Acute Myocardial Infarction Secondary to Left Main Coronary Artery Compression by Pulmonary Artery Aneurysm (Full Title Below)

J INVASIVE CARDIOL 2007;19:E375–E377
Angina is a common symptom among patients with primary and secondary pulmonary arterial hypertension and has commonly been attributed to right ventricular (RV) ischemia due to RV dilatation and hypertrophy.^1–2 Though a relatively rare entity, pulmonary artery aneurysm secondary to pulmonary arterial hypertension has been described to cause symptomatic and asymptomatic compression of the left main coronary artery (LMCA), resulting in angina, syncope and decreased exercise tolerance.^3–10 The optimal treatment of these patients remains unknown. This case report describes a patient with pulmonary arterial hypertension who presented with acute-onset jaw pain, electrocardiographic changes and elevated cardiac enzymes consistent with ST-elevation myocardial infarction (STEMI). The patient was found to have significant extrinsic compression of the LMCA by a pulmonary artery aneurysm. She was successfully treated by percutaneous stenting of the LMCA. To our knowledge, this is the first case report of a patient presenting with acute STEMI due to compression of the LMCA by pulmonary artery aneurysm. Case Report. A 51-year-old female with a history of severe pulmonary arterial hypertension diagnosed 15 years prior, possibly secondary to rheumatoid arthritis, and a history of recurrent syncope presented to the emergency department with accelerating chest pain. She had been in World Health Organization functional class II with good control of her dyspnea and right heart failure, but with intermittent exertional and nonexertional chest pain felt to be secondary to her pulmonary hypertension. She presented to a local hospital with accelerating chest pain and jaw pain associated with hemodynamic compromise and recurrent sustained ventricular tachycardia. An electrocardiogram (ECG) demonstrated ST-segment elevation in anterolateral leads with reciprocal ST-segment depression in the inferior leads (Figure 1). She underwent emergent catheterization, which demonstrated 70% left main stenosis and cardiogenic shock requiring placement of an intra-aortic balloon pump and support with vasopressors. She was transferred to UCLA for treatment of the LMCA lesion. Upon arrival, transthoracic echocardiography (TTE) followed by cardiac computed tomographic (CT) angiography were performed. TTE demonstrated severe right atrial (RA) and right ventricular (RV) enlargement with decreased function, elevated RV systolic pressures (70–75 mmHg), and normal left ventricular wall motion and function. A large aneurysm of the pulmonic artery and severe pulmonic valve regurgitation were noted. Cardiac CT angiography demonstrated a central pulmonary artery aneurysm measuring 11 cm in diameter (Figure 2), as well as dilated left and right pulmonary arteries (3.8 cm and 4.7 cm, respectively). Furthermore, the LMCA was significantly narrowed up to the bifurcation due to extrinsic compression from the aneurysm (Figure 2). Right heart catheterization revealed a right atrial pressure of 8 mmHg, RV pressure of 78/1 mmHg and pulmonary artery pressure of 86/15 mmHg. Due to the high surgical risk associated with severe pulmonary hypertension outside of the context of lung transplantation, the decision was made to perform an urgent percutaneous intervention with stent placement in the LMCA. Coronary angiography revealed a 70% narrowing of the LMCA and systolic compression of the left anterior descending artery (LAD) with a markedly inferior course due to the pressure from the pulmonary artery aneurysm (Figure 3). Intravascular ultrasound (IVUS) demonstrated no atherosclerosis in the LMCA, LAD or left circumflex arteries, but showed the LMCA minimum intraluminal diameter to be 1.7 mm during systolic compression (Figure 4). Successful angioplasty and stenting of the LMCA with a 5 mm x 13 mm Ultra bare-metal stent (Guidant Corp., Santa Clara, California) was performed. Following stent deployment, IVUS confirmed good apposition with a mid intraluminal diameter of 5.5 mm. Post procedure, the patient had resolution of angina and was successfully weaned off the intra-aortic balloon pump and ionotropic support. During 9 months of follow up, she has reported no further recurrence of angina or syncope. Follow-up CT angiography at 8 months demonstrated a patent LMCA stent without flow limitation. Discussion. Although angina is a common finding in patients with pulmonary arterial hypertension, occurring in as many as 40% of patients,¹ its etiology remains unclear. In the past it has been attributed to RV ischemia secondary to elevated pulmonary artery pressures and RV hypertrophy.^2–3 As these patients are often young, coronary artery disease is usually not considered. At least 14 asymptomatic cases of LMCA compression secondary to a pulmonary artery aneurysm have been reported in the literature, most discovered prior to evaluation for heart-lung transplantation.^3–10 Mitsudo et al performed serial angiography on a series of 16 patients with pulmonary hypertension secondary to large atrial septal defects but without angina. Of these, 7 patients (44%) had evidence of significant LMCA compression (defined as > 50% in at least one view, usually left anterior oblique (LAO), given the eccentric manner of the compression). During coronary angiography, the LMCA had a characteristic narrowing at the ostium with subsequent dilatation in the distal left main with otherwise normal coronary arteries.¹¹ The smooth, tapered appearance of the LMCA on coronary angiography suggested a process other than atherosclerosis. In another series, 12 patients with congenital heart disease and pulmonary arterial hypertension who underwent routine coronary angiography were found to have at least 50% compression of the LMCA. The LMCA stenosis was usually best seen in one view (LAO cranial), all had evidence of pulmonary hypertension (mean pulmonary artery pressure > 30 mmHg), and in all cases, the LMCA was inferiorly displaced by the pulmonary artery and in close contact with the left aortic sinus (mean angle of ± 13 degrees).¹² Corday et al in 1957 demonstrated that elongation, dilation and distention of the pulmonary trunk in pulmonary hypertension may distort or impinge upon the LMCA within the restrictive fibrous sheath that surrounds the great vessels.¹³ In 1963, Schaffer et al demonstrated that subjecting a normal pulmonary trunk to high intraluminal pressures was not sufficient to reproduce this phenomenon, suggesting that the pulmonary artery vascular remodeling process and the dilation that occurs as a consequence of long-standing pulmonary arterial hypertension are necessary for extrinsic LMCA compression.¹⁴ Furthermore, the anatomical proximity of the pulmonary artery and RV outflow tract to the LMCA in normal subjects has been further confirmed in studies using CT angiography.¹⁵ Our report corroborates these anatomic observations in vivo with evidence from coronary and CT angiography. The prognostic significance of LMCA compression by pulmonary artery aneurysms in patients without angina is unknown. Patients with pulmonary arterial hypertension are at high risk for sudden cardiac death (26%).¹⁶ Malignant arrhythmias from coronary artery compression with subsequent ischemia are likely contribute to this high incidence.¹⁷ Our report and others indicate that they may also be at risk for STEMI and LV ischemia, potentially serving as the etiology of arrhythmias leading to sudden death. The therapeutic approach in symptomatic patients or those presenting with ischemia is limited by a small number of case reports. Treatment of angina caused by LMCA compression has only been reported in 4 other cases.^3,5,10 One of these patients demonstrated anterior and anterolateral wall perfusion abnormalities via thallium scintigraphy.⁵ One patient underwent heart-lung transplantation. Three patients underwent successful stenting of the LMCA and had subsequent relief of their angina.^3,10 This patient had extremely long-standing pulmonary hypertension and was only successfully treated when therapy became available in the early 2000s with a combination of sildenafil, bosentan and treprostinil. Her pulmonary artery aneurysm had expanded during this time. Her years of intermittent chest pain attributed to pulmonary hypertension may have represented coronary angina secondary to LMCA compression. To our knowledge, this is the first report of a patient with pulmonary artery hypertension who presented with evidence of acute myocardial infarction manifested by ECG changes and elevated cardiac enzymes in addition to angina, and was found to have LMCA compression without evidence of atherosclerosis Cardiac CT angiography appears to be a useful tool in evaluating patients presenting with angina who are suspected of having this syndrome prior to consideration of angioplasty and stenting of the ostial LMCA. Placement of an intra-aortic balloon prior to stenting of the unprotected LMCA should also be considered. Acknowledgment. The authors would like to acknowledge the assistance of Adel K. Elbialy, MD, Shelley M. Shapiro, MD and Jonathan M. Tobis, MD. References 1. Rich S, Dantzker DR, Ayres S, et al. Primary pulmonary hypertension: A national prospective study. Ann Intern Med 1987;107:216–233. 2. Rich S. Primary pulmonary hypertension. Prog Cardiovasc Dis 1988;31:205–238. 3. 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