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J Am Coll Cardiol, 1998; 32:237-244
© 1998 by the American College of Cardiology Foundation
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CLINICAL STUDIES

Echocardiographic hemodynamic and morphometric predictors of survival after two-ventricle repair in infants with critical aortic stenosis1

John P. Kovalchin, MDa, Michael M. Brook, MD*, Geoffrey L. Rosenthal, MD, PhDa, Kenji Suda, MD*, Julien I. E. Hoffman, MD, FACC* and Norman H. Silverman, MD, FACC*

a Lillie Frank Abercrombie Section of Pediatric Cardiology, Texas Children’s Hospital and Department of Pediatrics, Baylor College of Medicine, Houston, Texas, USA
* Department of Pediatrics and Cardiovascular Research Institute, University of California San Francisco, San Francisco, California, USA

Manuscript received November 6, 1997; revised manuscript received March 24, 1998, accepted April 9, 1998.

Address for correspondence: Dr. John P. Kovalchin, Pediatric Cardiology, MC 2-2280, Texas Children’s Hospital, 6621 Fannin Street, Houston, Texas 77030
johnk{at}bcm.tmc.edu


   Abstract
Top
 Abstract
Methods
 Results
 Discussion
 References
 
Objectives. The purpose of this study was to identify echocardiographic hemodynamic and morphometric factors that would predict which infants with critical aortic stenosis could undergo relief of left ventricular outflow obstruction as opposed to the Norwood procedure.

Background. Echocardiographic predictors of survival in infants with critical aortic stenosis after two-ventricle repair have been mainly limited to morphometric factors, which have limitations. Echocardiographic hemodynamic predictors of survival in these patients have not previously been studied.

Methods. Doppler color flow mapping and pulsed Doppler techniques were used to obtain hemodynamic measurements of flow in the ascending, transverse and descending aorta, the ductus arteriosus, and across the aortic and mitral valves in infants with critical aortic stenosis. Morphometric measurements of the left heart structures were obtained, and comparisons were made between survivors and nonsurvivors for the hemodynamic and morphometric factors.

Results. Twenty-eight infants (mean age 1 ± .6 days, mean weight 3.6 ± .6 kg) with critical aortic stenosis were evaluated. Nineteen had a two-ventricle repair initially attempted, and nine had a Norwood operation. Among the patients with a two-ventricle repair, the hemodynamic factors associated with survival after two-ventricle repair included predominant or total antegrade flow in the ascending (p < 0.01) and transverse aorta (p < 0.05). Aortic valve gradient, mitral valve inflow and direction of flow in the ductus arteriosus and descending aorta were unrelated to outcome. The morphometric factors associated with survival after two-ventricle repair included the indexed aortic annulus (p < 0.0002), aortic root (p < 0.003), ascending aorta (p < 0.008) and left ventricular long-axis length (p < 0.01). Left ventricular volume, mass, ejection fraction and mitral valve area were not related to outcome after two-ventricle repair.

Conclusions. In infants with critical aortic stenosis, predominant or total antegrade flow in the ascending and transverse aorta was associated with survival after two-ventricle repair. Determination of a one- versus two-ventricle repair remains a complex issue in infants with critical aortic stenosis. In addition to established morphometric predictors, hemodynamic information on the direction of flow in the aorta may help to define candidates for the Norwood operation.

In infants with critical aortic stenosis, variability of left heart size and left ventricular function determine whether repair can be achieved by relieving the left ventricular outflow obstruction, preserving the left ventricle as a pump (two-ventricle repair), or whether the Norwood procedure should be performed (one-ventricle repair) (1). The left heart structures, including the aortic annulus, aortic root, mitral valve, left ventricle and aortic arch, may be of inadequate size to support the systemic circulation. Determining whether the structures are of adequate size to support the systemic circulation, and therefore a two-ventricle repair, before an initial interventional procedure can be difficult. This initial decision is crucial because a Norwood procedure after a failed attempt of a two-ventricle repair is associated with decreased survival (2). Echocardiography is generally the sole modality used in decision making and in determining the feasibility of valvotomy.

Several studies (2–12) have evaluated the size of the left heart structures and attempted to categorize the sizes that are adequate to support the systemic circulation. The usefulness of these predictors of outcome is controversial (2–4,8,13,14). Hemodynamic variables, however, have not been evaluated in this group of patients, despite evidence in utero that flow abnormalities correlate with outcome (15,16).

The present study therefore sought to 1) identify echocardiographic hemodynamic predictors of survival after two-ventricle repair in infants with critical aortic stenosis; 2) evaluate the established echocardiographic morphometric predictors of outcome after two-ventricle repair; and 3) define any additional morphometric predictors of survival.


   Methods
Top
 Abstract
 Methods
Results
 Discussion
 References
 
Patient selection.   The echocardiograms and medical records of all patients <2 months old who presented to the University of California, San Francisco from January 1, 1988 to June 30, 1996 with the diagnosis of critical aortic stenosis were reviewed. Critical aortic stenosis was defined as severe aortic valve stenosis seen echocardiographically as thickened immobile aortic valve leaflets with a narrow jet of antegrade flow across the valve. All patients had patent aortic and mitral valves and normal atrioventricular and ventriculoarterial connections. All patients had left ventricular dysfunction and clinical signs of congestive heart failure requiring urgent intervention. All patients required a procedure to augment blood flow from the left ventricle to the aortic arch within the first 2 months of life. This procedure was either a surgical or balloon aortic valvotomy, Ross procedure (17) or a Norwood operation. All patients with critical aortic stenosis were included regardless of the size of the left ventricle or the presence of an aortic arch abnormality, including aortic arch hypoplasia or coarctation.

Echocardiography.   All patients were examined by two-dimensional and Doppler echocardiography with an Acuson (128 XP/5 or 128 XP/10), Hewlett-Packard (Sonos 1000 or 1500) or Advanced Technologies Laboratory (Ultra Mark 8) ultrasound system with transducers appropriate for patient size. All studies were recorded on 0.5-in. super-VHS videotape, and selected still frames were subsequently analyzed. Measurements were performed off-line with a computer-assisted analysis system (Tomtec Imaging Systems).

Hemodynamic measurements.   The maximal instantaneous Doppler velocity across the aortic valve and left ventricular outflow tract was calculated from the peak spectral Doppler velocity by means of the modified Bernoulli equation. Aortic regurgitation was noted and, if present, was graded as follows: 1 = trivial (small, thin regurgitant jet, <1 to 2 mm in diameter, seen just below the valve leaflets); 2 = mild (slightly broader jet, 2 to 4 mm in diameter, limited to the left ventricular outflow tract); 3 = moderate (broad regurgitant jet, 4 to 6 mm in diameter, extending into the left ventricular cavity); or 4 = severe (wide regurgitant jet, >6 mm in diameter, filling the left ventricular outflow tract and left ventricle). Pressure half-time calculations, retrograde flow in the descending aorta and left ventricular dilation are indicators of aortic regurgitation severity that may be influenced by other factors often inherent to critical aortic stenosis (e.g., patent ductus arteriosus and left ventricular dilation) and may not reflect the degree of regurgitation. These factors were therefore excluded from the grading system. Flow in the ascending and transverse aorta was assessed with color, pulsed and continuous wave Doppler. The color flow map and size of the time–velocity integral were used to determine the direction of blood flow, and flow was categorized as either antegrade or retrograde. Antegrade flow in the ascending aorta was defined as blood moving from the region of the aortic valve to the ascending aorta at the origin of the innominate artery and similarly in the transverse aorta as flow moving from the proximal transverse arch near the innominate artery to the distal transverse arch at the aortic isthmus. Retrograde flow in the ascending aorta was defined as blood flow from the ascending aorta at the innominate artery to the region of the aortic valve and similarly in the transverse arch as flow from the distal transverse arch at the aortic isthmus to the proximal transverse arch at the innominate artery (Fig. 1). Some patients had flow in both directions in the aorta; when this occurred, the predominant amount of flow as determined by the size of the velocity–time integral, whether this occurred in systole or diastole, was used to determine the predominant direction of flow. Patients with no antegrade aortic flow were diagnosed as having aortic atresia and were excluded from the study. The presence or absence of a ductus arteriosus and the direction of flow were noted. If coarctation of the aorta was present, the maximal instantaneous Doppler gradient across the coarctation site was recorded. Flow in the descending aorta was evaluated at the level of the diaphragm with pulsed Doppler interrogation and described as either 1) good pulsatility (a waveform with a rapid upstroke and pulse amplitude >0.5 m/s; or 2) poor pulsatility (a waveform with a slow upstroke and pulse amplitude <0.5 m/s). Diastolic retrograde flow in the descending aorta at the level of the diaphragm was also noted and classified as either: 1) all antegrade flow, with no retrograde flow; or 2) retrograde flow in diastole. The mitral valve inflow pattern was evaluated with pulsed Doppler, and the maximal instantaneous gradient was recorded. The presence and degree of mitral regurgitation were noted. The presence of an atrial communication was noted as well as the direction and peak velocity of interatrial flow. The tricuspid valve was interrogated for regurgitation, and the peak velocity of regurgitant flow was noted.



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  		Figure 1 Suprasternal notch view of aortic arch. A, Doppler color flow demonstrates retrograde systolic flow in the transverse aortic arch. B, Pulsed Doppler demonstrates retrograde systolic flow in the transverse aortic arch. A = anterior; LCA = left carotid artery; LSA = left subclavian artery; S = superior.

 
Morphometric measurements.   The aortic valve annulus was measured in the parasternal long-axis view as the maximal distance between the hinge points of the valve leaflets in systole. From the same view, the aortic root dimension was measured as the maximal internal dimension at the level of the sinuses of Valsalva (Fig. 2A). The ascending aorta, transverse aortic arch and aortic isthmus were measured from high parasternal or suprasternal notch views at the maximal dimension in systole. The ascending aorta was measured just proximal to the origin of the innominate artery. The transverse aortic arch was measured at the base of the left common carotid artery. The aortic isthmus was measured just distal to the base of the left subclavian artery (Fig. 2B). The mitral and tricuspid valve annuli were measured in the parasternal long-axis and apical four-chamber views in diastole as the maximal distance between the hinge points of the valve leaflets (Fig. 2C). The mitral and tricuspid valve areas were calculated from these orthogonal diameters by using the formula for an ellipse . The relative mitral valve area was then calculated as the ratio of the two AV valve areas. Left ventricular volume and mass were calculated using the biplane Simpson method and the planimetered two-dimensional method of Schiller (18–20). The long-axis length of the left ventricle was measured as the maximal distance from the plane of the mitral valve to the endocardium of the left ventricular apex in diastole from the apical four-chamber view. The long-axis of the heart was similarly measured as the maximal distance from the crux of the heart to the apex of the ventricle that formed the apex of the heart. The relative left ventricular length was calculated as the ratio of the left ventricular long-axis length to the long-axis length of the heart. Whether the right or left ventricle formed the apex of the heart was also noted. The presence of endocardial fibroelastosis was noted and described as 1) no evidence of endocardial fibroelastosis or echodensity limited to the chordae tendineae and papillary muscles; or 2) diffuse involvement of the left ventricular endocardium as well as the chordae tendineae and papillary muscles.



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  		Figure 2 A, Schematic of parasternal long-axis view. Aortic annulus (1) and aortic root (2) diameters measured in systole. B, Schematic of suprasternal notch view. Ascending aorta (3), transverse aorta (4) and aortic isthmus (5) diameters measured in systole. C, Schematic of apical 4-chamber view. Tricuspid (6) and mitral (7) valves measured in diastole. Ao = aorta; LA = left atrium; LV = left ventricle; MV = mitral valve; RA = right atrium; RCA = right carotid artery; RSA = right subclavian artery; RV = right ventricle; TV = tricuspid valve; other abbreviations as in Figure 1.

 
To allow for comparison of our morphometric data with other established morphometric predictors of outcome in patients with critical aortic stenosis, several calculations and additional measurements were performed. The anatomic measurements were indexed to body surface area for comparison to previous studies and for calculation of various risk factor and discriminant scores (21). Left ventricular volume was also calculated by the biplane bullet method with subsequent mass calculations as described by Rhodes et al. (2) to use for comparison. Risk factor and discriminant scores were calculated as described by the methods of Rhodes et al. (2).

Patient outcome.   All interventions, outcomes, complications and clinical condition at the latest follow-up visit were recorded for each patient. The initial procedure was determined according to the preference of the attending physician and not on a protocol or random basis. In some patients, the criteria of Rhodes et al. (2) were factored into the decision. Patients who had a two-ventricle repair initially attempted were classified into two groups. Group 1 included patients who had a successful two-ventricle repair, defined as a balloon or surgical valvotomy or Ross-Konno procedure that resulted in the left ventricle completely supplying the systemic cardiac output. These patients survived the procedure or procedures and were discharged home in good condition. An unsuccessful or failed two-ventricle repair was defined as the inability of the left heart structures to support the systemic cardiac output after a valvotomy or Ross-Konno procedure that resulted in death of the patient or the performance of a Norwood operation.

Statistical analysis.   Results are expressed as mean value ± SD, as appropriate. Measurements of continuous variables were compared between groups by means of analysis of variance and unpaired Student t tests. Categoric variables were compared with contingency tables by means of chi-square or Fisher exact tests, where appropriate. Logistic regression analysis was performed to assess associations between hemodynamic and morphometric variables (SAS Institute, 1996). A p value < 0.05 was considered significant.


   Results
Top
 Abstract
 Methods
 Results
Discussion
 References
 
Patients.   Twenty-eight patients met the inclusion criteria (21 male, 7 female; mean age at initial presentation 1 ± 0.6 days; weight 3.6 ± 0.6 kg; body surface area 0.23 ± 0.03 m2). The mean age at initial operation was 9.9 ± 16.5 days (median 4). Twenty-five patients were receiving prostaglandin E1 and had a ductus arteriosus; in three the ductus arteriosus had closed. Nineteen patients had a two-ventricle repair initially attempted, and nine had a Norwood procedure initially performed. In one patient a two-ventricle repair was initially attempted; however, the patient had evidence of poor systemic cardiac output, and a Norwood procedure was subsequently performed. The procedures and outcome for each patient are shown in Table 1.


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  		Table 1 Patients, Procedures and Outcomes

 
Echocardiography.   Hemodynamic measurements
The echocardiographic hemodynamic factors evaluated are shown in Table 2. Of the 14 patients who had a successful two-ventricle repair, flow was predominantly or totally antegrade in the ascending aorta in 13 (p < 0.01) and in the transverse arch in 12 (p < 0.05). The direction of ductus arteriosus flow was unrelated to the success or failure of the two-ventricle repair. Three patients did not have a ductus arteriosus. All three of these patients had antegrade flow in the ascending and transverse aorta, and all had a successful two-ventricle repair. The maximal instantaneous Doppler gradient across the aortic valve and left ventricular outflow tract was approximately two times higher in patients with a successful than in those with a failed two-ventricle repair. Two patients in the two-ventricle repair group and two in the Norwood group had mild aortic regurgitation; none had more than mild aortic regurgitation. Both patients in the two-ventricle repair group had predominant or total antegrade flow in the ascending and transverse aorta. Repair was successful in one patient but failed in the other. Left ventricular ejection fraction was depressed in all patients, and there was no difference in outcome related to ejection fraction. Three patients had clinically recognizable aortic coarctation. Two were in the two-ventricle repair group and had a successful repair. Both had predominant or total antegrade flow in the ascending aorta, and one had predominant or total retrograde flow in the transverse aorta. Both had right to left flow at the ductus arteriosus. The other patient with coarctation died after a Norwood procedure. All patients with aortic coarctation had a ductus arteriosus, and the peak gradient across the coarctation site could not accurately be obtained.


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  		Table 2 Comparison of Hemodynamic Variables for Survival and Nonsurvival in Patients With Two-Ventricle Repair

 
Descending aorta flow signals were available in 23 of the 28 patients. The pulsatility of the Doppler signal in the descending aorta was categorized as good in 14 of 17 patients who had a two-ventricle repair; the type of descending aorta pulsatility was not associated with the success or failure of a two-ventricle repair. Seven of these 17 patients had diastolic retrograde flow in the descending aorta; the presence or absence of diastolic retrograde flow in the descending aorta was not associated with the success or failure of a two-ventricle repair.

Mitral valve inflow signals were available in 21 of the 28 patients. In all patients the peak inflow velocity was <1 m/s. The waveform was a short, narrow signal with an E/A summation pattern in all. In the two-ventricle repair group, 5 patients had mild, 4 had trivial and 10 had no mitral regurgitation. The presence or degree of mitral regurgitation was not associated with the success or failure of a two-ventricle repair. In the Norwood group, 2 patients had mild, 4 had trivial and 3 had no mitral regurgitation.

In the two-ventricle repair group, 16 patients had a patent foramen ovale with left to right shunting, and 3 patients had an intact atrial septum with left to right bowing. Of the patients with an intact atrial septum, one had a successful and two a failed two-ventricle repair. All patients in the Norwood group had a patent foramen ovale with left to right flow. Pulsed or continuous wave Doppler information was available in 18 of the 28 patients. In most patients a jet of left to right flow across the atrial septum was readily seen, and the mean peak velocity of flow was 1.7 ± 0.5 m/s. The peak velocity of flow across the atrial septum was not associated with the success or failure of a two-ventricle repair, and the peak velocity of flow was not different between the Norwood group and the two-ventricle repair group.

In the two-ventricle repair group, 5 patients had mild, 3 had trivial and 11 had no tricuspid regurgitation. The degree of tricuspid regurgitation was unrelated to the success or failure of a two-ventricle repair in this group of patients. In the Norwood group, five patients had mild, one had trivial and three had no tricuspid regurgitation.

Morphometric measurements.   Comparison of morphometric measurements is shown in Table 3. The morphometric factors associated with survival after two-ventricle repair included the indexed aortic annulus (p < 0.0002), aortic root (p < 0.003), ascending aorta (p < 0.008) and left ventricular long-axis length (p < 0.01). The transverse arch and aortic isthmus diameters; left ventricular volume, mass and ejection fraction; and mitral valve area were not related to the success or failure of a two-ventricle repair.


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  		Table 3 Comparison of Morphometric Variables for Survival and Nonsurvival in Patients With Two-Ventricle Repair

 
Twenty-four of the 28 patients had echocardiographic evidence of endocardial fibroelastosis. Four of the patients in the two-ventricle repair group had no echocardiographic evidence of endocardial fibroelastosis, and all were alive at the latest follow-up visit. In the two-ventricle repair group, extensive endocardial fibroelastosis was associated with failure of a two-ventricle repair (p < 0.002). Echocardiographic evidence of endocardial fibroelastosis was confirmed in four patients at autopsy and noted at operation in an additional four patients. The left ventricle formed the apex of the heart in 11 of the 19 patients undergoing a two-ventricle repair and in 1 of the 9 patients who had a Norwood operation. In the two-ventricle repair group, an apex-forming left ventricle was associated with a successful repair (p < 0.05).

Logistic regression analysis showed that there was a trend toward larger left ventricular outflow and aortic arch structures with the presence of predominant or total antegrade flow in the ascending aorta. However, in this small group of patients, these associations did not reach statistical significance.

Application of previous morphometric predictors.   The echocardiographic morphometric predictors of survival described by Rhodes et al. (2) were applied retrospectively to the patients in the present study. The discriminating score is an equation based on body surface area, aortic root index, left ventricular long-axis/heart ratio and indexed mitral valve area to predict survival after two-ventricle repair in infants with critical aortic stenosis. The discriminant score correctly predicted outcome in 14 (74%) of 19 patients in our study. The score was incorrect in 5 (26%) of 19 patients, for whom it predicted nonsurvival after a two-ventricle repair, yet the patients survived. The risk factor criteria are based on indexed aortic root, left-ventricular long-axis/heart ratio, indexed mitral valve area and indexed left ventricular mass. The risk factor criteria correctly predicted outcome in 14 (74%) of 19 patients. The criteria incorrectly predicted outcome in 5 (26%) of 19 patients. In three patients, although the risk factor criteria predicted survival after two-ventricle repair, the patients died; whereas in two patients the criteria predicted nonsurvival after a two-ventricle repair, yet the patients survived. The discriminating score and risk factor criteria agreed in 13 (68%) of 19 patients, correctly predicting outcome in 11 (58%) of 19 and incorrectly in 2 (11%) of 13. These correctly predicted outcomes included nine predictions of survival and two predictions of nonsurvival. The discriminating score and risk factor criteria predictions disagreed on the prediction of outcome in 6 (32%) of 19 patients. Of the 14 patients who survived a two-ventricle repair in the present study, the discriminating score correctly predicted survival in 9 patients (64%), and the risk factor criteria correctly predicted survival in 12 patients (86%). Of the nine patients who underwent an initial Norwood procedure, only one had a discriminant score predicting survival after two-ventricle repair; two patients had risk factor criteria predicting survival.

Outcome.   Among the 19 patients who underwent a two-ventricle repair, 14 had a successful repair (74%). The five failures were secondary to poor systemic output and left ventricular failure. These five patients died, one after an attempted Norwood operation as a second procedure. All deaths occurred during the initial hospital period, and there were no late deaths or failures after an initially successful two-ventricle repair. The rate of reintervention after aortic valvotomy was high, with 15 (79%) of 19 patients requiring another procedure for recurrent stenosis or regurgitation. Eight patients required valve replacement either in the short term (<4 months, seven patients) or long-term (52 months, one patient), and this was accomplished with a Ross or Ross-Konno procedure in all (22). At the latest follow-up visit (mean 34 ± 28 months), one patient who had an initial surgical valvotomy and repeat surgical valvotomy for recurrent stenosis now has moderate to severe aortic regurgitation. The remainder of the patients in the two-ventricle repair group, including eight who had a valve replacement, are asymptomatic and clinically doing well, with no more than mild residual aortic stenosis or regurgitation. Among the nine patients who had a Norwood operation, four died during the immediate postoperative period (44%). There were no late deaths. Of the five survivors, one has a completed Fontan repair, and the other four have undergone bidirectional Glenn procedures and are awaiting Fontan repair.


   Discussion
Top
 Abstract
 Methods
 Results
 Discussion
References
 
The present study demonstrates that hemodynamic echocardiographic variables offer additional useful information in determining the suitability of patients with critical aortic stenosis for initial intervention with either a valvotomy or a Norwood procedure. Predominant or total antegrade flow in the ascending and transverse aorta was associated with survival after a two-ventricle repair. The direction of ductus arteriosus flow, descending aortic flow, aortic valve Doppler gradient, degree of aortic regurgitation, mitral valve inflow, degree of mitral regurgitation, atrial level shunt and left ventricular ejection fraction were hemodynamic variables not associated with outcome.

Comparison with previous studies.   Hemodynamic measurements
Direction of blood flow in the distal aortic arch detected prenatally in fetuses with critical left ventricular outflow obstruction has been shown (15) to correlate with the ability of the left heart structures to support the systemic cardiac output postnatally. Additionally, in fetuses with congenital heart disease, reversal of flow seen at the foramen ovale or ductus arteriosus in utero has been associated with poor postnatal outcome (16). Other echocardiographic studies (23,24) have characterized flow in the aorta and ductus arteriosus in infants with aortic atresia or critical aortic stenosis with the use of pulsed Doppler techniques, and their findings on the direction of flow are supported by our data.

Hemodynamic factors evaluated at cardiac catheterization as predictors of outcome in patients with critical aortic stenosis have demonstrated variability. There is controversy over whether left ventricular end-diastolic pressure, left atrial pressure, mean pulmonary artery pressure and ejection fraction are associated with survival after two-ventricle repair (11–13). However, most studies (11–13) agree that the severity of the aortic valve gradient and the peak systolic left ventricular pressure are not associated with outcome.

Morphometric measurements
There is variability among the reported echocardiographic morphometric predictors. In the elegant study of Rhodes et al. (2), a larger indexed aortic annulus, aortic root, aortic arch, aortic isthmus, mitral area, left ventricular long-axis, left ventricular volume and left ventricular mass were all predictive of survival after two-ventricle repair. The morphometric factors that were associated with survival after two-ventricle repair in our study included a larger indexed aortic annulus, aortic root, ascending aorta and left ventricular long-axis length. Mitral area, left ventricular volume and mass were not associated with survival or nonsurvival in our study. This discrepancy may in part be explained by the fact that the Rhodes criteria were a factor in the decision process for some patients. This would tend to decrease the variability of these measurements in the two-ventricle group by removing the smaller values and make it more difficult to show a difference between survivors and nonsurvivors. In addition, some of the associations may have reached statistical significance with larger patient numbers.

The association of a larger left ventricle with survival after a two-ventricle repair has been controversial. Indeed some patients with critical aortic stenosis have hypoplastic left ventricles, whereas others have dilated left ventricles. The etiology of the discrepancy remains obscure. Some studies (2,3,6,8–10) have shown that a larger left ventricle is important for survival after two-ventricle repair, whereas ours and others (11,12) have shown no association with survival. Similarly, there is controversy over whether aortic valve annulus, aortic root or mitral valve size is associated with survival after a two-ventricle repair (2,4,7–9,12).

The presence of endocardial fibroelastosis was associated with poor outcome in our study, and this finding supports those of previous studies (7,25). Other investigators (4) found no association of endocardial fibroelastosis with outcome. The etiology of endocardial fibroelastosis remains unclear and may be related to subendocardial ischemia secondary to elevated left ventricular pressures. Alternatively, endocardial fibroelastosis may in some patients be a primary event in utero, rather than a secondary finding, leading to restriction to left ventricular inflow and subsequent underdevelopment of the left heart structures.

The morphologically based discriminating score and risk factor criteria described by Rhodes et al. (2) correctly predicted outcome in 74% of the patients in the present study when applied retrospectively. This is somewhat less than the 90% predictability in the initial series. Although these algorithms offer valuable information, there remain some limitations. The predictive value may be affected by institutional bias in selecting patients for a given type of initial repair. The left heart structures are often small, and minor errors or variation in the measurement or imaging techniques may affect a score and therefore the management of an individual patient, if these are the only factors evaluated (13).

Study limitations.   In addition to the issues discussed, the study is limited by its retrospective nature. Establishing a standard protocol for decision making and applying it prospectively would better evaluate the success. However, the low incidence of critical aortic stenosis makes this approach much less feasible. Even during an 8-year period, small numbers of patients were available for study. Some additional associations in the study might have reached statistical significance with larger patient numbers. Similarly, the effect estimates generated by the logistic regression may be imprecise; however, they are included to illustrate the relation between flow and the size of morphologic structures. Additionally, potential physician and institutional biases in the selection of patients for a particular repair affect not only the patient groups but also the predictability of the data.

Conclusions.   Despite advances in surgical and catheterization techniques, infants with critical aortic stenosis continue to have relatively high mortality and reintervention rates. Appropriate patient selection remains a difficult and complex issue, but the current study suggests that the combination of morphometric and hemodynamic factors may improve the selection of candidates suitable for two-ventricle repair. Appropriate selection criteria will become even more critical as the decision point for intervention moves toward the in utero patient, in whom the risk of intervention is likely to be significantly higher than in the neonate, requiring a more certain and more defined benefit.


   Footnotes
 
1 All manuscripts by authors from the University of California San Francisco have been reviewed by a Guest Editor. Back


   References
Top
 Abstract
 Methods
 Results
 Discussion
 References
 

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