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J Am Coll Cardiol, 2001; 38:253-261 © 2001 by the American College of Cardiology Foundation |
a Division of Cardiology, Department of Pediatrics and Department of Cardiovascular Surgery, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada
Manuscript received November 10, 2000; revised manuscript received March 8, 2001, accepted March 26, 2001.
Reprint requests and correspondence: Dr. Jeffrey F. Smallhorn, The Hospital for Sick Children, 555 University Avenue, Toronto, Ontario, Canada M5G 1X8
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Abstract |
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We sought to determine the accuracy of transthoracic echocardiography (TTE) in identifying risk factors in patients with an atrioventricular septal defect (AVSD).
BACKGROUND
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.
METHODS
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.
RESULTS
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.
CONCLUSIONS
Transthoracic echocardiography provides accurate preoperative information on AVSD.
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Methods |
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Classification of LVOT abnormalities.
Tunnel narrowing
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).
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Thick chordal tissue
Thick accessory chordal tissue arising from the anterior left AV valve leaflet, which was fixed to the ventricular septum (Fig. 1C) (8,9).
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).
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Combination of abnormalities
More than one abnormality (Fig. 2C).
Data collection. 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.
Missed diagnoses. 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 analysis. 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 t test 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.
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Results |
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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.
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Discussion |
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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 [19] 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.
Conclusions. 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.
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Footnotes |
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References |
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