INTRODUCTION

An absence of right atrioventricular connection, a condition also known as classic tricuspid atresia, is a cyanotic congenital heart disease conferring the physiology of a univentricular heart. Associated survival is very poor and mainly depends on the balance between the systemic and pulmonary circulation. When this balance is achieved, affected patients can reach adulthood.1 Patients with this condition can be divided into 2 main groups: those with absent right atrioventricular connection (Figure 1) and those with absent left connection (Figure 2). In hearts with absent right connection, there is no continuity between the right chambers, and the only connection is between the left atrium and left ventricle. The right atrium has a muscular floor and there is no tricuspid valve. Externally, a deep groove is seen between the right atrium and the right ventricle, which is missing the inlet and is generally underdeveloped. The left chambers are connected through the mitral valve, and the hypertrophic, dilated left ventricle acts as the main ventricle. The 2 ventricular chambers are connected by a subinfundibular ventricular septal defect. This usually presents an atrial septal defect similar to an ostium secundum, although there may be a patent foramen ovale or a common atrium. This basic morphological pattern can present several variants in individual cases, determined by the type of ventriculoarterial connection, size of the septal defects, and morphology of the cardiac valves (straddling mitral valve).

Figure 1. Interior view of the right atrium, showing absence of the atrioventricular connection. Observe the muscular floor of the atrium (asterisk) and the deep groove separating the atrium from the ventricle (arrow) (archived anatomic specimen). ASD indicates atrial septal defect; IVC, inferior vena cava; RA, right atrium; RV, right ventricle; SVC, superior vena cava.

Figure 2. Heart showing absence of a left atrioventricular connection. Observe inversion of the ventricles and the discordant ventriculoarterial connection (archived anatomical specimen). Ao indicates aorta; LA, left atrium; LV, left ventricle; PA, pulmonary artery; RA, right atrium; RV, right ventricle.

In hearts with absent left connection, the ventricles are inverted. The morphologic right ventricle positioned at the left does not maintain anatomic continuity with the left ventricle; it is the morphologic left ventricle located at the right that connects with the right atrium. The morphological variants of this condition are based on the same parameters as those mentioned above for absence of right atrioventricular connection.

The ventricle that receives the atrioventricular connection manages the blood volume from both the systemic and pulmonary circulation and, therefore, it hypertrophies and dilates, whereas the ventricle without connection receives flow from a ventricular septal defect, whose size determines the degree to which this ventricle develops. There is also an obligatory atrial septal defect to derive blood from the right atrium to the left atrium, or from the left to the right in hearts with absent connection between the left atrium and the morphologic right ventricle (when the ventricles are inverted), where the systemic and pulmonary flows mix.2,3

In hearts with absent right atrioventricular connection, the ventriculoarterial connection is generally concordant, with the great arteries emerging from their respective ventricles. Less often, the ventriculoarterial connection is discordant, with the aorta emerging from the right ventricle and the pulmonary artery from the left ventricle. Even less commonly, the connection may be a double ventricular outlet, and in rare cases, there may be a single outlet through the common trunk or a solitary aortic trunk. In hearts with absent left atrioventricular connection, a discordant ventriculoarterial connection is most common. Some patients progress with a certain degree of pulmonary stenosis, which protects the pulmonary vascular bed from hyperflow.2,4,5

In unoperated patients with this heart disease, survival above age 15 is rare and complications due to dysfunction of the main ventricle are common.6 Echocardiography is very useful to precisely determine the anatomic and functional features of this complex congenital heart disease.7,9

This study analyzes the clinical and morphologic characteristics that favor survival in adult patients with absence of a right or left atrioventricular connection and emphasizes the importance of echocardiographic diagnosis and follow-up, which enables the functional and anatomic aspects of this congenital heart condition to be shown in detail.

METHODS

Between January 1997 and January 2007, 24 adult patients with clinically suspected tricuspid atresia were studied, including 10 men (40%) and 14 women (60%), with a mean age of 28 (8) (range, 20-54) years. All patients underwent a clinical history, hemogram (normal hemoglobin ≤16 g/dL), arterial oxygen saturation testing (desirable, >80%), 12-lead surface electrocardiography, chest x-ray, and echocardiography; 24-hour Holter monitoring was additionally performed in all patients with a history of palpitations. In 67% of cases, cardiac catheterization was performed along with echocardiography.

Echocardiography was carried out with a Phillips Sonos 5500 unit, equipped with an S4 transducer and M-mode 2-dimensional Doppler. Sequential segmental analysis was used to characterize the heart disease.

The end-diastolic and end-systolic diameters of the main ventricle were determined by M mode in the parasternal long-axis view. The ejection fraction (EF) of the main ventricle was determined in the 4-chamber apical view, using the modified Simpson method.

Statistical Analysis

A descriptive analysis was made of the qualitative and quantitative variables with measurement of the central tendency by the mean, median, or percentage, according to the distribution of each one. Multivariate analysis with ANOVA was used for heterogeneous variances. Variables with a nonparametric distribution were analyzed with the Mann-Whitney U test. The survival analysis was performed with the Kaplan-Meier method and Cox regression, adjusted according to time and the following covariates: pulmonary stenosis, atrioventricular valve failure, preoperative pulmonary hypertension, hemoglobin level, atrial oxygen saturation, supraventricular arrhythmias, and ostium secundum atrial septal defect. Significance was set at a P value of ≤.05. SPSS version 14 was used for the analyses.

RESULTS

Clinical Manifestations

The mean time interval between birth and the diagnosis of absent atrioventricular connection was 13.8 (10) years (range, 3-23). Cyanosis was present in all patients, occurring since the first year of life in 23 (96%) patients and after the age of 6 years in 1 (4%); 21 patients (87.5%) presented acropachy.

Nearly all the patients (21/24; 87.5%) had some type of heart murmur. Among the total, 87.5% were in functional class I/II and 22.5%, in functional class III. Mean hemoglobin level was 18.2 (3.4) g/dL. Mean arterial oxygen saturation was 73% (16%).

The surface electrocardiogram showed sinus rhythm in 21 (87%) patients, atrial fibrillation in 13 (13%), significant arrhythmia in 8 (33.3%), episodes of supraventricular tachycardia in 6, and frequent atrial extrasystoles in 2. All patients had evidence of left ventricular enlargement.

On chest radiography, all patients presented some degree of cardiomegaly, including 79% (19/24) with grade II. In addition, 7 (29%) patients had evidence of pulmonary obstruction, 3 normal pulmonary flow, and 14 pulmonary hypovascularization.

Surgical treatment was undertaken in 54% of patients (13/24): Blalock-Taussig shunt in 8 (61%), pulmonary artery banding in 2 (16%), and total cavopulmonary bypass in 3 (23%). Among the operated patients, 85% (11/13) are alive, 10 in functional class I/II and 1 in functional class III. Two patients in this group died (Table 1). The mean follow-up time after surgery was 13 (8) years (range, 1-28). Among the patients who did not undergo surgery, 82% (9/11) are alive, 8 in functional class I/ II and 1 in functional class III. Two patients (18%) died (Table 1).

Medical treatment was given to 75% of patients (18/24); 2 of them had also undergone surgery (Table 1).

One 38-year-old woman had a spontaneous abortion, and another 25-year-old patient had a pregnancy that reached term. One patient presented systemic arterial hypertension, and the pertinent tests demonstrated the additional presence of Takayasu arteritis. Three patients had a cerebral infarction, 2 due to infectious endocarditis and cerebral embolism, and 1 due to neurocysticercosis.

Echocardiography Characteristics

Echocardiography showed the following features: 92% of cases presented situs solitus and 8%, right atrial isomerism; 88% of hearts were in levocardia and 12%, in dextrocardia; 92% presented absence of right atrioventricular connection (Figure 3) and 8% absence of left atrioventricular connection and ventricular inversion (Figure 4).

Figure 3. Echocardiographic images in a 4-chamber apical view showing absence of a right atrioventricular connection, in 2-dimensional imaging and with color Doppler. Note the echogenic area separating the right chambers (black asterisk) and the ventricular septal defect (white asterisk). Ao indicates aorta; LA, left atrium; LV, left ventricle; MV, mitral valve; RA, right atrium; RV, right ventricle.

Figure 4. Two-dimensional echocardiographic image in a 4-chamber apical view showing absence of the left atrioventricular connection (black asterisk) with ventricular inversion. Two ventricular septal defects are observed (white asterisk). The color Doppler image depicts severe mitral regurgitation. LA indicates left atrium; LV, left ventricle; MV, mitral valve; RA, right atrium; RV, right ventricle.

The ventriculoarterial connection was concordant in 71% of patients (Figure 5) and discordant in 17%; 12% had a double outlet.

Figure 5. Two-dimensional echocardiographic image in a 4-chamber apical view showing a concordant ventriculoarterial connection (the arrows indicate emergence of the coronary arteries). Ao indicates aorta; ASD, atrial septal defect; IVC, inferior vena cava; LA, left atrium; lb, left branch; LV, left ventricle; PA, pulmonary artery; RA, right atrium; rb, right branch; RV, right ventricle; SVC, superior vena cava.

All patients had an atrial septal defect, with a mean diameter of 27.6 (12) mm; 20 (83%) had an ostium secundum defect, with a mean diameter of 23.3 (7.4) mm, and 4 (17%) had a common atrium type, with a mean diameter of 48.7 (5.6) mm. In 19 (79%) patients, a subinfundibular (muscular) ventricular defect was found, and 3 of these patients also had a trabecular (muscular) ventricular septal defect. In another 3 (12%) patients, the ventricular septal defect was obliterated. In the 2 patients with absence of left atrioventricular connection, the ventricular septal defect was an infundibular subarterial variety (musculomembranous).

The mean diameter of the ventricular septal defect was 13.9 (7.4) mm. In the above-mentioned 2 patients, in particular, who are interesting and uncommon, the atrial septal defect was restrictive in 1 and wide in the other, and the ventriculoarterial connection was discordant in 1 and a double outlet of the main ventricle in the other; both patients had pulmonary stenosis and 1 of them presented right-sided isomerism.

Pulmonary flow was abnormal in 21 (87.5%) patients: 6 had pulmonary valve stenosis, 4 mixed (valvular and subvalvular) pulmonary stenosis, and 2 pulmonary subvalvular stenosis. Five had pulmonary hypoplasia, 4 pulmonary atresia, and 3 (12.5%) patients showed no pulmonary stenosis (Table 2).

The concomitant anomalies included Chiari network (2 patients), persistent ductus arteriosus (2 patients), and persistent left superior vena cava to the coronary sinus (1 patient).

In the overall group, mean left ventricular diastolic diameter was 61 (11) mm, mean right ventricular diameter was 16 (7) mm; and mean EF of the main ventricle was 55% (10%). When patients were divided into nonoperated and operated groups, EF of the main ventricle was 52% (12%) and 58% (8%), respectively (statistically nonsignificant differences).

Mitral failure, documented in 17 patients, was mild in 7 (41%) and moderate or severe in 10 (59%) (Table 2).

In the Kaplan-Meier survival analysis and Cox regression with relative risk function, the variables associated with decreased survival in these patients were presence of an ostium secundum atrial septal defect with respect to a common atrium, which was statistically significant by log rank test (P<.01) (Figure 6), and hemoglobin values >16 g/dL, which showed a trend to significance (P=.08).

Fig. 6. Tricuspid atresia. Patient survival as related to the size of the atrial septal defect. Statistically significant difference with the log rank test (P≤.01).

The mean survival of patients since a decrease in the EF of the main ventricle was detected (<50%) was 12 years after adjusting for time and the covariates (Figure 7).

Figure 7. Mean survival of patients from the moment at which a decrease in the ejection fraction of the main ventricle is detected (<50%), adjusted by time and covariates.

Sixteen patients (67%) underwent cardiac catheterization. Pulmonary hypertension was documented in 6 cases before surgery and in 3 cases following surgery (Table 2).

DISCUSSION

An absence of right atrioventricular connection (classic tricuspid atresia) has a broad spectrum of anatomic presentations. Survival to adulthood depends on the balance achieved between the systemic and pulmonary circulation.10 The condition is characterized by the presence of a main ventricle that must sustain the systemic, pulmonary, and coronary circulation. When an absence of right atrioventricular connection is detected in a timely manner and other factors are favorable, patients should undergo surgery for physiologic correction of the problem, ideally using a Fontan technique.11,12 In patients with a restrictive atrial septal defect, the systemic venous pressure is increased.

Patients with an absence of left atrioventricular connection with ventricular inversion have different hemodynamics, because the pulmonary venous return is affected, with a consequent elevation of venous and capillary pressure. Despite the problems associated with this condition, our 2 patients survived to adulthood; 1 was treated with a systemic-pulmonary shunt, and the other did not undergo surgery. The abovementioned factors indicate that the 2 types of absent connections present different hemodynamic patterns.

In our setting, some patients receive a late diagnosis and others do not meet the requisites for Fontan surgery, whereas other patients are opportunely diagnosed and undergo surgery.13-16 This study includes 24 patients who survived to more than 20 years of age, are independent, and carry out simple tasks, in general with a good functional class. Thirteen patients underwent some type of surgical intervention that allowed survival to this age. However, as would be expected considering the natural evolution of this condition, there were 4 deaths: 1 patient who had undergone pulmonary banding, 1 treated with Fontan surgery, and 2 who were not surgically treated.

Pregnancy is not recommended in patients with a univentricular heart physiology. In addition to the circulation that must be managed, the fetal/ placental circulation implies an even greater load on the main ventricle. Nonetheless, 1 patient in our series was able to bring her pregnancy to term despite the risks involved.17

Three patients presented cerebrovascular events during follow-up, which were associated with septic embolisms and neurocysticercosis. These cyanotic patients have a higher risk of cerebrovascular events than the general population, and the risk increases when there is hypertension, atrial fibrillation, or a history of phlebotomy or microcytosis (P<.05). In contrast, there was no relationship between cerebrovascular events and the patient's age, smoking habit, erythrocytosis, ejection fraction, or treatment with aspirin or coumarin derivatives.18 In our study the statistical analysis showed that patients with polyglobulia have a tendency to lower survival, although the difference was not statistically significant.

The echocardiographic study enabled determination of the patients' morphologic and functional characteristics. We found that although the main ventricle was dilated in all cases, systolic function was preserved both in patients who had undergone surgery and those who had not. This fact may have favored an adequate quality of life, as was indicated by their functional class. An ostium secundum atrial septal defect and decreased systolic function of the main ventricle were factors with a negative influence on survival. Most of the studies focusing on main ventricle function in this pathology have been performed in children15,19 the present study is among the first undertaken in a series of adult patients.

Fontan surgery has been of great help to these patients; nonetheless, 46% in our series did not undergo any type of surgery and survived to adulthood.13,16 The presence of pulmonary stenosis was essential in these patients because it protected the vascular bed from pulmonary hyperflow and consequent injury to the pulmonary vasculature, although, on the other hand, it also favored polyglobulia.

The patients who were treated with some type of surgery survived longer and in a better functional class than those who experienced the natural evolution of the condition, although these differences were only trends and were not statistically significant. The decision to administer medical treatment was based on the patient's functional class and systolic function of the main ventricle calculated by echocardiography.

The limitations of this study include the small number of patients with dysfunction of the main ventricle and/or a common atrium, and the possible modifications of the prognosis owing to medical treatment.

CONCLUSIONS

In this study, a large atrial septal defect, normal hemoglobin values, and systolic function of the main ventricle >50% were factors favoring survival to adulthood in patients with absent atrioventricular connection. Echocardiography is a highly useful noninvasive technique for the anatomic and functional diagnosis of this condition, and provides the clinician and surgeon with valuable information for establishing treatment decisions and assessing the progress of these patients during follow-up.

Correspondence: Dr N. Espinola Zavaleta.
Ecocardiografía en Consulta Externa. Instituto Nacional de Cardiología Ignacio Chávez.
Juan Badiano, 1. Colonia Sección XVI. CP 14800 Tlalpan. México DF. México.
E-mail: niesza2001@hotmail.com

Received July 1, 2008.
Accepted for publication December 11, 2008.