Anomalous origin of the left anterior descending artery from a separate ostium of the right sinus of Valsalva with abnormal stress test

The incidence of anomalous origin of the coronary arteries in the general population is unknown. Widespread application of coronary arteriography has resulted in more frequent detection of anomalies, and their clinical significance is becoming better appreciated. In reports from various cardiac catheterization laboratories, the incidence of all coronary anomalies ranges between 0.3% and 1.0%, with a prevalence of 0.3% at postmortem examination.¹,² The finding of a left anterior descending (LAD) artery originating from the right sinus of Valsalva is extremely rare. In a single report describing 39 patients found to have an abnormal origin of 1 or more coronary arteries, only 1 patient had an LAD artery that arose from the right sinus of Valsalva, and this was reported to occur in a patient with congenital heart disease.³ In the literature, a case of all 3 coronary arteries arising from 1 ostium of the right sinus of Valsalva and a case of a LAD artery arising from the right coronary artery have been reported.⁴,⁵ We report a case of an anomalous origin of the LAD coronary artery from a separate ostium of the right sinus of Valsalva without any congenital or acquired defects.

Case Report

A 67-year-old man with a history of previous smoking, hypertension, and type 2 diabetes mellitus was referred for coronary angiography after an abnormal response to a stress test. The patient underwent a stress test with Cardiolite (technetium-99 sestamibi for injection) as part of his preoperative evaluation for transurethral resection of the prostate. The patient's resting electrocardiogram (ECG) showed sinus rhythm with normal axis and intervals. There were voltage criteria for left ventricular hypertrophy, with associated mild, nonspecific ST-segment abnormalities. The patient had achieved a heart rate of 90% of the age-predicted maximum. He did not have any symptoms during and after exercise. At peak exercise, he had approximately 3 to 4 mm of upsloping ST-segment depression in the inferior leads as well as 2 to 3 mm of horizontal ST-segment depression in the anterolateral leads. During recovery, the ECG abnormality returned to baseline. Myocardial perfusion imaging showed decreased uptake in the anterior, apical, and inferolateral walls, and there were reversible defects, with a left ventricular ejection fraction of 55%.

Results of the patient's physical examination were normal except for a blood pressure of 180/90 mm Hg. Cardiac catheterization showed that a left main artery bifurcated into the ramus intermedius and left circumflex artery. The ramus had 50% stenosis proximally, and a small (2-mm) branch had 90% stenosis in the ostial portion. There was no hemodynamically significant stenosis in the circumflex artery. The right coronary artery arose from the right coronary cusp and had a normal course (Figure 1). There was mild disease in the right coronary artery. A separate anomalous small-sized left anterior descending artery was noted arising from the right sinus of Valsalva. It gave rise to a first septal artery at its origin and a diagonal branch. The anomalous LAD artery crossed the anterior free wall of the right ventricle, passing to the left and upward before it turned toward the apex. This course was described by Ishikawa and Brandt⁶ as a cranial anterior loop (Figure 2). The vessel had 40% stenosis at the distal portion but had no other hemodynamically significant narrowing, with no acute angulation, torsion, kinking, or interarterial course.

Figure 1. Right coronary

artery from the right sinus of Valsalva in the right anterior oblique projection.

Figure 2. Anomalous origin of the LAD artery

arising from a separate ostium of the right

sinus of Valsalva adjacent to the right

coronary artery and forming a cranial anterior

loop as it passes over the free wall of the right ventricular infundibulum near the pulmonary

valve. Close to its origin, it gives rise to the

septal artery. (Left) Right anterior oblique

view; (Right) steep left anterior oblique view.

Discussion

The origin of the LAD artery from the right sinus of Valsalva without associated congenital cardiac defects has been rarely described in the literature. There are several courses angiographically described: (1) anterior free wall course, in which the LAD artery follows the course of the conus branch, coursing to the left side of the heart anterior to the right ventricular infundibulum; (2) septal course, in which the artery runs an intramuscular course through the septum, along the floor of the right ventricular outflow tract; and (3) interarterial course, in which the LAD artery passes between the aorta and pulmonary trunk.⁶

In the absence of severe atherosclerosis, myocardial ischemia can occur in the case of a left coronary artery arising from the right coronary artery and coursing between the aorta and pulmonary artery (interarterial). This has been associated with myocardial ischemia and sudden cardiac death.⁷ The mechanism in this case is most likely transient occlusion of the left coronary artery caused by an increase in blood flow through the aorta and the pulmonary artery, resulting in kinking or pinching of the artery.⁷

In this patient, we did not place a catheter in the pulmonary artery during angiography. This would have more clearly demarcated the main pulmonary artery and may have helped in confirming the course of the anomalous LAD artery. However, using the classification set forth by Ishikawa and Brandt⁶ regarding the course of the LAD artery in right anterior oblique and left anterior oblique views—a cranial anterior loop for right ventricular anterior free wall course near the pulmonic valve—we feel confident that the course is the same as we have described. Ischemia can occur in this course, but it is rare, and its cause is unclear.⁸

Conclusions

We have presented a case of an anomalous origin of the LAD artery from a separate ostium in the right sinus of Valsalva, coursing the anterior free wall of the right ventricle. Exercise testing with Cardiolite strongly indicated exercise-induced hypoperfusion. However, we were unable to identify the mechanism of ischemia.