(689Kb)Agnoletti G, Bajolle F, Bonnet D, Sidi D, Vouhé
P. Late coronary complications after arterial switch operation for transposition
of great arteries. Clinical and therapeutic implications. Images Paediatr
Cardiol 2005;24:1-11
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(689Kb) |
Agnoletti G, Bajolle F, Bonnet D, Sidi D, Vouhé
P. Late coronary complications after arterial switch operation for transposition
of great arteries. Clinical and therapeutic implications. Images Paediatr
Cardiol 2005;24:1-11
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Service de Cardiologie et Chirurgie Cardiaque, Necker Enfants Malades, Paris |
| Transposition of Great Vessels | Coronary Vessels | Heart Defects, Congenital/*surgery |
| Diagnostic Imaging | Coronary Angiography |
Introduction
The arterial switch operation (ASO) has become the procedure of choice
for correction of transposition of great arteries (TGA). Compared with
the Mustard and Senning repairs, correction at the arterial level restores
the left ventricle as the systemic ventricle and offers improved outcome.
Coronary artery transfer was first described by Wernovsky in 1993 (figures
1 and 2).1
The transfer of the coronary arteries during ASO may be a difficult step in the case of abnormality of origin or distribution of these arteries and this technique is burdened by the risk of acute and subacute coronary occlusion.2 Various classifications of coronary anatomy in transposition of the great arteries exist. In our department we define coronary anatomy in accordance with Yacoub‘s classification (figure 2). Comparison of mortality between usual pattern and variant patterns showed that the presence of a single coronary and an intramural coronary was associated with a higher risk of occlusion (figure 3).2
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No guidelines exist concerning the management of coronary artery obstructions after ASO. We recently reviewed our institutional experience concerning the early and long term outcome of ASO, in order to: determine the prevalence of coronary arteries obstruction, establish possible implications between obstruction and late death, try to identify mechanisms involved in early and late coronary obstruction and propose a therapeutic approach. We present here our results.
Patients and methods
The series comprises 712 patients who underwent ASO in the neonatal
period for simple and complex transposition of the great arteries. All
patients had clinical evaluation, ECG and echocardiography 6 months after
surgery and every 6 months, until selective coronary angiography was performed.
Coronary angiography was performed: 1) Systematically at the age of 5 years
in asymptomatic patients, 2) When an ischemic event occurred, 3) When electrocardiographic
and/or echocardiographic findings suggesting myocardial ischemia were detected.
Myocardial perfusion imaging was performed: 1) Systematically at the age
of 3 years in asymptomatic patients, 2) When an ischemic event occurred
3) 6 months after surgical revascularization, percutaneous or medical treatment
of coronary obstruction.
Myocardial ischemia was defined as the presence of ST-T changes/Q waves on ECG or ultrasound anomalies, together with perfusion defect at scintigraphy, consistent with the localization of coronary obstruction.
Classification of late complication was: occlusion, major stenosis (>50 % of coronary artery diameter), minor stenosis (< 50% of coronary artery diameter) or stretching (diffuse narrowing). Coronary diameter was measured at end-diastole.
Functional status was determined on the basis of: clinical examination, electrocardiogram, echocardiography, selective coronary angiography, myocardial perfusion imaging (Thallium-201) at rest and after exercise or dipyridamole infusion.
Results
At a mean follow-up of 4,7 ± 2 years, we identified 39 children
with coronary obstruction (5.5%). Thirty three patients had isolated TGA
and 6 had TGA associated with ventricular septal defect and/or aortic coarctation.
Mean age at diagnosis of coronary obstruction was 3.1 ± 3 years.
Ten patients were identified from an anomalous selective coronary angiogram,
performed during a prospective study, to determine the long term outcome
of coronary anastomoses (figures 4 and 5).
Twenty nine patients were identified because of electrocardiographic
and/or echocardiographic anomalies suggestive of myocardial ischemia. Two
patients died suddenly at the age of 4 and 6 months. Both had a stenosis
of the left ostium diagnosed one month after surgery. One patient died
in the postoperative period of surgical revascularization. Type of coronary
obstruction according with myocardial scintigraphy is illustrated in figure
6.
Fifteen patients received a surgical intervention, 4 had medical treatment
and 17 had no treatment (figure 7).Our results and patients outcome are
summarized in figure 8.
All children undergoing surgical treatment had elective coronary angiography
1 month after surgical revascularization. All coronary ostia were patent
(figures 10-12).
Discussion
Arterial switch operation has dramatically changed the outcome of patients
with TGA. Although initially burdened by an elevated mortality, this technique
is now performed with good results in most centres. A previous report showed
that in our department this operation has a 10 year survival of 94%, and
a freedom from surgical reintervention of 78%.3
Risk factors that have been demonstrated to influence early mortality are right ventricular hypoplasia, lower birth weight and longer intraoperative support.4
Several authors underlined the occurrence of early or late coronary obstruction after ASO.2,4,5 The reported incidence of coronary obstruction varies between 5 and 8%.5-7 Some anatomical types are reported to have a higher incidence of early and/or late obstruction. In particular, in type B and type C anatomy, transfer of the coronary arteries may be a difficult step.8
Echocardiography has been show to be able to detect the presence of coronary anomalies and in particular to unmask an intramural course.9 Preoperative diagnosis is advantageous, because it helps to prevent accidental injury to the intramural coronary artery during transaction of he aortic root and excision of the coronary artery ostium from the aorta. In most centres, however, precise coronary anatomy is usually defined at surgery.
Diagnosis of ischemic obstruction is typically performed when an acute ischemic event occurs in the postoperative period or, after discharge, on the basis of echocardiographic signs of ischemia.
No guideslines exist concerning the follow up of children undergoing ASO. Different techniques have been reported to be a useful tool for diagnosis of coronary obstruction in this setting. In our department we decided to systematically perform coronary angiography and myocardial scintigraphy. We previously reported the usefulness of selective coronary angiography for detection of coronary obstruction in this setting. Even if invasive and potentially dangerous, selective coronary angiography allowed us to identify a subgroup of high-risk children with normal echocardiography.7 We also showed that aortic root angiography yields ambiguous results in ASO patients.7 In the absence of coronary lesions at systematic coronary angiography, children are monitored noninvasively after 2 and 5 years.
Myocardial perfusion imaging by thallium-201 is useful in selecting patients with coronary artery lesions who are candidates for myocardial revascularization. However, this technique does not identify hibernating territories that are expected to recover a normal contraction after revascularization.6,10 On the contrary, positron emission tomography (PET) assesses myocardial viability by coronary blood flow and metabolic myocardial activity. It allows the targeting of angioplasty to hibernating territories that have residual metabolic activity. It also allows the evaluation of coronary flow reserve. Other authors have underlined that ASO patients have a diminished flow reserve. The global impairment of stress flow dynamics may indicate altered vasoreactivity.11 Although noninvasive, this technique is irradiating and has a limited availability.
Prognostic significance of reduced coronary reserve in ASO patients needs to be determined. In particular, the long term impact on cardiac function has not been established. It has been demonstrated that aorto-coronary anastomoses can grow.12 However, alterations of sympathetic innervation after surgery is a well known phenomenon, that could justify an impaired regulation of coronary flow in ASO patients.13,14 It has also been shown that endothelial function could be altered in this setting.15,16 The prognostic significance of these findings needs to be determined.
Surgical angioplasty or medical treatment can be carried out to restore coronary perfusion. Detection of symptom free obstructions and their treatment are necessary for late myocardial protection. In fact, obstruction may progress and collateral circulation may become insufficient with growth. Treatment of coronary obstruction allows decreased side effects of chronic myocardial hibernation such as degeneration and ventricular dysfunction. Previous report have shown that early treatment can preserve myocardial function over long time.17-20 Surgical angioplasty of the coronary stems restores physiological coronary perfusion and patch enlargement of coronary ostia offers encouraging mid term results.18 Internal thoracic or mammary artery grafting can be considered a valid alternative to surgical angioplasty in the presence of long stenosis.18
Conclusions
Symtom free coronary obstruction is not infrequent after ASO. We recommend
systematic selective coronary angiography for detection of coronary obstruction.
Non-invasive methods to evaluate these patients will be hopefully available
soon. Surgical revascularization should be performed to preserve myocardial
function and avoid late ischemic events in case of myocardial ischemia.
However, concern exists with regard to late outcome of coronary revascularization
in children and on durability of coronary angioplasty. Optimal treatment
of coronary obstruction in ASO patients is not consensual.
References
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