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Because of the variety of their anatomy and clinical implications, coronary anomalies tend to confuse many observers. Recently, our group and other investigators have proposed that only 1 specific type of anomaly, by means of a specific mechanism, is able to cause both symptoms of myocardial ischemia and sudden death. This anomaly is known as anomalous origin of a coronary artery from the opposite sinus of Valsalva, with intramural course (ACAOS). Its defining pathophysiologic feature is that the proximal section of the ectopic artery has an intramural course, which leads to variable degrees of functional obstruction. Herein, we describe an unusual, previously unreported coronary anomaly: a “normal origin” of the left main coronary artery from the left sinus of Valsalva that resulted in progressive, critical ischemia. The proximal few millimeters of this artery were intramural, embedded into the aortic-sinus wall, and laterally compressed. Therefore, this anomaly may be regarded also as “ACAOS of the left coronary artery without an ectopic origin.” Angiography and intravascular ultrasonography revealed a variable degree of obstruction without intimal thickening and, likely, without spasm. Surgical repair, including ostioplasty, completely relieved the patient's clinical symptoms.
The coronary arteries supply the metabolic needs of the cardiac parenchyma. Arterial anatomy varies greatly from one individual to another. Only a detailed analysis of the involved morphology can determine both the normal range of variation (frequently defined as what is seen in more than 1% of a large, unselected population) and the variable functional consequences and clinical manifestations.1–4 Coronary origination depends on various fundamental factors, including the number, location, size, and intrinsic structure of the ostia.1 One of the less recognized features that defines the normality of the coronary ostia is the orientation of the proximal left main trunk. Normally, this structure is oriented at grossly a 90° angle with respect to the aortic wall. Here, we describe a previously unreported anomaly in which the left main trunk originated at a normal location, from the middle section of the left sinus of Valsalva, but had an exceptional anterior and inferior tilt, an intramural (aortic sinus) proximal course, and some degree of stenosis. Because of progressive ostial narrowing and worsening symptoms, surgical correction was required.
A 56-year-old woman was admitted to our hospital for a history of crescendo angina. At age 44 years, she had undergone repair of an atrial septal defect. At that time, preoperative coronary angiography showed no evidence of coronary artery disease. The patient also had congenital kyphoscoliosis of the dorsolumbar spine. As a child, she had undergone surgery for a cleft palate and an imperforate anus. Five years before the present admission, she underwent nuclear stress testing because of dyspnea during mild exertion and ST-segment depression during treadmill exercise; nuclear scintigraphy yielded normal results. Subsequently, the patient developed hyperlipidemia, systemic hypertension, and eventually recurrent chest pain that suggested myocardial ischemia. Because this condition rapidly progressed to angina at rest, accompanied by dyspnea, coronary angiography was recommended.
Upon admission to our hospital, the patient had a normal resting electrocardiogram. Selective coronary angiography revealed a critical stenosis of the left anterior descending coronary artery (LAD) just distal to the bifurcation of the circumflex artery (Fig. 1). Cannulation of the left main trunk with a Judkins left-sided diagnostic catheter proved unusually difficult, which suggested that the artery originated tangentially; nevertheless, it clearly originated from the middle section of the left sinus of Valsalva near its upper border (Fig. 1A). In different angiographic views, varying degrees of stenosis or spasm (or both) of the proximal left main coronary artery (LMCA) were observed (Fig. 1). Intravascular ultrasonography (IVUS) was performed to determine whether the source of the problem was spasm or a fixed, plaque-related ostial stenosis. On IVUS, the proximal LAD showed diffuse intimal thickening that caused severe luminal obstruction (Fig. 2). The proximal 5 mm of the LMCA (Fig. 2B) revealed absence of intimal thickening; lateral compression of the lumen, with mild systolic worsening; mild hypoplasia (a smaller circumference) with respect to the more distal portion of the artery (Fig. 2); and an acutely angled left main ostium (with the C sign,4 typical of tangential origin). The systolic cross-sectional-area stenosis was calculated as 50%. On the basis of these findings, we decided to proceed with stent-angioplasty of the LAD. A 3 × 23-mm Cypher® stent (Cordis Corporation, a Johnson & Johnson company; Miami Lakes, Fla) yielded excellent angiographic results (Fig. 3).
The patient remained asymptomatic for 45 days but then developed unstable angina and electrocardiographic signs of diffuse subendocardial ischemia at rest. When readmitted to our coronary care unit, she had a blood pressure of 80/60 to 100/70 mmHg. She also experienced recurrent resting chest pains and dyspnea, which quickly responded to sublingual nitroglycerin. Repeat angiography showed that, despite nitroglycerin administration, the ostial left main stenosis had progressed to critical degree, without in-stent restenosis at the LAD (Fig. 4).
The patient consented to surgical correction of the coronary anomaly, which was performed with the aid of extracorporeal circulation and retrograde and antegrade cardioplegia. Exploration of the aortic root through a transverse aortotomy revealed typical tangential origination of the left coronary artery (LCA) from a slit-like ostium, located just above the middle portion of the left sinus of Valsalva (Fig. 5). The proximal LCA seemed to be directed inferiorly, over the left sinus of Valsalva, and an ostial flap or flail membrane appeared to be present; the “membrane” seemed to be capable of moving to a more or less obstructive position, depending upon expansion of the aortic root. The extramural LCA was thoroughly explored in order to determine the exact anatomy of the defect. To correct the anomaly, we resected the “ostial membrane” and marsupialized the left main extramural segment after performing extensive microdissection to enable tissue transfer without undue tension. The patient recovered uneventfully and was discharged from the hospital after 6 days.
Three months after surgery, follow-up evaluation of the patient confirmed a continued absence of dyspnea, chest pain, and resting electrocardiographic ischemic changes. Routine follow-up computed axial tomography (Fig. 6) showed that the new LCA ostium was now located caudally—in the middle portion of the left sinus, along a vertical axis—and not at the sinotubular junction as before surgery. Cross-sectional and volume-rendering analysis suggested the presence of mild proximal LCA stenosis just past the coronary ostium. Echocardiography showed normalization of left ventricular systolic function; however, moderate pulmonary hypertension (peak pressure, 60 mmHg) persisted, likely secondary to the atrial septal defect that had not been repaired until the patient was an adult.
To our knowledge, this is the 1st report to describe a left main trunk with a tangential origin and an intramural course (as is typical of an anomalous coronary artery arising from the opposite sinus [ACAOS]2) in the absence of a clearly ectopic origin. Apparently, the essence of our patient's anomaly was an inferior tilt of the LMCA, which originated normally from the middle section of the left sinus. The defect in the LCA's course involved a short intramural segment, which appeared to undergo varying degrees of lateral compression (as shown by 3 angiographic studies performed over 5 years) and which correlated with progressive symptoms of angina and dyspnea. In ACAOS, spasm is a highly unlikely mechanism of variable stenosis, because no circular media is present around the intramural proximal LCA (the coronary artery shares its media with the aortic wall in such cases2,3). In our patient, intermittent displacement of the membrane (which was the inner wall of the aorta) likely accounted for the variable clinical manifestations and the angiographic appearance—a behavior that has not previously been reported. Aortic root dilation secondary to hypertension was the likely reason for the progressive ischemia in this middle-aged woman.3
Our interest in the detailed functional anatomy of ectopically originating proximal coronary arteries, as in ACAOS,2–5 has led us to recognize that, in several specific conditions,3 the ectopic coronary artery consistently has an intramural proximal course and a varying degree of lateral compression. These conditions include ectopic origination of the LCA from the right sinus of Valsalva (with a preaortic course); the right coronary artery from the left sinus of Valsalva (preaortic course); and the LCA from the noncoronary sinus of Valsalva (retroaortic course).3–5
When IVUS is used to study an ectopic, tangential origin of a coronary artery, subselective advancement of the relatively rigid, bulky guiding catheter may result in catheter-tip-related artifacts. Indeed, the catheter can potentially cause straightening and subtending of the severely stenotic, pliable arterial wall (ostial “membrane”) that is seen at a slit-like ostium.3 In addition, when guiding-catheter support is noncoaxial, the IVUS catheter's recording element may undergo systo-diastolic back-and-forth motion, which could be mistaken for phasic narrowing of the stenotic vessel. These observations point to the need for refinements in alternative, noninvasive technologies, such as multislice multidetector computed tomography.3 Although the latter technique is currently not as precise as is IVUS imaging,3 the next generation of radiologic equipment could feature crucial improvements. In our patient, accidental “transient” stenting of the LCA ostial stenosis indeed could have been the reason for the initially benign appearance of the lesion during IVUS evaluation (Fig. 3).
Several hypotheses might explain why our patient's coronary artery had a normal origin yet took an intramural course. This anomaly might be related to subtle rotation of the aortic root with respect to the dependent myocardial territories.6 In fact, if the aortic root were slightly malformed and congenitally rotated counterclockwise, as seen from the cephalic end, an otherwise normally positioned LCA would tend to have a tangential origin and, hence, a chance to develop a proximal intramural course, resulting in the anatomophysiologic changes observed here. Such a mechanism could not be confirmed by computed tomographic angiography in our patient.
Alternatively, the intramural location of the proximal LCA could be related to even a slight cranial displacement of the ostium at the sinotubular junction. (This would reopen the question, “What is the precise, normal location of the left coronary ostium?”) In our patient, this theory is supported by a comparison of the preoperative and postoperative images (Figs. 1 and and6).6). Postoperatively, after the removal of the inner wall of the ostial LCA (unroofing), the ostium moved caudally, without being reimplanted, along the vertical axis of the left sinus, to reach a mid-sinus position—in contrast with its preoperative location at the sinotubular junction. It is implicit in this theory that the LCA's “high origin” (although still within the currently accepted normal range of its locations) will lead to a risk that the proximal artery will have an intramural course, as in ACAOS.
Another theory—that the left main ostium could have undergone external compression from the dilated and hypertensive main pulmonary artery7–9—is not sustainable in our case because of the compelling surgical finding of the intrinsic nature of the abnormal architecture (an intramural, tangential coronary origin).
In view of the present case, an inferior tilt of a dominant LCA needs to be considered as a possible cause of ostial left main stenosis. The use of IVUS is essential to differentiate this condition from the more common atherosclerotic forms of stenosis. Manifestations of clinical ischemia can vary with time, ranging from subtle to dramatic. In similar cases, significant stenosis is difficult to define even on angiographic grounds, because the stenosis may appear to be severe only in some projections (Figs. 1 and and44).
In patients such as ours, surgical treatment is clearly the best solution; however, it necessitates the use of delicate techniques that must be tailored to the individual anatomy in each instance.5
“Left ACAOS without an ectopic origin” is a previously unreported coronary anomaly that can cause severe clinical manifestations. In addition to being interesting in its own right, our case is relevant to the ongoing discussion regarding the definition of normal coronary anatomy. If the anatomic spectrum of normality is defined by strictly statistical criteria,1 then variants such as the present one could be “normal” on an anatomic basis but quite abnormal with respect to physiology and prognosis. For now, it remains to be clarified how often this coronary ostial location involves an intramural course.
We thank James Philpot, of the Department of Visual Communications Services, Texas Heart Institute at St. Luke's Episcopal Hospital, for his assistance in preparing the figures.
Address for reprints: Paolo Angelini, MD, P.O. Box 20206, Houston, TX 77225-0206