British Journal of Radiology (2009) 82, e8-e10
© 2009 British Institute of Radiology
doi: 10.1259/bjr/35749180
British Journal of Radiology 82 (2009),e8-e10 ©2009 The British Institute of Radiology
Coronary myocardial bridging in Noonan syndrome: definitive diagnosis with high-resolution CT
M LEYE, MD
1
G CALCAGNI, MD
1
F BRUNELLE, MD
2
D BONNET, MD, PhD
1
D SIDI, MD, PhD
1 and
P OU, MD, PhD
2
Departments of 1 Pediatric Cardiology and 2 Pediatric Radiology, University Paris Descartes, Hôpital Necker-Enfants Malades, AP-HP, Paris, France
Correspondence: Doctor Phalla Ou, Department of Pediatric Radiology, Hôpital Necker-Enfants Malades, 149, rue de Sèvres 75743 Paris Cedex 15, France. E-mail: phalla.ou{at}nck.ap-hop-paris.fr
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Abstract
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Noonan syndrome is an autosomal dominant disorder reported at an incidence of 1 in 1000–2500 live-born patients. Pulmonary stenosis with a dysplastic pulmonary valve and hypertrophic cardiomyopathy are often associated with this syndrome. We report on a 9-year-old patient affected by Noonan syndrome with left ventricle hypertrophy, in whom a sudden clinical presentation of chest pain after effort led to the clinical suspicion of associated coronary myocardial bridging, which was confirmed by high-resolution CT. We also review the literature on this topic.
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Introduction
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A 9-year-old boy affected by Noonan syndrome was admitted to our department with persistent retrosternal thoracic pain that appeared after effort. He was undergoing treatment with β-blockers for a previous diagnosis of hypertrophic cardiomyopathy, which had been followed since the age of 6 months.
On physical examination, a systolic murmur 3/6 was found. No heart failure was identified. The usual physical dysmorphisms associated with Noonan syndrome were identified. No electrocardiogram (ECG) signs of myocardial infarction were present. A transthoracic echocardiogram revealed situs solitus and levocardia with atrioventricular and ventriculoarterial concordance, along with the previously diagnosed moderate hypertrophic cardiomyopathy with a medioventricular obstruction by mitral valve leaflets. No pulmonary outflow obstruction was found. ECG-gated cardiac CT was performed to exclude any coronary artery lesion, with the following parameters: 64-slice CT scanner (LightSpeed VCT; General Electric, Milwaukee, WI), slice thickness 0.625 mm, speed of rotation 0.35 s, pitch 0.16, 80 kV, ECG mA modulation during the acquisition, and peripheral injection of contrast agent (iohexol, 300 mgI ml–1; volume, 1.5 ml kg–1; flow rate of the injection, 2.5 ml s–1). The acquisition lasted 3.3 s and the entire examination lasted approximately 15 min.
ECG-gated CT showed global hypertrophy of the left ventricle. In addition, CT clearly demonstrated a myocardial bridge across the middle segment of the left anterior descending artery (Figure 1
). There were no other abnormalities with regards to the coronary artery tree. The patient was treated conservatively with β-blockers and a calcium antagonist.
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Figure 1. Curved reconstruction of the left coronary artery. Note the myocardial hypertrophy of the left ventricle and the bridging involving the middle segment of the left anterior descending coronary artery(arrows).
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Discussion
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Noonan syndrome is an autosomal dominant syndrome involving multiple congenital abnormalities: short stature, typical facial dysmorphology (e.g. hypertelorism), antimongoloid slant of the palpebral fissures with ptosis and low-set posteriorly rotated ears with a thickened helix, webbed neck, chest deformity, mild intellectual deficit, cryptorchidism, poor feeding in infancy, bleeding tendency and lymphatic dysplasias. The incidence of Noonan syndrome is estimated to be between 1 in 1000 and 1 in 2500 live births [1, 2].
The most frequent congenital heart defect involved is pulmonary stenosis with dysplastic leaflets (50–62%) [3]. Hypertrophic cardiomyopathy has been reported in 20% of patients. Other congenital cardiac defects, such as persistent ductus arteriosus, atrial septal defect or atrioventricular canal with left subaortic obstruction, and structural anomalies of the mitral valve have been reported in the literature [1, 2, 4, 5]. To the best of our knowledge, no case of coronary artery bridging associated with Noonan syndrome has been reported previously.
First mentioned by Reyman et al [6] in 1737, coronary myocardial bridging is a congenital anomaly, usually considered benign. It occurs when the epicardial coronary arteries are intramyocardial. This can result in systolic compression of the coronary artery. In 90% of cases, myocardial bridging is localized in the middle segment of the left anterior descending coronary artery [7, 8]. Its prevalence rate has been reported as being 1–3% of the general population but, in patients with hypertrophic cardiomyopathy, it appears to be more frequent — 5–86% in an autopsy/post-mortem series and 0.5–16% in a coronary angiographic series. [9, 10].
There are reports in the literature of a close association between myocardial coronary bridging in hypertrophic cardiomyopathy and sudden death. Yetman et al [11] compared patients with and without coronary bridging, and found a greater incidence of chest pain, cardiac arrest with subsequent resuscitation and ventricular tachycardia in patients with bridging. They postulated that myocardial ischaemia linked to the bridging was responsible for the poor outcome of patients with coronary bridging associated with hypertrophic cardiomyopathy.
The clinical significance of a myocardial bridge depends upon its anatomy, length and depth. Ferreira et al [12] distinguished between two different models of myocardial bridging: (i) superficial bridging (over 75% of cases), which crosses the artery perpendicularly or at an acute angle toward the apex; and (ii) muscle bundles arising from the right ventricular apical trabeculae (25% of cases), which cross the left anterior descending coronary artery transversely, obliquely or helically before terminating in the interventricular septum [12, 13].
Coronary multislice CT has been proposed by Goitein et al [14] as the gold standard non-invasive technique for diagnosis of myocardial bridging. It offers several potential advantages over angiography. In myocardial bridging, CT visualizes the coronary artery lumen, its wall and the surrounding myocardium, as well as the length, depth and precise anatomical position of the myocardial bridge. In symptomatic patients, medical treatments include negative inotropic and/or negative chronotropic agents, e.g. β-blockers and calcium antagonists. The rationale of β-blocker treatment is to normalize the systolic/diastolic flow ratio and symptomatic angina [15].
In patients refractory to medical treatment, surgical myotomy has been suggested, with dissection of the muscle fibres overlying the tunnelled segment in order to abolish clinical signs and increase coronary flow [15]. Recently, minimally invasive myotomy was successfully reported by Pratt et al [16]. In 1995, Stables et al [17] reported the first coronary stent as an interventional approach to severe myocardial bridging refractory to medication, normalizing the intracoronary flow.
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Summary
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Myocardial bridging of the coronary arteries should be considered as a cause of chest pain or cardiac ischaemia in any patient with known hypertrophic cardiomyopathy, including those associated with Noonan syndrome.
Gated CT coronary angiography is a definitive investigation to demonstrate myocardial bridging of the coronary arteries and can replace invasive coronary angiography in this situation. CT coronary angiography can be used to plan the best surgical or interventional approach. It is easy to perform in paediatric patients, is non-invasive and provides optimal anatomical resolution.
Received for publication July 20, 2007.
Revision received November 27, 2007.
Accepted for publication December 4, 2007.
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References
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Abstract
Introduction
