Ventricular Septation for Double Inlet Left Ventricle

Morphology

Double inlet left ventricle (DILV) is the anatomic type of single ventricle anomaly which is most suitable for ventricular septation. There are two major types of DILV (Figure 1). The first type is characterized by L-looping of the ventricular mass and is referred to as single ventricle, DILV, {S,L,L}. In this type of DILV, the dominant ventricle of left ventricular morphology is associated with a rudimentary subaortic right ventricular (RV) outlet chamber with ventricular septal defect (VSD). The VSD is alternatively referred to as a bulboventricular foramen (BVF) in the classification of the International Pediatric and Congenital Cardiac Code (IPCCC). ^5,6 The aorta arises from the left-sided rudimentary right ventricle which is located anteriorly in relation to the dominant morphological left ventricle. The entire morphological mitral valve (right-sided) and the major portion of the morphological tricuspid valve (left sided) open into the large morphological left ventricle (right sided). The interior of the large left ventricle (right sided) can be easily approached through the mitral valve (right sided).

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Figure 1.

Two types of double inlet left ventricle (DILV). T indicates tricuspid valve; M, mitral valve; RV, right ventricle; LV, left ventricle; green asterisk, atrioventricular node and bundle.

The second type has D-looping of the ventricular mass. This type includes single ventricle, DILV, {S,D,N} (alternatively {S,D,S}) as classified in the IPCCC. ^5,6 In this type, there is a subpulmonary rudimentary RV outlet chamber. The entire morphological mitral valve (left sided) and the major portion of the morphological tricuspid valve (right sided) open into the large morphological left ventricle (left sided). This anomaly is known as Holmes heart. Because of the presence of concordant atrioventricular connection, the atrioventricular node and bundle are in a posterior location, as in a normal heart. Ventricular septation by transatrial/transtricuspid valve approach for Holmes heart is somewhat difficult because exposure of the left ventricle (left sided) through the tricuspid valve (right sided) is limited.

Finally, in the setting of concordant atrioventricular connection (D-looping) and discordant ventriculoarterial connection, classified as single ventricle, DILV, {S,D,D} with subaortic RV outlet chamber, performance of ventricular septation requires a concomitant arterial switch procedure.

Conduction System and Surgery in Single Ventricle, DILV, {S,L,L}, Subaortic RV Outlet Chamber with VSD (BVF)

Single ventricle, DILV, {S,L,L} with subaortic RV outlet chamber has anterior node and bundle as in congenitally corrected transposition of the great arteries (Figure 2). ^7,8 Initial sutures are placed in the subpulmonary tissue (Figure 2—two orange points), several sutures from the left to the right (as in the technique introduced by deLeval ⁹ ) along the outlet (infundibular) septum and the anterior septum (Figure 2—five red points), several sutures across the left bundle branch along the anterior septum (Figure 2—four yellow points), transmural sutures at the anterior wall and the apex (Figure 2—four blue points), meticulously placed sutures between the mitral and tricuspid papillary muscles at the posterior wall (Figure 2—seven yellowish green points), and several sutures along the mitral annulus (Figure 2—three green points).

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Figure 2.

Anatomy of the conduction system and suture placement for ventricular septation in right-sided large left ventricle of DILV, {S,L,L}, subaortic RV outlet chamber. Green asterisk indicates anterior atrioventricular node; green points, divided point of anterior bundle; white asterisk, bifurcating bundle of right bundle branch; LBB, left bundle branch.

When the morphological left ventricle (right sided) is approached through the morphological mitral annulus (right sided), the anterior descending bundle is anticipated along the anterior septum (Figure 3). Then, deLeval sutures ⁹ are employed in this particular area. Because of the restrictive nature of the VSD (BVF), the posterior margin of the VSD is resected to enlarge the VSD. A large patch is fashioned (Figure 4) and plunged into the left ventricle after threading sutures. Pledgeted sutures along the mitral annulus near to the coronary sinus are placed at a distance from the anticipated area of the anterior atrioventricular (AV) node. Echocardiography (Figure 5) shows that there was no septum in the large morphological left ventricle before ventricular septation, and the large left ventricle was subsequently divided into two ventricular chambers by an artificial septum following the ventricular septation procedure.

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Figure 3.

deLeval suture in ventricular septation for DILV, {S,L,L}, subaortic RV outlet chamber. A, Transmitral view: Green line indicates anticipated anterior descending bundle along anterior septum. B, deLeval suture through mitral valve from left side at anterior septum. C, Needle stitched from left side to middle at anterior septum as in B.

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Figure 4.

Ventricular septation for DILV, {S,L,L}, subaortic RV outlet chamber. A, Large composite patch of Dacron and bovine pericardium. B, Patch was plunged in left ventricle after threading sutures. C, After ventricular septation, three pledgeted sutures along mitral annulus near to coronary sinus are away from anterior AV node (green asterisk). DILV indicates double inlet left ventricle; RV, right ventricle; AV, atrioventricular.

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Figure 5.

Echocardiogram before and after ventricular septation. A, Before septation; B, after septation.

Patients

Thirty-four patients underwent ventricular septation procedures for single ventricle, DILV from 1971 to 2000 at Tokyo Women’s Medical University and Jikei University. ^{3,10 –13} One of the three patients reported by Sakakibara and Arai in 1973¹⁰ had a morphology of common ventricle with a large VSD (which is not DILV) and hence is excluded from this series. The DILV, {S,L,L} was present in 28, DILV, {S,D,D} in four, and DILV, {S,D,N} in two. Age ranged from 3 months to 24 years (mean 6.1 ± 5.7 years). Pulmonary artery banding was previously done in 21 patients. Preoperative end-diastolic volume of the ventricle was 291% ± 111% of normal (N = 10) and the ejection fraction was 0.59 ± 0.07. ¹⁴ One patient had common atrioventricular valve which was concomitantly divided into two AV valves. ¹⁵ Restrictive VSD (BVF) was enlarged in 14 patients. Of the four patients with DILV, {S,D,D}, three concomitantly underwent an arterial switch procedure and one underwent a Rastelli procedure.

Comment

The concept of surgical septation of the main chamber to establish two parallel circulations emerged from the Mayo Clinic in 1956. ^1,2 In their initial case, the preoperative diagnosis had been congenitally corrected transposition of the great arteries with ventricular septal defect, but the true diagnosis became evident after opening, what proved to be a single ventricle. The patient died about six months after operation, probably in a Stokes-Adams episode. The concept of septation was then further developed by Sakakibara in 1972 to 1973³ and by Edie and Malm in 1973. ¹⁹ Three long-term survivors were reported in 1973 by Arai and Sakakibara ¹⁰ and one by Ionescu. ²⁰ McGoon et al published several reports describing the experience at the Mayo Clinic; 36 patients in a report in 1977, ¹ 34 patients from April 1973 to March 1978 in a report in 1979, ²¹ and 45 patients from 1973 to June 1978 in a report in 1981. ²² In the latest of those reports, the hospital mortality was 21 (47%) of 45 patients and eight (18%) patients died during follow-up. ²² The right atrial approach was introduced by Doty in 1979. ²³ In 1982, McKay and Pacifico reported 16 cases with seven deaths. ²⁴ In 1984, Ebert reported five cases of staged partitioning without any deaths. ²⁵

Since 1978, several morphological studies of the conduction system in single ventricle, of types DILV and DIRV (double inlet right ventricle), have been reported. ^{26 –28} We precisely studied the conduction system of single ventricle, DILV, {S,L,L}. ⁸ This type always has an anterior node and bundle as in congenitally corrected transposition of the great arteries, ^7,29 although DIRV, {S,L,L}, with subaortic outlet chamber may occasionally have twin nodes and a sling of bundle or only a posterior node and bundle. ³⁰

We revived ventricular septation by transatrial approach in 1986 and reported 12 cases without death in 1990. ¹¹ In that report, the hemodynamic performance was compared between patients who had undergone either ventricular septation or Fontan procedures. Cardiac output was higher in the septation group than in the Fontan group under the same level of central venous pressure (right atrial pressure). Since then, ventricular septation has been our first choice of surgery for single ventricle, DILV with large volume-loaded ventricle. Enlargement of restrictive VSD (BVF) was not a risk factor for rhythm disturbance. ¹⁵ However, ventricular hypertrophy was one of the risk factors for ventricular septation, which had a tendency to progress with age. ³¹ Fontan operation is hardly applicable for patients with high pulmonary resistance. Those patients could be a candidate for ventricular septation after pulmonary artery banding. ³²

Shimazaki reported ventricular function after ventricular septation in two patients. Cardiac output in response to exercise was excellent in one and poor in another. ³³ Ohuchi and Yagihara reported that peak oxygen uptake was higher after ventricular septation without AV valve replacement (AVVR) than after ventricular septation with AVVR or after Fontan. There was no significant difference in peak oxygen uptake between ventricular septation with and without pacemaker implantation. They concluded that ventricular septation without AVVR provides excellent future exercise capacity in selected patients with DILV. ³⁴

Fontan's procedure was reported in 1971⁴ just before several surgeons reported their initial experience of ventricular septation. ^3,10,19,20 Because of this historical nearness and the relative technical ease of Fontan's operation, popularity of the Fontan procedure spread rapidly throughout the world. With widespread acceptance of the Fontan procedure, ventricular septation has lingered only in a few centers. ^{11,12,21,33 –38} Pregnancy in a woman after ventricular septation could follow a favorable course. ³⁹ Despite the occurrence of arrhythmias and/or heart failure in some patients, the quality of life is fairly good in most patients after ventricular septation. Mid- and long-term results are acceptable. ^{11,13,33 –36} Current criteria for ventricular septation include anatomic diagnosis of single ventricle, DILV, {S,L,L} or DILV, {S,D,N} with large volume-overloaded hearts, two well-functioning atrioventricular valves, and absence of severe ventricular outlet obstruction.

In conclusion, ventricular septation is an anatomical and functional biventricular repair, which has better hemodynamic performance than univentricular repair of the Fontan type. Ventricular septation could be a reasonable alternative to the Fontan operation in selected patients with single ventricle, DILV.