Bridging Leaflets Research Articles

Predisposing factors of valve regurgitation in complete atrioventricular septal defect

Objectives. We sought to determine the intrinsic risk factors of valve regurgitation in complete atrioventricular septal defect.Background. Progression of regurgitation varies in each case, although the structure of the common atrioventricular valve itself is a predisposing factor.Methods. In 90 consecutive patients undergoing surgical repair, we evaluated the preoperative and postoperative regurgitation, valve morphology, age at surgery and associated anomalies. A regurgitation jet with a high velocity reaching the deep left atrial wall by echocardiography was estimated as marked regurgitation.Results. None of the 40 patients with Rastelli type C and an undivided inferior bridging leaflet had preoperative regurgitation in the first year of life, and 12% of them (95% confidence intervals [CI]: 0% to 28%) showed regurgitation at the age of 2. Of the remaining 50 with Rastelli type A and/or a divided inferior leaflet, regurgitation was determined in 21% (95% CI: 6% to 35%) of those 1 year old and in 49% (95% CI: 29% to 69%) of those 2 years old (p < 0.01). All patients underwent corrective surgery using the double-patch technique, with the “cleft” being sutured adequately. Irrespective of the valve morphology, regurgitation remained in 52% (12 of 23) of those with preoperative regurgitation, whereas regurgitation developed postoperatively in 28% (16 of 58) of those without regurgitation (p < 0.001).Conclusions. Those with Rastelli type C and an undivided inferior leaflet had a lesser degree of progression of preoperative regurgitation. However, regurgitation was likely to exist even after adequate repair once regurgitation had already advanced. Therefore, early primary repair before progression of the regurgitation may be the key to maintaining better competence of the atrioventricular valve.

Interventricular communication in complete atrioventricular septal defect

Background. Little attention has been paid to whether the interventricular communication in complete atrioventricular septal defect is different beneath the superior and inferior bridging leaflets, a feature of obvious surgical significance. Methods. We searched for a defect under the bridging leaflets and examined the valve morphologies in 98 autopsied and 86 surgical patients. Of the overall specimens, 27 were associated with Fallot’s tetralogy, and a further 20 had subaortic stenosis, aortic coarctation, or both. In the autopsied specimens, we also measured the degree of deficiency of the ventricular septum. Results. No communication was found under the inferior bridging leaflet in 30% (29 of 98) of the specimens. All 29 hearts except two without such communications showed an undivided inferior leaflet. In contrast, all patients undergoing operation except 1 had a communication beneath both bridging leaflets ( p < 0.001). The absence of a communication beneath the inferior leaflet was observed more in hearts with Fallot’s tetralogy (seven of 14) or those with subaortic stenosis, aortic coarctation, or both (eight of 18) than in those without associated anomalies (14 of 66; p < 0.01). Those with a communication under the inferior leaflet showed a greater deficiency of the inlet ventricular septum than did those without it ( p < 0.001). Conclusions. In a certain percentage of patients with complete atrioventricular septal defect, there will be no communication under the inferior bridging leaflet. Surgeons should be aware of this possibility, particularly when confronted with a patient with obstruction in either ventricular outlet.

Atrioventricular septal defect with common valvar orifice and tetralogy of Fallot revisited: making a case for primary repair in infancy.

Atrioventricular septal defect with common valvar orifice and tetralogy of Fallot is a rare combination of congenital cardiac anomalies. Approaches to this lesion have tended to emphasize either staged repair or complete repair beyond infancy. Between July 1992 and August 1997, nine patients underwent repair of complete atrioventricular septal defect with tetralogy of Fallot. One patient, aged 9.6 years at the time of repair, had previously undergone construction of a modified Blalock-Taussig shunt. Primary complete repair was performed in the other 8 patients at ages ranging from 2.5 to 16 months (median 4.6 months), and all but one were infants. All patients had a Rastelli type C defect, a single ventricular septal defect with inlet and outlet components, and malalignment of the muscular outlet septum with subpulmonary stenosis. A single patch technique, with closure of the zone of apposition ('cleft') in the left atrioventricular valve, was used in all eight patients undergoing primary repair, while a double patch was employed in the previously palliated older patient. In all cases of repair using a single patch, the anterosuperior bridging leaflet was divided obliquely to the right, following the malaligned outlet septum, in order to avoid subaortic obstruction. Repair of the right ventricular outflow tract included infundibular myectomy in eight, pulmonary valvotomy in four, infundibular or transannular patching in three and one, respectively, and reconstruction with a valved allograft conduit in two patients. There was no early mortality or significant morbidity. At a median follow-up of 45 months, there had been one death related to non-cardiac causes and no reinterventions. Left atrioventricular valvar regurgitation was moderate or mild in two patients, and right atrioventricular valvar regurgitation was mild in one patient. No patient had more than mild pulmonary regurgitation or a gradient across the right ventricular outflow tract in excess of 18 mm Hg. Our results demonstrate that primary repair of atrioventricular septal defect with tetralogy of Fallot can be performed with excellent early and mid-term results in young infants. Although it has been suggested that a technique utilizing oblique division of the anterosuperior bridging leaflet may lead to high rates of atrioventricular valvar regurgitation, medium-term atrioventricular valvar function in the present cohort of patients has been excellent.

Morphometric Analysis of Atrioventricular Septal Defect With Common Valve Orifice

Objectives. We sought to analyze morphometric features of atrioventricular septal defect (AVSD) in autopsy specimens and to consider the developmental implications of obstruction in either ventricular outflow tract.Background. Left ventricular outlet obstruction (LVO) is more prevalent in patients with Rastelli type A morphology. When tetralogy of Fallot (ToF) complicates this malformation, there is usually a free-floating superior bridging leaflet. The reasons for these associations are uncertain.Methods. In 133 hearts with AVSD and common atrioventricular (AV) valve orifice, we measured the degrees of horizontal and anterior deviation of the great arteries from the AV valve, the diameters of the ventricular outlets and the great arteries and the degree of deficiency of the ventricular septum.Results. In Rastelli type A morphology, the great arteries were deviated more leftward than in type C morphology (p < 0.01). Type A hearts also had a relatively small aorta, with a long and narrow subaortic tract. The presence of obstruction in either ventricular outlet was associated with a more oblique arrangement of the great arteries, with the pulmonary trunk being more leftward than in hearts without LVO (p < 0.01). In combination with ToF, the aorta was dextroposed and the pulmonary trunk was located more posteriorly (p < 0.01). No heart with type A morphology showed ToF (p < 0.01).Conclusions. The geometric arrangement of the great arteries correlated significantly with obstruction in either ventricular outflow tract and with the Rastelli subtypes. Malrotation of the developing outlet septum may be an embryologic factor producing obstruction, with horizontal deviation of the outlets also influencing the morphology of the superior bridging leaflet.

The left ventricular outflow tract in atrioventricular septal defect revisited: Surgical considerations regarding preservation of aortic valve integrity in the perspective of anatomic observations

Objective: The anatomy of the left ventricular outflow tract in hearts with atrioventricular septal defect has been widely investigated, but controversies remain regarding detailed aspects of left ventricular outflow tract anatomy in the perspective of operative techniques to either prevent or relieve outflow tract obstruction. Methods: We investigated 29 postmortem hearts with an atrioventricular septal defect. Measurements were taken of the circumferences and of the widths of the components that make up the outflow tract, that is, the interventricular septum, the superior bridging leaflet, the left ventricular free wall, and the length of the tendinous cords. Results: The circumference of the left ventricular outflow tract immediately underneath the aortic valve was not different from that at the middle part of the outflow tract. Hearts with the partial type defect, characterized by separate atrioventricular orifices, had a smaller outflow tract than those with the complete variety. Although the anatomic constituents that contribute to left ventricular outflow tract obstruction are complex, this study showed that a reduced width of the interventricular septum was most intimately related to narrowing immediately underneath the aortic valve. Obstruction at the middle part of the left ventricular outflow tract was largely caused by reduced width of the interventricular septum together with short tendinous cords. Conclusions: On the basis of these observations, we recommend detailed investigation of the anatomy of the left ventricular outflow tract immediately underneath the aortic valve, before surgical attempts to relieve outflow tract obstruction, because in some procedures the integrity of the aortic valve will be at stake. (J Thorac Cardiovasc Surg 1997;114:586-9)

Patch augmentation of regurgitant common atrioventricular valve in univentricular physiology

Regurgitation of the common atrioventricular valve in patients with univentricular atrioventricular connection has a negative impact on outcome in the Fontan operation. Because severe regurgitation of the common atrioventricular valve may not be sufficiently reduced by a volume-reducing operation alone, the addition of a valvuloplasty may be a necessary adjunct to achieve competence of the common atrioventricular valve. A modified technique of valvuloplasty of the common atrioventricular valve and its medium-term results are presented. Two infants and 1 young child with isomeric right atrial appendages, complete atrioventricular canal, univentricular atrioventricular connection with a double-inlet right ventricle through a common atrioventricular valve, pulmonary atresia (n = 2) or pulmonary stenosis (n = 1), and bilateral superior venae cavae presented with marked dilatation of the annulus of the common atrioventricular valve and severe regurgitation between the bridging leaflets. All 3 patients previously had been palliated with a generous central aortopulmonary shunt. The repair technique consisted of patch augmentation of the central bridging leaflets with an autologous pericardial patch. In addition, bilateral bidirectional cavopulmonary anastomoses were constructed and additional sources of pulmonary blood flow were eliminated. Intraoperative echocardiography demonstrated competence of the large central leaflet, excellent coaptation between the central leaflet and the bilateral mural leaflets, and decrease of the anteroposterior diameter of the annulus of the atrioventricular valve from 24, 29, and 34 mm preoperatively to 20, 23, and 29 mm, respectively. In all 3 patients, echocardiographic follow-up at 17, 14, and 6 months showed continued competence of the atrioventricular valve. Pericardial patch augmentation of the bridging leaflets may be a valuable adjunctive technique in the reconstruction of the regurgitant common atrioventricular valve in hearts with univentricular atrioventricular connection, especially if a volume-reducing operation alone does not result in competence of the valve.

Pericardial patch augmentation of the tissue-deficient mitral valve in common atrioventricular canal

Pericardial patch augmentation of the tissue-deficient mitral valve in common atrioventricular canal

Pericardial patch augmentation of right atrioventricular valve in atrioventricular canal

Untreated pericardial patch was successfully used to augment tissue-deficient bridging leaflets of the right atrioventricular valve in a patient after previous repair of complete common atrioventricular canal. Medium-term echocardiographic follow-up showed excellent tricuspid valve function with trivial central regurgitation.

Relationship between scooping of the ventricular septum, morphology of the inferior bridging leaflet and electrocardiographic findings in atrioventricular septal defect with common valvar orifice

AbstractWe described previously that the degree of deficiency of the ventricular septum (scooping) affects electrocardiographic findings in atrioventricular septal defect with separate right and left atrioventricular orifices. The aim of this study was to clarify the clinicomorphological relationships of the degree of scooping, the precise morphology of the atrioventricular valve, and electrocardiographic findings in hearts having a common atrioventricular orifice. In 63 patients with usual atrial arrangement, the outlet, scoop and inlet dimensions of the ventricular septum were measured by biplanar cineangiography and were compared with the body surface area. The scoop/outlet ratio and inlet/outlet ratio were also compared with the body surface area, atrioventricular valvar morphology, electrocardiographic findings, and severity of regurgitation of the atrioventricular valve. The results showed that the three individual dimensions of the septum correlated significantly with the body surface area, even though the scoop/outlet ratio and inlet/outlet ratio did not. A correlation was found between the scoop/outlet ratio and the degree of left axis deviation on the electrocardiogram (r=0.74, p&lt;0.001). In 16 patients with division of the inferior bridging leaflet, there was a lower scoop/outlet ratio than in the remaining 37 with an undivided bridging leaflet (p&lt;0.01). Of 24 patients with counterclockwise rotation in the horizontal loop of the vectorcardiogram, 22 had an undivided inferior bridging leaflet (p&lt;0.01). The morphology of the superior bridging leaflet, in contrast, was not associated with the scoop/outlet ratio, and neither was the severity of valvar regurgitation. We conclude that the degree of scooping of the ventricular septum is related not only to electrocardiographic findings, but also to the morphology of the inferior bridging leaflet in atrioventricular septal defect with common atrioventricular orifice.

Subaortic stenosis in the spectrum of atrioventricular septal defects: Solutions may be complex and palliative

From July 1982 through September 1994, 19 children had operative treatment of subaortic stenosis associated with an atrioventricular septal defect. Specific diagnosis were septum primum defects in 7, Rastelli type A defects in 6, transitional defects in 4, inlet ventricular septal defect with malattached chordae in 1, and tetralogy of Fallot with Rastelli type C defect in 1. Twenty-seven operations for subaortic stenosis were performed. Surgical treatment of the outlet lesion was performed at initial atrioventricular septal defect repair in 3 children and in the remaining 16 from 1.2 to 13.1 years (mean 4.9 years, median 3.9 years) after repair. Eighteen of the 19 children had fibrous resection and myectomy for relief of obstruction. Seven children had an associated left atrioventricular valve procedure. One child received an apicoaortic conduit. Seven children (36.8%) required 8 reoperations for previously treated subaortic stenosis. Time to the second procedure was 2.8 to 7.4 years (mean 4.9 years). Follow-up is 0.4 to 14.0 years (median 5.6 years). Six-year actuarial freedom from reoperation is 66% ±15%. The angle between the plane of the outlet septum and the plane of the septal crest was measured in 10 normal hearts (86.4 ±13.7) and 10 hearts with atrioventricular septal defects (22.2 ±26.0; p <0.01). The outflow tract can be effectively shortened, widened, and the angle increased toward normal by augmenting the left side of the superior bridging leaflet and performing a fibromyectomy. Conclusion: Standard fibromyectomy for subaortic stenosis in children with atrioventricular septal defects leads to a high rate of reoperation. Leaflet augmentation and fibromyectomy may decrease the likelihood of reoperation. (J T HORAC C ARDIOVASC S URG 1995;110:1534-42)

Valve morphology in complete atrioventricular septal defect: Variability relevant to operation

The remodeling of the atrioventricular valves in patients with complete atrioventricular septal defects is the crucial part of surgical repair. Variability in valve morphology is an important factor. This study evaluates the variability in morphology of the anterior and posterior leaflets in 30 heart specimens. All hearts had an anterior bridging leaflet: Rastelli type A in 12, type B in 2, and type C in 16. The posterior leaflet revealed four morphologic pattems: a right- and left-sided posterior leaflet, both inserting directly onto the crest of the ventricular septum (5 hearts); a common posterior leaflet attached to the septal crest by a membrane (2 hearts); a common posterior leaflet attached to the septal crest by multiple chordae (13 hearts); and a virtually free-floating posterior leaflet (11 hearts). The categorization is surgically relevant in making a distinction between hearts with and the posterior leaflet. Surgically relevant variations occurred also in arrangement and positioning of chordae originating from the right septal side. There was no relationship between the Rastelli classification of the anterior leaflet and that of the posterior leaflet. The variability in morphology of the posterior leaflet and its attachments to the ventricular septum appear equally crucial for successful repair as that of the anterior leaflet.

A case report of double-orifice tricuspid valve

A heart specimen with double-orifice tricuspid valve is described. The tricuspid valve was divided into the anterior and posterior orifices by a bridge of leaflet tissue. The valve was stenotic because of the arcade deformity of the anterior papillary muscle to which the bridging leaflet tissue had short chordal insertions. The anterior orifice was regurgitant as a result of a deficient septal leaflet. Clinical correlation was obtained by magnetic resonance imaging of the specimen. The functional significance of the malformed valve was assessed by three-dimensional reconstruction of the two-dimensional magnetic resonance images.

Surgical significance of morphological variations in the atrial septum in atrioventricular septal defect for determination of the site of penetration of the atrioventricular conduction axis.

The morphological variation in the recognized landmarks for the atrioventricular conduction system was studied grossly in 94 hearts with atrioventricular septal defect, assessing 20 hearts with normal atrioventricular septation as a control. In all the hearts with intact atrioventricular septal structures, the tendon of Todaro demarcated the superior boundary of the triangle of Koch. In hearts with atrioventricular septal defect, however, the landmarks for the conduction axis made up a separate nodal triangle. The tendon of Todaro, along with a bridging tendon not found in the normal heart, were variably developed in hearts with atrioventricular septal defect and formed a further triangle unrelated to the axis for atrioventricular conduction. The opening of the coronary sinus was also variable in its location and size. It was the location of the inferior bridging leaflet as it crossed the ventricular septum that was the best surgical landmark to the site of penetration of the atrioventricular conduction axis.

Echocardiographic evaluation of atrioventricular orifice anatomy in children with atrioventricular septal defect

In atrioventricular (AV) septal defect, the common AV valve can have a common orifice or can be divided by bridging leaflet tissue into two separate orifices. To determine the accuracy of a two-dimensional echocardiographic technique devised specifically for evaluation of the number of AV valve orifices, all 69 children undergoing surgical repair of AV septal defect from April 1987 to August 1999 were examined prospectively. The presence of bridging leaflet tissue and the number of AV valve orifices were determined with use of a subcostal imaging plane. From a standard subcostal four-chamber view, the plane of sound was rotated 30 ° to 45 ° clockwise until the AV valve was seen en face. The plane of sound was then tilted from a superior to an inferior direction so that cross-sectional views of the AV valve were examined from the inferior margin of the atrial septum to the superior margin of the ventricular septum.Of the 69 patients, 6 (9%) were excluded because the appropriate subcostal images were not obtained (in 3 because of obesity and in 3 as a result of operator failure). The remaining 63 children, ranging in age from 1 day to 13.5 years and in weight from 1 to 55 kg, constituted the study group. Echocardiographic results were compared with surgical observations in 62 patients and with autopsy findings in 1 patient.With the two-dimensional echocardiographic technique, 32 of 33 patients with a common orifice and 28 of 30 patients with two separate AV valve orifices were correctly identified. By chi-square analysis, the echocardiographic technique allowed correct identification of a common orifice valve with 94% sensitivity and 97% specificity. For correct identification of two separate orifices, the echocardiographic technique had 97% sensitivity and 94% specificity. The positive predictive value of the echocardiographic technique was 97% for a common orifices and 93% for two separate orifices. Thus, in patients with AV septal defect, the presence of bridging leaflet tissue and the number of AV valve orifices can be accurately determined with use of a subcostal two-dimensional imaging plane.

The morphology and diagnosis of atrioventricular septal defects

SummaryIn this review, we discuss and describe those features which distinguish hearts with abnormal atrioventricular septation from the normal heart. The hearts, best described as atrioventricular septal defects, are unified by having a common atrioventricular junction guarded by a valve having five leaflets. The left component has three leaflets and cannot be interpreted in terms of a cleft in a normal mitral valve. The papillary muscles supporting this valve are also markedly dissimilar from the arrangement seen in normal hearts. The subaortic outflow tract is displaced superiorly compared to the normal heart, and is no longer wedged between the left valve and the septum. There is marked discrepancy in the inlet and outlet lengths of the ventricular mass, these dimensions being equal in hearts with normal atrioventricular septation. Although having the above features in common, atrioventricular septal defects show anatomic variations related to the arrangement of the bridging leaflets and their relationship to the septal structures. There may be a common valvar orifice or separate right and left orifices. The anatomic potential for shunting may be at atrial or ventricular levels, or both. Rarely, the septal structures may be intact. Other important features include ventricular dominance, the left ventricular outflow tract, and the disposition of the atrioventricular conduction tissues.

Surgical anatomy of the atrioventricular septum and atrioventricular septal defects

SummaryDefects of the atrioventricular septum impose changes in the septal architecture, atrioventricular valves, and conduction system that must be well understood for optimal repair. The atrioventricular node and bundles are shifted to more posterior and inferior positions that can be anticipated by the surgeon so as to maintain the integrity of atrioventricular conduction. The atrioventricular valve is a five leaflet structure that possesses a common orifice or separate orifices depending on characteristics of the superior and inferior bridging leaflets. These features are demonstrated by intraoperative photographs viewed from the surgeon's position.

Left Ventricular Outflow Tract Obstruction in Atrioventricular Septal Defects: A Pathologic and Morphometric Evaluation

Subaortic stenosis has been described with increasing frequency as an ominous feature of atrioventricular septal defect (AVSD), especially following surgical correction of the anomaly in non-Down's syndrome patients. In order to study the surgical anatomy of the left ventricular outflow tract in this malformation, 48 hearts featuring AVSD were examined. Obstructive lesions were classified into unequivocal forms (class A, 13.5%) and potential ones (class B, 10.8%). In the remaining hearts (class C, 75.7%) no obstruction was noted. In class A, subaortic stenosis was due to exaggeration of the anticipated anomalous arrangement of atrioventricular valve tensor apparatus, to the persistence of a subaortic muscular infundibulum, and to a discrete fibrous diaphragm. A potential for subaortic stenosis is provided by the unwedged position of the aortic valve. The left ventricular outflow tract is transformed into a long, forward-displaced fibromuscular channel. Morphometric analysis showed in AVSD (with both common annulus and separate orifices) a significantly (p less than 0.01) lower inflow/outflow tract ratio, and a significantly (p less than 0.01) lower right ventricular/left ventricular outflow length ratio than normal hearts. These results suggest that AVSD is characterized not only, as commonly stated, by inflow tract shortening, but by outflow tract lengthening as well. On these anatomical grounds, nearly all cases of AVSD could harbor the potential for subaortic stenosis; however, this becomes a real hazard (class B) only when associated with forward displacement of the left anterior papillary muscle, or direct insertion on the ventricular septum of the anterior bridging leaflet, and it may be converted to an actual obstruction by the effects of surgery.(ABSTRACT TRUNCATED AT 250 WORDS)

Anterolateral muscle bundle of the left ventricle in atrioventricular septal defect: Left ventricular outflow tract and subaortic stenosis

The anatomy of the left ventricular outflow tract (LVOT) in 77 hearts with atrioventricular septal defect (AVSD), 36 with a separate A V orifice and 41 with a common A V-orifice, were investigated. In all specimens, an anterolateral muscle bundle of the left ventricle was identified between the superior bridging leaflet and the left coronary aortic cusp. It displaced the attachment of the superior bridging leaflet, resulting in its clockwise rotation. The muscle bundle frequently bulged into the LVOT, but was never prominent enough to have caused significant subaortic stenosis. Measurement of the LVOT aortic ratio was possible in 54 hearts and ranged from 36-100%. In 23 cases (43%), there was mild to moderate subaortic narrowing with a ratio ranging from 53-88%. In six cases (11%), unequivocal subaortic stenosis was present, mainly in AVSD with separate A V orifices (five of six) and iatrogenic in one case with surgically corrected complete defect. A decreased ratio was mainly due to decreased anteroposterior width of the septum in the subaortic area, with anterior displacement of the superior bridging leaflet in cases with dense septal attachment of the superior bridging leaflet (i.e., in AVSD with separate A V orifices, type A complete defect with small ventricular septal defect, or surgically corrected complete defect). Significant subaortic stenosis was caused by hypertrophy of the ventricular septum in the subaortic area with anteroseptal twist in four cases, by anomalous chordal insertion of the superior bridging leaflet in one case, and iatrogenic in one case after surgical correction with left A V valve replacement in type C complete defect.(ABSTRACT TRUNCATED AT 250 WORDS)

Anomalies of the left atrioventricular valve and related ventricular septal morphology in atrioventricular septal defects

A characteristic feature of atrioventricular septal defects is a deficiency of the inlet part of the ventricular septum that results in a "scooped out" appearance. The depth of the scoop in relation to the disposition of the atrioventricular valves has been debated. To clarify the relation between the morphology of the ventricular septum and the disposition of the atrioventricular valves, we quantified these anatomic features in 151 hearts at autopsy to determine whether those features identified particular groups within the overall lesion. We found that 137 hearts had left atrioventricular valves with three leaflets. The left valve in the other 14 hearts exhibited a dual orifice, a two-leaflet or one-leaflet arrangement, or was imperforate. These anomalies could be analyzed in terms of a sequence of diminishing formation of the commissures. Also, three-leaflet valves displayed a variability in which the angular size of the mural leaflet correlated negatively with that of the inferior leaflet. In some of the hearts with a common atrioventricular orifice, the bridging leaflets did not meet over the ventricular septum, thus creating a "gap." The mural leaflet's angular size corresponded to a deficiency of the combined inferior-mural leaflet complex. Hearts with an abnormal disposition of the left atrioventricular valve had the ventricular septum "scooped" to a greater extent than those with a common orifice, although most had separate right and left atrioventricular orifices.

Correlation of morphology of the left ventricular outflow tract with two-dimensional Doppler echocardiography and magnetic resonance imaging in atrioventricular septal defect

In atrioventricular (AV) septal defect, the architecture of the left ventricular (LV) outflow tract differs consistently from the normal tract. In patients with separate AV valves and in those with a common valve with septal attachment of the superior bridging leaflet (Rastelli type A), the LV outflow tract below the anteriorly positioned aorta is long and narrow. Possible obstruction of this outflow tract has been attributed to abnormal papillary muscles 1,2 and to an “atrial fold” that is the anterior wall of the left atrium reinforcing the aortic-left AV fibrous continuity. 3 Less known is the anterolateral muscle bundle, 4 often very prominent in AV septal defect. 5 This muscle bundle that replaces the left coronary-AV fibrous continuity could well contribute to a possible stenosis of the LV outflow tract. We carried out Doppler echocardiography and magnetic resonance imaging studies to evaluate the role of the anterolateral muscle bundle in the possible systolic narrowing of the subaortic outflow tract.