Robotic trans-atrial and trans-mitral ventricular septal resection

Abstract

Localized ventricular septal hypertrophy, also known as idiopathic hypertrophic subaortic stenosis or idiopathic hypertrophic subaortic septal obstruction (IHSS), can create severe ventricular outflow obstruction. This often results in a high sub-aortic pressure gradient with potentially lethal symptoms. In 1960, Braunwald described the hemodynamic characteristics of IHSS, and thereafter, Morrow developed a trans-aortic approach to resect a large part of the ventricular septum, enlarging the outflow tract. The Morrow operation has remained the gold standard for surgically treating this pathology. However, in patients with a small aortic annulus, a severely hypertrophied septum, and a long anterior mitral leaflet, the trans-aortic approach may be more difficult, resulting in an inadequate resection and/or systolic anterior leaflet motion. The latter usually increases the obstruction and can cause mitral regurgitation. Herein, we describe a minimally invasive trans-left atrial robotic approach to treat IHSS. First, the anterior mitral leaflet is incised radially to reveal the aortic outflow tract and ventricular septum, which are located posteriorly. Thereafter, a deep "block" of septum is excised, beginning at the right valve cusp nadir and continued counterclockwise toward the left fibrous trigone. This excision is extended to the anterior papillary muscle base, where any septal connections must be divided. Subsequently, the anterior leaflet is re-suspended and the repair is completed with a flexible annuloplasty band. If necessary, the anterior leaflet can be augmented with a pericardial patch. The "wristed" robotic instruments and magnified 3-D vision definitely facilitate an adequate septal resection and anterior papillary muscle mobilization. Moreover, it is possible that this fine control helps to reduce complications, such as heart block or a ventricular septal defect.

Keywords: Hypertrophic; cardiomyopathy; idiopathic hypertrophic subaortic septal obstruction (IHSS); resection; robotic.

Figure 1

A long-axis 2D transesophageal echocardiogram is shown for this patient who has severe subvalvular aortic outflow tract muscular obstruction. Note the markedly hypertrophied septal “knob” (S). The anterior leaflet (AL) is shown to appose the septum during systole (systolic anterior motion or SAM) resulting in even greater outflow tract obstruction. This often induces AL malcoaptation with the posterior leaflet and therefore concomitant valvular regurgitation. Note that the aortic-mitral annular plane angle is very acute, predisposing to SAM as well.

Figure 2

This illustration shows the level of proposed septal resection. Generally, the resection should be approximately two-thirds of the septal thickness. The resection must be uniform and carried out to the base of the anterior papillary muscle. In this region, septal-papillary muscle bands often tether the papillary muscle into the outflow tract. All of these should be divided to mobilize the papillary muscle posteriorly. One can see where the anterior leaflet has been incised, leaving a 2-mm rim attached to the annulus. This allows direct endoscopic vision through the left atrium of both the septum and papillary muscle.

Figure 3

This photograph shows that the anterior mitral leaflet (AL) has been incised and ‘draped’ out of the operative field. This provides superb exposure of the hypertrophied interventricular septum (S). The arrow indicates the direction of the aortic outflow tract toward the aortic valve (AV). Note the subvalvular fibrous ridge (SVR) that has eventuated from the back of the AL hitting the septum during systole.

Figure 4

The anterior leaflet has been incised, exposing the septum. For orientation, A₁, A₂ and A₃ denote the different regions of the anterior leaflet and mirror similar locations of P₁, P₂ and P₃ of the posterior leaflet. The septal resection is commenced at the nadir of the right aortic cusp (Rt) and continues clockwise under the left cusp (L) to the left fibrous trigone (LFT). RFT, right fibrous trigone.

Figure 5

Septal resection. (A) The septal resection is commenced at the nadir of the right aortic cusp, continuing counterclockwise past the left aortic cusp and to the left fibrous trigone; (B) this photograph shows the robotic septal resection (S), beginning just under the nadir of the right aortic cusp and continuing counterclockwise. The block resection is carried to the base of the anterior papillary muscle. AV, aortic valve; AL, anterior leaflet of the mitral valve, which has been divided and released.

Figure 6

Anterior papillary muscle mobilization. (A) The left (L) and right (Rt) aortic valve cusps are shown for reference. The septal muscle resection has been completed and septal-papillary muscle bands are being divided. It is important to divide all of them as well as any abnormal leaflet non-suspending chordae tendineae; (B) this photograph shows that septal muscular connections (SC) have been divided to the base of the anterior papillary muscle (APM). For orientation, the right (RFT) and left (LFT) fibrous trigones and displaced anterior leaflet (AL) are shown. The suction instrument is in front of the septal resection region. Robotic curved scissors are shown and are used for all muscular resections.

Figure 7

Anterior leaflet resuspension. (A) After muscle resections are complete, a 4-0 PTFE suture is used to re-suspend the anterior leaflet to the residual annular rim; (B) most often the suture line is carried from the right fibrous trigone toward the left fibrous trigone, where it is tied. Alternatively, the suture can be started at both trigones and run to the middle of the leaflet. Care must be taken not to injure the aortic valve leaflets; (C) the anterior leaflet has been re-suspended. If the anterior leaflet is shortened, it is best to extend its length with a large pericardial patch. This helps prevent the development of systolic anterior motion (SAM).

Figure 8

The mitral repair is usually completed with a flexible posterior band. This promotes better leaflet coaptation without overly reducing the distance between the septum and lateral annulus. We avoid complete rings in this operation.

Video

Robotic trans-atrial and trans-mitral ventricular septal resection.