Bland, White and Garland first reported the association of anomalous origin of left coronary artery from pulmonary artery with a hypertrophied left ventricle and attacks of dyspnea, pallor and profuse sweating in a boy who died at the age of 3,5 months . The estimated incidence of BWG syndrome is 1/300.000 live births (between 0,24% and 0,46% of all congenital cardiac anomalies). Some believe that this is a significant underestimation of the true incidence, as many patients may be asymptomatic until their death and therefore remain undiagnosed . BWG syndrome develops before birth when the systemic and pulmonary arterial pressures are equal and there is antegrade flow in both the left and right coronary artery. In the neonatal period, this gradually changes as the pulmonary blood pressure diminishes, the ductus arteriosus closes and the flow in the left coronary artery reverses. The development of collateral circulation between the right and left coronary artery during closure of the duct and lowering of the pulmonary pressure will determine the extent of myocardial ischemia. Patients with well established collaterals have been classified as the "adult type" and those with no collaterals as the "infantile type". Edwards believes that these functional states, actually represent different phases in collateral circulation and the changes engendered by each patient determine his clinical course. Rarely, patients may survive to the sixth or seventh decades of life .
Onset of symptoms is usually observed in the neonatal period. Beginning at 1 to 3 months, feeding or crying induces dyspnea, profuse sweating, pallor, fatigue and a semblance of pain. Between attacks, physical examination is frequently normal. Signs of heart failure and failure to thrive are common. However, cases of totally asymptomatic adult patients have been reported [7, 8]. Our patient had no symptoms until the age of 44 years and had 2 uncomplicated pregnancies and deliveries. Nightingale et al and Maeder et al similarly reported three patients with uneventful pregnancies [9, 10]. It can be presumed that the asymptomatic course of our patient was due to an optimal balance between sufficient collateral flow from the right to left coronary arteries, a minimal coronary steal from the pulmonary artery and a systemic blood supply to the left coronary artery. The possibility of atherosclerosis of the collateral circulation could be a reason why this patient at the age of 45 years became symptomatic. There was no proof for this systemic collateral supply but the continuous outflow of the blood from the left coronary ostium during extracorporeal circulation is a strong evidence. Magnetic resonance imaging and angiography were recommended to the patient postoperatively but she declined. There are three similar cases describing BWG syndrome with a possible systemic collateral supply [11–13]. Only in one of them, angiography confirmed systemic blood supply from a bronchial artery.
Electrocardiographic abnormalities of BWG syndrome include left axis deviation, abnormal Q-waves in leads I and aVL, poor R-wave progression resembling lateral myocardial infarction and left ventricular hypertrophy (with or without ST-segment depression). In theory, the more extensive the coronary collaterals, the better preserved the myocardial function due to lack of ischemia, although the degree of coronary steal may then become significant.
Pulmonary hypertension gradually develops because of combined left-to-right shunting, left ventricular dysfunction and mitral regurgitation. Mitral regurgitation is thought to result from the dysfunction of the ischemic papillary muscles and adjacent myocardium. Rarely, mitral regurgitation is due to prolapse or an associated lesion such as mitral cleft or short chordae . In our case severe regurgitation was due more to myxomatous degeneration of the mitral valve than ischaemic mitral regurgitation, as indicated by the pathological findings of the excised valve.
Surgery is recommended in patients with BWG syndrome, even in the absence of symptoms or a significant left-to-right shunt syndrome, given the risk of ventricular arrhythmias and sudden death . Whenever possible and especially in children, a 2-coronary system will be established by the direct implantation of the left coronary artery into the ascending aorta. Alternative options more preferable in adult patients include the ligation of the left coronary artery ostium combined with aortocoronary bypass grafting using venous grafts, the internal mammary artery or the radial artery . Reimplantation is technically difficult in adults because of stretching on the coronary repair and the friable nature of the dilated coronary artery. A simplified technique has recently described by Laks et al . According to this technique the left coronary artery and a cuff of pulmonary artery wall are excised as a button and transferred to the aorta. The defect in the pulmonary artery is replaced with a pericardial patch. The need to clamp the aorta in an ischemic myocardium probably contributes to the mortality with this procedure. The intrapulmonary technique designed by Takeuchi et al is another solution but has the potential disadvantages of pulmonary artery stenosis, aortic regurgitation or tunnel stenosis . In our case an off pump LIMA to LAD anastomosis was carried out initially, followed by ligation of the anomalous origin of the left coronary artery and mitral valve replacement. It is very difficult to say whether the patient's clinical improvement was due to the mitral valve replacement or correction of the coronary artery abnormality or both.
Although BWG syndrome is a rare condition presenting in adulthood, awareness of this congenital abnormality is important, since early diagnosis and treatment may prevent irreversible damage to the myocardium and subsequent complications including myocardial infarction, heart failure, mitral regurgitation and sudden death. Certain echocardiographic findings are highly suggestive of the syndrome, including the demonstration of a dilated right coronary artery arising from the aorta, a continuous blood flow from the left coronary artery into the pulmonary artery and visualisation of dilated interventricular septal collaterals. Diagnosis usually established by a coronary angiogram, which shows a dilated and tortuous right coronary artery with collateral filling of the left coronary system. Nuclear magnetic resonance imaging is also able to locate the origin of left coronary artery.
The present case illustrates that BWG syndrome can be asymptomatic over a long time, even during pregnancy. Systemic collateral blood supply to the coronaries may be the cause for the asymptomatic course and patient's survival.