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Ann Thorac Surg 2001;71:1995-2002
© 2001 The Society of Thoracic Surgeons
a Department of Cardiothoracic and Vascular Surgery, Cardiothoracic Centre, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, India
b Department of Cardiology, Cardiothoracic Centre, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, India
Accepted for publication February 4, 2001.
Address reprint requests to Dr Airan, Department of Cardiothoracic and Vascular Surgery, All India Institute of Medical Sciences, Ansari Nagar, New Delhi-110029, India
e-mail: bairan{at}medinst.ernet.in
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Abstract |
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Methods. Fifty consecutive patients, aged 4 months to 42 years, underwent intracardiac repair along with a superior cavopulmonary connection. Twenty-seven of the patients had had previous surgical palliation. Repair consisted of patch closure of the ventricular septal defect (n = 25), tricuspid valve repair (n = 26), reconstruction of the right ventricular outflow tract (n = 34), transpulmonary annular patch (n = 34), right ventricle to pulmonary artery homograft conduit (n = 4), and concomitant repair of atrioventricular canal (n = 9). Ten patients were left with a fenestration in the atrial septum.
Results. There were six hospital deaths (12%) and two late deaths (4.5%). Forty-two survivors were followed from 8 months to 116 months. Eighty-eight percent are in functional class I. Actuarial survival at 97 months was 74%.
Conclusions. Moderate right heart hypoplasia constitutes a safe anatomic category for a pulsatile bidirectional Glenn. It is advisable not to proceed with a one and a half ventricle repair if postoperative residual pulmonary artery hypertension is anticipated. Patients requiring an intricate intracardiac repair and those with concomitant right heart hypoplasia may be better suited for a Fontan type of repair to reduce the complexity of the procedure.
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Introduction |
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TopAbstractIntroductionPatients and methodsResultsCommentAcknowledgmentsReferences |
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A hypoplastic but potentially or partially usable right ventricle occurs in a variety of clinical situations. The disease spectrum includes patients with (1) right ventricular outflow tract obstruction and a hypoplastic right ventricle; (2) inlet ventricular septal defect and a straddling tricuspid valve; (3) pulmonary atresia with intact ventricular septum; (4) rare variants of tetralogy of Fallot; (5) tricuspid stenosis with atrial septal defect; (6) Ebstein’s anomaly; and (7) complete atrioventricular canal with (a) extreme left ventricular dominance, (b) tetralogy of Fallot, (c) double outlet of the right ventricle, or (d) pulmonic stenosis [1–11].
Treatment strategies for these groups of patients include (1) the bidirectional Glenn shunt, (2) a Fontan type of repair, or (3) a biventricular repair with atrial septal fenestration [5, 10, 12, 13]. As originally described by Billingsley and colleagues [1], the one and one-half ventricle repair recruits the hypoplastic right ventricle, presumably providing kinetic energy and pulsatility to pulmonary blood flow, while the bidirectional Glenn reduces the volume load of the right ventricle. Herein we present a retrospective review of our experience with this approach in 50 patients whose right ventricle was judged too small to accommodate the entire systemic venous return following septation. We have attempted to define the physiologic and morphologic criteria for candidate selection and to provide certain guidelines for the use of this approach.
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Patients and methods |
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TopAbstractIntroductionPatients and methodsResultsCommentAcknowledgmentsReferences |
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Assessment of right ventricular hypoplasia was based on the classification of Milliken and colleagues [2]. In the severely hypoplastic group, the tricuspid valve, right ventricular cavity, and outflow tract were one third of normal size or smaller. In the moderately hypoplastic group, the tricuspid valve and the right ventricular cavity size were approximately one to two thirds of normal, without an adequate right ventricular outflow tract. In the mildly hypoplastic group, the tricuspid valve and right ventricular cavity size were approximately two thirds of normal, and there was a well-developed right ventricular outflow tract [2].
The following measurements—tricuspid valve Z score lower than -4.8, tricuspid valve diameter less than 45% of normal, tricuspid valve to mitral valve ratio of less than 0.54, and right ventricular diastolic volumes less than 45% of predicted normal—were considered as the cutoff points from one-ventricle repair. These values were taken as the lower limits of tricuspid valve size acceptable for inferior vena caval blood alone.
The following measurements—tricuspid valve Z score greater than -1.5, tricuspid valve diameter 70.5% of normal, tricuspid valve to mitral valve ratio of 0.80, and right ventricular diastolic volumes greater than 75% of predicted normal—were considered as the cutoff points from two-ventricle repair.
A combination of pulmonary atresia with intact ventricular septum, right ventricle coronary artery fistulas, and right ventricular coronary dependence was taken as a contraindication for right ventricular decompression and thus for one and a half ventricle repair [1, 2, 11].
Indications for repair included increasing cyanosis (n = 43) and excessive pulmonary blood flow (n = 7). The decision to perform a one and a half ventricle repair was made after taking into consideration morphologic and functional issues.
Tricuspid valve assessment
Preoperative echocardiographic assessment
The echocardiograms obtained before one and a half ventricle repair were retrospectively reviewed. In each patient, the tricuspid valve was measured, and the largest diameter obtained from an apical four-chamber view was indexed for body surface area and compared with the normal values of King and colleagues [14].
The data for the mean normal diameters and their standard deviations were obtained from the table provided by Rowlatt and colleagues [15]. Appropriate equations were used to compute the Z values of the tricuspid valve [16]. The tricuspid valve diameter, expressed as percentage of normal, was calculated as diameter of tricuspid valve/normal x 100 - Z value. The mitral valve diameter was measured, and the ratio of the tricuspid valve to mitral valve diameter was obtained.
Preoperative echocardiographic data revealed the following: (1) the tricuspid valve diameter expressed as percentage of normal was between 45.0% and 70.5%, (2) the tricuspid valve diameter to mitral valve diameter ratio ranged between 0.54 and 0.80, and (3) the Z value for the tricuspid valve was -1.5 to -4.8.
Intraoperative assessment
At operation, the right ventricle was confirmed to be hypoplastic in each patient, and the tricuspid valve diameter was measured using Hegar’s dilators. Intraoperative tricuspid valve diameters were indexed for body surface area and compared with the published autopsy data of Rowlatt and colleagues [15]. The Z values for the tricuspid valve were determined retrospectively using the data tables published by the same authors [15].
The tricuspid valve diameter expressed as percentage of normal was between 50% and 72.5%, and the mean Z value for the tricuspid valve at operation was -3.7 (range = -4.5 to -1.5).
Surgical technique
Surgery was performed after interrupting prior existing systemic to pulmonary shunts. The superior vena cava was cannulated near the innominate vein to facilitate a Glenn, which was performed routinely on cardiopulmonary bypass on a beating perfused heart, onto the superior surface of the ipsilateral pulmonary artery. The azygos or hemiazygos vein was ligated. Eight patients with a persistent left superior vena cava underwent a bilateral bidirectional Glenn. The concomitant cardiac procedures are tabulated in Table 3.
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Three patients with variants of tetralogy of Fallot with tricuspid valve and right ventricular hypoplasia and an anomalous left anterior descending coronary artery crossing the right ventricular outflow tract and 1 patient with pulmonary atresia and intact ventricular septum received a right ventricle to pulmonary artery homograft conduit (Table 3).
Atrioventricular septal defects were repaired using a two-patch technique with a comma-shaped extension of the Dacron (DuPont, Wilmington, DE) patch to route the left ventricle to the dextraposed aorta. The atrioventricular valve was repaired as needed to achieve competence. The atrial septal defect was closed separately using a patch of autologous pericardium, with the coronary sinus left to drain into the right atrium. All had postrepair right atrioventricular valve diameters that were at least two standard deviations below the normal expected value for body surface area.
We used an adjustable atrial septal fenestration in all patients with tricuspid valve diameter less than 50% of normal and in selected patients with pulmonary artery hypertension. After the patient was weaned from bypass, the snare was adjusted, keeping the right atrial pressure less than 12 to 15 mm Hg. The fenestration was left open in 10 patients.
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Results |
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TopAbstractIntroductionPatients and methodsResultsCommentAcknowledgmentsReferences |
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The remaining 44 patients had an uncomplicated postoperative course. Thirty-six patients were extubated within 48 hours after operation. Eight patients remained ventilator dependent for 5 to 7 days. Supraventricular arrhythmias were present in 20.4% of survivors. There was significant pleural effusion in 22.7% of survivors.
All patients were routinely started on oral angiotensin-converting enzyme inhibitors before weaning dopamine and sodium nitroprusside. Postoperatively, digoxin, diuretics, and angiotensin-converting enzyme inhibitors were discontinued within 6 months in the majority of patients.
Late outcome
There were two late deaths (4.5%). Two children with pulmonary atresia and intact ventricular septum died suddenly at 8 and 12 months postoperatively. Presumed cause of death was arrhythmias, as the patients were otherwise doing well.
All survivors were periodically evaluated every 6 months by institutional cardiologists and surgeons. Their records were reviewed for all pertinent preoperative and postoperative information including echocardiogram and catheterization data.
Forty-two survivors have been followed up for periods ranging from 8 months to 116 months (mean ± SE = 98 ± 6 months; 95% CI = 86 to 109 months). Actuarial survival was 74% at 97 months (Fig 1). Thirty-seven patients (88%) were in New York Heart Association functional class I at their last follow-up visit, with good left ventricular function, and none have any significant atrioventricular valve regurgitation. Only 5 patients are on diuretics and oral vasodilators late postoperatively.
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Oxygen saturation ranged from 84% to 95% (mean 88%) in patients having a functioning fenestration, at a mean follow-up period of 30.4 months. Three of these patients (30.0%) had spontaneous closure of their fenestration. There was no incidence of cerebrovascular accidents. We have not closed any fenestration electively.
Postoperative echocardiogram confirmed unobstructed flow through the bidirectional cavopulmonary anastomosis to the lungs and pulsatile flow from the right ventricle to the pulmonary arteries (Figs 2, 3). Postoperatively, there was little change in the tricuspid valve annulus relative to body surface area. The right ventricular volume increased markedly in 6 patients, from 8 to 9 mL/m2 (preoperative) to 12 to 20 mL/m2 (postoperative).
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Caveats of study design
The retrospective, nonrandomized nature of this study and the inclusion of a variety of complex heart lesions with hypoplastic right ventricle do not allow meaningful statistical study through multivariate analysis. The wide age range of the study population and the small number of patients in each subgroup are additional limitations. Careful systematic long-term studies and planned trials of different treatment strategies between comparable disease substrates are needed to resolve many poorly understood issues in this area.
In addition, choice of procedures for various degrees of right heart hypoplasia has been traditionally guided by previous anecdotal cases and published series. Incorporation of atrial septal fenestration has become more widespread with increasing experience.
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Comment |
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TopAbstractIntroductionPatients and methodsResultsCommentAcknowledgmentsReferences |
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The pulmonary ventricle may be compromised by problems that are morphologic, functional, or both. The morphologic defect may be defined by tricuspid valve Z value [16]. In general, this value also reflects the corresponding ventricular volume [16]. Some patients have a normal tricuspid Z value and yet an anatomically small or functionally abnormal right ventricle [8, 12]. The smallest right ventricular dimension that will allow forward passage of the entire systemic venous return without causing excessive right atrial–right ventricular hypertension or low cardiac output postoperatively may vary from patient to patient [8, 12]. Available angiographic confidence limits for the lowest normal right ventricular end diastolic volume have a very wide range (1 SD = 86%, 2 SD = 68% of predicted body surface area) [17]. It is doubtful that such numerical criteria reliably separate a small normal from a truly hypoplastic right ventricle [6].
The "normal" valve sizes published by Rowlatt and colleagues [15] based on autopsy analysis are somewhat smaller than the valve sizes reported by de Leval and colleagues [18]. However, in the present series, the Z values obtained preoperatively by echocardiography were almost the same as those obtained intraoperatively. It is unlikely that the decision to use the data of Rowlatt and colleagues [15] could have adversely affected the analysis of tricuspid valve size and therefore had a negative impact on the outcomes.
We limited the use of this operation to patients with a tricuspid valve Z score between -1.5 and -4.8 and a tricuspid valve diameter between 45% and 70% of normal. Other authors have expanded the tricuspid disease score to -5 or -6 on a few patients [3, 11]. However, the mean Z scores in those series are similar to the mean Z score in this study, and the reported number of patients is small indeed. We would perform a univentricular repair for this group of patients with these extremely low tricuspid valve diameters.
In the 1993 Congenital Heart Surgeons’ Society multiinstitutional study [4], the predicted prevalence of biventricular repair at 5 years was less than 30% for a Z value of -3 and less than 50% for a Z value of -2. The authors concluded that patients with a tricuspid valve diameter in this range may be the most suitable candidates for one and a half ventricle repair.
We agree with Muster and colleagues [6] that absolute sizes of the right ventricle and tricuspid valve Z scores may not be the only factors for operative success. Right ventricular compliance, tricuspid regurgitation, right ventricular outflow tract, relative pulmonary artery hypoplasia, and pulmonary vascular resistance are important additional considerations in preoperative candidate selection [6].
Pulmonary artery entry was an exception rather than the rule for preoperative cardiac catheterization in patients with severe pulmonic stenosis. In these patients, pulmonary venous wedge pressure was used as a substitute for pulmonary artery pressure. Because of these technical reasons, pulmonary vascular resistance could not be obtained routinely in all patients.
The safe upper limit of pulmonary artery pressure and pulmonary vascular resistance for patients undergoing one and a half ventricle repair is unknown. The failures in the present series show that patients with probability of postoperative pulmonary artery hypertension should not undergo a one and a half ventricle repair. Examples include: (1) patients with raised pulmonary vascular resistance; and (2) patients with increased chances of having residual ventricular septal defects, such as multiple muscular ventricular septal defects. In this series, in spite of high pulmonary artery pressure and pulmonary vascular resistance, some patients were selected for a one and a half ventricle repair because of dominant high-flow left to right shunt. However, 3 out of 7 patients with raised pulmonary artery pressure did not tolerate the residual pulmonary arterial hypertension and eventually succumbed. A two-ventricle repair with atrial pop-off may be a more desirable option in such patients. Patients with mean pulmonary artery pressure greater than 18 mm Hg (p = 0.001) and pulmonary vascular resistance more than 4 U/m2 (p = 0.003) were found to be at significantly higher risk. Presently, we would be reluctant to perform one and a half ventricle repair in this group.
Ventricular diastolic function is often difficult to assess at preoperative catheterization in patients with ventricular volume loads of threefold or more than normal. Thus, elevated ventricular end diastolic pressure may be secondary to increased ventricular volume load or to ventricular hypertrophy and fibrosis. On analyzing the results, in light of the caveats mentioned above, it is difficult to correlate ventricular end diastolic pressure with the postoperative outcome.
In the setting of a one and a half ventricle repair, a patent azygos vein would theoretically provide a vent for the upper compartment in the event of a rise in pulmonary artery pressure. In addition, it would permit blood to flow to the upper compartment during exercise, when the hypoplastic right heart is incapable of handling increased systemic venous return [10]. However, there have been reports of development of a semicircular circulation in which blood is diverted down and recirculates back to the heart [5]. In this series, the azygos or hemiazygos vein was ligated in all cases to avoid systemic venous runoff to inferior vena cava.
The impact of pulmonic insufficiency in the setting of one and a half ventricle repair needs further elucidation [9, 12]. It is assumed that free pulmonic regurgitation may lead to a backflow of blood from the superior vena cava to the right ventricle, thereby compromising the functional efficiency of an already abnormal right ventricle. The smooth postoperative course in patients in this series with a transannular patch suggests that the hypoplastic right ventricle copes adequately with the altered hemodynamics. Pulmonary valve incompetence would probably help in increasing right ventricular diastolic dimensions. Whether this will be deleterious or beneficial is at present conjectural.
Right pulmonary artery banding has been advocated to decrease the excessive pulsatility in the superior vena cava associated with pulmonary regurgitation and to avoid the risk of an aneurysmal superior vena cava [10]. We have not performed the hybrid type of pulmonary circulation described by Gentles and colleagues [10]. Four out of 6 patients who died in hospital had evidence of superior vena caval hypertension. Although they were subject to atrial decompression, right pulmonary artery banding proximal to cavopulmonary anastomosis or conversion to a classic Glenn are the alternative options. Long-term follow-up is needed to evaluate the impact of banding, particularly the risk of development of pulmonary arteriovenous malformations and right lung development [12].
In patients with Ebstein’s anomaly, dilated right atrium and right ventricle, this operation has a favorable impact on arrhythmias and ventricular function [9]. In addition, it has been used as an alternative or a bridge to heart transplantation in patients with severe right ventricular dysfunction [9].
This series revealed insignificant change in the tricuspid valve annulus over a mean postoperative follow-up period of 98 months. This is probably because of the existence of structurally abnormal tricuspid valve in all patients.
Patients requiring an intricate intracardiac repair with concomitant right heart hypoplasia may be better suited for a Fontan type of repair to reduce the complexity of the procedure. Examples might include: (1) the patient with an inlet ventricular septal defect and a straddling tricuspid valve; (2) the patient with d-transposition of the great arteries, conoventricular septal defect, and a small right ventricle; (3) the patient with double-outlet right ventricle and noncommitted ventricular septal defects, where the internal complex morphology of the heart does not allow a surgical septation; and (4) those requiring a conduit. We have performed conduit repair of the right ventricular outflow tract in selected patients with anomalous major coronary artery crossing the right ventricular outflow tract and in patients with pulmonary atresia with moderate right ventricular hypoplasia. Features related to prolonged cardiopulmonary bypass could probably be implicated in the death of 2 patients in this group. Such risk of prolonged cardiopulmonary bypass time for dedicating the inferior vena caval blood alone should be carefully balanced.
Another difficult issue is selection of candidates for concomitant atrial septal fenestration. Ten patients in this series had atrial septal fenestration. Four patients who died early postoperatively of low cardiac output and high right atrial pressure would theoretically have benefited from an elective open fenestration. Presently, we perform atrial septal fenestration in patients with tricuspid valve between one third and one half of normal. If the postoperative right atrial pressure is more than 12 mm Hg, we will leave the adjustable fenestration open. High right atrial pressure or a failing one and a half ventricle repair should prompt immediate reopening of the atrial septal defect without delay. The other option is to convert them to bidirectional Glenn alone.
Cardiac catheterization and exercise testing in older patients are in progress to examine the postulate that inclusion of a hypoplastic right ventricle in the systemic circuit actually augments resting or exercise cardiac output as compared to a Fontan type connection.
Based on our results, we would recommend the following guidelines for candidate selection:
Whether a pulsatile Glenn is actually advantageous over the present-day one-ventricle repair is still uncertain. Given low pulmonary artery pressures, it can be performed successfully in the category of moderate tricuspid valve hypoplasia. However, early survival is only one of the aims. The other is to provide a late functional outcome superior to that of a single-ventricle repair. The answer to that question is still forthcoming.
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Acknowledgments |
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TopAbstractIntroductionPatients and methodsResultsCommentAcknowledgmentsReferences |
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References |
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TopAbstractIntroductionPatients and methodsResultsCommentAcknowledgmentsReferences |
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