Right Coronary Artery Arising from the Main Pulmonary Artery

Abstract

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A 30-year-old man was admitted to our hospital with incidental chest pain. Two-dimensional transthoracic echocardiography revealed a dilated vessel in front of the aorta. Color-flow Doppler echocardiographic imaging showed a retrograde, chiefly diastolic flow from near the pulmonary valve into the main pulmonary artery (Fig. 1) and adequate intercoronary collateral vessels within the ventricular septum, anterior wall, and inferior wall. The origin of the right coronary artery (RCA) was not visible from the right sinus of Valsalva. The configuration of the RCA appeared to be anomalous. On the basis of the echocardiographic findings, the diagnosis of anomalous origin of the right coronary artery from the main pulmonary artery (ARCAPA) was made. Subsequent 64-multislice computed tomographic 3-dimensional reconstruction imaging of the coronary arteries confirmed the echocardiographic diagnosis, and 3-dimensional computed tomographic volume-rendered reformation showed only a single large left coronary artery that arose from the ascending aorta. The left anterior descending coronary artery was noticeably dilated and particularly tortuous (Fig. 2). An enlarged and tortuous RCA originated at the main pulmonary artery and coursed in front of the aorta (Fig. 3), and there was a mesh of thin collateral vessels between the RCA and the left coronary artery (Fig. 4). Curved multiplanar reconstruction imaging showed that the RCA arose from the pulmonary artery. The RCA was markedly denser than the pulmonary artery and was approximately as dense as the aorta (Fig. 5). This indicated a coronary steal phenomenon. Because the patient was only mildly asymptomatic, he declined surgical correction.

Fig. 1 Color-flow Doppler echocardiography (short-axis view) shows an abnormal retrograde blood flow (chiefly in the diastolic phase) into the main pulmonary artery.

AO = aorta; LA = left atrium; PA = pulmonary artery; RA = right atrium; RCA = right coronary artery

Real-time motion image is available at www.texasheart.org/journal.

Fig. 2 Three-dimensional, 64-multislice computed tomographic volume-rendering reformation displays the left coronary artery (LCA) arising from the ascending aorta (AO), and the dilated and tortuous left anterior descending (LAD) and left circumflex (LCX) coronary arteries.

Fig. 3 Three-dimensional computed tomographic volume-rendered reformation shows enlarged right coronary artery's origin from pulmonary trunk and its course in front of the aorta.

AO = aorta; PA = pulmonary artery; RCA = right coronary artery

Fig. 4 Three-dimensional computed tomographic volume-rendered reformation displays a mesh of thin collateral blood vessels between the right and left coronary arteries.

Fig. 5 Curved multiplanar computed tomographic reconstruction shows the right coronary artery (RCA) arising from the pulmonary artery (PA). The RCA was markedly denser than the pulmonary artery and was approximately as dense as the aorta (AO).

Comment

Anomalous origin of the RCA from the main pulmonary artery is a rare congenital cardiac malformation. No more than 80 cases of ARCAPA have been reported. Most patients with isolated ARCAPA are, like our patient, asymptomatic when diagnosed, because they usually have adequate intercoronary collateral vessels to maintain perfusion of the RCA territory and good ventricular function.¹ Our patient's left ventricular systolic function was normal, and his left ventricular ejection fraction was 0.58. Nonetheless, the collateral vessels can produce a coronary steal phenomenon due to the relative differences in diastolic pressure between the pulmonary and the systemic arterial beds,² and the steal can lead to myocardial ischemia and even sudden death during increased myocardial oxygen demand. Surgical correction with implantation of the aberrant vessel into the aorta is recommended.³

Early detection and evaluation of coronary artery anomalies are essential because of the risk of sudden cardiac death. Echocardiography is helpful in the early detection of ARCAPA and is a rapid, inexpensive, noninvasive method. Computed tomographic 3-dimensional reconstruction imaging of the coronary arteries is also recommended in order to evaluate the degree of shunting and to view the entire length and the extent of tortuosity of the RCA.