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J Thorac Cardiovasc Surg 2007;133:569-572
© 2007 The American Association for Thoracic Surgery
Brief Communication |
a Cardiothoracic Surgery Unit, Monash Medical Centre, Clayton, Victoria, Australia
b Department of Paediatric Cardiology, Monash Medical Centre, Clayton, Victoria, Australia
c Department of Surgery (MMC), Monash University, Clayton, Victoria, Australia.
Received for publication September 12, 2006; accepted for publication September 19, 2006. * Address for reprints: Julian A. Smith, MS, FRACS, Cardiothoracic Surgery Unit, Monash Medical Centre, 246 Clayton Rd, Clayton, Victoria 3168, Australia. (Email: julian.smith{at}med.monashi.edu.au).
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The arterial switch operation (ASO) has become the preferred procedure for repair of d-loop transposition of the great arteries, and this anatomic correction has been applied to the treatment of right ventricular dysfunction after atrial switch procedures, as well as primary curative repair in newborns. On the other hand, this operation involves radical manipulation of the base of the great arteries. Both great arteries are transected and reanastomosed above the sinuses of Valsalva, and the coronary arteries are translocated. The native pulmonary valve becomes the systemic outflow valve, and the anatomic pulmonary root is subjected to systemic blood pressure. Neoaortic root dilatation, which is one of the postoperative complications after ASO, is thought to occur as a result of these atypical hemodynamic and anatomic features.1
Neoaortic root dilatation might be recognized during late follow-up,2,3 and some patients might require a neoaortic root or valve operation at some stage after an ASO.3,4 Careful assessment of the individual anatomic situation is essential before surgical repair because coronary artery distribution and the positional relationship of the great arteries affect the conduct of the operative procedure. We describe a case of neoaortic root dilatation accompanied by a huge saccular aneurysm, which was detected during pregnancy. The patient had undergone an ASO for Taussig–Bing anomaly (double-outlet right ventricle with subpulmonary ventricular septal defect) 14 years previously. We also discuss some of the important issues regarding the assessment of neoaortic root dilatation after an ASO.
The patient, a 26-year-old woman, was born with the Taussig–Bing anomaly accompanied by subpulmonary stenosis. She underwent a Senning operation at the age of 8 months as a radical repair after balloon atrial septostomy on her third day of life. At the age of 2.5 years, she subsequently had a resection of the subpulmonary fibrous membrane and muscle for moderate-to-severe left ventricular outflow tract obstruction. For the treatment of progressive right ventricular dysfunction, she underwent banding of the pulmonary artery, followed 9 months later by an ASO and a takedown of the Senning repair at the age of 12.5 years. Her coronary anatomy was type E of Yacoub’s classification; the right coronary artery (RCA) and the left anterior descending branch took origin from the left ostium, and the circumflex branch alone took origin from the right ostium. A concomitant neoaortic valve replacement with a 21-mm SJM mechanical valve (St Jude Medical, Inc, St Paul, Minn) was required because of massive neoaortic regurgitation caused by an abnormal native pulmonary valve. The left anterior neoaortic sinus was reconstructed with the use of an autologous pericardial patch to prevent obstruction of the left-sided coronary artery. She did well for 14 years until late in her first pregnancy, when she was found to have an asymptomatic saccular aneurysm of the neoaortic root. Chest radiography showed an abnormal mediastinal shadow and mild cardiomegaly (cardiothoracic ratio, 54%; Figure 1, A).
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Multisliced computed tomography (CT) and magnetic resonance imaging clearly delineated the neoaortic root and coronary arterial anatomy. Neoaortic root dilatation was shown with a lobulated saccular aneurysm in the left anterior sinus, measuring 64 x 88 x 50 mm and extending leftward in the chest (Figure 1, B). There was no intimal flap, thrombus, or extra saccular fluid collection. The main pulmonary artery was located and displaced to the right anteriorly and marginally compressed by the aneurysm (Figure 2). The RCA originated anteromedially, about 3.1 cm above the aortic valve from the right anterior sinus. The left anterior descending branch arose (just distal) at the origin of the RCA. The circumflex branch originated posteromedially from the left posterior sinus (at the level of the aortic root), which was compressed by the huge aneurysm (Figure 2). Neither CT angiography nor coronary angiography revealed significant coronary artery narrowing.
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The proximal ascending aorta and neoaortic root were grossly dilated, with significant effacement of the coronary ostia. The saccular aneurysm extended laterally into the left hemithorax. The distal ascending aorta was 3.0 cm in diameter and minimally diseased. After systemic heparinization, an arterial cannula was inserted through the left femoral artery, and a 2-stage venous cannula was inserted through the right atrium. Cardiopulmonary bypass was established, and cardioplegic arrest was rapidly achieved and maintained by means of the infusion of initial and intermittent boluses of antegrade and retrograde cold blood cardioplegia. The left pulmonary artery was divided to facilitate a sufficient exposure to the ascending aorta, and the ascending aorta was transected. The 21-mm SJM mechanical prosthesis was well seated, with minimal pannus formation. The wall of the aorta was extremely thin, and its aneurysmal change extended around the entire neoaortic annulus, which indicated that a redo aortic root replacement was necessary. The previously inserted mechanical prosthesis was removed with the debridement of the annulus, and a 21-mm aortic mechanical valved graft (ATS OPEN PIVOT; ATS Medical, Inc, Minneapolis, Minn) was placed in a supra-annular position. Subsequently, the coronary ostia were mobilized with ease and anastomosed to the conduit. A terminal warm blood cardioplegia was delivered after the completion of distal conduit anastomosis. Spontaneous cardiac rhythm was restored after release of the aortic crossclamp. The left pulmonary artery was reconstructed during reperfusion with a 21-mm interposition Dacron graft to reestablish the continuity without tension. The patient was weaned from cardiopulmonary bypass with the assistance of low-dose inotropes. The postoperative course was uneventful, and she was discharged from the hospital on the seventh postoperative day. She remains well 6 months later, with an excellent surgical result seen on echocardiography.
Neoaortic root dilatation has been reported as one of the postoperative complications after an ASO. There is usually a rapid dilatation of the neoaortic root in the early postoperative period, and the root dimensions tend to stabilize without significant progression over time.2,3 However, progressive development of neoaortic root dilatation can be associated with significant complications, and thus, close postoperative monitoring of the neoaortic root is essential.
Many factors can influence the development of neoaortic root dilatation after ASO. Murakami and colleagues1 demonstrated the impaired distensibility of neoaorta after ASO in 36 patients and suggested 3 possible mechanism of neoaortic root dilatation: (1) "surgical manipulation such as the suture of coronary buttons," (2) "characteristics of the native pulmonary artery in a high-pressure position," and (3) "damage to the vasa vasorum."1 Schwartz and associates3 identified the most significant risk factor as previous pulmonary artery banding in 335 patients who underwent ASO for primary repair of d-loop transposition of the great arteries or Taussig–Bing anomaly. In a retrospective longitudinal study of 144 patients, Hutter and coworkers2 observed the growth of the neoaortic valve and neoaortic root by means of echocardiography and evaluated the influence of associated cardiac malformations, such as ventricular septal defect, Taussig–Bing anomaly, and coarctation of the aorta. Furthermore, false aneurysm formation was common in patients who underwent cardiac operations with the use of prosthetic materials, such as an artificial valve or a pericardial patch.5-7 In consideration of the risk factors mentioned above, our patient was considered to be at a higher risk.
Saccular aneurysms are mostly observed in patients who underwent a patch aortoplasty for repair of coarctation of the aorta.8,9 This aneurysm formation is considered a rare life-threatening complication after aortic surgery as a result of disruption of at least 1 layer of the vascular wall. McGiffin and associates10 described the aortic wall stress profile after the coarctation repair with a patch aortoplasty. In their mathematic models the authors suggested that excessive aortic wall stress caused by patch geometry can be responsible for aneurysm formation. Our patient had a pericardial patch for reconstruction of the left anterior coronary sinus to prevent compression of the left-sided coronary artery, and this might have lead to saccular aneurysm formation accompanied by neoaortic root dilatation.
Despite regular review and echocardiographic evaluation since her previous operation, the development of neoaortic root dilatation had not been observed, and her current pathology accompanied by saccular aneurysm was only detected during her first pregnancy when she was referred back to her cardiologist. Generally, cardiac output and stroke volume increase up to 30% to 50% by 16 weeks’ gestation, and the peak level is sustained until 36 weeks’ gestation.11,12 Therefore it might be postulated that acute development of her neoaortic pathology occurred during her pregnancy period. Studies have suggested that pregnancy might result in aortic root dilatation in patients with Marfan syndrome.13,14 There are no data on the influence of the pregnant state on congenitally abnormal hearts.
Preoperative anatomic evaluations are essential to clearly delineate the neoaortic root pathology and to plan surgical repair. The position of the great arteries and the coronary arterial pattern are critical pieces of information. Multidetection CT is particularly helpful, and its value in planning repeat cardiac operations has been demonstrated.15,16 Contrast-enhanced 3-dimensional images clearly visualized the anatomic relationship between the pathological neoaortic root and the coronary arteries in this case.
In summary, we have described a patient with neoaortic root dilatation accompanied by a huge saccular aneurysm formation after ASO, which was detected during her first pregnancy. Although neoaortic root dilatation is a rare complication after an ASO, careful follow-up of the neoaortic root and evaluation of risk of such dilatation are essential.
References
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