MMCTS
(September 15, 2008). doi:10.1510/mmcts.2008.003426
Copyright © 2008 European Association for Cardio-thoracic Surgery
Procedure
Modified Konno operation for diffuse subaortic stenosis
Olivier Metton,
Walid Ben Ali,
Olivier Raisky and
Pascal R. Vouhé*
Department of Pediatric Cardiac Surgery, Sick Children Hospital, Paris, France
* Corresponding author: Service de Chirurgie Cardiaque Pédiatrique, Hôpital Necker – Enfants Malades, 149, rue de Sèvres, 75015 Paris, France. Tel.: +33-1-4438 1867; fax: +33-1-4438 1911 pascal.vouhe{at}nck.aphp.fr
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Summary
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The modified Konno operation is designed to provide relief of diffuse subaortic stenosis, while preserving the native aortic valve. The aorta and the right ventricular infundibulum are opened. The upper part of the subaortic stenosis is incised through the aortic orifice. The conal septum is incised and the septotomy is extended across the stenotic area. The obstructive tissue is removed (mainly from the left-handed rim of the septotomy) and the conal septum is enlarged with a prosthetic patch. The aorta is closed and the right ventricular infundibulum is enlarged. Early and late mortality rates are low. Potential morbidity (complete heart block, residual ventricular septal defect, iatrogenic aortic insufficiency, right ventricular outflow tract obstruction) should be minimized by a careful surgical technique. The modified Konno operation is indicated in patients with diffuse subaortic stenosis and a normal aortic orifice; this includes patients with severe forms of hypertrophic obstructive cardiomyopathy and children with tunnel subaortic stenosis and a normal aortic orifice; the modified Konno procedure provides long-lasting relief of the obstruction. In patients with tunnel stenosis and a borderline-sized aortic annulus, residual obstruction may develop at the valvar level and need reoperation; the modified Konno operation can, however, delay aortic valve replacement.
Key Words: Diffuse subaortic stenosis • Hypertrophic obstructive cardiomyopathy • Modified Konno operation
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Introduction
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In patients with localized subaortic stenosis, resection of the stenosis through the aortic orifice (with or without associated myectomy), usually yields adequate and long-lasting relief of the left ventricular outflow tract (LVOT) obstruction. On the contrary, in diffuse subaortic obstruction, the conventional transaortic approach often fails to provide satisfactory results [1, 2]. Only more aggressive approaches can achieve adequate relief: insertion of a left ventricular apicoaortic valved conduit, aortoventriculoplasty (Konno procedure) [3], and total aortic root replacement using a homograft or a pulmonary autograft (Ross–Konno operation) [4].
In many patients with diffuse subaortic stenosis, the aortic valve is not normal (stenotic and/or insufficient, often with annular hypoplasia); replacement of the valve is mandatory. However, in some patients, the aortic orifice is normal and it should be preserved. This is the goal of the modified Konno operation to allow adequate relief of diffuse subaortic obstruction, while preserving the native aortic valve [5, 6].
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Surgical technique
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The basic steps of the procedure are illustrated in Schematic 1.
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Schematic 1 Basic steps of the modified Konno operation. (A) Aortotomy and right ventricular infundibulotomy. (B) Exposure of conal septum and septotomy. (C) Enlargement of conal septum after adequate subaortic resection. (D) Closure of aortotomy and infundibular enlargement.
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After initiation of cardiopulmonary bypass and cardioplegic arrest, the ascending aorta and the pulmonary trunk are dissected apart as near as possible to the aortic annulus; a longitudinal incision in the aorta is carried obliquely down toward the top of the commissure between the right and left aortic cusps (top of the left anterior fibrous triangle) (Video 1). The aortic orifice and the subaortic area are examined carefully, first to confirm that the aortic orifice can be preserved (morphology of the leaflets, size of the annulus) and, second, to ascertain that the subaortic lesion is too diffuse to allow simple resection through the aortic orifice. The right ventricular infundibulum is opened transversely below the pulmonary valve. The region of the conduction tissue is identified, located to the right of a line between the nadir of the right coronary aortic cusp and the septal attachments of the septal leaflet of the tricuspid valve (conal papillary muscle) (Video 2).
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Video 1 The aorta is opened longitudinally toward the top of the left anterior fibrous triangle, with care taken to stay away from the left and right coronary ostia (one of which may be abnormally located). The aortic orifice and the subvalvar area are exposed and examined.
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Video 2 The right ventricular infundibulum is opened transversely. Care is taken to avoid damaging the pulmonary valve cusps. The infundibular incision is extended toward the aortic incision, at the top of the left anterior fibrous triangle. Coronary artery branches are preserved. The right ventricular side of the interventricular septum is exposed. The conal papillary muscle of the tricuspid valve is identified.
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Working through the aortic orifice the top of the subaortic stenosis is incised, close to the aortic valve, exactly as it is done for a conventional myectomy; the lesion is incised but not resected (Video 3). This step is essential to achieve adequate resection of the upper part of the stenosis and to prevent damage to the aortic cusps during the subsequent surgical steps.
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Video 3 Through the aortic orifice, a stay suture is placed on the subaortic stenotic tissue. The upper part of the subaortic stenosis is incised by making two parallel longitudinal incisions, the first beneath the commissure between the right and the left coronary cusps and the second beneath the nadir of the right coronary cusp. These incisions are connected superiorly with a third incision close to the aortic valve. A deep wedge is created in the septal tissue but no resection is performed.
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A right-angle instrument is introduced through the aortic orifice into the septal wedge and the tip of the instrument is used to perforate the conal septum (Video 4).
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Video 4 A right-angle instrument is introduced into the septal wedge previously created and the tip of the instrument is used to perforate the conal septum. This represents the upper point of the septal incision.
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Another right-angle instrument is used to expose the conal septum and the septal incision is completed (Video 5). It is essential (1) to incise the conal septum well to the left of the conduction tissue location, (2) to extend the incision only below the first perforating point (to avoid damage to the aortic cusps), (3) to extend the incision downward, as far as necessary, in order to divide entirely the stenotic area, and (4) to avoid dividing completely the anterior limb of the septomarginal trabecula (the biggest septal coronary artery usually courses in the lower border of this structure).
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Video 5 A second right-angle instrument is introduced in the same orifice but in the opposite way (from the right ventricle toward the left ventricle). Once in the left ventricular cavity, the tip of the instrument is directed toward the left ventricular apex and the instrument is slightly opened. This maneuver protects the mitral valve, exposes the conal septum and facilitates the septotomy. The incision of the conal septum is extended downward as far as necessary to get below the stenotic area, but avoids complete division of the anterior limb of the septomarginal trabecula.
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Resection of the subaortic obstructive fibrous and/or muscular tissue is then performed, extensively on the left-handed (superior) side of the septotomy (Videos 6 and 7) and very carefully on the right-handed (inferior) side to avoid damaging the conduction tissue (Video 8). Divided septal arteries (easily identified when cardioplegia is administered) must be sutured to avoid the postoperative development of coronary-left ventricular fistulas. Anomalous mitral papillary muscles or chordae attached to the ventricular septum are divided or excised. Perfect opening of the left ventricular cavity must be obtained to ensure adequate relief of the subaortic obstruction.
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Video 6 Stay sutures are placed on both sides on the right ventricular side of the septotomy. Another stay suture is placed on the left ventricular side of the superior (left-handed) rim of the septotomy to help exposure. The obstructive tissue is incised.
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Video 7 The resection of the obstructive tissue is completed on the superior (left-handed) side. Efforts are made to remove the obstructive tissue in a single piece. The upper part of the stenosis (which had been previously incised through the aortic orifice) is removed at that time.
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Video 8 The obstructive subaortic tissue is also removed from the inferior (right-handed) rim of the septotomy. However, in order to stay away from the conduction tissue, resection is limited to the distal part of the septotomy. Adequate opening toward the main left ventricular cavity must be achieved.
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The septal incision is closed using a prosthetic (PTFE) patch to provide adequate widening of the left ventricular outflow tract (Video 9). Before closing the aortotomy, the integrity of the aortic valve is ascertained and the subaortic area is inspected to assess the adequacy of the relief of the LVOT obstruction. The right ventricular infundibulotomy is closed using an heterologous pericardial patch to prevent obstruction of the right ventricular outflow tract (Video 10).
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Video 9 A prosthetic (PTFE) patch is used to close and enlarge the conal septum. The pach is secured using interrupted running sutures with pericardial strips on the right ventricular septal side. Great care is taken to avoid residual septal defects, particularly in the distal part of the incision where right ventricular trabeculations make closure more difficult.
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Video 10 A patch of heterologous pericardium is used to close and enlarge the right ventricular infundibulum, thus avoiding right ventricular outflow tract obstruction.
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Videos 11 and 12 show the pre- and postoperative echocardiographic result in a child with severe hypertrophic obstructive cardiomyopathy.
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Video 11 Preoperative echocardiography in a child with severe hypertrophic cardiomyopathy.
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Video 12 Postoperative echocardiography in the same patient showing a widely patent left ventricular outflow tract.
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Results
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From January 1990 to December 2007, 31 patients with diffuse subaortic stenosis underwent a modified Konno operation. There were 16 males and 15 females with a median age of 8.8 years (range 6 months to 34 years). Seventeen patients had tunnel fibro-muscular subaortic stenosis; 3 had associated anomalies of the subvalvar mitral apparatus; 5 had had previous cardiac operations (resection of discrete subaortic stenosis in 3, closure of ventricular septal defect in 2). Fourteen patients had severe hypertrophic obstructive cardiomyopathy with persistent symptoms under optimal medical treatment. The mean preoperative peak systolic gradient across the LVOT was 114±25 mmHg (range 84–200 mmHg). The mean aortic annulus size Z-score was –0.05 (range –2.2 to +2).
There was no early mortality. Four patients (13%) developed complete heart block and needed pace-maker implantation (all during the first five years of this experience). Permanent left bundle branch block was noted in two patients (6.5%). One patient needed early reoperation for iatrogenic aortic insufficiency; aortic valve repair was performed. Mean peak systolic gradient across the LVOT was 15±10 mmHg at hospital discharge. Using Cox's proportionate hazard modeling, an aortic annulus size Z-score below –1 was associated with a worse early reduction in LVOT peak systolic gradient.
Mean follow-up was 95±50 months (range 6 months to 17 years). One patient (3.2%) (with hypertrophic obstructive cardiomyopathy (HOCM)) died suddenly 108 months postoperatively. Two patients required late reoperation. One patient had residual obstruction at the valvar level (due to annular hypoplasia) and underwent a Ross–Konno procedure 43 months postoperatively. Another patient (previously mentioned) who underwent early reoperation, developed progressive massive aortic regurgitation and needed aortic valve replacement 11 years postoperatively. Minimal to mild aortic insufficiency was noted in 10 patients but the regurgitation remained stable during the follow-up period and did not require reoperation. Trivial residual ventricular septal defect was observed in three patients but there was no reoperation for residual ventricular septal defect. At last follow-up, the mean peak systolic gradient was 10±20 mmHg.
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Discussion
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Indications
In patients with subaortic stenosis, it is essential to remove entirely the obstructive lesion and to eliminate completely flow disturbances in order to reduce the incidence of recurrence and the risk of late aortic insufficiency [7]. In patients with diffuse lesions, this, usually, cannot be obained by simple resection through the aortic orifice. When the aortic orifice is abnormal (severe annular hypoplasia, valvular stenosis or regurgitation), agressive approaches, such as Konno or Ross–Konno operations are indicated [3, 4]. In the presence of a normal aortic orifice, the modified Konno procedure provides satisfactory and long-lasting results. When the aortic annulus size is borderline, it is common to observe a residual obstruction at the valvar level and the need for late reoperation is increased [7].
The modified Konno operation is indicated in the fibro-muscular diffuse form of subaortic stenosis (tunnel subaortic stenosis), whether it is a primary lesion or it develops after the correction of a cardiac defect (ventricular septal defect, atrio-ventricular septal defect, discrete fixed subaortic stenosis). However, the frequent association of aortic annular hypoplasia limits the possibility of valve-sparing surgery and, as stated previously, the indication must be discussed carefully in the borderline cases.
The need for modified Konno operation in patients with HOCM is controversial. Excellent results can be obtained, even in the most severe forms of the disease, using extended myectomy [8,9,10]. However, it is usual to note, in the very severe forms and particularly in children, midventricular obstruction and anomalies of the subvalvar mitral apparatus [9]. The modified Konno approach provides excellent access to the midventricular area and allows safe resection of mitral anomalies (anomalous papillary muscle or chordae). We therefore share the opinion that the modified Konno operation is indicated in the most severe forms of HOCM, particularly in infants and small children [11].
Results
Surprisingly, relatively little attention has been paid to the modified Konno operation. The results of the reported series [7, 12,13,14] are summarized in Table 1.
The early mortality is low. Because of the usual severe myocardial hypertrophy, particular attention must be given to intraoperative myocardial preservation. It is usual to divide the first septal coronary artery. However, division of the second septal artery (usually the biggest of all septal arteries) should be avoided to prevent severe septal myocardial infarction; this artery nearly always courses in the lower border of the anterior limb of the septomarginal trabecula [15]; therefore, complete division of the anterior limb of the septomarginal trabecula should not be performed. Routine coronary angiography has been recommended to evaluate unusual anatomy of the septal coronary arteries; this is probably useless, provided the anterior limb of the septomarginal trabecula is identified and preserved. There is a risk of postoperative complete heart block. Careful identification of the conduction tissue axis and minimizing (or even avoiding) tissue excision from the inferior (right-handed) rim of the septal incision should reduce this risk. In our experience, the incidence of complete heart block has been reduced in the recent years by a strict respect of these recommendations. Similarly, the incidence of permanent left bundle branch block is low.
The late mortality rate is very low. However, it remains to determine if the risk of sudden death is decreased on the long-term in patients with hypertrophic obstructive cardiomyopathy.
Late reoperation is necessary in a few patients. Residual lesions such as ventricular septal defect, right ventricular outflow tract obstruction or severe iatrogenic aortic insufficiency, should be avoided by a perfect surgical technique. Moderate aortic insufficiency may develop in some patients, but remains stable in most cases; reoperation for severe aortic insufficiency has been rare to date. Residual or recurrent obstruction at the subvalvar level is extremely rare. Recurrent left ventricular outflow tract obstruction may develop at the valvar level, due to failure to grow of a native small aortic annulus; reoperation for Konno or Ross–Konno operation is then necessary.
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Conclusions
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The modified Konno operation is a safe procedure which provides efficient and long-lasting relief of the obstruction in patients with diffuse subaortic stenosis. This is the procedure of choice when the aortic orifice is normal. In patients with a borderline-sized aortic annulus, residual obstruction may develop at the valvar level and late reoperation may be necessary; however, the modified Konno operation may at least delay the need for more aggressive surgery which includes aortic valve replacement.
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References
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Summary
Introduction