Only a few cases of a single coronary ostium and retroaortic course of the coronary artery have been described. Almost all cases reported so far had additional coronary artery or valvar disease. However, myocardial ischaemia may be caused by the coronary malformation alone. A 40 year old woman with severe myocardial ischaemia in the absence of clinically relevant coronary atherosclerosis is described. To clarify the origin and mechanisms of ischaemia, intracoronary Doppler, pressure and ultrasound studies were performed using microtransducers. In its outer portion along the course behind the ascending aorta, coronary blood flow velocities were increased, there was an external elliptical compression, and distal coronary flow reserve was reduced. Furthermore, an overshoot in diastolic pressure above aortic pressure was detectable within this portion. Dobutamine stimulation exaggerated the observed intracoronary haemodynamics and induced myocardial ischaemia. The intracoronary diagnostic procedures performed were helpful in clarifying the pathophysiological mechanisms of functional coronary obstruction and ischaemia in this malformation. Bypass surgery was successfully performed with symptomatic improvement.
- coronary anomaly
- intravascular ultrasound
- single coronary ostium
- congenital disorders
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A solitary coronary ostium in or immediately cephalad to the right aortic sinus and the course of the left coronary artery dorsal to the ascending aorta is a very rare congenital anomaly. This coronary malformation has been classified as the type IV.A.2a according to the classification of Roberts.1 At present, only a few cases with this abnormality have been described in the literature. In most of these patients, the diagnosis was incidental either during angiography or necropsy. Most patients had significant concomitant coronary atherosclerosis causing symptoms of angina, or myocardial ischaemia and infarction.2-4 Even in the absence of severe coronary atherosclerosis, myocardial ischaemia can occur in cases of anomalous origin of the left coronary artery from the right sinus of Valsalva, if the left coronary artery passes posterior to the aorta.5The pathophysiological mechanisms leading to myocardial ischaemia in the absence of coronary artery disease are incompletely understood. This is in contrast to other coronary anomalies where the left coronary artery arises from the right coronary artery and courses between the aorta and pulmonary artery (interarterial or intertruncal course). This has been associated with myocardial ischaemia and sudden death.6-10 The mechanism in this scenario is most likely a 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.5 ,6 In contrast, in the abnormality presented here, coronary obstruction is usually absent on angiography.11
We present the first report describing myocardial ischaemia, and its potential pathophysiological mechanisms, in a patient with a left coronary artery originating from the right sinus of Valsalva coursing posterior to the aorta in the absence of clinically relevant coronary atherosclerosis.
A 40 year old woman reported a four week history of exercise induced angina pectoris; ST segment elevation was documented during bicycle ergometry in the anterior electrocardiographic leads (V2–V5) (fig 1). Immediately after exercise testing, torsade de pointes occurred. There was no history of coronary artery disease or hypertension. The patient had a history of cigarette smoking for a few years before admission. Physical examination revealed an otherwise healthy woman. Coronary angiography revealed a solitary ostium in the right aortic sinus associated with an aberrant retroaortic course of the left coronary artery (figs 2 and 3). There was a 30% atherosclerotic stenosis in the mid-portion of the right coronary artery. Despite several additional angiographic projections, it was impossible to demonstrate a significant phasic luminal narrowing of the left main within its retroaortic course.
Intracoronary Doppler flow velocity and pressure measurements using miniaturised 0.014 inch guidewire transducers and intravascular ultrasound were performed at rest and during dobutamine stimulation.12-16 Intravascular Doppler showed only slightly increased blood flow velocities along the curved retroaortic segment of the left main stem (arrow, fig 3), which were enhanced during intravenous infusion of dobutamine (5–20 μg/kg) (fig 4A), compared with measurements at rest (fig 4B) and with measurements at the proximal or distal portions of the left coronary artery (not shown). Distal coronary flow reserve, measured as the ratio of maximal flow velocity after stimulation with 12 mg of intracoronary papaverin to baseline flow velocity, was significantly reduced at 1.7.17
Intracoronary pressure measurements demonstrated a local overshoot in diastolic pressure (fig 5) at the site of accelerated flow velocity within the course of the left descending coronary artery. In vitro validation of pressure measurements within squeezed coronary segments using the 0.014 inch pressure microtransducer has recently been demonstrated.18 Intravascular ultrasound demonstrated only a slight systolic and diastolic reduction of cross sectional area at this portion (fig 4A) compared with a normal distal portion (fig 4B), without signs of atherosclerosis. Measurements during intravenous infusion of dobutamine demonstrated augmentation of blood flow velocities and of intravascular pressure (fig 5), and a further reduction in cross sectional area. Moreover, angina symptoms with ST segment elevation in the anterior leads occurred similar to those during exercise testing. In view of the severity of symptoms and objective evidence of ischaemia and ischaemia induced malignant arrhythmias, the patient had aortocoronary bypass surgery with the left internal mammary artery to the left anterior descending coronary artery. Intraoperatively, the course of the left coronary artery behind the aorta was confirmed. No relevant stenosis of the left coronary artery along its course was evident. At eight weeks’ follow up the patient was free from angina, and arrhythmias did not occur during or after exercise testing.
Congenital coronary malformations are rare causes of angina, myocardial infarction or malignant arrhythmias.19 Usually, the diagnosis is incidental and clinical symptoms are attributed to other associated disorders, most commonly coronary artery disease. Five possible anatomical anomalies with a single coronary orifice in the right sinus of Valsalva with different clinical implications are known.
The left coronary artery crosses between aorta and pulmonary artery (interarterial, intertruncal). This anomaly has been associated with sudden death from coronary obstruction during or shortly after exercise in otherwise healthy subjects5-10
The left coronary artery crosses anterior to the pulmonary infundibulum, in which the left coronary artery is a branch of the conus branch of the right coronary artery. Myocardial ischaemia can occur, but is rare and its cause unclear5
The left coronary artery has a septal (intermuscular, subpulmonic) course within the crista supraventricularis and the ventricular septum. Several case reports have been reported with this anomaly but without any clinical significance20 ,21
The left coronary artery crosses posterior to the atrioventricular valves, which is known as the most common course without clinical relevance
The left coronary artery crosses posterior to the aorta (retroaortic), which is the case here, and in which myocardial ischaemia may occur but its mechanisms are unknown.
None of the mechanisms for myocardial ischaemia suggested above can be invoked in the present anomaly, as the retroaortic course of the left main stem would not explain external vessel compression or obstruction at its origin. In addition, none of the previously reported patients with this coronary anomaly had overt ischaemic symptoms or myocardial infarction (or scar tissue at necropsy) that could be related to the malformation. However, this report demonstrates the early onset of severe angina with anterior ST segment elevation and ischaemia induced malignant arrhythmias in a patient without significant coronary artery or other heart disease. Coronary angiography was unrevealing in terms of the cause of ischaemia. Intracoronary Doppler flow velocities at rest were only slightly increased; however, coronary flow reserve during hyperaemic provocation was significantly reduced indicating the presence of a functional obstruction. Dobutamine stimulation resulted in a further increase in flow velocities and ECG changes with significant ST segment depression and angina symptoms. Furthermore, use of an intracoronary pressure transducer made it possible to identify a localised pressure phenomenon that occurred at the most “external” point of the retroaortic course of the left main stem as illustrated in fig 3. The pressure curves were characterised by an overshoot in diastolic pressure above the aortic diastolic pressure. The existence of higher intramural than aortic or intraventricular pressures has been described before, and a similar pressure phenomenon with higher intracoronary than aortic pressures was recently validated in vitro and in patients with myocardial bridges.18 ,22 ,23 In these intramural courses of coronary artery segments, the overshoot in systolic pressure is most likely caused by a central high pressure segment connected to more compressed proximal and distal segments.
Intravascular ultrasound demonstrated an external phasic diastolic vessel compression producing an elliptical shaped vessel lumen that was most evident during dobutamine stimulation. This phenomenon did not occur in any other portion of the coronary artery.
The intracoronary haemodynamic alterations were most likely caused by the diastolic extension of the aortic bulbus and sinus of Valsalva compressing the left main coronary artery at the outer most portion of its retroaortic course. Most likely, the left coronary artery was unable to compensate for the expansion of the aortic bulbus by its own motion as the vessel was more or less fixed at the aortic origin and during its distal course. Intraoperatively, it appeared that the left main stem was compressed at the above described location, while the other segments of the left coronary artery were completely normal. It remains unclear why the patient was asymptomatic until age 40 and why symptom onset was relatively sudden; reduced flexibility of the elastic properties of the vessel wall by age might in part serve as an explanation.
In summary, we demonstrate a case of severe myocardial ischaemia in a patient with a single coronary orifice in the right sinus of Valsalva and a retroaortic course of the left coronary artery. Intravascular diagnostic procedures at rest and during pharmacological stimulation demonstrated the mechanisms leading to myocardial ischaemia in this rare coronary anomaly. Intracoronary Doppler, pressure and ultrasound measurements were clearly of benefit in this patient in diagnosis and hence in guiding treatment.