Single Coronary Artery with the Absence of a Left Anterior Descending Artery

Congenital coronary anomalies are asymptomatic and usually go unrecognized until the time of sudden cardiac death, especially in young athletes participating in competitive sports.¹ The incidence of anomalous origin of coronary arteries ranges from 0.17% in autopsy studies to 1.2% in populations undergoing coronary arteriography.^2,3 Davis et al., in a recently published prospective series of 2,388 children, identified anomalous origin of coronary arteries by transthoracic echocardiography in 0.17% of the study population.4 Case Report. A 40-year-old white woman presented with intermittent hemoptysis, epistaxis, cough and dyspnea on minimal exertion. Her past medical history was significant for hypertension, and her only medication was captopril. Physical examination revealed a blood pressure of 106/70 mmHg, a pulse rate of 84 beats per minute, an oxygen saturation of 92% on room air, and elevated jugular venous pressure. Cardiac auscultation revealed a normal first heart sound, a fixed splitting of the second heart sound, with increased intensity of the pulmonic component, and a grade II/VI ejection systolic murmur in the pulmonic area. Laboratory evaluation at the time of admission revealed the following: white blood cell count of 8,200/mm³, hemoglobin of 14.1 mg/dl, hematocrit of 41.6%, platelet count of 185,000/mm³, prothrombin time of 15 seconds, with an INR of 1.2, partial thromboplastin time of 29 seconds, sodium level of 141 mEq/L, potassium level of 3.9 mEq/L, BUN of 13 mg/dl, creatinine level of 0.9 mg/dl, and glucose level of 85 mg/dl. A chest X-ray revealed prominent pulmonary arteries and no other significant findings. The electrocardiogram showed normal sinus rhythm, right axis deviation and right ventricular hypertrophy. The transthoracic echocardiogram findings were significant for color flow across the atrial septum, with a positive microbubble study (consistent with a septal defect at the atrial level), tricuspid regurgitation and an elevated right ventricular systolic pressure of 70 mmHg. Atrial septal defect of the secundum type was confirmed with transesophageal echocardiogram (Figure 1). There was no evidence of anomalous pulmonary venous drainage or any mitral valvular pathology. The echocardiographic findings were confirmed by right and left heart catheterization. Right heart catheterization revealed a step up in oxygen saturations at the mid-atrial level (Tables 1 and 2). Left heart catheterization (Figures 2, 3 and 4) showed the following findings: a) Failure to selectively engage the left Judkins catheter into the left sinus, and also by multiple aortic root angiograms (Figure 5). b) A large right coronary artery (RCA) originating from its normal origin at the right aortic sinus and running its normal course. c) The left circumflex artery originated from the proximal part of the RCA, then took a course anterior to the major vessels to supply the left side of the heart. d) Absence of a left anterior descending artery. Postcardiac catheterization course. The patient underwent a prostacyclin challenge test to assess the reversibility of pulmonary vascular resistance (PVR) at bedside. It showed a 32% reduction in the PVR at a peak dose of prostacyclin. Surgical repair of the fenestrated atrial septal defect (Figure 1) was performed, and even the surgical team could not locate the left anterior descending artery. The patient developed right heart failure in the postoperative period and was started on a prostacyclin drip which was successfully tapered off in 48 hours. The patient remained symptom-free during follow-up. Discussion. The single coronary artery was first described in 1903 by Banchi.⁵ The single coronary artery refers to the origination of both the the left and right coronary arteries from a single aortic sinus, without the origin of a coronary artery from the pulmonary trunk. In a study of 142 patients with a single coronary artery,⁶ the single coronary artery arose from right aortic sinus in 49% of patients, and from the left aortic sinus in 45% of patients. It also included some patients with a single coronary artery originating from the pulmonary trunk. Yamanaka et al. reported a single coronary artery arising from the right sinus of Valsalva in 0.019% of the population in a large series of 126,595 patients undergoing coronary arteriography.⁷ The combination of a single coronary artery originating from the right sinus of Valsalva and an absent left anterior descending (LAD) artery is an extremely rare abnormality. However, in our case, this rare anomaly was seen in a patient with a secundum-type atrial septal defect — an association that makes this an exceptional case report. It seems that this coexistence is a coincidental finding, as was also reported by Antonelli et al.⁸Classification. The single coronary artery has been classified according to three different systems that include the classification systems of Smith, Ogden-Goodyear and Lipton. Smith (1950). In 1950, Smith⁹ classified the single coronary artery into three groups. (I) Single coronary artery that follows the course of the right coronary artery (RCA), then continues into the left circumflex (LC) artery, which then continues as the LAD, or a single left main (LM) artery that branches into the LAD and the LC, the latter of which extends across the crux to form the RCA. (II) After its origin, the main trunk divides into the right and LM arteries, or into a RCA, LAD and LC, which then reach their standard locations. (III) The single coronary artery branches so atypically that there is little similarity to the coursing of the three major arteries. Ogden and Goodyear (1970). Ogden and Goodyear,⁶ in 1970, classified the single coronary artery into five types (depending upon the anatomic distribution of the branches), subdivided by the letters “R” and “L” to indicate the side of the ostial origin. Lipton (1979). Lipton et al.,¹⁰ in 1979, proposed a classification system using features of both Smith and Ogden and Goodyear. Lipton’s system offered a better explanation for angiographers. The anomalous coronary artery is first designated with letter the “L” or “R”, depending upon whether the ostium is located in the left or right sinus of Valsalva, respectively. It is then designated a group according to Smith’s classification. The final designation describes the relationship between the anomalous artery, the aorta and the pulmonary artery with the letters “A”, “B” and “P”, referring to “anterior”, “between” and “posterior” patterns. However, in our patient, the anatomy does not follow any of the classifications mentioned because of the absence of the LAD, along with the presence of a single coronary artery (Figure 4). The single coronary artery originating from the right aortic sinus¹¹ has also been categorized, as shown in Table 3. Coronary artery anomalies are also classified into benign or potentially serious anomalies. The most common variety of benign anomalies is an aberrant origin of the left circumflex coronary artery (LC) from the RCA, with a retro-aortic course of the anomalous circumflex vessel.¹² A single coronary artery is a rare condition, particularly in the absence of other heart anomalies. It is usually associated with a bicuspid aortic valve, mitral valve prolapse and ventricular septal defect. However, the coexistence of a single coronary artery with atrial septal defect has only rarely been reported in the literature. Anomalies of the LAD are seen most frequently in association with Tetrology of Fallot,¹³ since development of the the LAD is influenced by the development of the pulmonary conus. The coexistence of a coronary anomaly and ASD is probably incidental on the basis of different stages of ontological determination of the coronary arteries and the atrial septal defect (a single RCA is determined at an earlier embryological stage, i.e., horizons XVI through XIX, as compared to the atrial septum).¹⁴ A single coronary artery is usually associated with hypoplasia of the ventricles, since a lack of coronary circulation during embryologic development would induce hypoplasia of the dependent myocardium; conversely, myocardial hypoplasia would cause “hypoplasia” of its coronary branch.^15,16 In our case, there was no associated hypoplasia of any ventricle, probably due to an oversized opposite coronary artery, which represents an alternative coronary pattern. Anomalies of coronary arteries should be suspected in young patients presenting with syncope. LAD agenesis has been reported as a benign variant or as a hypoplastic coronary artery that can cause myocardial ischemia,¹⁶ conduction defects or sudden death at a young age.^17,18 Occasionally, when associated with other major cardiovascular malformations, the presentation may be more insidious due to symptoms from an associated cardiovascular abnormality, as was seen in our patient. Recognition of the single coronary artery is critical because proximal occlusion of the dominant artery could be fatal, and can also possibly be confused with atherosclerotic coronary artery disease. However ischemic symptoms are rare in this group of patients, particularly in the absence of atherosclerosis or valvular disease. It is important to recognize the anatomic relationships of these anomalies on cardiac angiography in order to determine the appropriate course of treatment or surgical intervention. Other imaging modalities, including computerized tomographic angiography, magnetic resonance imaging, three-dimensional magnetic resonance angiography, multiplane transesophageal echocardiography — and even contrast-enhanced electron beam computerized tomography — have been utilized to delineate the origin and course of these coronary anomalies. The interest in our case was sparked by the uniqueness of this anomaly and its implications. The possible mechanisms of symptomatology may include right ventricular overload due to the presence of an atrial septal defect leading to right ventricular enlargement and, consequently, symptoms such as dyspnea. Relief of our patient’s symptoms subsequent to the ASD repair suggests that the simultaneous surgical approach to both the coexisting congenital heart disease like ASD, and the high-risk coronary anomaly, should be recommended to prevent further clinical deterioration and future cardiac events.

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