Ann Thorac Surg 2000;69:121-125
© 2000 The Society of Thoracic Surgeons
Original Articles
A new technique for debridement in rheumatic valvular disease: the rasping procedure
Nobuo Kitamura, MDa,
Shinichi Uemura, MDa,
Ryuji Kunitomo, MDa,
Junichi Utoh, MDa,
Sakashi Noji, MDb
a Department of Surgery I, Kumamoto University School of Medicine, Kumamoto, Japan
b Department of Cardiovascular Surgery, Osaka National Hospital, Osaka, Japan
Address reprint requests to Dr Kitamura, Department of Surgery I, Kumamoto University School of Medicine, 1-1-1 Honjo, Kumamoto, 860-0811, Japan
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Abstract
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Background. Valve repair is superior to valve replacement in terms of postoperative risk. However, the conventional techniques used for valve repair in patients with rheumatic valvular disease have not resulted in a good long-term outcome.
Methods. We developed a novel "rasping procedure" using an electric rasper for debridement in rheumatic valvular diseases. Between April 1986 and December 1996, the rasping procedure was performed on the aortic valve (A-rasping) of 24 patients who exhibited moderate stenosis with mild regurgitation. Between June 1992 and December 1996, this procedure was performed on the mitral valve (M-rasping) of 12 patients who exhibited mitral stenosis with mild regurgitation.
Results. Among the 24 patients on whom A-rasping was performed, 4 patients did not show any improvement after the A-rasping procedure, and required valve replacement. In each of the remaining 20 cases, the transvalvular pressure gradient decreased, and regurgitation disappeared, or was reduced to a trivial level. In all 12 patients on whom M-rasping was performed, the transvalvular pressure gradient significantly decreased, orifice area significantly increased, and the regurgitation disappeared. Postoperative echocardiographic examinations were performed during a mean follow-up period of 110 months in the patients who received A-rasping, and that of 50 months in the patients who received M-rasping. A significant change in the valve requiring subsequent surgery was not seen in any of the patients.
Conclusions. The rasping procedure is an effective technique for excising rheumatic valvular hypertrophic lesions. It resulted in good intermediate to long-term outcome.
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Introduction
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This paper introduces a novel debridement technique using an electric rasper, termed the "rasping procedure," which we developed as a repair technique for rheumatic valvular disease. We began using this technique clinically on mild rheumatic aortic valve disease combined with severe mitral valve lesions requiring valve replacement beginning in 1986 [1, 2]. Encouraged by the results on mild rheumatic aortic valves, we began to use this method on mitral valve disease combined with severe mitral valve lesions requiring valve replacement beginning in 1992.
Here we report the intermediate to long-term results of our clinical experience both in Osaka National Hospital and Kumamoto University Hospital with the rasping procedure on aortic and mitral valve repair.
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Material and methods
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Surgical technique of the A-rasping procedure
In the A-rasping procedure, a commissurotomy on the fused commissure that contributes to the aortic stenosis should be performed first. In cases where the free edges of the cusps were most thickened in the center, after the shape and movement of the cusps were carefully observed, we made an incision at the median site on the ventricular side of the cusp, and began to divide the thickened part, as indicated in Figure 1A. We partially excised the thickened part of the free edge of the cusp. We performed this dissection only on the ventricular side, and never on the aortic side, as the tip of the blade could damage the aortic side of the cusp. We repeated this technique for each cusp of the valve. After dividing the cusps in this way, we performed the rasping procedure on the thickened area that was exposed, as indicated by the shaded area in Figure 1B. We used an electric rasper operating at 20,000 rpm (Proxxon Minirouter No. 28500; Kiso Power Tool Co, Osaka, Japan) (Fig 2). The tip of the rasper is interchangeable, and tips of many shapes and sizes are available. We rasped each cusp until it became sufficiently pliable. When the rasping was completed, we evaluated the mobility of each cusp, and the coaptation of the three cusps. When we were uncertain as to the results, we evaluated it using a fiberscope with a water nozzle (type BF. 6C; Olympus Co, Tokyo, Japan) after closing the aorotomy [3]. We tried to ensure perfect coaptation of the three cusps, leaving no triangular defect in the center, and maintained an aortic root pressure of over 50 mm Hg (Fig 3B, left).
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Fig 1. Technique of A-rasping. (A) First, the prominent, thickened part of the edge of the cusps is removed by the blade. (B) After commissurotomy of each commissure, the rasping procedure is performed on the shaded area of the edge of the cusps, and on the surface of the cusp itself.
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Fig 2. Electric rasper. This rasper makes 20,000 revolutions per minute. The tip is interchangeable; tips of many shapes and sizes are available.
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Fig 3. Fiberscopic view of the aortic valve of a patient in the A-rasping group. (A) Preoperative rheumatic aortic valve, which exhibits stenoinsufficiency. (B) Fiberscopic view of the aortic valve: (right) aortic valve before the rasping procedure; (left) fiberscopic view after the rasping procedure shows perfect coaptation of the cusps, leaving no triangular central defect, at an aortic root pressure of 50 mm Hg.
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Surgical technique of the M-rasping procedure
The rasping technique used for repairing the mitral valve (M-rasping), is essentially the same as the procedure used on the cusps of the aortic valve (A-rasping). In each patient who had mitral stenosis, we first performed a conventional commissurotomy, and then rasped the surface of the cusps on the atrial side only. After the commissurotomy, we rasped the thickened part of the coaptation zone of the cusps. We believe that it is most important to rasp the coaptation zone near the commissures; in addition, the clear zone of the cusp should be rasped if there is thickening, making it thinner for better pliability. After the valve repair, we evaluated the function of the valve by filling the left ventricle with cold saline, and checking for regurgitation and coaptation of the cusps. We also checked mitral valve function by transesophageal echocardiography, after the heart had recovered its beat.
Patient population
This study included a total of 36 patients who underwent the rasping procedure for rheumatic valvular disease between April 1986 and December 1996 (Table 1). A-rasping, the rasping procedure on the aortic valve, was performed on 24 patients (14 males, 10 females), whose ages ranged from 25 to 73 years (mean 59 years).
All of the patients exhibited mild to moderate aortic stenosis with mild regurgitation of under grade III. Eighteen of the 24 patients underwent A-rasping with mitral valve replacement (MVR). Included in the A-rasping group is one patient who underwent A-rasping and M-rasping for combined mitral valve disease. Three patients underwent coronary artery bypass grafting for combined ischemic heart disease. The remaining 2 patients underwent the A-rasping procedure alone.
The rasping procedure on the mitral valve (M-rasping) was performed on 12 patients (7 males, 5 females), whose ages ranged from 47 to 68 years (mean 57 years). All of these patients exhibited mitral valve stenosis (orifice area 1.25 ± 0.32 cm2), without regurgitation of over Sellers [4] grade III. Only 1 of the 12 patients, a 46-year-old female, underwent both the A-rasping and M-rasping procedures, for combined aortic and mitral valvular stenosis. This patient is the same one who was included in the A-rasping group.
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Results
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Of the patients who received the A-rasping procedure (n = 24), 4 patients had severely calcified layers of aortic valves, with Sellers grade III regurgitation and a transvalvular pressure gradient of over 30 mm Hg. These patients did not show any improvement after the rasping, and subsequently required valve replacement with a prosthetic valve. However, in the remaining 20 cases, the rasping procedure was effective, and improved valve function (Table 2).
Of the patients who received the M-rasping procedure (n = 12), M-rasping was effective in improving valve function in 11 patients. The remaining patient had severely calcified cusps (Sellors [5] type III) in which the cusps, chordae, and papillary muscles are fused into a rigid, fibrous, funnel-shaped structure, and underwent a mitral valve replacement. No patient died from the rasping procedure. Early results were assessed by predischarge echocardiography and cathe-angiography (Table 2).
In 17 grade I cases of the A-rasping group, regurgitation had either disappeared, or it was reduced to a trivial level. Regurgitation improved from grade III to II in 2 cases. However, 1 patient showed no change in his grade II regurgitation (Fig 4, left). There was a significant decrease in the mean transvalvular pressure gradient from a preoperative mean value of 31.8 ± 6.8 mm Hg, to 10.9 ± 3.8 mm Hg postoperatively (Fig 4, right).
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Fig 4. Results of the A-rasping procedure (n = 24). (AVR = aortic valve replacement; OP = operation; M = month; Grade = Sellers grade.)
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Of the patients in the M-rasping group, postoperative catheterization data showed that there was a significant decrease in the mean transvalvular pressure gradient from 16.4 ± 6.7 to 6.1 ± 2.6 mm Hg, and a significant increase in the mean orifice area from 1.25 ± 0.32 to 2.81 ± 0.42 cm2 postoperatively. Other parameters in these patients, except for the left ventricular end-diastolic Dimension (LVDd), also improved (Table 2).
Annual echocardiograms were performed on all of the patients after the rasping procedure (Table 3). In December 1997, the longest interval after the rasping procedure, during which we followed 20 patients in the A-rasping group, was 11 years 8 months (mean 9 years, 2 months). For the patients in the M-rasping group, it was 5 years, 5 months (mean 4 years, 2 months).
Regarding postoperative events, 2 patients in the A-rasping group died, 1 and 4 years after the rasping procedure. Both patients died from heart failure due to endocarditis on the prosthetic mitral valve, which was used in addition to the mitral valve replacement. Under no anticoagulant therapy after the rasping procedure, 1 patient in the M-rasping group suffered a cerebral thromboembolism 2 months after surgery. A mild progression of aortic stenosis was recognized in 1 patient of the A-rasping group 4 years after the surgery. In the other patients, it stayed at the postoperative level. There was progressive regurgitation in 1 of the 24 cases in the A-rasping group 6 years after the surgery.
No patient in our study required a subsequent operation for their repaired valves after the rasping procedure. However, 2 patients in the A-rasping group required a second mitral valve replacement because of malfunction of the prosthetic valve. During this procedure, we did not observe progression of the morphological abnormality of the aortic valve in either of these 2 patients; the aortic valve was functioning well. Therefore, we did not replace the aortic valve in either patient.
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Comment
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Aortic valve plasty, as well as mitral valve plasty, has recently again become a topic of discussion. In 1960, Mulder and associates reported several techniques of aortic valve plasty, including decalcification, cusp unrolling, bicuspilization, and cusp enlargement. However, good long-term results were not obtained, as it was difficult to remove the calcified tissue on the cusp, and excessive debridement often resulted in left aortic regurgitation [6, 7, 8].
In 1986, we developed a novel aortic valve debridement technique using an electric rasper [1]. At first, we started to use this technique in patients with mild rheumatic aortic valve disease, combined with severe rheumatic mitral valve lesions requiring valve replacement.
This rasping procedure scrapes off mainly the hyaline-degenerative tissue and partially the hypertrophic collagen fiber tissue. It does not damage the normal structure of the valve, and does not involve the implantation of foreign materials. We believe that this rasping technique can scrape both the concave aortic side and the convex ventricular side of the aortic leaflet, and makes them easily more smooth and pliable than conventional techniques using cavitron ultrasonic surgical aspirator (CUSA) [9–11] or a surgical knife.
The ultrasonic decalcification is effective in removing the localized calcified nodules on leaflets, but can not make the thickening leaflets uniformly thin and get enough pliability of them.
In our study, in the patients who received the A-rasping procedure, the pressure gradient significantly decreased, the residual regurgitation remained at less than Sellers grade I, and cardiac function improved.
In previous studies, the proportion of patients who did not require a subsequent operation after aortic valve plasty has been reported to be 53.6% over a period of 7 years [8]; 48% over a period of 10 years [12]; and 60% over a period of 9 years [13]. As yet, no patient in the A-rasping group in our study has required a subsequent operation.
Encouraged by the results of our A-rasping technique, in 1992 we began to use the rasping technique on patients with rheumatic mitral valve stenosis.
The conventional technique for mitral valve stenosis repair has been limited to comissurotomy using a surgical knife. If slight superficial calcification or moderate to severe hypertrophic mitral cusps were present, a full mitral valve replacement would be required.
On the other hand, the rasping technique enables thickened cusps to recover their pliability, by scraping off the layer of hyaline degenerative tissue and the partial layer of hypertrophic collagen tissue on atrial surface of the mitral cusps. Therefore, we believe that the rasping technique is applicable for mitral valve repair, in cases of mitral valve stenosis in which the cusp is not flexible due to overall thickening without all layers calcification.
But valvuloplastic surgery is a means of repairing the valve itself. If a diseased valve is beyond repair, then plasty is no longer appropriate.
In studying the limits of the rasping procedure, we concluded that this technique is effective only on the mild to moderate stenosis combined with the mild regurgitation of under grade II. However, the calcification was the greatest problem. If the calcification was superficial, the rasping procedure is applicable, but if it penetrated through all the layers of leaflets and cusps were severely retracted, this technique is not appropriate.
Especialy on the mitral valve lesion, we do not recommend M-rasping for severely calcified valves, or Sellors [5] type III mitral valves, in which the cusps, chordae, and papillary muscles are fused into a rigid, fibrous, funnel-shaped structure directed towards the ventricle.
Thus, although this study was in a small population, we have obtained good intermediate to long-term results with the A-rasping and M-rasping techniques in valves that were mildly to moderately damaged by rheumatic disease.
We also have used the CUSA for the repair of partially calcified, hypertrophic valves, but could not get enough pliability, as provided by the rasping procedure.
We believe that this technique is quite more effective than ultrasonic decalcification for restoring enough pliability of the patient’s own valves by scraping the thickened areas equally on all the surfaces of the leaflet to make it thin, thus resulting in a low incidence of significant regurgitation or stenosis in long-term results.
But, an additional, long-term follow-up study, in a much larger population, on the results of this technique is necessary. We have started to improve the electric rasper, in terms of the shape and size of its tips, and its grip, for clinical use in valvuloplastic surgery.
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References
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Accepted for publication June 21, 1999.
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Abstract
Introduction
