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Ann Thorac Surg 2003;76:99-104
© 2003 The Society of Thoracic Surgeons

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Original article: cardiovascular

Up to 7 years’ experience with valve-sparing aortic root remodeling/reimplantation for acute type a dissection

^a Clinic for Cardiac Surgery, University Clinic of Luebeck, Luebeck, Germany

Accepted for publication February 4, 2003.

^* Address reprint requests to Dr Sievers, Klinik für Herzchirurgie, Universitätsklinik Lübeck, Ratzeburger Allee 160, 23538 Lübeck, Germany.
e-mail: herzchir{at}medinf.mu-luebeck.de

	Abstract

Top Abstract Introduction Patients and methods Results Comment References

 
BACKGROUND: Aortic valve-sparing operations for acute type A dissection are appealing and innovative but less well defined surgical techniques requiring further evaluation.

METHODS: We reviewed all consecutive patients with acute type A dissection who underwent either the remodeling (group 1, n = 21) or the reimplantation valve-sparing technique (group 2, n = 15) since October 1994. Patients were followed up clinically and echocardiographically for as long as 41.3 months (group 1) and 87 months (group 2).

RESULTS: Hospital mortality was 19% (n = 4) for group 1 and 20% (n = 3) for group 2. Permanent new neurologic symptomatology occurred in 1 patient (3.6%). Three patients in group 1 required reoperation owing to redissection. No patient had an aortic insufficiency of more than grade 1. No late neurologic or thrombembolic events occurred. There was no statistically significant difference between both groups with respect to clinical and hemodynamic data.

CONCLUSIONS: Remodeling and reimplantation aortic valve-preserving operations in acute type A dissection can be performed with adequate perioperative risk and excellent midterm aortic valve function. We found no evidence of one technique being superior to the other, however durability of the remodeling technique needs critical consideration especially in Marfan syndrome and when glue is used.

	Introduction

Top Abstract Introduction Patients and methods Results Comment References

 
Acute dissection of the ascending aorta (Stanford classification type A [1]) requires emergent surgical intervention to prevent life-threatening complications and remains a major challenge to cardiovascular surgery. Usually the entry is located in the ascending aorta just above the valve commissures [2]. In the majority of the patients the aortic root is also involved by retrograde dissection leading to acute aortic insufficiency when the commissural area is detached and prolapsing. However the dissecting process does not affect the aortic annulus nor the aortic leaflets [3, 4]. That may encourage reconstructive surgical techniques on the root sparing the valve leaflets. Compared with the mostly used standard technique of composite aortic valve replacement with a mechanical substitute in a prosthetic tube valve-sparing operations theoretically offer the advantage of native tissue and near physiologic valve function [5–10]. Anticoagulation with its inherent bleeding complications is not necessary, facilitating thrombotic obliteration of the distal false lumen and thereby reducing the risk for aneurysmal dilatation [11].

In addition to supracommissural replacement of the ascending aorta in all patients principally two different surgical techniques are used aiming at the preservation of the aortic valve leaflets: firstly the conventional reconstruction of the dissected sinuses with Teflon felt or glueing techniques including resuspension of the detached commissures; and secondly replacement of the diseased sinuses with prosthetic material according to Yacoub (remodeling technique) [12] or David (reimplantation technique) [7]. First experience with these novel techniques for type A dissection were reported to be encouraging [8]. However longer term follow-up studies are necessary for further judgment. This study presents our experience up to 7 years comparing the remodeling and the reimplantation techniques for aortic root replacement in type A dissection preserving the aortic valve leaflets.

	Patients and methods

Top Abstract Introduction Patients and methods Results Comment References

 
Patients
Patient records and the clinical database were reviewed retrospectively for all 121 consecutive patients who underwent surgery for acute type A dissection at our institution from October 1994 to November 2001 (composite replacement [n = 19], supracommissural replacement of the ascending aorta only [n = 19], conventional reconstruction of the aortic root with Teflon felt or glue [n = 47], remodeling of the aortic root according to Yacoub [n = 21], and reimplantation of the aortic valve according to David [n = 15]). This study compares the latter two valve-sparing techniques by remodeling (group 1) or reimplantation (group 2).

Most patients were operated upon within 24 hours after onset of symptoms. There was no statistical significant difference between the preoperative variables (Table 1). The diagnosis of acute aortic dissection was confirmed in the majority of the patients by computed tomography or transthoracic/transoesophageal echocardiography. Clinical characteristics of Marfan syndrome were present in 3 patients in group 1. No patient had a prior cardiac surgical procedure.

Surgical details
Standard cardiopulmonary bypass with a membrane oxygenator (Hollow Fiber Oxygenator, Spiral Gold, Baxter, Puerto Rico) at profound hypothermia (15 to 18°C) for circulatory arrest, and antegrade cold crystalloid or blood cardioplegia for myocardial protection were used. Arterial cannulation was performed in the first 4 years through the femoral artery (n = 24) and in the last period through the right subclavian artery (n = 6) or the ascending aorta in the nondissected area (n = 6). Venous cannulation was performed predominantly through the right atrium and seldom through the femoral vein (n = 7).

Gelatin-resorcinol-formaldehyde glue ([GRF] Cardial, Saint E’tienne, France) was used in some patients to readapt the dissected components of the root after transsecting the ascending aorta 3 mm above the commissures (Table 2). Thereafter the sinuses were excised and the two different techniques performed. Intraoperative details are listed in Table 2. The operative technique for group 1 (remodeling) is described in detail elsewhere [12]. Briefly, after excision of the diseased sinuses the end of the Dacron tube (Hemashield Gold; Meadox Medicals, Oakland, NY) was trimmed to produce three separate tongue-shaped extensions that were fixed to the aortic annulus with 4-0 Prolene continuous sutures followed by reimplantation of the coronary ostia. The size of the graft was determined as the distance between the straightened commissures giving a macroscopic picture of appropriate leaflet adaptation [4]. The operative technique for group 2 (reimplantation) is described in detail elsewhere [7]. In brief, after excision of the sinuses the tube size was determined as described before and the graft was anchored beneath the aortic annulus with 2-0 Teflon felt pledged sutures. Thereafter the aortic valve is implanted inside the Dacron tube similar to the implantation of an aortic homograft followed by reimplantation of the coronary ostia. In both valve-sparing techniques the coronary buttons were buttressed with Teflon felt strips. The distal anastomosis was performed in an open fashion using circulatory arrest in 33 patients if hemiarch replacement was necessary (Table 2).

Definition of neurologic complications
Neurologic complications were defined as new hospital neurologic events that occurred perioperatively. The diagnosis was determined clinically and by cerebral computed tomography. Two patients had preoperative stroke or coma and 6 patients were sedated and intubated on admission with unknown neurologic status. Their special neurologic outcome is separately presented in Table 3.

Follow-up
Twenty-two reoperation-free survivors completed echocardiographic and clinical follow-up examination between November 2001 and January 2002. For evaluation of the 3 reoperated patients in group 1 we reviewed our hospital patient records for the last available data. Thus 13 patients who died early and late were not integrated into the follow-up study as well as 1 patient whose follow-up time after operation was too short to be integrated into the program, leaving 22 patients for follow-up study. Twelve patients in group 1 and 10 patients in group 2 were followed up for a median (mininum, maximum) period of 29.6 months (1.6, 41.3) and 11.3 months (0.7, 87), respectively.

Echocardiographic data acquisition and measurements
A Hewlett Packard Sonos 2500 system with 2.5- and 5.0-MHz ultrasound transducers during routine follow-up was used for echocardiography at rest with constant blood pressure (cuff sphygmomanometry; Dinamap; Siemens, Erlangen, Germany). Echocardiographic data were determined by two independent observers from video-recorded studies and the average value of 5 consecutive beats in sinus rhythm was taken.

Conventional continuous-wave and pulsed-wave Doppler as well as color-flow Doppler techniques were applied. Aortic regurgitation was assessed by color-flow Doppler techniques in the standard transthoracic and transesophageal views and graded as follows using the ratio of jet height/left ventricularoutflow tract height: ratio of 1% to 24%, grade I; 25% to 46%, grade II; 47% to 64%, grade III; and 65% or more, grade IV [13]. Calculations of cardiac output, stroke volume, ejection fraction, and transvalvular pressure gradient were performed as described earlier [14].

Statistics
Dichotomous variables are presented as absolute numbers and relative frequencies. Because some variables were not normally distributed continuous data are given as median and range. For analysis, Fisher’s exact test, the Mann-Whitney U test, and the Kruskal-Wallis H test were used. Survival and reoperation rates were analyzed using the Kaplan-Meier method. All tests were two-sided. A p value of 0.05 or less was considered to indicate statistical significance. All tests were performed using SPSS 9.0 (SPSS, Chicago, IL).

	Results

Top Abstract Introduction Patients and methods Results Comment References

 
Hospital mortality
Four patients (19%) in group 1 died and 3 patients (20%) in group 2 died. Five of these patients were admitted in cardiogenic shock. The death of 1 patient in group 2 occurred 8.7 months after surgery and is unexplained.

Neurologic complications
Four patients in group 1 experienced a neurologic event perioperatively. Two of these patients were admitted either in cardiogenic shock or ongoing resuscitation. The other 2 patients were admitted with stable hemodynamics without preoperative neurologic impairment. Both had a perioperative nonfatal ischemic insult related to the arteria cerebri media with complete remission of symptoms in 1. Three patients in group 2 had a stroke. All were hemodynamically compromised on admission either in cardiogenic shock or ongoing resuscitation.

Two patients (1 in each group) presented with transitory neurologic symptoms with complete remission postoperatively. One had a transitory ischemic attack preoperatively as the primary symptom of dissection and the other was admitted in cardiogenic shock. No late neurologic events occurred during follow-up.

Late mortality
Five patients died during follow-up in group 1 between 5 and 44 months. Except for 2 patients who died 16 and 32 months postoperatively of unknown reasons, the other 3 deaths were not related to the dissection disease.

Follow-up
Nine of the 12 survivors in group 1 (75%) and 9 of 11 survivors in group 2 (80%) were in New York Heart Association (NYHA) grade I; the other 3 (25%) in group 1 and 2 (20%) in group 2 were in NYHA class II. None of the patients in either group reported thrombembolic events.

Echocardiographic data (Table 4) were not different between groups. No patient had more than grade I aortic insufficiency.

View larger version (12K): [in this window] [in a new window]   Fig 1. Actuarial freedom from reoperation for the whole group of patients after valve-sparing aortic root replacement for acute type A dissection. Number of patients at risk: 36 at baseline, 15 at 500 days, 10 at 1,000 days, 5 at 1,500 days, 3 at 2,000 days, and 1 at 2,500 days.

	Comment

Top Abstract Introduction Patients and methods Results Comment References

The appeal of valve-preserving techniques is based on maintaining the potential benefits of native tissue such as regeneration, growth potential, thromboresistance and lack of thrombembolic events, optimal hemodynamic performance, ventriculoarterial coupling, left ventricular function, cardiac output, and coronary flow. Furthermore anticoagulation is not necessary, reducing the risk of anticoagulation-related complications and facilitating the thrombotic obliteration of the distal false lumen [11]. The conventional technique to preserve the aortic leaflets by using glue or Teflon felts for reconstruction of the dissected sinuses is attractive because it shortens the operation time but it involves the risk of a high reoperation rate [16] and is not applicable to severe dissected and aneurysmatic pathology. Alternative surgical techniques such as the remodeling [12] or reimplantation technique [7] can be applied. Both techniques have proven their usefulness in elective cases of root aneurysm [8, 14], the remodeling technique with more physiologic characteristics of leaflet movement [14] in comparison with the reimplantation technique.

In general the primary determinants for judging the value of a special surgical technique are hospital mortality, reflecting in part the complexity of the procedure in relation to the underlying pathology and the condition of the patient, the postoperative rate of procedure-related complications, and the functional results. The valve-sparing techniques for type A dissections are innovative complex operations and as yet not well defined especially for longer-term follow-up. Preliminary results in a small series in our center were encouraging with low hospital mortality [17]. With increased follow-up however, the hospital mortality rate increased to 19% and 20% respectively for remodeling and reimplantation. Similar mortality rates were reported by other authors such as Niederhauser and associates [18] with 23.6% and Fukunaga and colleagues [19] with 26.6% using the conservative valve-sparing or the composite replacement technique. These data reflect the experience of the international registry for acute aortic dissection with 26% early surgical mortality [20] regardless of the operative technique used. The clinical condition of most of the patients who died in our series was severely impaired by the disease itself, preoperatively. They were either unconscious, intubated or in cardiogenic shock indicating that the disease related preoperative clinical state of the patient is a meaningful predictor of early survival which was also reported by other authors [21–23]. Thus, there is growing evidence that valve-sparing surgical techniques may not increase surgical risk neither the remodeling nor the reimplantation technique. To decrease hospital mortality in general probably needs more than surgical improvements, predominantly refinement of wider spread awareness and clinical index of suspicion, to alleviate the most important surgical risk factor, which is the disease-related impact on the patient. Nevertheless it must be kept in mind that the valve-sparing techniques are complex procedures, particularly the remodeling technique requiring extensive surgical experience with valve surgery.

The postoperative results were promising. The reoperation rate was low. None of the patient undergoing the reimplantation technique had to be reoperated on for as long as 7 years, but 3 patients (2 with Marfan syndrome) had to undergo reoperation after using the remodeling technique. Whether this relates to an unsatisfactory suture technique, the tissue weakness at the sinus suture line especially in the Marfan patients, or to the potentially harmful tissue damaging properties of the GFR glue [24] which was used in all 3 cases—remains speculative. However it can also not be excluded that the recommended protocol of the manufacturer was always followed exactly. Nevertheless Bingley and associates [24] could demonstrate that GFR glue may lead to necrosis of tissue with reduced wear resistance. We also found in all 3 cases sutures that were torn out of the previously glued area.

Our observations provide some hint that the durability of the remodeling technique in acute type A dissection may be affected by the pathologic tissue properties especially in Marfan syndrome and also by glue application. However there was no progressive dilatation of the aortic root in remodeling survivors.

The hemodynamics of the aortic valve remained excellent and stable over the years with none of the patients presenting aortic insufficiency more than grade I and with no pathologic pressure gradient.

There were no events of endocarditis or thrombembolism without the use of anticoagulation supporting the rationale of using these valve-sparing techniques. Whether these advantages over composite replacement or the conventional reconstructive techniques using Teflon felts or glue have any effect on long-term survival remains to be established. Fann and colleagues [15] reported a survival rate of 55% after 5 years and 37% after 10 years in a large series using different surgical techniques; and Bachet and coworkers [25] reported 56% after 10 years using root reconstruction and composite replacement techniques. These survival rates are comparable with those obtained with the valve-sparing techniques in our series. Although the survival rate for the remodeling technique was lower compared with the reimplantation technique, that was not statistically significant. Furthermore 3 of the late deaths in the remodeling group were not procedure related. Thus there seems to be no clear advantage of survival for one or the other surgical method.

The statistical evaluation of this study has some shortcomings: the lack of a randomized protocol, the small number of patients, the heterogeneity of pathology, and the complexity of the operation rendering comparability and generally applicable conclusions difficult. Thus these results can only describe our center’s experience.

In conclusion we did not find significant differences regarding clinical and hemodynamic data for as long as 7 years postoperatively between the remodeling and reimplantation technique used for replacement of the aortic root in acute type A dissection. Owing to the small number of patients definite conclusion cannot be drawn. However concerning the durability of the reconstruction, the remodeling technique needs critical consideration especially in Marfan pathology and when GFR glue is used at the proximal anastomosis.

	References

Top Abstract Introduction Patients and methods Results Comment References

 

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