Surgical options in subaortic stenosis associated with endocardial cushion defects

The role of abnormal subaortic morphometry as a substrate for left ventricular outflow tract obstruction following atrioventricular septal defect repair

OBJECTIVES

Although left ventricular outflow tract (LVOT) obstruction is a recognized risk after atrioventricular (AV) septal defect (AVSD) repair, quantitative assessments to define the substrate of the obstruction are lacking.

METHODS

Morphometric analyses were based on measurements from early 2-dimensional echocardiographic scans (within 3 months postoperatively) for 117 patients (82 CAVVO = common AV valve; 35 SAVVO = separate AV valve orifices), which were compared to 50 age/weight matched controls (atrial septal defect/ventricular septal defect). Late echocardiographic analyses were performed in 57 patients with AVSD (follow-up range, 1.2-10.7 years).

RESULTS

Adequate z scores (above -2.5) were observed in 109 (93%) patients with AVSD at the aortic annulus and in 89 (76%) with AVSD in the subaortic area. Compared to the control group, patients with AVSD had lower median z scores at the aortic annulus (-0.64 vs 0.60; P < 0.001) and the subaortic areas (-1.48 vs 0.59; P < 0.001), disproportionate subaortic/aortic annulus ratio <1.00 (67% vs 22%; P < 0.001), narrower annuloaortic-septal angle (94.0 vs 104.0; P < 0.001) and annuloaortic left AV valve angle (78.0 vs 90.0; P < 0.001). Compared to patients with CAVVO, those with SAVVO had narrower annuloaortic-septal angles (P = 0.022) that persisted at late analysis, with lower subaortic/aortic annular ratios (P = 0.039). In patients with CAVVO, lower early postoperative subaortic z scores were found following modified single-patch repairs (median -2.12 vs -1.02 in two-patch repairs; P = 0.004). A total of 6/117 (5%) patients (4 CAVVO, 5% and 2 SAVVO, 6%) required reoperations for LVOT obstruction (mean 6.9 years postoperatively), with no difference in morphology or types of operations.

CONCLUSIONS

Despite having adequate z scores, patients with AVSD demonstrated abnormal LVOT morphometrics early postoperatively. Besides intrinsic morphology, repair techniques may have an impact on postoperative LVOT morphometrics and requires further evaluation.

Modified Konno procedure: surgical management of tunnel-like left ventricular outflow tract stenosis

Left ventricular outflow tract stenosis represents 1-2 % of all congenital anomalies. In particular, tunnel-like left ventricular stenosis which is one type of fixed left ventricular outflow stenosis requires aggressive surgery to reduce the left ventricular outflow gradient. The purpose of the modified Konno procedure is to release fixed left ventricular outflow tract stenosis while preserving the native aortic valve and its function. Although the clinical results of the modified Konno procedure are acceptable, it is necessary to precisely understand this procedure and the anatomy of the left ventricular outflow tract in order to avoid complications.

Partial atrioventricular canal: pitfalls in technique

Partial atrioventricular (AV) canal represents approximately 25% of all AV septal defects. While often grouped with secundum ASD from the perspective of cardiopulmonary physiology, clinical presentation, and timing of surgical correction, their optimal management truly requires an understanding of their anatomic similarities to other forms of common AVC defects. By most measures, outcomes for surgical management of partial AV canal has improved over the last four decades, though some aspects of these defects continue to pose important challenges. Current experience has witnessed the reduction in early mortality and only rare complete heart block. Left AV valve dysfunction remains the most common indication for reoperation (10%) with LVOT stenosis the next most common reason (10% to 15% incidence, 5% to 10% reoperation rate). It is important to understand in this population that postoperative left AV valve problems and LVOT stenosis may be intimately linked, both from an etiologic standpoint, and with respect to their management.

Surgical treatment of subaortic obstruction in adolescent and adults: long-term follow-up

Subaortic stenosis (SAS) is a wide spectrum of anatomical derangements ranging from a discrete fibrous membrane to tortuous fibrous tunnel with or without aortic annulus hypoplasia. We have reviewed 88 patients undergoing surgery for SAS over a 15-year period. There were 47 male and 41 female patients with a mean age of 19.8 +/- 10.6 years (range 11 to 39). Fifty-eight patients had discrete subaortic membrane, and 30 patients had diffuse tunnel subvalvular stenosis. The mean systolic pressure gradients were found to be 86.5 +/- 31.4 mmHg (range 48 to 145 mmHg). Ten patients had mild and 13 patients had moderate-to-severe aortic insufficiency (AI) preoperatively. Nine patients had bicuspid aortic valve. Forty patients (45.4%) had associated cardiac lesions. Isolated membranectomy was performed in six patients. Membranectomy associated with septal myectomy was done in 52 patients. Fifteen patients of them associated hypoplasia of the aortic orifice necessitated aortic valve replacement (AVR) using the Konno-Rastan procedure. Fifteen patients with tunnel SAS and normal aortic valves underwent a combined approach for valve sparing, a modified Konno procedure with patch septoplasty. Also eight patients required AVR because of the severity of AI and five patients aortic reconstruction procedures. Aortic commissurotomy was performed to relief of stenosis in four patients. There were three early deaths (3.4%) and one late death (1.1%) all after the Konno-Rastan procedure. Eight patients (9.1%) had permanent conduction abnormalities. Postoperative left ventricle-aorta gradient was significantly decreased at early postoperative period (p < 0.001) and ranged from 10 to 25 mmHg (mean 14.1 +/- 4.3). Fourteen patients (16.5%) were reoperated for recurrent obstruction or progression of AI. The mean reoperation interval was 4.4 +/- 1.7 years (range 2 to 8 years). Five-year reoperation-free survival was 88.0 +/- 3.6% and 12.5-year reoperation-free survival was 75.5 +/- 7.0%. Our results of aggressive surgical approach of subvalvular aortic stenosis produces relief of obstruction and frees the valve leaflets, significantly reducing associated AI with long-term survival and long-term adequate relief of left ventricular outflow tract obstruction.

The modified Konno procedure for complex left ventricular outflow tract obstruction

BACKGROUND

Complex left ventricular outflow tract (LVOT) obstruction with normal aortic valve function requires aggressive resection in the subaortic region and preservation of the aortic valve. The modified Konno procedure allows generous exposure of the LVOT from the left ventricular apex to the inter leaflet trigones of the aortic valve. Widespread use of this procedure has been limited by concern over injury to the aortic valve, the conduction system, and possibility of residual ventricular septal defect (VSD).

METHODS

Retrospective analysis of pertinent data for all patients undergoing the modified Konno procedure (1994 to 2001) at the University of Iowa were reviewed.

RESULTS

The modified Konno procedure was used in 18 patients (age 1 to 31) for LVOT obstruction associated with diffuse narrowing of the LVOT (n = 7), a discrete fibrous ring (n = 7), or a fibrous ring associated with abnormal mitral attachments (n = 4). Eight patients had previously undergone LVOT resection. There were no perioperative deaths. Estimated LVOT peak gradients by echocardiogram were 70.4 +/- 24.2 mm Hg (preoperative) and 19.2 +/- 20.4 mm Hg (postoperative) at most recent followup (p < 0.001 vs preop). Aortic insufficiency was moderate in one patient (present preop) and mild or less in all other patients. There were no cases of permanent heart block. Small residual VSDs were present in five patients (28%). Median follow-up is 3.1 years.

CONCLUSIONS

The modified Konno procedure can effectively relieve complex LVOT obstruction and preserve aortic valve function. Extension of this procedure for use in the initial presentation of LVOT may be appropriate in cases at increased risk of recurrent LVOT obstruction.

Reoperation after repair of atrioventricular canal defects

Late events requiring reoperation after atrioventricular canal defect are most commonly related to failure of the repair of the mitral component of the common atrioventricular valve. The need for reoperation also occurs with new developments in the left ventricular outflow tract in the form of subaortic stenosis, particularly in patients with partial atrioventricular canal. Reoperations for other reasons in the population of operated patients with atrioventricular canal defects are rare events. Copyright 1998 by W.B. Saunders Company

Echocardiographic assessment of obstructive lesions in atrioventricular septal defects

OBJECTIVES

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. Reoperation 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.

Surgical management of complex and tunnel-like subaortic stenosis

BACKGROUND

Relief of primary or secondary subaortic stenosis (SAS) remains a surgical challenge. Heart block, aortic valve regurgitation and recurrent obstruction have been persistent problems.

METHODS

Forty six patients who underwent surgery for complex and tunnel-like SAS between January 1990 and November 1998 were reviewed. In 45 of the 46 patients SAS developed following repair of a primary congenital heart defect and only one patient presented with de novo tunnel-like SAS. Fifteen of the 45 patients had undergone repair of double-outlet right ventricle (DORV) and the remaining 30 had undergone repair of a variety of defects. The median age at the time of surgery was 5 years. The modified Konno procedure was performed in 15 patients, Konno procedure in three, Ross-Konno procedure in two and resection of the conal septum in 12 patients. Five patients with DORV underwent replacement of the intraventricular baffle and two patients underwent an aortic valve-preserving procedure in conjunction with mitral valve replacement.

RESULTS

There were no deaths. None of the patients had an exacerbation of aortic regurgitation and none developed complete heart block. The median follow-up was 3 years (range 1 month-8.5 years). Two patients developed recurrent SAS defined as a gradient of 40 mmHg or greater diagnosed by transthoracic echocardiography. Freedom from SAS at 1, 3 and 5 years was 100, 94 and 86%, respectively.

CONCLUSIONS

We favor the modified Konno procedure and conal resection to the Konno or the Ross procedure, since insertion of a prosthetic valve or homograft is avoided and aortic valve function is preserved. Excellent relief of tunnel-like SAS can be achieved without damage to the conduction tissue.

Operation for partial atrioventricular septal defect: a forty-year review

BACKGROUND

We describe the long-term outcome of repair of partial atrioventricular septal defect by determining the rates of survival, reoperation, and occurrence of left atrioventricular valve regurgitation, left atrioventricular valve stenosis, left ventricular outflow tract obstruction, and arrhythmia.

METHODS

We studied 334 patients who underwent repair of partial atrioventricular septal defect before 1995.

RESULTS

The 30-day and 5-, 10-, 20-, and 40-year survival were 98%, 94%, 93%, 87%, and 76%, respectively. Closure of the left atrioventricular valve cleft (P =. 03) and age less than 20 years at operation (P <.001) were associated with better survival. Reoperation was performed for 38 patients (11%). Repair of residual/recurrent left atrioventricular valve regurgitation or stenosis was the most common reason for reoperation. Left ventricular outflow tract obstruction occurred in 36 patients, and 7 patients underwent reoperation to relieve this obstruction. Supraventricular arrhythmias were observed in 58 patients (16%) after the operation. Supraventricular arrhythmias increased with increasing age at primary operation (P =.001). Complete atrioventricular block occurred in 9 patients (3%). Permanent pacemakers were implanted in 11 patients.

CONCLUSIONS

Long-term survival after repair of partial atrioventricular septal defect is good. It is important to close the cleft in the left atrioventricular valve. Reoperation for persistent or recurrent left atrioventricular valve malfunction and relief of left ventricular outflow tract obstruction is necessary in approximately 11% of patients.

Accessory and anomalous atrioventricular valvar tissue causing outflow tract obstruction: surgical implications of a heterogeneous and complex problem

OBJECTIVES

The purpose of this study was to determine the effect of accessory or anomalous atrioventricular valvar apparatus on relief of outflow tract obstruction.

BACKGROUND

Outflow tract obstruction due to accessory tissue or anomalous attachments of the atrioventricular valvar apparatus is an unusual but well-recognized problem. In addition to obstruction, anomalous attachments of the atrioventricular valvar apparatus may interfere with procedures to relieve outflow tract obstruction or perform outflow tract reconstruction.

METHODS

Since 1992, we have operated on 21 patients (median age 4 years) with systemic (n=13), pulmonary (n=5) or bilateral (n=3) outflow tract obstruction due to accessory atrioventricular valvar tissue and/or anomalous attachments of the subvalvar apparatus. Primary diagnoses were isolated obstruction of the systemic outflow tract or aortic arch (n=7), transposition complexes (n=6), previously repaired atrioventricular septal defect (n=3), functionally single ventricle (n=3) and ventricular septal defect with pulmonary outflow obstruction (n=2). Outflow tract gradients ranged from 20-110 mm Hg (median 58 mm Hg).

RESULTS

Complete relief of obstruction due to atrioventricular valvar anomalies was possible in 14 patients. In six patients, the planned procedure either had to be modified or only partial relief of the obstruction was achieved. In the remaining patient, who had borderline functionally single ventricle heart disease (unbalanced atrioventricular septal defect) and systemic outflow obstruction due to accessory and functional valvar apparatus, support was withdrawn because the parents refused univentricular palliation and the valvar anomalies precluded a Ross-Konno procedure. There were two early deaths. At follow-up ranging from 1 to 66 months (median 27 months), there was one death, and there has been no recurrence of outflow tract obstruction or residual atrioventricular valvar tissue.

CONCLUSIONS

Outflow tract obstruction caused by accessory or anomalous atrioventricular valvar structures is an uncommon and heterogeneous group of conditions that can have significant surgical implications. In the majority of cases, tailoring of surgical techniques will permit complete relief of obstruction. However, such anomalies may limit standard surgical options and necessitate an innovative approach in some patients.

Primum atrial septal defect in children: early results, risk factors, and freedom from reoperation

BACKGROUND

Repair of primum atrial septal defect in children usually is associated with a low operative mortality, except for a subgroup of children with congestive heart failure. To determine the early mortality and incidence of reoperation in children with primum atrial septal defect, we analyzed retrospectively the results of patients who underwent repair of this defect.

METHODS

Between July 1982 and December 1996, 180 children underwent repair of primum atrial septal defect. The mean age at repair was 4.6 years (median, 3.6 years; range, 1 month to 16.4 years); of the 180 children, 23 were infants less than 1 year of age. Absent or mild symptoms were present in 145 (80%), whereas 34 (20%) of children presented with severe symptoms or congestive heart failure.

RESULTS

Early mortality occurred in 3 (1.6%); 2 were less than 1 year of age. Follow-up ranged from 2 months to 14.5 years (mean, 6 +/- 4.2 years). Actuarial survival is 98% at 10 years with no late deaths. Age less than 1 year is a predictor of death. During follow-up, 17 (9%) of the 180 patients underwent reoperation, 5 of whom were in the infant group. Five underwent reoperation for subaortic obstruction, and 12 for left atrioventricular valve regurgitation of whom 11 were repaired; and 1 required valve replacement. Age and preoperative moderate-to-severe left atrioventricular valve regurgitation were predictors of reoperation.

CONCLUSIONS

Results of the repair of primum atrial septal defect during childhood are favorable. Infants have a higher risk for death and reoperation. Left atrioventricular valve insufficiency and subaortic stenosis are important late complications and can be repaired safely at reoperation.

Modified Konno-Rastan procedure for subaortic stenosis: indications, operative techniques, and results

BACKGROUND

Diffuse or unresectable subaortic stenosis (SAS) necessitates an aggressive surgical approach for the elimination of left ventricular outflow tract obstruction. In this article we report our experience with the modified Konno-Rastan procedure, with inherent preservation of the native aortic valve and annulus, in the treatment of diffuse or unresectable SAS.

METHODS

Sixteen children (age range, 21 months to 18 years) underwent the modified Konno-Rastan procedure through either a transventricular (n = 12) or a transatrial approach (n = 4) to the conal septum. Indications for operation were recurrent SAS (n = 3), hypertrophic obstructive cardiomyopathy (n = 3), tunnel stenosis (n = 2), SAS related to a canal (n = 3), and SAS after ventricular septal defect closure (n = 5). Eleven patients had undergone previous procedures and 5 underwent the modified Konno-Rastan procedure as their primary operation.

RESULTS

The mean preoperative left ventricular outflow tract gradient of 50 +/- 17 mm Hg was reduced to 3 +/- 7 mm Hg (p < 0.001) after surgical repair. Postoperative complications included sternal infection (n = 1), heart block (n = 2), mediastinal bleeding (n = 1), and renal and cerebral ischemia (n = 1). There was 1 late postoperative death caused by pneumonia 2 years after operation (6.2% mortality rate). The mean follow-up period was 62 +/- 39 months and all patients had complete relief of preoperative symptoms and were in New York Heart Association class I. One patient underwent a successful redo modified Konno-Rastan procedure 7 years after the first operation for residual left ventricular outflow tract obstruction immediately below the aortic valve. One patient is awaiting reoperation for aortic incompetence unrelated to conal enlargement 1.5 years after the first procedure.

CONCLUSIONS

The modified Konno-Rastan procedure represents an excellent therapy for diffuse or unresectable SAS in patients with a normal aortic valve. In addition, it produces excellent results in a limited number of patients with hypertrophic obstructive cardiomyopathy, in whom the Morrow procedure traditionally has been performed. Although it usually is performed through a transventricular approach, the modified Konno-Rastan procedure also can be performed through a transatrial approach; this is particularly useful in patients who have had previous ventricular septal defect closure associated with SAS occurring proximal to the prosthetic patch.

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.

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.

Regression of hypertrophic cardiomyopathy after modified Konno procedure

BACKGROUND

Septal myotomy-myectomy has been known to decrease the incidence of sudden death and produce regression in hypertrophic obstructive cardiomyopathy. Use of beta-blockers or calcium-channel blockers generally does not cause regression of the disease.

METHODS

Having successfully performed modified Konno procedures in 13 patients with effective relief of diffuse subaortic stenosis, we applied the procedure in 2 patients with hypertrophic obstructive cardiomyopathy. Both patients (18 and 12 years old, respectively) presented with syncope, angina at rest, and dyspnea despite being on calcium channel blocker therapy. The echocardiographic outflow gradients were 66 mm Hg and 88 mm Hg, respectively, with moderate mitral regurgitation.

RESULTS

Both patients had uneventful postoperative course. At 2 years and 1.5 years postoperatively, both patients were free of angina and syncopal episodes. Echocardiography showed absence of outflow gradients and mitral regurgitation. In 1 patient the septal and posterior wall thickness decreased from 3.4 and 1.7 cm preoperatively to 2.6 and 0.9 cm, respectively, postoperatively. In the other patient, the thickness decreased from 2.4 and 0.9 cm preoperatively to 0.8 and 0.7 cm, respectively, postoperatively. Left atrial diameter decreased from 5.4 to 4.7 cm in 1 patient, 3.5 to 2.6 cm in the other.

CONCLUSIONS

We believe that the modified Konno procedure could produce more effective relief of obstruction and, therefore, significant regression and further reduction in sudden death in hypertrophic obstructive cardiomyopathy. On the basis of our experience, albeit limited, we encourage its application.

Recognition and management of accessory mitral tissue causing severe subaortic stenosis

Failure to recognize the presence of accessory mitral tissue causing subaortic stenosis can lead to not only the performance of inappropriate operations, but the persistence and recurrence of obstruction or even death. Over a 12-month period, we treated 2 children with severe subaortic stenosis caused by accessory mitral tissue. In 1 patient, who was 4 years old, the echocardiogram showed the accessory mitral tissue to be attached to the anterior mitral leaflet and ballooning into the subaortic area. The other patient, as a newborn, underwent simultaneous repair of a complete canal defect and coarctation. Two years later, the patient was seen because of syncopal episodes, progressive mitral insufficiency, and subaortic stenosis thought to be caused by anterior displacement of the anterior mitral leaflet. Mitral valvuloplasty and a conal enlargement procedure were planned. Intraoperatively, after the mitral valvuloplasty had been done, the subaortic stenosis was found to be due to a tight subaortic ring formed by accessory mitral tissue located at the septum and its fibrous extension to the anterior mitral leaflet. In both patients, excision of the accessory mitral and fibrous tissues resulted in a wide-open subaortic area. Both patients had an uneventful hospital course, and follow-up echocardiography showed no noteworthy residual left ventricular outflow gradient. We believe that increased awareness and sophisticated echocardiographic techniques should lead to an increased recognition of accessory mitral tissue causing subaortic stenosis. Simple resection of the accessory mitral tissue and its secondary fibrous tissues can be curative.