Author + information
- Received November 10, 2000
- Revision received March 8, 2001
- Accepted March 26, 2001
- Published online July 1, 2001.
- Rekwan Sittiwangkul, MDa,
- R.Y Ma, MDa,
- Brian W McCrindle, MD, MPH, FACCa,
- John G Coles, MDa and
- Jeffrey F Smallhorn, MBBSa,*
- ↵*Reprint requests and correspondence:
Dr. Jeffrey F. Smallhorn, The Hospital for Sick Children, 555 University Avenue, Toronto, Ontario, Canada M5G 1X8
We sought to determine the accuracy of transthoracic echocardiography (TTE) in identifying risk factors in patients with an atrioventricular septal defect (AVSD).
Atrioventricular septal defect is a common lesion, and many decisions about it are based on echocardiography alone. The identification of associated left-sided inflow and outflow obstructive lesions is important, as they are responsible for mortality and morbidity.
Between 1983 to 1998, 549 patients with AVSD underwent repair. The TTE findings were correlated with surgery, angiocardiography, autopsy or postoperative TTE. Papillary muscle measurements were made in those with either a left ventricular outflow tract (LVOT) or left ventricular inflow abnormality and compared with those measurements from control subjects. Measurements of the LVOT were made in patients with an identified LVOT abnormality.
There were 63 missed lesions, decreasing over time. Double-orifice left atrioventricular valve (DOLAVV) and nonobstructive chordae in the LVOT were more often missed. Re-operation was performed to address a missed lesion in 2 of 68 patients. Two of 55 patients died of reasons related to a missed lesion. In 67% of patients, DOLAVV was missed. Abnormal papillary muscle angles were seen with either a LVOT abnormality or DOLAVV. High insertion of the anterolateral papillary muscle was a risk factor for death or residual LVOT obstruction. Abnormal LVOT measurements were found in patients with tunnel obstruction and those with an acquired subaortic ridge.
Transthoracic echocardiography provides accurate preoperative information on AVSD.
The echocardiographic features of the atrioventricular septal defect (AVSD) have been well documented (1,2). Echocardiography provides sufficient preoperative data on patients with a partitioned atrioventricular valve orifice and an intact ventricular septum (3), as well as on small case series of complete AVSD (4,5). We sought to determine the accuracy of transthoracic echocardiography (TTE) in identifying potential associated anatomic risk factors that, when missed, are associated with postoperative complications and mortality (6–11). We also sought to determine the prevalence and characteristics of left ventricular outflow tract (LVOT) and inflow tract abnormalities in AVSD, as determined by preoperative TTE.
Study group and characteristics of LVOT abnormalities
The data bases of the Divisions of Cardiology and Cardiothoracic Surgery were searched to identify patients with a diagnosis of AVSD who had complete surgical repair between January 1983 and July 1998. Patients with associated left atrial isomerism who were thought to be suitable for a biventricular repair were included. Associated right atrial isomerism, tetralogy of Fallot and obvious unbalanced AVSD were excluded. Of note, no volumetric data were available for analysis.
Classification of LVOT abnormalities
A diffuse tubular narrowing of the LVOT by thickened tissue along the outflow septum and anterior left atrioventricular (AV) valve leaflet, often associated with annular hypoplasia (12)or a marked discrepancy between the aortic annulus and subaortic area during systole (Fig. 1A).
An immobile ridge located at the ventricular septal crest in the LVOT (Fig. 1B).
Thick chordal tissue
Thin, mobile chordal tissue
Thin accessory chordae from the anterior left AV valve leaflet, which may or may not be fixed to the ventricular septum (Fig. 2A).
Abnormal papillary muscle
Combination of abnormalities
More than one abnormality (Fig. 2C).
Data were collected from the patients’ medical records, including echocardiographic, cardiac catheterization, surgical and autopsy reports. Preoperative anatomic diagnoses were noted from the TTE reports. This study met the ethics guidelines of the Hospital for Sick Children.
Anatomic features and associated lesions were defined as having been missed if they were not noted or documented in the preoperative TTE reports, but were noted on the reports from the other modalities. For all patients, postoperative echocardiographic reports were reviewed to identify missed obstructive lesions at the LV inflow and outflow level. A missed patent ductus arteriosus was defined for only those patients with either preoperative or postoperative evidence of flow through the ductus or patency at autopsy. A similar approach was taken for the definition of missed small muscular ventricular septal defects (VSDs). Missed atrial septal defects refer only to those in the ostium primum. All TTE videotape recordings for patients with a missed diagnosis were reviewed to determine whether the missed lesion could have been identified.
Data are described as frequencies, median values with ranges and mean values with standard deviations, as appropriate. The number of patients with missed diagnoses and the number of missed diagnoses per patient were identified. Likewise, the proportion of each anatomic diagnosis, as well as associated lesions that were missed, was noted. Careful review of patients with missed lesions was performed to determine whether the missed lesions had a direct relationship with mortality or re-operation. The Student ttest was used to compare patients between groups. A p value <0.05 was considered significant.
Papillary muscle measurements
We determined the location of both papillary muscles (Fig. 3A)in patients with a double-orifice left atrioventricular valve (DOLAVV) or LVOT (13). For comparison, similar measurements were made in a control group of subjects with no documented LVOT abnormality and no DOLAVV who were chosen randomly from the patient group.
Measurements of LVOT
In all patients with LVOT abnormalities, the subaortic region (the narrowest point during systole) and aortic annulus diameters were measured, and their ratio was calculated (Fig. 3B)(14). To determine preoperative risk factors for the development of a subaortic ridge during follow-up after repair, we measured the aortoseptal angle (Fig. 3B)in 15 patients with an acquired ridge, and we compared the results with those of the remaining 49 control subjects without an acquired ridge at follow-up. The findings in those patients who met the criteria for the presence of tunnel-like subaortic narrowing were compared with those of a different group of age- and AVSD type-matched control subjects chosen at random from the study group.
From January 1983 to July 1998, 549 patients had surgical repair of their AVSDs. Preoperative echocardiography was performed in all, with 149 of 549 patients also having had cardiac catheterization. Down syndrome was present in 327 patients (60%). Associated cardiac lesions are noted in Table 1. A common AV valve orifice was believed to be present in 388 patients (71%), whereas 161 patients had partitioned orifices, 120 of whom had no VSD. Previous operations had been performed in 67 patients (12%). The median age at repair was 8.2 months (range 14 days to 18.4 years). Re-operation was performed in 68 patients. Kaplan-Meier estimates of freedom from first re-operation (deaths are censored) were 96% at 1 month (95% confidence interval [CI] 94% to 98%), 93% at 1 year (CI 91% to 96%), 82% at 5 years (CI 77% to 87%) and 70% at 10 years (62% to 78%). The most frequent re-operations (some in combination) included left AV valve repair in 43 patients (replacement in 13) and subaortic resection in 15. Death after repair occurred in 55 patients (10%). Kaplan-Meier estimates of survival after repair were 92% at 1 month (9% CI 89% to 94%), 90% at 1 year (CI 87% to 92%) and 88% from 5 to 10 years (CI 86% to 91%). Forty-five patients died within one month after the operation. The numbers of deaths decreased over the study period, with deaths in 31 (16%) of 192 patients who had surgical repair during 1983 to 1988, 20 (12%) of 169 patients during 1989 to 1993 and 4 (2%) of 188 patients during 1994 to 1998 (p < 0.001).
There were a total of 63 lesions missed by preoperative TTE in 57 patients (10%). Over time, the proportion of patients with missed lesions decreased, and the types of lesions missed changed (Tables 2 and 3). ⇓⇓On review of videotape recordings (J.F.S. and R.S.), 32 (51%) of 63 missed lesions could be identified (Table 3). The remaining 49% of missed lesions were not seen due to inadequate visualization or lack of color Doppler imaging.
Control group measurements
Double-orifice left AV valve
There were 21 patients with DOLAVV, 13 of whom (62%) had partitioned orifices. Of these 21 patients, 7 (33%) had Down syndrome and 7 had associated left-sided lesions. The distance between the two papillary muscles of these patients was significantly less than that in control subjects (p < 0.001) (Table 4). Tables 2 and 3outline the rates of diagnoses and missed diagnoses in patients with DOLAVV. In the 18 patients in whom it could be characterized on review, the accessory orifice was associated with the posteromedial valve leaflet in 13 (Fig. 4)and the anterolateral leaflet in 4 (1 single papillary muscle). The ratio of the orifice diameters ranged from 20% to 83%. Left AV valve regurgitation before repair was moderate in 2 of 21 patients, mild in 12 and absent in 7. The outcome included early postoperative death in 5 patients, with 1 late death and 2 subsequent left AV valve surgeries.
Abnormalities of the LVOT
There were 64 patients with a LVOT abnormality (Table 6), 55 of whom had a diagnosis at the time of repair, with the remaining 9 patients developing a subaortic ridge during follow-up. Of these 64 patients, 30 (47%) had Down syndrome. Only 10 of the 55 patients with a preoperative LVOT abnormality had a pressure gradient. There were 12 preoperative missed diagnoses, none with a pressure gradient at repair (Table 2). For the 59 patients with a LVOT abnormality and two papillary muscles, the position of the anterolateral papillary muscle was not significantly different from that of the control subjects (p = 0.25) (Table 4). However, the posteromedial papillary muscle was rotated counterclockwise, as compared with that of the control subjects (p = 0.001) (Fig. 3, arc B). Only patients with LVOT tunnel narrowing or an acquired subaortic ridge had an abnormal ratio of aortic annulus to subaortic diameter, as compared with the control subjects (Table 5).
The ratio of aortic annulus to subaortic diameter in the 13 patients with tunnel narrowing (including 5 with combined lesions) was significantly different from that of control subjects (p < 0.001) (Table 5). Associated cardiac anomalies were noted in six patients, with one death during the early postoperative period. During follow-up of two to seven years, four patients developed a subaortic ridge requiring surgical repair, with two patients having a residual pressure gradient and one lost to follow-up.
Isolated subaortic ridge
Two patients had an isolated subaortic ridge before the first operation (Table 6), one of whom had a preoperative gradient. Despite resection, both had a residual gradient at follow-up. Another nine patients with a normal LVOT developed a fibromuscular ridge one to six years after their initial repair. Surgical resection was performed in seven patients, one of whom had a recurrence requiring re-operation and four of whom had a residual gradient.
Accessory chordae from the anterolateral left AV valve
Twelve patients had thick, fixed chordae crossing the LVOT, all diagnosed before repair. Of these, six had a preoperative gradient (Table 6). The chordae arose from the base of the superior bridging leaflet, inserting directly onto the septum. All underwent resection at the initial repair, with four having a residual gradient, one of whom required further surgical repair due to incomplete resection. There were 24 patients with thin chordae that arose from the base of the superior bridging leaflet, none of whom had a preoperative gradient. The chordae attached to the ventricular septum in 9 patients, whereas 15 patients had free-floating chordae. Of these 15 patients, eight underwent resection and seven were left unattended. Only one patient without resection developed a gradient at follow-up. In those with thin, fixed chordae, two were resected at repair, with no recurrences. Of the seven unresected patients, two developed a subaortic ridge at follow-up, four developed a gradient at 1 to 11 years and one had no late obstruction.
Combination of abnormalities
Six patients had combined LVOT abnormalities (Table 6). One patient had enlargement of the LVOT, with no residual gradient after 10 years of follow-up. Another patient died in the early postoperative period after a complex left AV valve repair. The third patient had associated coarctation of the aorta and underwent repair of the coarctation, as well as chordal resection. This patient died suddenly two years after repair, with no follow-up data. On another review of the preoperative TTE data, there was evidence of high insertion of anterolateral papillary muscle. The fourth patient had a subaortic ridge, tunnel narrowing and thin chordae, with a preoperative gradient of 30 mm Hg. Eight months after repair, including subaortic resection, there was a residual gradient of 30 mm Hg. The fifth patient died early and had tunnel narrowing, a subaortic ridge without a gradient and DOLAVV. The sixth patient died of acute LVOT obstruction due to high insertion of the anterolateral papillary muscle.
Lesions of the LVOT associated with a papillary muscle abnormality
There were three patients in this category. The first patient had an accessory band from the anterolateral muscle, which attached to the base of ventricular septum and was resected at repair. The second patient, who had unobstructive chordae in the LVOT, which attached to an abortive papillary muscle, underwent successful resection. The third patient had high insertion of the anterolateral papillary muscle; this patient had an early postoperative death due to a complex left AV valve repair, with the LVOT abnormality detected at autopsy.
Papillary muscle measurements of patients with a LVOT abnormality
The two patients with high insertion of the anterolateral papillary muscle had an angle of 151° and 152°, respectively (Fig. 3, arc A) (control subjects: 181 ± 15°) (Table 4). Using an angle of 150° (Fig. 3, arc A) as a cut-point, and applying this to the total group with LVOT abnormalities, we identified four additional patients who had measurements that fell below that value (140° to 150°). Two patients had associated left-sided abnormalities, both with a residual post-repair gradient across their LVOT. The other two patients died after repair; one early and one late, with no autopsy.
Aortoseptal angle measurement
Of the 15 patients with an acquired ridge, 9 had a normal LVOT, 4 had tunnel narrowing and 2 had unresected thin chordae. The mean aortoseptal angle of those with an acquired ridge was 129 ± 8°, compared with a mean of 137 ± 11° in 49 patients without an acquired ridge (p < 0.02).
Impact of missed lesions
Of 68 patients who had a re-operation, 9 (13%) had a missed lesion. Of these, only two re-operations were done specifically to address the missed lesion. One patient with a missed patent ductus arteriosus required subsequent ligation, and one missed aortic coarctation required repair. Of the 55 patients who died after repair, 14 (25%) had a missed lesion. Of these 14 patients, the cause of death was related to the missed lesion in only two. One patient had a missed high insertion of the anterolateral papillary muscle in the LVOT, and the other had a similar finding in the right ventricular outflow tract.
Despite improvement in surgical mortality over time, there are some patients who appear to be at a higher risk of early death and late complications after AVSD repair. As noted in our study, abnormalities of the left AV valve and LVOT are two major risk factors. Although mortality decreased throughout the duration of the study, freedom from re-operation was only 70% at 10 years, with the majority of re-operations being for left AV valve dysfunction or LVOT obstruction.
The potential impact of missed lesions on mortality and morbidity was an important component of this study. The most frequently missed lesion was DOLAVV, followed by the presence of nonobstructive chordae in the LVOT. Although there are several echocardiographic studies (15,16)that address the features of DOLAVV, they are retrospective. A prospective study of 95 patients with AVSD by Tworetzky et al. (17)had findings similar to those in our study, with a general inability to reliably detect DOLAVV. Other missed lesions in our study were frequently extracardiac, similar to previous reports (5,16), and reinforce the need for a complete and thorough evaluation. Some missed diagnoses, such as small associated muscular VSDs, are to be expected (17,18), whereas others are more rare (absent mural leaflet and high insertion of the anterolateral papillary muscle) and require vigilance to detect them. Missed lesions infrequently resulted in death or the need for re-operation, which indicates that TTE is adequate for assessment.
Double-orifice left AV valve
This lesion has been identified as a risk factor for repair (6,7)and, in our study, was associated with a higher mortality. As noted by our papillary muscle measurements, these patients have papillary muscles that are closer together (20,21). Although, in some patients, the second orifice represents a slit in the valve, without supporting tension apparatus; the majority of second orifices are supported, which aids in making the diagnosis. Why, then, did we miss so many patients with DOLAVV? The two orifices can be of varying sizes, and, in some patients, the second orifice can be very small, making recognition more difficult. In addition, in many patients with a single orifice, the abnormal appearance of the left AV valve may mask a double orifice, unless the examiner pays close attention to the short-axis view. Frequently, the valve appears to fold on itself as it closes and/or has accessory chordae, both of which can disguise a true double orifice. Close inspection of the valve in the short axis, in conjunction with frame-by-frame analysis, is a key aspect of the examination. On review of the tapes, we applied this approach, which accounted for the improved diagnostic rate, as compared with that at the initial evaluation.
Abnormalities of the LVOT
In many patients with AVSD, the left AV valve is septophilic; however, most of these cases represent primary chordae that attach to the ventricular septum. In others, secondary chordae arise from the base of the superior bridging leaflet and may result in LVOT obstruction. Some have thick, fixed secondary chordae that are more likely to be associated with outflow obstruction, whereas, in others, these secondary chordae are thin and without obstruction. The data from our study are consistent with those of previous reports (22), where LVOT abnormalities are more prevalent in patients with a partitioned orifice. We noted in our study that the presence of fixed, secondary chordae in the LVOT is a risk factor for late obstruction, even in the absence of a gradient. This appears to be independent of whether the accessory tissue appears thin or thick. Isolated tunnel narrowing appears to be a significant risk factor for death or residual obstruction, resulting in a varied surgical approach through the utilization of a modified KONNO procedure (8), with or without relocation and patching of the superior bridging leaflet (9,23). The group of patients with obstruction at multiple levels had substantial mortality, which raises the question as to whether these patients would have been better served by a different surgical approach. Our study suggests that both an acute aortoseptal angle and an abnormal aortic to subaortic ratio are risk factors for late subaortic stenosis. An abnormal aortoseptal angle has been identified as a risk factor for subaortic stenosis in patients without AVSD (14), reinforcing the findings in our study.
High insertion of anterolateral papillary muscle
The position of the posteromedial papillary muscle is rotated counterclockwise in patients with AVSD compared with subjects with a normal heart (13). This rotation is important to understand the mural leaflet length and position of the “cleft” in AVSD, but it does not result in LVOT obstruction. Absolute measurements of the anterolateral papillary muscle location in patients with a proven abnormality indicated that the location differed considerably from that of the control group. When we chose a cut-point of 150° as abnormal and applied it to the group with LVOT abnormalities, we identified several other patients with a similar measurement who appeared to be at a higher risk of mortality and morbidity. Therefore, it is important to pay attention to the location of the anterolateral papillary muscle. How these should be managed surgically is somewhat unclear, as this is a major papillary muscle group.
Study strengths and limitations
Our study has a large enough sample size, covers a long time span and attempts to address the limitations and errors of echocardiography employed in patients with AVSD. The approach of selecting patients with a balanced AVSD, on subjective grounds, appears to have been appropriate, as death due to missed ventricular hypoplasia did not appear to be a risk factor in our study. Because we did not review every patient, it is possible that some of the aforementioned risk factors could have been overlooked. Although this is possible, it is probably unlikely, as all of our patients had surgical confirmation of their pathology, with the majority having follow-up echocardiograms. Because our study only spans 16 years, it is possible that other patients with acquired subaortic stenosis may present in the future. Our definition of thin and thick accessory chordae was subjective, so there may be some overlap between these groups. Could the outcome have been improved if all of the patients had undergone angiocardiography as well as echocardiography? Certainly some of the extracardiac abnormalities would have had a higher chance of detection, but in general, these had a minimal impact on management, and the number of errors in this group decreased with time. Persistent errors throughout the course of our study, particularly DOLAVV and nonobstructive chordae, and the abnormal position of the anterolateral papillary muscle are unlikely to have been imaged by angiocardiograhy. The patients’ age at the initial echocardiogram has not varied throughout the years, so these abnormalities were most likely missed because they are more subtle, requiring a more detailed evaluation, which was one of the end points of this study.
Echocardiography provides reliable and adequate data on the preoperative assessment of AVSD. Abnormalities of the left AV valve and LVOT are the two major risk factors for morbidity and mortality. Obtaining absolute measurements of the LVOT and papillary muscle location should aid in the identification of potential risk factors for mortality and late morbidity.
☆ Dr. Sittiwangkul was supported by the Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand.
- atrioventricular septal defect
- double orifice left atrioventricular valve
- left ventricle
- left ventricular outflow tract
- transthoracic echocardiogram
- right ventricular outflow tract
- ventricular septal defect
- Received November 10, 2000.
- Revision received March 8, 2001.
- Accepted March 26, 2001.
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