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Ann Thorac Surg 2000;69:597-601
© 2000 The Society of Thoracic Surgeons

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Original Articles

Surgical closure of apical ventricular septal defects through a right ventricular apical infundibulotomy

^a Departments of Cardiovascular Surgery and Pediatrics, University of Padova Medical School, Padova, Italy
^b Departments of Cardiology and Pathology, Children’s Hospital, and the Departments of Pediatrics and Pathology, Harvard Medical School, Boston, Massachusetts, USA

Address reprint requests to Dr Stella Van Praagh, Children’s Hospital, 300 Longwood Ave, Boston, MA 02115
e-mail: gaskill{at}a1.tch.harvard.edu

	Abstract

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Background. We present a new understanding of the anatomic position of apical ventricular septal defects and its surgical relevance. These defects occur between the left ventricular apex and the infundibular apex, rather than between the left and right ventricular apices. Often a sizable apical recess, the infundibular apex lies anteriorly and inferiorly to the moderator band and is the most leftward part of the right ventricle.

Methods. Four patients (2 boys and 2 girls) with a mean age of 109 days (range, 48 to 217 days) underwent patch closure through an apical infundibulotomy, which allowed complete visualization of the muscular apical ventricular septal defect.

Results. There were no early or late deaths at operation. No significant residual shunt at ventricular level was detected by postoperative two-dimensional and Doppler echocardiography. Intraoperative comparison of right atrial and pulmonary arterial blood samples showed a difference of less than 5%. At a mean follow-up of 18 months, all the patients are asymptomatic and growing well.

Conclusions. The successful outcome of these 4 patients indicates that surgical closure of apical ventricular septal defects can be achieved safely and completely in early infancy through a limited right ventricular apical infundibulotomy. Long-term follow-up of these and similar patients is needed to provide further evaluation of this approach.

	Introduction

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Identification and surgical closure of apical ventricular septal defects (VSDs) remains a difficult problem because of their location in the ventricular septum distal to the moderator band, making adequate visualization and complete closure from the right atrium almost impossible. The anatomic location of apical VSDs is detailed in this report.

It was the realization by one of us (SVP) that apical VSDs are located between the apex of the left ventricle and the apex of the infundibulum, rather than between the apices of the left ventricle and the right ventricle, which prompted us to attempt their surgical closure through a small right ventricular apical infundibulotomy.

	Material and methods

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Patients
Between September 1996 and November 1997, 4 patients with an echocardiographic diagnosis of apical muscular VSD underwent surgical repair at the Cardiovascular Surgical Department of the University of Padova, Italy. There were 2 boys and 2 girls, with a mean age of 109 days (range, 48 to 217 days) and a mean weight of 4.4 kg (range, 3.3 to 5.8 kg). The preoperative diagnosis and surgical anatomic findings are summarized in Table 1.

At presentation, all patients showed moderate to severe congestive heart failure with failure to thrive. The latter was particularly severe in patient 3 (body weight, less than third percentile). The mean cardiothoracic ratio in the posteroanterior chest roentgenograms was 0.63, ranging from 0.57 to 0.70. Electrocardiography revealed biventricular hypertrophy in all 4 patients. Before surgical repair, anticongestive therapy was required in all 4 patients. The diagnosis of apical muscular VSD was made in all patients within the first month of life by two-dimensional echocardiography with color-flow Doppler. The apical VSD was best visualized in the parasternal short axis and apical four-chamber views (Fig 1). Cardiac catheterization was performed in patient 3 in an unsuccessful attempt to balloon dilate diffusely hypoplastic pulmonary artery branches.

View larger version (114K): [in this window] [in a new window]   Fig 1. Patient 1. Four-chamber view of apical muscular ventricular septal defect (lower arrow), which lies below the moderator band (upper arrow). (LA = left atrium; LV = left ventricle; MB = moderator band; RA = right atrium; RV = right ventricle; VSD = ventricular septal defect.) Note that the ventricular septal defect is between the left ventricular apex and the infundibular recess (below the moderator band), not between the apices of the left and right ventricles.

View larger version (97K): [in this window] [in a new window]   Fig 2. (A) Opened normal right ventricle (RV). The apex of the right ventricle inflow is proximal to the apex of the outflow tract (infundibulum). There normally is a muscular partition, including the moderator band (MB), between the inflow and the outflow apices. The outflow or infundibular apex typically is further to the left and closer to the left ventricular apex. (PB = parietal band; PV = pulmonary valve; SB = septal band; TV = tricuspid valve.) (Reproduced with permission from Van Praagh and colleagues [1].) (B) A waxed specimen of a normal heart viewed from above. Part of the anterior wall of the right ventricular inflow and outflow have been removed to expose the septal–moderator band junction and the entry into the infundibular apex (Inf. Apex). (Ao = aorta; PA = pulmonary artery; RAA = right atrial appendage; SVC = superior vena cava.) (Reproduced with permission from Kumar K, Lock JE, Geva T. Apical muscular ventricular septal defects between the left ventricle and the right ventricular infundibulum. Diagnostic and interventional considerations. Circulation 1997;95:1207–13 [3].

With apical muscular VSDs, the infundibular apex becomes even larger (Fig 3A). Apical muscular VSDs are located in the part of the interventricular septum that separates the left ventricular apex from the infundibular apex, both in D- and L-loop ventricles [3, 4] (Fig 3).

View larger version (87K): [in this window] [in a new window]   Fig 3. The heart of an 8-day-old twin girl with visceral heterotaxy, asplenia, double-outlet right ventricle with only subpulmonary conus, inversus atria, L-loop ventricles, with the aortic valve posterior and to the left of the pulmonary valve, and severe subaortic and aortic valve stenosis. (A) Opened left-sided right ventricle. The right ventricular exit of the apical ventricular septal defect (VSD) involves the infundibular (Inf Apex) apex, not the right ventricular apex (RV Apex). (Inn = innominate artery (left-sided); PB = parietal band; PDA = patent ductus arteriosus (right-sided); PV = pulmonary valve). (Modified from Van Praagh and colleagues [4].) (B) Opened right-sided atrium and right-sided left ventricle (LV). Large apical ventricular septal defect (VSD) is present. (AVC = atrioventricular canal; CAVV = common atrioventricular valve; HPV = hepatic vein.) (Reproduced with permission from van Praagh S, Geva T, Friedberg DZ, et al. Aortic outflow obstruction in visceral heterotaxy: a study based on twenty postmortem cases. Am Heart J 1997;133:558–68 [4].

A longitudinal incision of 10 to 15 mm was made into the infundibular apical free wall, parallel to and to the right of the distal part of the left anterior descending coronary artery (Fig 4). Through this small incision, the infundibular apical septal surface was easily exposed. In patient 1, the VSD extended above and below the moderator band, necessitating gentle retraction of the moderator band to expose the entire defect. Once clearly identified, the VSD was closed with a polytetrafluoroethylene patch, using 5-0 polypropylene continuous running suture in all patients.

View larger version (27K): [in this window] [in a new window]   Fig 4. Diagrammatic presentation of the apical infundibulotomy parallel to the distal portion of left anterior descending (LAD) coronary artery. Inset shows the exposed apical ventricular septal defect (VSD). In this diagram and in some cases of apical ventricular septal defects, the defect extends above and below the moderator band (MB). (MPA = main pulmonary artery; other abbreviations, see Figs 2 and 3.)

	Results

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All patients were weaned easily from cardiopulmonary bypass. The mean cardiopulmonary bypass time was 120 minutes, ranging from 84 to 153 minutes. The mean aortic cross-clamp time was 61 minutes, ranging from 48 to 88 minutes. The deep hypothermic arrest time in patients 1 and 2 was 40 and 47 minutes, respectively.

No significant residual shunts were detected intraoperatively at the ventricular level by epicardial two-dimensional echocardiography with color-flow Doppler. Intraoperative comparison of right atrial and pulmonary arterial blood samples showed an oxygen saturation difference of less than 5% in all patients.

The postoperative course in the intensive care unit ranged from 2 to 11 days. Postoperative complications were as follows: In patient 2, there were repeated pulmonary hypertensive crises on postoperative day 0 despite deep sedation and hyperventilation, requiring treatment with inhaled nitric oxide. In patient 3, there was severe low cardiac output on postoperative day 0, refractory to infusion of inotropic drugs and requiring support by extracorporeal membrane oxygenation for 48 hours. Upon discharge from the intensive care unit, all patients were extubated, breathing spontaneously, and in good hemodynamic condition.

The subsequent postoperative hospital course was uneventful in all patients. Two-dimensional and Doppler echocardiography before discharge confirmed the absence of residual shunt at the ventricular level. The mean left ventricular ejection fraction was 71%, ranging from 61% to 85%. The left ventricular shortening fraction was 40%, ranging from 31% to 51%.

On discharge, all patients were in good condition, in sinus rhythm, and were treated with oral digoxin and diuretic therapy.

On follow-up, there were no late deaths. Patient 2 required reoperation 5 months after discharge for coarctation of the aortic isthmus, which had become clinically and anatomically significant at the time of the follow-up visit. The mean duration of follow-up was 18 months, ranging from 10 to 24 months. All patients were asymptomatic and growing well. Their electrocardiograms continued to show sinus rhythm, without ST-segment or T-wave changes. Two-dimensional echocardiography with Doppler interrogation confirmed normal left and right ventricular function, and absence of any residual shunt at the ventricular level in all patients.

	Comment

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Anatomic considerations
Morphologically the right ventricle is composed of the right ventricular inflow tract or sinus, derived from the proximal part of the bulbus cordis, and the right ventricular outflow tract—also known as the infundibulum or conus—derived from the distal part of the bulbus cordis [1, 2]. The junction between the right ventricular sinus and the infundibulum is formed by a ring of conal musculature consisting of the conal septum that extends out onto the parietal or free wall as part of the parietal band, and by the septal band, and the moderator band [1, 2]. This infundibular or conal ring demarcates and slightly separates the right ventricular sinus posteroinferiorly from the infundibulum anterosuperiorly.

What is commonly regarded as the right ventricular apex is composed of two distinct apices, which are separated by multiple trabeculae that form a septumlike structure containing multiple fenestrations (Figs 2 and 3). Posteriorly, inferiorly, and to the right of this septumlike structure is the apex of the right ventricular sinus, whereas anteriorly, inferiorly, and to the left of this fenestrated septumlike structure is the apex of the infundibulum. Thus, apical muscular VSDs, which have ordinarily been regarded as defects between the left and right ventricular apices, are in fact defects in the apical portion of the ventricular septum that separates the left ventricular apex from the infundibular apex. This is observed in both D-loop and L-loop ventricles (Fig 3).

This understanding led us to the realization that a direct and minimally traumatic approach to the surgical closure of apical muscular VSD could be through an incision in the infundibular apical free wall (Fig 4). The proposed incision, which is parallel to and to the right of the distal portion of the anterior descending coronary artery, does not injure any major coronary arteries or any conduction system pathways and avoids incision of the systemic ventricle.

Surgical considerations
It is now well known that patch closure of large apical VSDs through the right atrium is very difficult or almost impossible [6–8]. The area of the ventricular septum separating the left ventricular apex from the infundibular apex—where, as a rule, apical VSDs occur—is not visible as the surgeon inspects the ventricular septum through the orifice of the tricuspid valve. The moderator band and the multiple trabeculations beneath it create a multiperforated wall that hides the apical muscular VSD in a transtricuspid view.

It was for this reason that an apical left ventriculotomy was introduced by Aaron and Lower in 1975 [9]. Apical left ventriculotomy was rapidly adopted as the most effective approach for surgical closure of midmuscular and apical VSDs [10–14]. However, late complications including apical left ventricular aneurysms or dyskinesis [7, 8, 15, 16] have created the need for a safer approach.

From an anatomic standpoint, these late complications are not surprising. Apical left ventriculotomy gives excellent exposure of the Purkinje network of the left ventricular conduction system—numerous fine whitish threadlike fibers that pass from the left ventricular septal surface to the left ventricular free wall surface at the base of the anterolateral and posteromedial papillary muscles. To occlude the apical muscular VSD with a patch, it is often necessary to transect some of these fibers, resulting in left ventricular apical dyskinesis and aneurysm formation.

Visualization of apical VSDs through a small apical infundibulotomy is, in our experience, surprisingly easy and the precise margins of the defect can be identified readily. The apical infundibulotomy that has been performed in our 4 patients has never been longer than 15 mm, involving exclusively the infundibular free wall.

The postoperative course was complicated in patients 2 and 3; we believe that the associated cardiac lesions played an important role in causing these complications. In patient 2, the VSD was the largest (20 mm in diameter in a 49-day-old baby weighing 4.3 kg), which may have contributed to the pulmonary hypertensive crises immediately postoperatively.

Patient 3 had diffuse hypoplasia of the pulmonary artery branches with a peak systolic gradient between the right ventricle and the distal pulmonary arteries of 61 mm Hg. We believe that possible residual stenosis of the pulmonary artery branches may have played an important role in causing low cardiac output postoperatively, requiring extracorporeal membrane oxygenation for 48 hours. However, both of these patients recovered and are doing well.

Primary reparative operation of congenital heart disease in early infancy offers the benefits of early correction of cardiac malformations and avoids secondary damage of the cardiovascular and other organ systems such as the brain and the lungs [6, 8].

The patients reported here and the experience of other surgeons [17, 18] indicate that apical VSDs can be well visualized and completely patch closed through a small apical infundibulotomy, even in very young and critically ill infants. Nevertheless, further experience and longer follow-up of these and similar patients are needed.

In conclusion, (1) large apical muscular ventricular septal defects typically are located in that part of the ventricular septum that separates the left ventricular sinus apex and the infundibular apex, rather than between the left and right ventricular sinus apices. (2) A small apical infundibulotomy is an easy and effective approach to achieve complete closure of apical ventricular septal defects, allowing excellent exposure of the borders of the defect. (3) The early postoperative results of our four successfully operated patients are highly satisfactory. If the long-term results of these and similar patients remain good, patch closure through a small apical infundibulotomy into the low right ventricular outflow tract may become the procedure of choice for the surgical treatment of apical VSDs.

	Acknowledgments

 
We thank Emily and Bill McIntosh for art work and photography, and Gloria Gaskill for secretarial assistance. This study was supported in part by the Karen Arbia Scholarship Fund, Boston, MA.

	References

Top Abstract Introduction Material and methods Results Comment References

 

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