Show notes
CardioNerds (Amit Goyal & Karan Desai) join Massachusetts General Hospital cardiology fellows (Daniel Pipilas, Rachel Frank and Kemar Brown) on a luxurious sailboat for iced coffees and Modern Pastry delicacies! They discuss a rare case of Anomalous Left Coronary Artery from the Pulmonary Artery (ALCAPA). Program director, Dr. Doreen DeFaria Yeh provides the E-CPR and a message for applicants. Episode notes were developed by Johns Hopkins internal medicine resident Evelyn Song with mentorship from University of Maryland cardiology fellow Karan Desai.
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Patient Summary
A women in her early 30s who's a Jehovah's witness presented with three days of intermittent chest pain. Past medical history included anxiety. Initial vitals and physical exam were unremarkable. Labs were notable for an elevated troponin T of 360 ng/L and a low TSH of 0.02 mIU/L with an elevated free T4 of 5.1 ng/dL. EKG demonstrated lateral and inferior ST depressions. TTE demonstrated a normal LVEF of 58% with a subtle anterolateral wall motion abnormality. Given her lack of conventional risk factors for CAD, resolution of her chest pain, and downtrending troponin, coronary CTA was obtained next which did not show any CAD but demonstrated an anomalous left main coronary artery (LMCA) arising from the main pulmonary artery with evidence of left to right shunting from the left main into the PA and extensive coronary and bronchial collateralization. The anterior wall hypokinesis was also seen on CT, consistent with ischemia due to myocardial steal phenomenon. Given the abnormal thyroid function tests, thyroid US was also obtained which showed patchy heterogeneity consistent with thyroiditis. Ultimately, the patient was diagnosed with ALCAPA and her chest pain was attributed to steal phenomenon due to hyperthyroidism and increased cardiac demand. She was treated with long-acting nitrates and beta-blocker with resolution of symptoms and was referred to cardiac surgery on discharge.
After a multidisciplinary discussion involving the cardiac surgery team, patient underwent ligation of LMCA with SVG bypass to LAD. One month after operation, she developed palpitations and chest pain during exertion and was taken to the hospital. Labs showed an elevated hs-troponin T of 711 ng/L and she was treated for type 1 NSTEMI with aspirin, heparin drip, and statin. Repeat TTE demonstrated normal LVEF and lack of WMA. LHC showed occlusion of SVG graft and possible thrombus in LAD near the site of graft anastomosis. RCA was large and patent, providing adequate collaterals to the left coronary system. Ultimately, PCI was deferred and medical management was pursued because she had adequate collaterals from right coronary system. She was treated with DAPT, beta-blocker, and atorvastatin and has been doing well since.
Case Media
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Episode Schematics & Teaching
The CardioNerds 5! – 5 major takeaways from the #CNCR case
How are the coronary arteries formed during embryology and how are anomalous coronary arteries formed? During embryology, according to one theory, the coronary ostia and artery formation begins with ingrowth of a capillary plexus into the aortic sinuses. This complex process heavily depends on the proliferation and migration of cells that originate outside the heart at the sinus venosus and then differentiate into endothelial cells, vascular smooth muscle cells, and fibroblasts. Proper migration of these cells to aorta, creating the coronary ostia, depend heavily on expression of growth factors like FGF-2, PDGF, and VEGF. Anomalous origin of a coronary artery from the aorta or from the pulmonary artery have a common defect: the cells of the capillary plexus surrounding the aorta and pulmonary artery fail to reach and/or penetrate the normal sites of developing aorta. This can be caused by different mutations affecting the growth factor signaling pathways. What is ALCAPA? ALCAPA stands for anomalous left coronary artery (LCA) origin from the pulmonary artery. There's also ARCAPA which is anomalous RCA origin from the pulmonary artery. It occurs at an incidence of 1 in 300,000 live births or 0.25 to 0.5% of all congenital heart disease. It is difficulty to diagnose during infancy as it presents similarly to other more common pediatric conditions such as infantile colic, food intolerance, GERD, and bronchiolitis. The usual symptoms include inconsolable crying, poor feeding, rapid breathing, or symptoms of significant distress. Infants may develop myocardial infarction and CHF and a majority of them will die within the first year of life without surgical repair. Infants with ALCAPA rarely manifests in teenagers and adults, unlike the patient in our case. What are the hemodynamic consequences seen in ALCAPA? In fetal life, pulmonary artery pressure is the same as systemic pressure which allows adequate myocardial perfusion from the pulmonary artery to LCA. After birth, pulmonary vascular resistance falls precipitously and subsequently pulmonary artery pressure drops lower than systemic pressure. Furthermore, the pulmonary artery carries oxygen-poor blood; therefore, LCA is now perfused with desaturated blood at low pressure, resulting in inadequate perfusion to the myocardium, especially during exertion such as feeding or crying. Collateral vessels from a normally arising coronary artery can provide perfusion to the anomalous coronary; however, this can lead to "coronary steal" phenomenon and L-to-R shunt. The steal phenomenon and shunt occur because as the pulmonary resistance decreases further, the LCA and the collateral flow tends to pass into the low-pressure pulmonary artery rather than into the high-resistance myocardial blood vessels, resulting in coronary steal phenomenon and myocardial ischemia. When there are adequate collaterals, symptoms can be absent or very minor, allowing patients with ALCAPA to grow into adulthood. Adults with ALCAPA can either be asymptomatic or have exertional chest pain or even sudden cardiac death. What are some factors that will enable patients with ALCAPA to survive to adulthood? Factors that ultimately result in adequate perfusion of myocardium by the LCA will all enable patients survive to adulthood. These factors include: Abundant collateral vessels between the RCA and LCA allowing retrograde LV perfusion from the RCA system. Right dominant system which allows a smaller myocardial area to be supplied by the LCA, leading to less extensive myocardial ischemia. Ostial stenosis of the LCA or a restrictive opening into the pulmonary artery limits the left-to-right shunt and minimizes coronary steal from the pulmonary artery. Development of systemic blood supply to the LCA can occur when collaterals develop from the bronchial artery, providing adequate oxygenated blood flow and perfusion to the myocardium. What are some treatment options for ALCAPA? If an adult patient presents with CHF, medical management consists of the standard GDMT of afterload reduction, diuretics, and inotropic agents if needed. Once the patient is stabilized, surgical correction should be pursued. Previously, a simple ligation of the LCA at its origin was performed to prevent the steal phenomenon and myocardial ischemia. Essentially, the heart is converted to a one-vessel coronary system, entirely dependent on collaterals from the RCA. However, the one-vessel coronary system approach is no longer favored due to its high rate of complications such as recanalization of the ALCAPA, a greater risk of atherosclerosis, severe MR, and a persistent risk of SCD due to silent ischemia. Current surgical procedures are directed toward establishing a two-coronary vessel system through 3 main methods: Coronary button transfer which is direct reimplantation of the anomalous LCA into the aorta or left subclavian artery, after the pulmonary artery is transected. This is the most commonly used method in newborns. If done in adults, coronary friability increases the risk of tearing, bleeding, and kinking of the LCA. Takeuchi procedure which is creation of an aortopulmonary window - the pulmonary artery is opened and a baffle is created between the aorta and LCA. This method is commonly used in infants when coronary button transfer is not feasible but is rarely needed. Complications include supravalvular pulmonary stenosis, aortic insufficiency, and baffle obstruction or leaks. Placement of a coronary artery bypass graft (CABG) combined with ligation of the origin of LCA can be done to restore adequate perfusion. This is the preferred method in adults and what was done in this case. Complications include graft stenosis and occlusion which is what happened in this case.
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