British Journal of Radiology (2004) 77, 508-511
© 2004 British Institute of Radiology
doi: 10.1259/bjr/24835123
MRI evaluation of congenital coronary artery fistulae
J R Parga, MD
1
N M Ikari, MD
2
L N P Bustamante, MD
2
C E Rochitte, MD
1
L F R de Ávila, MD
1 and
S A Oliveira, MD
3
1 Magnetic Resonance Section, 2 Congenital Cardiology Department and 3 Surgery Division, Heart Institute (InCor), University of Sao Paulo Medical School, Brazil. Av. Dr. Eneas de Carvalho Aguiar, 44, Sao Paulo, SP, Brazil, 05403-000
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Abstract
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Congenital coronary artery fistula is a rare disease and MRI is a promising technique that may be useful to demonstrate the coronary artery tree. We report three patients who underwent cardiac MRI to investigate right coronary artery fistulae. On clinical examination, a continuous murmur was heard along the left sternal border, and chest X-ray showed moderate cardiomegaly with enlargement of right chambers in all patients. Transthoracic Doppler echocardiography showed fistulae in two cases; the third case was not demonstrated by transthoracic or transoesophageal echocardiography. MRI demonstrated the course of the fistulous vessels in all patients. All patients underwent surgical closure of their coronary artery fistulae. MRI may show detailed anatomy of congenital coronary artery fistulae and may be useful as an additional non-invasive method in their investigation.
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Introduction
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Congenital coronary anomalies occur in 1% to 2% of the population [1] and coronary fistulae comprise 14% of these anomalies, accounting for 0.1–0.2% of all patients undergoing coronary angiography [2, 3]. The most common origin is the right coronary artery (RCA) and a single termination is found in the majority of patients [1, 4]. In general, symptoms of angina, palpitations and cardiac failure may occur in patients aged over 30 years, with the cardinal clinical finding of a continuous murmur similar to a patent ductus arteriosus. This murmur is usually heard at the middle left or right sternal border or even at the lower sternal border [4].
The diagnosis may be established non-invasively by echocardiography, demonstrating the dilated coronary artery and the fistula (including its entry site into the chamber or vessel). Colour-flow mapping may be used to display flow abnormalities within the vessel [5].
Few reports describe the use of MRI to demonstrate coronary artery fistula [6–8]. We report three patients who underwent cardiac MRI, using a 1.5 Tesla Cvi GE magnet, a cardiac 4-element dedicated coil, with cine MR, double inversion recovery (IR), 2D spiral and 3D contrast enhanced angiography to investigate RCA fistulae.
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Case 1
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An asymptomatic 7-year-old girl was referred for assessment of a continuous murmur heard on the lower left sternal border. Clinical examination was otherwise unremarkable. Chest X-ray showed moderate cardiomegaly with enlargement of the right heart chambers. The electrocardiogram showed diffuse ST-T rectification. Transthoracic Doppler echocardiography showed mild dilation of the right cardiac chambers and a fistula from the RCA to the right ventricle. Cine MRI depicted mild right ventricular (RV) dilation, a tortuous and dilated vascular structure on the RV contour with flow turbulence in the posterior junction of the interventricular septum and the right ventricle in the short axis MRI (ECG triggered fast gradient echo, repetition time (TR)/echo time (TE)=9.7/5.3 ms, field of view (FOV)=30 cm, matrix=256 x 256, slice thickness=5 mm, number of excitations (NEX)=1, views per segment (VPS)=8, 20 cardiac phases/cycle). Cardiac catheterization and surgery confirmed the presence of a fistula from the RCA to the right ventricle (Figure 1
).
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Figure 1. MR images with the fistula course and entry site (A and B), the angiogram and the surgical closure (C and D). LV, left ventricle; RV, right ventricle.
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Case 2
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A symptomatic 10-year-old boy with complaints of dyspnoea and fatigue (New York Heart Association functional class II; NYHA II) had a continuous murmur along the left sternal border. Chest X-ray showed moderate global cardiomegaly. The electrocardiogram showed right ventricular hypertrophy and inferior wall ventricular repolarization abnormalities. Transthoracic Doppler echocardiography revealed a fistula from the RCA to the coronary sinus. MRI showed moderate right chamber enlargement and RCA origin dilation in the Double IR (i.e., black blood) sequence (ECG-gated double-inversion recovery fast spin-echo, TR/TE=2RR/41.4 ms, echo train length (ETL)=32, FOV=26 mm, matrix=256 x 256, slice thickness=5 mm). The RCA course and fistula entry site were demonstrated on ECG-gated 2D spiral sequence (TR/TE=10.6/6.0 ms, FOV=30 mm, matrix=256 x 256, slice thickness=4 mm). Cardiac catheterization was performed to confirm the MRI findings and the fistula was closed surgically (Figure 2).
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Figure 2. MR images with the fistula course and entry site (A, B and C) and the angiogram (D, E and F). RCA, right coronary artery; C. sinus, coronary sinus.
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Case 3
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A 20-year-old symptomatic female patient with symptoms of dyspnoea, syncope and chest pain (NYHA II) and a continuous murmur along the upper sternal border was referred for assessment. Chest X-ray showed moderate global cardiomegaly. The electrocardiogram was normal. Transoesophageal Doppler echocardiography revealed a ventricular septal defect and right coronary sinus aneurysm. The fistula was not clearly delineated. Double IR MRI sequence (ECG-gating double-inversion recovery fast spin-echo, TR/TE=2RR/41.4 ms, ETL=32, FOV=28 mm, matrix=256 x 256, slice thickness=6 mm) demonstrated right coronary sinus dilation at the level of the aortic root on both coronal and transverse planes. A 3D time of flight (TOF) contrast-enhanced MR angiography (TR/TE=5.1/1.2 ms, FOV=32 mm, phase FOV=28.8 mm, flip angle (FA)=45, NEX=1, matrix=256 x 160, slice thickness=3 mm/–1.5 overlap) clearly delineated the fistula from the RCA to the right atrium. The patient was operated on without cardiac catheterization (Figure 3).
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Figure 3. MR images with the fistula and entry site. Transoesophageal echocardiogram shows aortic valve leaflets with a dilated right coronary sinus. Ao, aorta; RCA, right coronary artery; RA, right atrium; NCS, non-coronary sinus; LCS, left coronary sinus; RCS, right coronary sinus.
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Discussion and conclusions
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About 55% to 65% of congenital coronary artery fistulae arise from the RCA and 90% of them drain into the lesser circulation. The right ventricle is the most common site of drainage (45%) followed by the right atrium (25%), pulmonary artery (15–20%) and coronary sinus (7%). Small fistulae draining into the pulmonary artery are more frequent from the left coronary artery and may rarely arise from more than one coronary artery (4–5%). Our findings of fistulae arising from the RCA and their different entry site locations are consistent with these reports [1, 4].
The clinical presentation of congenital coronary artery fistulae may vary considerably, dependent on their anatomy and the size of the fistulous connection to the left or right side of the heart. In general, symptoms are rare under the age of 20 years. Dyspnoea or congestive heart failure may occur and angina pectoris is seen in 80% of these patients over 50 years of age.
Doppler echocardiography is currently used as the non-invasive method to establish the diagnosis and evaluate management of coronary artery fistulae [9], however in one of our cases, the fistula was not clearly demonstrated even by transoesophageal echocardiography. New MR sequences have improved image quality with better anatomical definition [7, 8], and MRI has become an alternative method to evaluate anatomy, flow and function [6–8]. Cine MR sequences are useful to show dynamics and especially flow turbulence as seen at the entry site of our first case. Black-blood imaging has improved image quality over conventional spin echo sequences, allowing better visualization of the lumen and the vessel wall. Spiral imaging is a fast sequence [10] that is now available. This technique demonstrated the coronary dilation and entry site in our second case. Finally, the anatomy seen in the black-blood sequence was better defined by the 3D contrast enhanced angiography, allowing multiplanar reformatting in our third case. The MR images acquired in these three patients contributed better anatomical and physiological information than the echocardiography.
Cardiac catheterization is usually performed in order to confirm anatomy and plan surgical treatment. Our MR images matched the angiography findings in the first two cases so closely, that surgery was performed without catheterization in our last patient.
The closure of coronary artery fistulae at the time of diagnosis is recommended even in asymptomatic patients, since perioperative morbidity and mortality increases in older patients [11] and long-term results are excellent [12]. Our results confirm that MRI allows detailed delineation of cardiac anatomy and is useful as an additional non-invasive method in the diagnosis of coronary artery fistulae.
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Acknowledgments
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The authors wish to thank Ricardo Loureiro, MD for his technical assistance during the manuscript preparation.
Received for publication December 3, 2002.
Revision received June 27, 2003.
Accepted for publication August 20, 2003.
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References
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Abstract
Introduction
