstein's anomaly has facilitated biventricular repair with decreased mortality. We reviewed the relevant literature on this subject in detail and describe its rationale, indications and its early and late results.

The new concept of univentricular heart

The concept of univentricular heart moved from hearts with only one ventricle connected with atria [double inlet ventricle or absent atrioventricular (AV) connection] to hearts not amenable to biventricular repair, namely hearts with two ventricles unable to sustain separately pulmonary and systemic circulations in sequence. In the latter definition, even hearts with one hypoplastic ventricle are considered "functional" univentricular hearts. They include pulmonary/aortic atresia or severe stenosis with hypoplastic ventricle, and rare conditions like huge intramural cardiac tumors and Ebstein anomaly with extreme atrialization of right ventricular cavity. In this setting, the surgical repair is univentricular with "Fontan" operation, bypassing the ventricular mass. In other words, functionally univentricular heart is a condition in which, after surgery, only one ventricle sustain systemic circulation. Univentricular hearts (double inlet or absent AV connection) almost invariably show two ventricular chambers, one main and one accessory, which lacks an inlet portion. The latter is located posteriorly when morphologically left and anteriorly when morphologically right. As far as double inlet left ventricle, this is usually associated with discordant ventriculo-arterial (VA) connection (transposition of the great arteries) and all the blood flow to the aorta, which takes origin from the hypoplastic anterior right ventricle, is ventricular septal defect (bulbo-ventricular foramen) dependent. If restrictive, an aortic arch obstruction may be present. Double inlet left ventricle may be rarely associated with VA concordance (Holmes heart). As far as double inlet right ventricle with posterior hypoplastic left ventricular cavity, ventriculo-arterial connection is usually of double outlet type; thus the term double inlet-outlet right ventricle may be coined. Absent right or left AV connection may develop in the setting of both d- or l-loop, whatever the situs. In this condition, the contra-lateral patent AV valve may be either mitral or tricuspid in terms of morphology and the underlying ventricle (main chamber) either morphologically left or right. Establishing the loop, whatever right or left (also called right or left ventricular topology), is a fundamental step in the segmental-sequential analysis of congenital heart disease.

The conduction system in hearts with pulmonary atresia and intact ventricular septum

BACKGROUND

Although a regular course of the conduction system is anticipated in hearts with pulmonary atresia and intact ventricular septum (PAIVS), it has never been demonstrated anatomically. In view of one of the surgical options in repair being debulking of the right ventricular wall, it is important to establish the location of the major conduction pathways.

METHODS

Four hearts belonging to fetuses aged 18, 20, 22, and 29 weeks were examined. Entire hearts were serially sectioned and step sections were stained. The sinus node and atrioventricular conduction bundles were identified and their locations described.

RESULTS

The conduction system in hearts with PAIVS is similar to that in normal hearts, although there was a minor variation in one of them. This was a heart affected by Ebstein malformation of the tricuspid valve. In this case, the right bundle branch terminated abruptly soon after its origin.

CONCLUSIONS

Confirmation of the regular course of the cardiac conduction system is important to the development of strategies for surgical repair of PAIVS.

Pulmonary atresia with intact ventricular septum: range of morphology in a population-based study

OBJECTIVES

We describe the morphologic variability in pulmonary atresia with intact ventricular septum (PAIVS) within a population-based study.

BACKGROUND

An uncommon disease, PAIVS shows considerable morphologic heterogeneity. Clinical reports, based mostly on small samples of patients, may not reflect the true spectrum of pathology of this condition. We have studied the entire range of morphology in a prospective population-based study of patients over a five-year period (1991 to 1995). METHODS; As part of the United Kingdom and Ireland Collaborative Study of PAIVS, all 18 pediatric cardiac centers were visited by a single investigator. Morphologic features of each case were determined by direct review of the echocardiograms and angiocardiograms, from surgical and autopsy reports, and by review of pathology specimens where available.

RESULTS

Among 183 live-born infants, atresia was valvar (membranous) in 74.7% and muscular in 25.3%. Muscular obliteration of the apical trabecular cavity, and in some cases its infundibulum, resulted in "bipartite" right ventricle (RV) in 33.6%, and a "unipartite" chamber in 7.7%. The remaining 58.7% had "tripartite" morphology. Coronary arterial abnormalities were identified in 45.8%, including arterial stenoses, interruptions and ectasia in 7.6%. Ebstein's malformation coexisted in 18 patients. Median tricuspid valvar size and RV inlet Z-scores were -5.2 and -5.1, respectively.

CONCLUSIONS

This study provides unique data on the diverse pathology of PAIVS in an unselected population. This will help determine if published reports reflect the true spectrum of pathology of the condition.

Bidirectional Glenn shunt in association with congenital heart repairs: the 1(1/2) ventricular repair

BACKGROUND

The bidirectional Glenn shunt has been used to incorporate a smaller tripartite ventricle into the circulation and create pulsatile pulmonary artery flow. We reviewed our operative experience and assessed hemodynamics of the bidirectional Glenn shunt in 1(1/2) ventricular repair or in conjunction with other repairs of congenital heart defects.

METHODS

Between 1992 and 1998, 15 patients (mean age, 8.1+/-7.9 years) had bidirectional Glenn shunt in association with repair of congenital heart defects. Eighty-seven percent had at least one previous operation. All patients had simultaneous or previous intracardiac repair and had bidirectional Glenn shunt to volume unload the small right ventricle (group A, n = 7), to unload the poorly functioning right ventricle (group B, n = 2), to redirect superior vena cava-pulmonary venous atrial connection to treat cyanosis (group C, n = 2), or to unload the pulmonary left ventricle for residual intracavitary hypertension in patients with L-transposition of the great arteries, ventricular septal defect, and pulmonary stenosis (group D, n = 4). Intraoperative hemodynamic assessment was done in 2 patients in group A by selective use of inflow occlusion and flow probes.

RESULTS

All patients survived. Four patients had successful, concurrent arrhythmia circuit cryoablation for Wolf-Parkinson-White syndrome (n = 1) or atrial reentry tachycardia (n = 3). Superior and inferior vena caval flow averaged 36% and 64% of cardiac output, respectively. Postoperative superior vena caval pressure (n = 13) was 13.7+/-4.0 mm Hg with pulmonary arterial flow pattern contributed by the ventricle in systole (pulsatile) and the superior vena cava in diastole (laminar).

CONCLUSIONS

The bidirectional Glenn shunt is an effective adjunct to congenital heart repair to treat pulmonary ventricular pressure-volume problems and anomalous superior vena caval to left atrial connections.

Which hearts are unsuitable for biventricular correction?

BACKGROUND

The surgical option of biventricular repair requires two ventricles, each fully capable of supporting the systemic or pulmonary circulation. The morphologic substrates that may preclude some hearts from biventricular repair need to be assessed.

METHODS

Heart specimens were reviewed to assess the morphologic mechanisms that produce an unbalanced ventricular mass and to identify features that would, potentially, be a contraindication for biventricular repair.

RESULTS

Hearts with solitary and indeterminate ventricles, and hearts with essentially solitary ventricles, often have associated abnormalities of venoatrial connections and arrangement of the atrioventricular valves. In the majority of hearts with univentricular atrioventricular connections, the rudimentary and incomplete ventricle of either right or left morphology may be too small to support either the systemic or the pulmonary circulation. Straddling with overriding of the atrioventricular valve, unbalanced atrioventricular septal defect, and gross hypoplasia of one of the ventricles in hearts with biventricular connections are other mechanisms producing ventricular imbalance, which could preclude biventricular repair.

CONCLUSIONS

The morphologic mechanisms that result in ventricular imbalance are mainly related to the sizes and morphology of the ventricles, septal malalignment, valvar morphology, and component make-up of the ventricles. These features will influence decision-making in considering the option of biventricular repair.