One of the advantages of the CS technique compared with the IS technique is that the use of the thrombogenic material (no pledgets or braided suture knots) in valve replacement is not required. In our CS technique, the sutures were tied inside the aorta without pledgets, and the knots were fixed on the aortic sinus. This technique is also simpler and easier than previously reported techniques [1
] in which the knots were placed buttressed by pledgets on the outside of three commissures. Such a suture technique may be more complex to perform.
In the IS group, most patients underwent AVR with horizontal mattress sutures buttressed by pledgets at the ventricular side. When pledgets are placed at the ventricular side, the annular margins may be exposed into the valve opening, which may disturb the leaflet movement of the mechanical valve or reduce the valve area in mechanical or bioprosthetic valves. With the CS technique, however, the annular tissue is buried in the CS line without the annular tissue being exposed to the prosthetic valve opening.
The suture plane in the aortic annulus is curvilinear, not horizontal, because it is the lowest at the nadir of each annulus and the highest at each commissure. With the IS technique, the suture line is compulsorily flattened by the hard sewing ring of the mechanical valve. The soft sewing ring of the bioprosthetic valve can be forced into an undesirable shape by the stronger curvilinear annulus. In the CS technique, however, the prosthesis is comfortably seated without regard to the curvilinear suture plane. Because each stitch in the CS technique is as high as the en bloc stitch, the prosthetic sewing ring is placed above the nadir of the annulus (supra-annular position) and below the commissure (infra-annular position). The flexible bioprosthetic sewing ring also maintains its original shape, and the hard sewing ring of the mechanical valve does not affect the annular shape of the aortic root. One study [3
] reported that the CS technique is advantageous in that a prosthesis one size larger than the largest size usable in the IS technique can be placed, because the aortic annulus is enlarged to some degree by the complete removal of the valve and the loosening of the contracted annulus. This results in better hemodynamic performance [4
]. However, we did not observe this advantage in our study.
Prosthetic valve endocarditis is a rare but serious postoperative complication. With the CS technique, the risk of postoperative prosthetic endocarditis may be reduced without the use of pledgets or braided sutures. Some reports have noted that CS for AVR results in a shorter aortic cross-clamp time and a shorter bypass time [1
]. However, we allowed for more time to make more stitches and thorough suture traction to ensure a secure suture line. We believe that a secure suture line is more important than a shorter operating time.
There has been some controversy regarding the increased incidence of perivalvular leak with the CS technique for AVR. Hjelms et al. [5
] reported that the incidence of perivalvular leak was 8.8% in 80 patients undergoing AVR with the CS technique. Because the incidence of perivalvular leak was as high as 26% among patients with pure aortic insufficiency, they suggested that the CS technique was not suitable for patients with pure aortic insufficiency. In a recent study [3
] with a 10-year follow-up after AVR, the incidence of moderate to severe paravalvular leak was 12% in the CS group, while the incidence was 0% in the IS group. However, Laks et al. [6
] reported that the incidence of paravalvular leak with the CS technique was only 2.3%, which is comparable to that of the IS technique. Dhasmana et al. [7
] reported that periprosthetic leakage without endocarditis was unrelated to the suture technique (interrupted versus continuous), but was related to suture size and annular calcification. They suggested the importance of meticulous annular decalcification and the use of a suture of smaller size, as in our experience. In a case report of significant paravalvular leakage seven years after AVR with the CS technique, the complication was caused by a broken suture [8
]. The suture material used in most previous reports was 2/0 polypropylene with a thick needle, which may result in tissue injury during traction with a nerve hook to tighten the stitches. In the CS technique, special care should be taken to avoid trauma to the suture material during suturing. We suggest that a 17-mm, 1/2-circle needle is sufficient to make en-bloc annular stitches and that 3/0 polypropylene is strong enough to secure the suture line without tissue injury during traction of the stitches. In the CS group, no patients developed perivalvular leak during the follow-up period of 22.5±10.8 months (range, 3 to 40 months), but in the IS group, one patient had a significant perivalvular leak and one patient had a minor leak. One factor for the satisfactory achievement attained in this study may be the CS technique, in which deep stitches are made and which include the ventricular muscle (in the muscular part) or the adjacent strong fibrous tissue (in the aorto-fibrous continuity part) as well as the annulus. The stitch should also be deep in the subcommissural portion (interleaflet triangle). The height of each en-bloc stitch can ensure that the planes between the aortic annulus and the prosthetic sewing ring are well accommodated in the different levels. This mechanism of comfortably seating the valve is more important in aortic stenosis, which shows a hard curvilinear annulus due to the pathologic changes of marked thickening and contracture. Although the outcome of the CS technique for AVR in our cases has been satisfactory for about four years, long-term studies of the outcomes of this suture technique should be performed.