INTRODUCTION

The number of patients with disease of the aortic valve and ascending aorta requiring surgical repair of both structures is constantly growing. Although valve-sparing repair procedures have gained ground recently, for more than 30 years the classic Bentall prodedure1 has been the conventional surgical treatment with excellent short- and long-term results even in patients with Marfan's syndrome.2 Physiologically, repair operations are preferable to valve replacement as they preserve aortic root anatomy and eliminate the need for permanent anticoagulation.3-5

However, little has been published on the use of homografts and autografts for these conditions. These prostheses favor improved physiology of the aortic root, reduced incidence of endocarditis, and low incidence of thromboembolic disease, and eliminate the need for anticoagulant treatment.6-11

In the present study, we describe our first experience of aortic root and ascending aorta replacement with cryopreserved homografts.

PATIENTS AND METHODS

Between October 1999 and August 2003, 22 consecutive patients underwent procedures for disease of the ascending aorta and aortic valve. Patient characteristics are in Table.

All patients underwent preoperative transthoracic and transesophageal echocardiography and spiral computed tomography (CT) to determine the condition of the thoracic aorta, and coronary angiography to determine coronary artery status.

Ascending aorta replacement was indicated for diameter >50 mm, dissection, or diameter twice that of the descending aorta. Indication for surgery was dilated ascending aorta in all cases.

Cryopreserved homografts were obtained from external tissue banks and thawed according to supplier protocols.

Surgical Technique

Operations were performed with extracorporeal circulation (ECC) by median sternotomy with moderate hypothermia even in the 4 patients who required repair of the dissection or aortic arch. Femoral cannulation was used to establish ECC.

Homograft size was determined from aortic annulus measurement in preoperative transthoracic echocardiography by reference to the short axis of the left ventricular outflow tract from the aortic-mitral valvar curtain to the interventricular septum. Mean diameter was 24.26 mm (range, 23-27 mm). Homograft implantation was performed by total root replacement with reimplantation of coronary arteries in all patients. Resection of the ascending aorta, aortic valve and coronary arteries left a ~2 mm aorta button. Homografts were prepared by trimming the muscle of the mitral valve and trigonum fibrosum leaving the cylindrical form of the left ventricle outflow tract. An interrupted 4/0 suture was performed following the anatomical form so the structures would coincide. Coronary arteries were reimplanted with 6/0 polypropylene continuous sutures and followed by direct distal anastomosis with the native aorta or aortic arch. In 6 patients, homograft length was insufficient for direct anastomosis distal to the aorta and a prosthetic conduit was needed. In these patients, we conserved the sinotubular junction of the homograft to maintain total functionality of the aortic root. During surgery, hemodynamic performance was constantly monitored by transaortic gradient and echocardiography to determine aortic root function (valve failure, dilation, etc).

One-month, six-month and one year follow-up consisted of personal clinical interview to analyze functional status, echocardiography to measure ventricular function (systolic and diastolic diameters, left ventricular wall thickness, ascending aorta size), and continuous, color-contrast pulsed Doppler to determine homograft and aortic valve function. Aortic root morphology was monitored by spiral CT. No patient received anticoagulant therapy during follow-up.

RESULTS

In-Hospital

All patients survived surgery. One required reoperation for bleeding, 3 had atrial fibrillation episodes requiring restoration of sinus rhythm with amiodarone, and 1 evolved slowly presenting systemic inflammatory response syndrome. Mean hospital stay was 7.85 days. Mean duration of ischemia was 89.17±13.97 min (range, 66-117 min) and bypass time was 117.83±18.61 min (range, 90-156 min). One patient required >6 h inotropic support but no untoward neurological effects were observed.

Follow-up

Mean follow-up was 12.1 months (range, 2-36 months). Echocardiographic studies detected mild aortic insufficiency in 2 patients. Mean postoperative aortic valve gradient was 5.17±4.09 mm Hg. Reduction in ventricular diameters was statistically significant at 1-month and this was maintained throughout the follow-up (Table and Figure 1). Ascending aorta size measured by CT was normal (~30 mm) (Figure 2) in all but 1 of the patients, who presented a 40 mm caliber (this patient presented previous atherosclerotic disease in ascending aorta). We did not observe morphological changes such as the presence of calcium or pseudoaneurysms in the aortic root or ascending aorta. None of the patients presented signs of myocardial ischemia. One patient presented a transient thromboembolic event at 2 months after surgery, making a full recovery.

Fig. 1. Reduction of ventricular diameters (*P<.002; 95% CI, 5.82-15.18. **P<.005; 95% CI, 1.69-9.11).

Fig. 2. CT image of homograft replacement for native ascending aorta.

DISCUSSION

The aortic root is a complex structure and all components from the sinotubular junction to the left ventricular outflow tract are essential to its correct functioning. Preserving anatomy and physiology in aortic root repair procedures is essential.11,12 This has led to the current trend for aortic root repair operations for patients with aneurysms3-5 and the use of homografts to correct valvular disease.6,7

In the literature, there are few references to the number of patients with aortic valve and ascending aorta disease who have received homografts as the elective surgical technique.8 However, reports on large-scale series of homografts do include some references.6,7

We believe the procedure has not gained popularity because of the technical difficulties caused by differences in homograft and native aortic root diameters. However, allograft replacement of the aortic root and ascending aorta enables us to conserve the anatomy of the sinotubular junction thus maintaining aortic root function. This is especially important in patients who need prosthetic extension of the ascending aorta by locating a conduit above the junction.

The use of homografts for aortic root replacement favors restoration of normal or nearly normal flow in the aortic root, sinuses of Valsalva and coronary flow3,7, resistance to infection, reduced thromboembolism, and maintenance of total aortic root physiology ensuring better hemodynamic performance; it also removes the need for permanent anticoagulation. This leads to improved recovery of left ventricular function with a reduction in left ventricular hypertrophy as it presents significantly lower gradients than those associated with conventional prostheses.13,14 Our patients had a statistically significant reduction in ventricular diameters. This is important as long-term survival studies of homografts indicate it improves homograft durability.3

Major disadvantages of homograft use are durability, the more demanding surgical technique, and the limited supply of homografts by comparison with conventional prosthetic valves. However, we know that cryopreserved homografts implanted in total aortic root replacements give better long-term results than antibiotic-sterilized homografts and subcoronary implants.6,7,15,16 This may be because total root replacement preserves the anatomy and valve function from the left ventricular outflow tract to the sinotubular junction.7,15 In our study this is important as all patients received cryopreserved homografts in total root replacement procedures. Durability is also influenced by other factors, most of which depend on donor age.6,7

Homograft failure appears in the form of calcification and valve failure. In these patients, primary tissue failure is of considerable importance and any measure destined to reduce this is desirable. Tissue failure seems to be associated with degenerative processes17 but due to our limited follow-up period we have not detected it.

In patients of this kind, stentless bioprostheses can be used in total aortic root18 and aortic valve reconstruction procedures as alternatives to biological material.

Reconstruction procedures were not used with our patients due to calcium present in valves and annulus or because valve anatomy was thought likely to impede adequate repair. Subcoronary homograft implantation is impossible in patients with dilated aorta because of the aortic geometry.

Absence of thromboembolism during long-term follow-up was positive. Only one event occurred and this was probably associated with surgery as it happened within the first 3 months in the absence of atrial fibrillation and carotid artery disease. As yet, follow-up has been short-term. In 1 patient with arteriosclerosis we found allograft dilatation to a diameter of 40 mm, but ascending aorta measurements in the rest of the patients are within normal range. We found no dysfunction due to calcium or degeneration. This would be more likely in younger patients19 and the mean age of our group was high. We think the procedure is a valid alternative for these patients, and concur with several authors who advocate the use of homografts in treating complex aortic root disease.20

Full English text available at: www.revespcardiol.org

Correspondence: Dr. A. González Pinto.
Juan A. Mendizábal, 50. 28008 Madrid. España.
E-mail: agp@eresmas.net