Interact CardioVasc Thorac Surg 2007;6:177-181. doi:10.1510/icvts.2006.143289
© 2007 European Association of Cardio-Thoracic Surgery
Institutional report - Valves |
Comparison of distensibility of the aortic root and cusp motion after aortic root replacement with two reimplantation techniques: Valsalva graft versus tube graft
Masamichi Matsumori,
Hiroshi Tanaka,
Yujiro Kawanishi,
Tetsuari Onishi,
Keitaro Nakagiri,
Teruo Yamashita,
Kenji Okada and
Yutaka Okita*
Division of Cardiovascular, Thoracic, and Pediatric Surgery, Kobe University Graduate School of Medicine, 7-5-2, Kusunoki-cho, Chuo-ku, Kobe, 650-0017 Japan
Received 5 September 2006;
received in revised form 1 December 2006;
accepted 18 December 2006
 Presented at the joint 20th Annual Meeting of the European Association for Cardio-thoracic Surgery and the 14th Annual Meeting of the European Society of Thoracic Surgeons, Stockholm, Sweden, September 10–13, 2006.
*Corresponding author. Tel.: +81 78 382 5942; fax: +81 78 382 5959.
E-mail address: yokita{at}med.kobe-u.ac.jp (Y. Okita).
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Abstract
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The aim of this study is to evaluate distensibility of the aortic root and function of the aortic cusp after aortic root replacement using valve sparing procedure. Between October 1999 and August 2006, valve sparing aortic root replacements were performed in 39 patients who had annuloaortic ectasia (AAE) and aortic valve regurgitation. Reimplantation type of valve-sparing procedure was performed with a tube graft (n=12) or a Valsalva graft (n=27). Echocardiographic studies were performed six months after the operation comparing Valsalva graft (Group V, n=15), tube graft (Group T, n=5), and normal control (Group C, n=5). Percent changes in radius (PCR) of the aortic root were measured as indices of distensibility. Rapid valve opening velocity (RVOV/HR (mm/s/min)) and rapid valve closing velocity (RVCV/HR (mm/s/min)) of the aortic cusp were analyzed in each group. Root distensibility of sinus in Group T (1.9±1.1) was significantly smaller than Group C (7.2±1.8) (P=0.003). RVOV/HR in Group T was highest among the three groups (T: 48.2±6.2, V: 36.2±11.9, C: 33.7±9.6). RVCV/HR showed no difference among the three groups (T: 26.1±6.7, V: 40.7±16.6, C: 28.4±16.3). In conclusion, sinus distensibility of the Valsalva graft was well preserved and valve-opening characteristics with the Valsalva graft were identical to normal.
Key Words: Valve sparing operation; Aortic root distensibility; Aortic valve function; Aortic root replacement
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1. Introduction
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The surgical approach for annuloaortic ectasia (AAE) is still controversial. Bentall procedure was commonly performed for AAE [1]. However, with this procedure, patients are obligated to accept the disadvantage of lifelong anticoagulation, risk of thromboembolism, hemorrhage and prosthetic valve deterioration. In patients with aortic root disease associated with aortic regurgitation, the aortic valves are usually structurally normal, and valve incompetence is the result of leaflets being stretched open by a dilated aortic root. For the patients of this entity, valve sparing procedure has been introduced in several series. The remodeling technique was introduced by Yacoub in 1979 [2] and the reimplantation technique by David in 1988 [3]. Recently, many reports have shown low operative risk and excellent freedom from thromboembolism and endocarditis with valve sparing procedure. In regard to freedom from re-operation, some authors demonstrated that reimplantation provides a better outcome than the remodeling procedure [4]. This result might be caused by lack of annular stabilization in the remodeling procedure. On the other hand, Leyh et al. [5] have shown that absence of sinuses after reimplantation with a straight graft abnormal leaflet motion comparing the remodeling procedure. Grande-Allen et al. [6] have shown in a finite element study that re-creation of the sinuses reduces leaflet stress during valve closure, which theoretically should improve leaflet durability. The opening and closing characteristics of the aortic valve have been repeatedly studied [5, 7, 8]. However, no study was reported to clinically compare the reimplantation procedure with the Valsalva graft with the same operation using a straight conduit. We compared distensibility of the aortic root and motion of the aortic cusp after reimplantation procedure in patients who underwent aortic root replacement with a Valsalva graft or a straight graft.
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2. Patients and methods
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Between October 1999 and August 2006, valve sparing aortic root replacements were performed in 39 patients with a diagnosis of annuloaortic ectasia (AAE) and aortic valve regurgitation. Fourteen of 39 patients had Marfan syndrome. In this period, we exclusively performed reimplantation technique except in two patients who underwent remodeling technique. From October 1999 to July 2002, we performed the reimplantation type of valve-sparing procedure with a tube graft (n=12). Since July 2002, we switched to the Valsalva graft (Gelweave Valsalva; Sulzer Vascutek, Renfrewshire, Scotland) (n=27). In this study, we selected 20 patients in whom the echocardiography six months after surgery was possible: five patients of the first period (tube graft: group T), 15 patients of the second period (Valsalva graft: group V) and five healthy persons without abnormalities in the valve function, ventricular function, or aortic root anatomy (normal control: group C). Patient characteristics are indicated in Table 1. All patients were evaluated by cardiologists, and informed consent was obtained before follow-up evaluation and echocardiography.
2.1. Operative technique
All patients were operated upon using median sternotomy and cannulation of ascending aorta and right atrium. In presence of acute aortic dissection, femoral artery, superior vena cava and inferior vena cava were selected for cannulation. Standard cardiopulmonary bypass at mild hypothermia (32 °C–33 °C) or deep hypothermic circulatory arrest (20 °C–23 °C) was used. Intermittent antegrade or retrograde blood cardioplegia was used for myocardial protection. After excision of sinuses, approximately 4–5 mm of remnant sinus tissue remain attached to the annulus. The coronary arteries are mobilized widely. Twelve to fifteen 4-0 braided polyester, pledgetted horizontal mattress sutures are passed under the annulus at the nadir of each aortic leaflet from inside outward. In the case of using Valsalva graft, the proximal collar of the graft is trimmed to 2–3 rings. The subannular sutures are passed inside out through the bottom of the graft and tied. The commissures are fixed to the appropriate position of the graft using 4-0 polypropylene mattress sutures almost 120 degrees apart from each other. In the case of Valsalva graft, the commissures are fixed to the level of the sinotubular ridge of the graft. Continuous 5-0 polypropylene sutures are used to fix the sinus remnant and annulus with the graft, starting at the bottom of each sinus and sewing upward to the commissure tops. The left and the right coronary buttons were anastomosed with 5-0 polypropylene. Finally, the distal graft is anastomosed to the aorta using continuous 4-0 polypropylene sutures. Air is evacuated from the heart, the aortic crossclamp is removed, and the heart is resuscitated.
2.1.1. Echocardiography
All patients underwent transthoracic or transesophageal echocardiography in the early postoperative period and six months after the operation. Data acquisition and measurements followed the protocol described by Leyh and associates [5]. Two-dimensional echocardiography was used to measure aortic root dimension at the level of annulus, the sinuses of Valsalva and the sinotubular junction (ST junction) from systolic to diastolic phase. Percent changes in radius (PCR): (PCR=mean diameterx100/largest diameter – smallest diameter) were measured as indices of distensibility. Finally, transthoracic or transesophageal echocardiography M-mode echocardiography at a paper speed of 100 mm/s was used to record the motion of aortic leaflets and to measure the following: rapid valve-opening velocity and rapid valve-closing velocity (Fig. 1).
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Fig. 1. (a) Actual M-mode picture of the aortic root in a patient of group V. Arrows show RVOV (rapid valve opening velocity) and RVCV (rapid valve closing velocity). (b) Schematic drawing of an M-mode tracing of aortic valve opening and closing characteristics.
D1=maximal leaflet displacement, D2=leaflet displacement before rapid valve closing, RVOT=rapid valve opening time, RVOT=rapid valve closing time, ET=ejection time, RVOV (cm/m)=D1/2/RVOT, RVCV (cm/m)= D2/2/RVCT.
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2.2. Statistical analysis
Results were expressed as means±S.D. A two-way analysis of variance (ANOVA) was used for comparison of continuous parameters among the three groups. Statistical significance was established at a P-value <0.05. Statistical analysis was performed with Stat View software (version 4.5) for Windows.
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3. Results
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No patients died, and all patients were in New York Heart Association class I or II. No endocarditis or thromboembolic events occurred without taking anticoagulant therapy. Aortic regurgitation was reduced from preoperatively grade 2.5±0.8 (range 0–4) to postoperatively 0.7±0.6 (range 0–2) (Fig. 2). One patient (group V) required reoperation for recurrent aortic regurgitation. The cause of failure was recurrent cusp prolapse. Hemodynamic characteristics of the three groups at follow-up echocardiography at six months after surgery were similar (Table 2).
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Fig. 2. Aortic root distensibility at three different levels.
a: PCR at the level of annulus; b: PCR at the level of sinus; c: PCR at the level of ST junction; PCR=Percent changes in radius.
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3.1. Root dimension (Table 3)
The diameter of Valsalva sinus in group T was smaller than in group C (P=0.01). There was no significant difference in the diameter of annulus and ST junction among three groups.
3.2. Root distensibility (Table 4)
At the level of annulus, PCR showed no difference among three groups; (T: 3.5±0.6, V: 4.0±3.0, C: 7.0±1.8); (Fig. 2a). Root distensibility of sinus PCR in Group T (1.9±1.1) was significantly smaller compared with Group C (7.2±1.8) (P=0.003); (Fig. 2b). There was no significant difference in sinus PCR between group V (4.4±2.5) and group C (7.2±1.8). At the level of ST junction, PCR in Group C (9.8±6.2) was significantly larger than the other two groups. (Group C (9.8±6.2) vs. Group T (3.6±1.9) (P=0.03); Group C (9.8±6.2) vs. Group V (2.9±2.7) (P=0.003)); (Fig. 2c).
3.3. Valve motion (Table 5)
RVOV/HR in group T was higher compared with Group C (group T (48.2±6) vs. group C (33.7±9.6); P=0.03). RVCV/HR showed no difference among three Groups (T: 26.1±6.7, V: 40.7±16.6, C: 28.4±16.3).
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4. Discussion
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Bentall procedure has been commonly performed for AAE [1], and many studies have reported low operative risk and excellent late results [9, 10]. Nevertheless, patients who had mechanical valves are required life-long anticoagulation and carry risk of thromboembolism and hemorrhage. On the other hand, bioprosthetic valves are likely to require explantation for valve deterioration in younger patients. Since valve sparing procedures were introduced by Yacoub and David, excellent clinical outcome has been reported. Theoretically, the remodeling technique was supposed to be a more anatomically favorable procedure compared with the reimplantation technique. Reconstructing sinus reduces stress and strain of the cusps [6], and sinus distensibility is important to prevent premature degeneration of the cusps [11]. However, David and some other authors showed excellent clinical results with reimplantation [4, 12]. David also demonstrated that freedom from moderate or severe aortic regurgitation at 10 years was 85±5% for all patients, but it was 94±4% after reimplantation and 75±10% after remodeling (P=0.04) [4]. These results might be derived from lack of annular stabilization with remodeling procedure. De Paulis et al. [13] proposed that a novel Dacron conduit (Valsalva graft) would stabilize the annulus and preserve sinuses, minimizing leaflet stress and maintaining natural valve movement. The opening and closing characteristics of the aortic valve have been repeatedly studied [5, 7, 8]. However, none of these reports clinically demonstrated for the reimplantation procedure comparing the use of a tube graft with a Valsalva graft regarding the opening and closing characteristics of the aortic cusps.
This study evaluated the aortic root distensibility and cusp motion after reimplantation using different types of grafts (tube graft or Valsalva graft). With the Valsalva graft, aortic root dimensions were similar to healthy normal control. According to aortic root distensibility at the level of sinus, the Valsalva graft is more physiological than the tube graft. However, at the level of ST junction, distensibility in Group C was significantly larger than the other two groups. This restricted distensibility did not affect valve opening characteristics, which were largely normal in group V. The valve starts to open even before forward blood flow because of a slight increase in the aortic root diameter [14]. They also demonstrated changes in root dimension during the cardiac cycle that are thought to be important for the functioning of the aortic valve. Because the valve starts to open only because of root expansion during the beginning of systole in an animal model, in this study, valve opening was slower using a Valsalva graft than using a tube graft. However, we observed faster rapid valve closing velocity in group V than in group T. This rapid valve closure is determined by the radial thrust of the sinus vortices on the sinus surface of the leaflets during the deceleration phase of aortic blood flow. The lower closing speed for this movement of group T patients is probably also related to the lack of sinus configuration and, thus, the closing forces of sinus vortices to push the leaflets to the midline [5].
Because of lack of annulus stability, there is a tendency toward progressive aortic insufficiency with the remodeling technique. Furthermore, there is the possibility that one or more leaflets could touch the Dacron wall in full systole with the reimplantation technique using a tube graft. Normal leaflet motion would give the patients a higher chance of maintaining normal leaflet longevity. Thus, greater durability of reimplantation procedure using a Valsalva graft compared with using a tube graft can be expected. Recently, David et al. (T. David – IV) [4], and Miller et al. (T. David – V: Stanford modification) [15], reported some modification of the reimplantation technique to create neo-sinus, and demonstrated that the technique had better aortic root physiology compared with the original technique of reimplantation.
Several limitations of this protocol have been already recognized in a similar study [5]. (1) It could be argued that the resolution of the ultrasound technique is not sufficient to define accurate instantaneous movements of the aortic root and the leaflets. The fact that the aortic root itself moves during measurement could induce errors. However, these errors would apply to all groups and, therefore, should not affect comparative results. (2) Another limitation relates to the significantly longer period of follow-up in group T than in group V (63.4±10.0 vs. 25.4±14.5 months) and this was not a randomized study. Also, Group C was younger than the other groups. Our result might be limited by the relatively small number of patients in each group. (3) The expansion and contraction characteristics of the graft are unknown in the future.
In conclusion, sinus distensibility of the Valsalva graft was well preserved at least up to six month postoperatively. Valve-opening characteristics with Valsalva graft were identical to normal. Compared with a standard tube graft, reimplantation procedure with Valsalva graft seems to provide better root physiology. We expect that more leaflet longevity might be expected by this procedure.
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Conference discussion
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Dr. R. Frater (Bronx, New York): In the echo you showed of a Valsalva graft, there was leaflet fluttering. Now, leaflet fluttering is not something you see in normal human beings at all but you do see it commonly in stent-mounted devices, and I wonder if you had leaflet fluttering in more than that one case. You showed one echo in one Valsalva graft. Did you notice leaflet fluttering in the valves that were inside a tube, whether it was a Valsalva tube or a straight tube?
Dr. Okita: In the tube graft, we see a very rapid opening with fluttering, and in the Valsalva graft, we sometimes see the fluttering, but if you use a little bigger Valsalva graft, no fluttering. Sometimes you see it, but more often in a tube graft.
Dr. Frater: I think the classic obvious conclusion to come to is that the sinotubular junction is far less mobile in either of the two synthetic grafts compared with normal. The sinotubular junction is not going through its normal expansion and contraction.
Dr. Okita: Anyway, we use Dacron, and it is going to be stiff in the future.
Dr. J. Pepper (London, United Kingdom): A very difficult study but a very nice study. Could I ask whether the construction of the two grafts were similar? Were they both made of collagen-impregnated Dacron or was there a difference in the mesh between the two?
Dr. Okita: Initially we used a Dacron woven Interguard graft, woven, very stiff, and the Valsalva graft was made by Gelweave, also woven, but a little bit softer.
Mr. Pepper: But some of these grafts, the mesh is closer at the annular end compared to the aortic end, in other words, giving an effective cone shape, if you follow me, rather like the thromboembolic stocking where the mesh is closer at the ankle than it is at the thigh. There wasn't any construction like that?
Dr. Okita: No.
Dr. C. Yankah (Berlin, Germany): I would like to know whether you had a significant difference in the opening velocity between the straight graft and the graft with sinus of Valsalva which could have an impact on the systolic flow?
Dr. Matsumori: Opening velocity was higher in the tube graft group compared with the straight graft.
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References
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Abstract
1. Introduction
