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Clinical case: Long ectopic left main coronary artery
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This article is based on a case report published in the Journal "Case Reports in Surgery" in 2015, by Caroline C. Jadlowiec, Beata E. Lobel, Namita Akolkar, Michael D. Bourque, Thomas J. Devers, and David W. McFadden.
It has been modified and reviewed by Joel A. Vilensky PhD, Carlos A. Suárez-Quian PhD, Aykut Üren, MD.
Objectives
After reviewing this case you should be able to describe the following:
- The anatomical/physiological basis of stress (exertional) angina pectoris. How does it differ from a myocardial infarction?
- The anatomical basis of coronary angiography.
- What is the clinical value of a cardiac stress (treadmill) exam.
- The anatomical basis of heart dominance.
Case description
History and physical exam
A 35-year-old diabetic and hypertensive man presented with stress (exertional) angina pectoris. He was 5 feet tall and weighed 115 lbs. His vitals were stable and a cardiovascular system examination found nothing remarkable.
Paraclinical exams and imaging
There were no obvious signs of myocardial ischemia or infarction in the electrocardiogram. His treadmill test was strongly positive for a diagnosis of a stress induced myocardial ischemia.
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Echocardiography revealed normal left ventricular systolic function with an ejection fraction of 60% and insignificant mitral valve regurgitation. Coronary angiography was performed through the right radial artery route. During this procedure, the cardiologists probed for the LCA (left coronary artery or LMCA or left main coronary artery) from its typical origin from the ostium in the left aortic sinus but were unable to visualize it (Figure 1-2).
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Finally, the LCA was selectively cannulated from the right aortic sinus, and shown to branch into the anterior interventricular artery (or left anterior descending artery or LAD) and the CxA (Circumflex artery) (Figure 3). Thus this patient had a known but rare variant of the origin of his LCA. The angiogram also revealed critical stenoses in the CxA (Figure 3), which were presumably responsible for his angina.
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The RCA (right coronary artery) was visualized in its normal path and to be dominant in this patient (Figure 4).
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A CT angiogram was done a few days later to better show the anomalous origin of LCA from the right sinus that was seen on radiographic angiography. Further, a 3D reconstruction of the LCA based on the CT revealed that it travelled superiorly after its origin and then underwent a reverse U-turn, while it was coursing anteriorly over the right ventricular outflow tract (RVOT) before finally giving rise to the anterior interventricular artery and CxA (Figure 5).
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Anatomical and procedural considerations
The LCA normally arises from the left aortic sinus (sinus of Valsalva) and has a diameter ranging from 3 to 6 mm and a length ranging from 10 to 15 mm. In this patient, the artery’s length was close to 60 mm. The clinical significance of this especially long LCA is that this excessive length has to be considered if any interventional procedures are contemplated for this patient such as balloon angiography and placement of a stent to alleviate the patient’s exertional angina.
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LCA arising from the right sinus of Valsalva is a rare congenital coronary anomaly. This anomaly is either benign or serious; depending especially on the relation of the anomalous LCA to the aorta and pulmonary artery. Potentially, the most serious anomaly is associated with sudden cardiac death and warrants prophylactic coronary bypass surgery.
This particular patient’s anomalous left coronary artery had a prepulmonic course, anterior to the pulmonary outflow tract. This variant is not associated with sudden cardiac death. However, in some patients, the aberrant LCA originates from the right aortic sinus and then courses between the aorta and the pulmonary trunk (Figure 6). This variant is considered the most serious variant because the pressure in the larger vessels can likely compress the LCA, especially during strenuous exercise. This condition is believed to be responsible for “sudden cardiac death” in some young athletes.
Objective explanations
Objectives
- The anatomical/physiological basis of stress (exertional) angina pectoris. How does it differ from a myocardial infarction?
- The anatomical basis of coronary angiography.
- What is the clinical value of a cardiac stress (treadmill) exam.
- The anatomical basis of heart dominance.
Exertional angina pectoris: Anatomy and physiology
Angina pectoris, sometimes referred to as simply, angina, is the perception of chest pain, pressure, and squeezing sensations. It is most often associated with insufficient blood flow to the myocardium due to (partial) blockage or spasm in the coronary arteries (Figure 7). There is a surprisingly poor relationship between the severity of pain and the degree of oxygen deprivation in the myocardium (i.e., there can be severe pain with little or no risk of a myocardial infarction and an infarction can occur with little or no prior angina pain).
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Exertional angina pectoris is also referred to as stable angina because it only occurs when the heart is subject to stress as occurs during exercise, in some cases, even mild walking. When the patient rests, the pain resides. In a myocardial infarction, blood flow to a region of the myocardium is fully occluded and that specific area of heart muscle undergoes death and degeneration. Resulting mortality or morbidity depends on the size of the area affected and length of time the area is deprived of oxygen.
Coronary angiography: Anatomy
Coronary angiography is a radiographic procedure that uses contrast material to detect blockages in the coronary arteries that are caused by plaque buildup. The procedure is often done after chest pain, sudden cardiac arrest, an abnormal EKG, or an exercise treadmill test. For this procedure a catheter is threaded through an artery, typically the femoral or radial (in the case described here it was done through the radial artery). Using fluoroscopy the catheter is manipulated until it is in position at one of the aortic sinus ostia. Once there, the contrast material is injected through the catheter so that blockages to blood flow are highlighted, as shown in Figure 3. If blockages are found, percutaneous coronary interventions, such as coronary angioplasty and stent placement may be used to increase blood flow to the affected area of the heart. Or, if the blockage is severe, coronary bypass procedures may be surgically implemented.
Cardiac stress (treadmill) test
In a cardiac stress (treadmill) test the patient is asked to walk/run while on a treadmill and his cardiac signs and symptoms are monitored for any indication of coronary artery disease (CAD). Although a cardiac stress test may suggest CAD, it is not definitive and may suggest CAD when it does not exist or may fail to indicate CAD when the patient does have the condition (false positive and false negative results, respectively). Thus, although these tests are diagnostically useful, they are not 100% reliable.
Heart dominance
Coronary dominance is determined by whether the LCA (typically via the CxA) or RCA supplies the posterior interventricular artery (or inferior interventricular artery or posterior descending artery, PDA). 85% of hearts are right dominant. The remainder may be left dominant or co-dominant. In the latter, both the LCA and RCA contribute to the blood flow within the posterior interventricular artery.
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