Assessing the Valves and Adjacent Structures

Structural cardiac lesions in IE include (a) lesions that existed prior to the onset of the disease and (b) new lesions caused by IE (Table 8.2). Preexisting lesions may include mitral valve prolapse, any valvular stenosis or insufficiency, congenital defects such as bicuspid aortic valve and residual lesions from previous IE, including those related to prosthetic valve implantations. Lesions caused by the current IE include vegetations (most frequent IE lesions), leaflet/cusp perforation, rupture of chordae ten-dinae, annular dilatation, abscesses, aneurysm/ pseudoaneurysm, and annular or septal fistulae. The type and extent of lesions determine the surgical technique; and hence, the operation can be anywhere along a spectrum of technical difficulty, from simple suturing of a leaflet/cusp perforation to complex reconstruction and replacement techniques including homograft implantation.

Table 8.2. Structural Lesions in Infective Endocarditis

Lesion

Remarks

Common Lesions

Vegetations

On ventricular aspect of aortic valve, atrial aspect of mitral valve

Leaflet Perforation

Usually in the anterior mitral leaflet; anterior mitral leaflet involvement also caused by

vegetative aortic IE

Abscesses

Mostly seen in S. aureus IE; more common in PVE; in NVE, up to 50% in aortic valve and

5% in mitral valve IE

Aneurysm/Pseudoaneurysm/Fistula

Usually develops from abscess

Uncommon Lesions

Stenosis

More common in mitral and tricuspid valves, PVE and fungal IE

Suppurative pericarditis

Seen in myocardial perforation

Myocardial infarction/Ruptured chordae rendinae

Due to coronary emboli or vegetations on subvalvular structures

Preexisting valvular lesions

Especially mitral valve prolapse and degenerative aortic valve changes

The most common lesions in IE and technical considerations in their surgical management are the following:

1. Vegetations: These are the most common lesions in IE. They are usually found on the ventricular aspect of the aortic valve and on the atrial side in the mitral valve. The size and site of the attachment of the vegetation and the relation to the leaflet/cusp size are important. Removal of large or multiple vegetations leaves a large defect in the leaflet that is more difficult to repair and valve replacement might be the proper or only choice in extensive vegetative IE. Due to smaller surface areas of aortic cusps compared to mitral leaflets, the size of a lesion that could be readily repaired in the mitral leaflet may be too large for aortic cusp repair. This is one main reason why mitral valve repairs are more commonly performed than aortic valve repairs. Vegetations should be removed in one piece to avoid fragmentation, and cardiac manipulation should be minimized to prevent dislodging potential embolic material. The location of vegetation attachment is also important. Repair of lesions in the middle of a leaflet is more feasible compared to vegetations with a base involving two leaflets/cusps and/or the annulus. Discrete lesions in the free margin of the anterior mitral leaflet can be removed with a triangular resection, and for posterior leaflet lesions, a quadrangular resection is usually used (Figure 8.1). Infection involving both mitral leaflets at or near the commissures dictates leaflet resection and debridement of the annulus. In such cases, it may be feasible to perform direct suturing to reconstitute the commissure and to plicate the annulus with pledgetted sutures (Figure 8.2).

2. Perforation: Not infrequently, IE leaves behind a perforation in the leaflet/cusp, causing valvular insufficiency. Perforations are more common in the anterior leaflet of the mitral valve, and they may be caused by satellite vegetation due to aortic valve IE. Thus, the anterior mitral leaflet should always be carefully examined for the presence of erosions and perforations in patients with aortic IE. Small perforations with smooth, regular margins may be closed by direct suturing of the edges. Prolene sutures are preferred for their lack of spaces between interwoven threads and probably lower risk of recurrent IE. Larger perforations, and defects left behind from partial leaflet resection, can be repaired using autologous or bovine pericardial patches (Figure 8.1B,C). Autologous pericardium is harvested and stripped of fat and connective tissue. Pericardial patches may be used fresh or preserved intraopera-tively in a glutaraldehyde-buffered solution and rinsed in saline prior to use [26]. Separate sutures are preferred to continuous sutures, and reinforcing pledgets should be considered with caution, due to the fact that

Figure 8.1. A: Surgical approach to repair the mitral valve in the setting of vegetations or perforations. B: Small perforations with regular margins may be repaired by directly suturing the edges. C: The defect in the anterior mitral leaflet caused by the removal of vegetation can be repaired using a pericardial patch. D: Triangular resection for the removal of a lesion in the free margin of anterior mitral leaflet. E, F: Quadrangular resection and sliding plasty for discrete lesions in the posterior mitral leaflet.

Figure 8.1. A: Surgical approach to repair the mitral valve in the setting of vegetations or perforations. B: Small perforations with regular margins may be repaired by directly suturing the edges. C: The defect in the anterior mitral leaflet caused by the removal of vegetation can be repaired using a pericardial patch. D: Triangular resection for the removal of a lesion in the free margin of anterior mitral leaflet. E, F: Quadrangular resection and sliding plasty for discrete lesions in the posterior mitral leaflet.

Figure 8.2. A: Lesions involving both anterior and posterior mitral leaflets at the posteromedial commissure. The dashed lines outline where the leaflets will be resected. B: Diseased portions of both anterior and posterior leaflets are resected. The affected annulus is also debrided. C: Reconstruction is performed by directly suturing the edges of the anterior and posterior leaflets and plicating the annulus with pledgetted sutures.

Figure 8.2. A: Lesions involving both anterior and posterior mitral leaflets at the posteromedial commissure. The dashed lines outline where the leaflets will be resected. B: Diseased portions of both anterior and posterior leaflets are resected. The affected annulus is also debrided. C: Reconstruction is performed by directly suturing the edges of the anterior and posterior leaflets and plicating the annulus with pledgetted sutures.

they add more foreign material exposed to recurrent infection. Debridement of the perforation prior to patch repair is of utmost importance.

3. Perivalvular abscesses: They must be carefully searched, evaluated, and treated. Extensive debridement of abscesses is the key to immediate and long-term surgical success. Abscesses are predominantly associated with IE caused by Staphylococcus aureus and are much more common in aortic IE than in mitral IE (25-50% in aortic vs. 1-5% in mitral IE) [27]. However, they have more severe adverse impacts in the mitral position. In aortic IE, abscesses mostly form at the weakest location of the annulus, near the membranous portion of the interventricular septum, in the vicinity of the atrioventricular node [8]. This anatomical predilection of abscesses explains the development of new conduction blocks resulting from abscess formation. Abscesses below left coronary cusp, between posterior wall of the left ventricle (LV) and left coronary ostium, are also not uncommon and tend to extend toward the anterior mitral leaflet and the non-coronary cusp section of the annulus.

Mitral annular abscesses usually occur in the posteroinferior portion, and this part should be carefully inspected for abscesses when mitral valve is being resected. A well-defined, small abscess can be drained, debrided, and the remaining defect can be corrected with a peri-cardial patch. When discontinuity is present between LV and left atrium (LA), a modified technique for valve replacement can be used, which consists of interrupted horizontal mattress sutures with pledgets placed on the LV side of mitral annulus, carried up through the LA side of the debrided annulus, and then through the sewing ring of the prosthetic valve. However, the distance between the edge of LV and LA after debridement and the fragility of the infected tissue poses a failure risk on such a technique either immediately in the operating room or during postoperative period. To avoid excessive tension on weakened ventricular or atrial structure, a good alternative is to reconstruct the annulus with pericardium, attached first to the LV with running 4-0 or 3-0 prolene suture, and then attached to the atrium. Prosthetic valve will then be placed with pledgetted sutures in the upper portion (atrial side) of the pericardial patch (Figure 8.3). Thus, the prosthesis will be more atrially positioned rather than in the ventricular cavity. Biological glue can be used as a good adjunct to such a reconstructive procedure. Glue can be spread posteriorly to the pericardial patch after completion of ventricular suture and before completion of atrial sutures of the patch. The risk of postoperative AV discontinuity is considerably reduced with this procedure.

In aortic valve IE repair is also preferred to replacement, although repair is less frequently feasible with the aortic valve compared to the mitral valve, as previously discussed. Lesions limited to one cusp, sparing the annulus (Figure 8.4A) can be removed and reconstructed with tailored pericardium. When the annulus is also involved (Figure 8.4B), annuloplasty accompanies cusp reconstruction. Extensive disease of the noncoronary sinus involving the annulus and the anterior mitral leaflet (Figure 8.4C) requires a more complicated procedure involving removal of the lesion, reconstruction of the

Figure 8.3. A: Surgical approach to treat abscess involving the mitral annulus. B: The infection is extensively debrided, leaving behind a defect at the atrioventricular junction.The anterior and posterior mitral leaflets are also resected, leaving a narrow rim of leaflet remnant. C: The atrioventricular defect is repaired with a patch tailored from the pericardium or, occasionally when the anterior leaflet is not diseased,from the anterior mitral leaflet.The patch then serves as a part of the anchorage for the prosthetic mitral valve.

Figure 8.3. A: Surgical approach to treat abscess involving the mitral annulus. B: The infection is extensively debrided, leaving behind a defect at the atrioventricular junction.The anterior and posterior mitral leaflets are also resected, leaving a narrow rim of leaflet remnant. C: The atrioventricular defect is repaired with a patch tailored from the pericardium or, occasionally when the anterior leaflet is not diseased,from the anterior mitral leaflet.The patch then serves as a part of the anchorage for the prosthetic mitral valve.

resulting structural defect with a pericardial patch, reconstruction of the noncoronary cusp using a piece of pericardium, and annuloplasty.

If the abscess or other structural damage involves the aortic structures extensively, aortic root replacement will be the procedure of choice. Root replacement is done in the usual fashion following debridement of the infected tissue. Extra care is taken to place the proximal suture line low (proximally) enough in the LV outflow tract that any discontinuity between the LV and proximal aorta is eliminated. Homograft aortic roots provide a good means for this type of operation. The anterior mitral leaflet is involved when there is extensive aortic root destruction and extension to the aortomitral curtain. Involvement of this critical intersection of aortic and mitral valves requires complicated surgical approach through both LA and ascending aorta. Homografts which often include the anterior mitral leaflets offer the optimal material to repair such defects. This may involve extensive debridement and reconstruction of LA roof and atrial septum with pericardial patch which also serves as anchor for suturing in place the aortic homograft (Figure 8.5). Alternatively, the aortomitral curtain of the aortic homograft can be used to repair the defect resulting from the debridement (Figure 8.6)

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Responses

  • Helen
    Do pledgetted sutures resorb?
    11 days ago

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