Benign or Malignant Anomaly? Very High Takeoff of the Left Main Coronary Artery above the Left Coronary Sinus

Abstract

Very high takeoff of the left main coronary artery in the absence of another coronary anomaly is a rare finding. The pathologic consequences of this anomaly are unclear, and the literature on this subject does not agree on whether the condition is dangerous. We present our findings in 2 patients who were discovered to have this anomaly upon noninvasive computed tomographic coronary angiography, and we discuss our analysis of the literature and our management of these patients.

It is commonly assumed that the coronary arteries arise from the aortic sinuses rather than from the tubular aorta. Often, however, the coronary ostia are located above the sinotubular junction, usually by only a few millimeters.¹

Very high takeoff of the coronary ostia, well above the sinotubular junction, occurs in less than 1% of the population,² and data concerning this rare finding are confined to scattered case reports. Opinions differ as to whether these anomalies are benign or malignant.

We present images from computed tomographic (CT) angiograms of 2 patients in whom we found very high takeoff of the left main coronary artery (LMCA). We review the medical literature to arrive at recommendations regarding the appropriate definition of high takeoff and the management of patients with this finding.

The first patient, a 38-year-old man with atypical chest pain and strong risk factors for coronary disease, underwent evaluation by means of a treadmill stress test. He exercised for 7 minutes and achieved 91% of the predicted targeted heart rate without electrocardiographic (ECG) changes during the examination, but during the recovery phase he again experienced his presenting chest pain, with nonspecific ECG changes. Given these equivocal findings, we ordered a 64-slice computed tomographic coronary angiogram (CTCA).

The patient had only minimal coronary artery plaque, but he was found to have an anomalous LMCA—the origin of which was approximately 2.2 cm above the coronary sinus. There was no tortuosity of the ostium, and the orifice was normal in size and conformation (Fig. 1). Although the location of the ostium was unusual, we felt that the location and orientation of the artery was not an impediment to coronary flow and not the source of his chest pain.

Fig. 1 Patient 1. Coronary computed tomographic angiograms. A) Three-dimensional view of the coronary tree shows the takeoff of the left main coronary artery (arrow) high above the left coronary cusp. B) Multiplanar reformatted view shows the ostium of the artery to be approximately 22 mm above the aortic valve. C) “Navigator” view (as seen from inside and above the aortic valve) shows the downward orientation of the artery.

AoV = aortic valve; LM = left main coronary artery

This initial patient was monitored clinically for about a year without incident when a second patient with the same anomaly was seen. A 55-year-old man with a history of tobacco use and hypertension had experienced 3 or 4 episodes of chest pain in association with physical activity. He had minor, nonspecific ST changes at baseline. A stress echocardiogram did not show abnormalities of wall motion, but changes in his ECG with exercise suggested ischemia. A CTCA of the second patient's heart revealed no significant plaque, but a very high LMCA takeoff was noted (Fig. 2).

Fig. 2 Patient 2. Coronary computed tomographic angiograms in A) 3-dimensional and B) multiplanar reformatted views show a very high takeoff of the left main coronary artery from above the left coronary sinus. No significant atherosclerosis is noted.

LAD = left anterior descending coronary artery; LCx = left circumflex coronary artery; LM = left main coronary artery; RCA = right coronary artery

Discussion

The overall incidence of anomalous origin of the LMCA above the coronary sinus has ranged from 0.019% to 0.04% in catheterized populations.^3,4 In many cases, this seems to be a normal variant. In 44% of the cases examined by Vlodaver and colleagues,⁵ one or both of the coronary ostia arose above the sinotubular junction: most frequently the LMCA (30%), followed by the right coronary artery (8%), and by both vessels (6%).

A “high takeoff” is variably defined in the literature. Some authors classify any coronary artery with its origin above the sinotubular junction as anomalous. However, this definition appears to be inappropriately broad, because it includes many anatomically normal variants. Other authors restrict the definition of high takeoff to ostia that are more than 1 or 2 cm above the sinotubular junction. The highest reported origin of a coronary artery has been 5 cm above the sinotubular junction, in a case involving a right coronary artery.⁶

The rarity of very-high-takeoff coronary arteries reported in the clinical literature is illustrated by some large series. Alexander and Griffith⁷ noted high-takeoff coronary arteries (of any degree) in only 10 of 18,950 autopsies. Similarly, 4 recent, large, 64-slice coronary CT series^8–11 reported very low frequencies of coronary takeoff anywhere above the sinotubular junction: only 16 of 6,014, 6 of 700, 1 of 540, and 4 of 1,879 patients, respectively, had this finding. In one of the largest retrospective studies,³ a high takeoff of the LMCA occurred in 5 of 126,000 patients (0.013%).

The pathologic significance of a high-takeoff coronary ostium is debated. For example, Waller¹² suggested that coronary arteries with high takeoff are dangerous because they are linked to ischemia and sudden death, due to decreased coronary perfusion. Other investigators have suggested that the aortic sinuses are not “crucial in optimizing coronary arterial flow,” but are more important in the way that they affect valve closure.¹³ Some series³ have placed high takeoff in the category of “benign” findings, as long as it is not associated with an origin from the opposite coronary cusp.

In our review of the literature, we were not able to find any cases wherein a high-takeoff LMCA was associated with ischemia or sudden death independent of a well-recognized, dangerous coronary anomaly. For example, the case most cited is that of a 30-year-old athlete with sudden death during exertion who was found to have a high-takeoff right coronary artery, along with hypoplastic coronary arteries that extended only halfway to the apex of the heart.¹⁴ In common with that case, the few other reported cases of adverse events involving high-takeoff coronary arteries all displayed additional coronary abnormalities, such as hypoplastic coronary arteries, atherosclerotic disease, ostial stenosis, intramural tunneling, or a course between the aorta and pulmonary artery—all of which are well-recognized causes of ischemia and sudden death.^7,15–17

Although it is hypothesized that a high takeoff from the ascending aorta would impair coronary flow, there are no reports of in vivo hemodynamic studies, such as might be performed with a Doppler flow wire. Bellhouse and colleagues¹⁸ used a rigid model of the aorta to indicate that systolic flow velocity is diminished by positioning the coronary ostium outside of the sinus, but their description of methods and confidence limits was sparse, and their report ignored the importance of diastolic coronary flow. It is difficult to implicate, in isolation, a high-takeoff coronary artery as pathogenic.

We should recognize that high-takeoff coronary arteries might be predisposed to associated abnormalities, due to their location higher on the aorta. For example, single coronary arteries, in which the LMCA also supplies the right coronary distribution, frequently have a high takeoff.^19,20 There are reported cases wherein the vertically oriented proximal artery segment runs intramurally in the aorta, which can lead to compression and reduced flow.²¹ There appears to be a frequent association between high-takeoff arteries and abnormalities of their ostia (which are described as funnel-shaped or narrowed); again, that predisposes the patient to ischemia.²¹

High-takeoff coronary arteries can present challenges during catheter cannulation. When the anomaly has not been recognized, there have been cases of inadvertent transection and coronary cross-clamping during open-heart procedures.²² Computed tomographic coronary angiography enables a precise display of the relationship between the coronary ostia and the aortic sinuses, and it more easily defines anomalous origins of vessels than does conventional invasive angiography.²³ When a high-takeoff coronary artery is identified, CTCA appears to be ideally suited to further define the ostium and the course of the vessel, thereby enabling the discovery (or exclusion) of abnormalities that might produce ischemia.

Conclusion

We recently encountered 2 patients who presented with the unusual anomaly of high-takeoff LMCA. Both of these discoveries were made incidentally during the course of CTCA and probably would not have taken place before the adoption of this technology for the evaluation of low- to moderate-risk patients who present with chest pain. Although these patients were technically “symptomatic,” in neither case did we think it necessary to pursue revascularization, because the anomaly was not considered to be life-threatening and the pain was atypical of angina. During one or more years of follow-up, neither patient had any significant clinical events.

Given the increased use of CTCA, it is likely that more patients with this rare anomaly will be seen. Because a high-takeoff LMCA is often associated with other, dangerous anomalies, some care must be taken to define the location, orientation, and course of the artery. Our impression, formed as a consequence of our clinical evaluation and a thorough review of the literature, is that the finding of a very high takeoff of the LMCA in isolation is not pathologic and needs no further intervention.