Case background: A 79-year-old female was referred for incidental CT finding of cardiac mass in the context of colon cancer surveillance. Gated cardiac CT revealed a large, partially thrombosed right coronary artery (RCA) aneurysm measuring 5.7 x 5.1 x 4.8 cm, exerting mass effect on the right atrium and ventricle. The patient was asymptomatic.
Past medical history includes type 2 diabetes, hypertension, dyslipidemia, hypothyroidism, and hiatal hernia. One year prior, echocardiogram showed a small idiopathic pericardial effusion that resolved three months later. She is a remote smoker and denied alcohol / recreational drug use. Family history revealed a sibling with an intracranial aneurysm, mother who died suddenly of a “coronary event” without further details and another family member with abdominal aortic aneurysm.
Initial investigations were unremarkable including complete blood count within normal range, normal creatinine (62 µmol/L), brain natriuretic peptide 10 ng/L, low-density lipoprotein 1.36 mmol/L, non-high-density lipoprotein 2.81 mmol/L, and glycated hemoglobin 6.4%. Autoimmune disease bloodwork was normal: c-reactive protein 0.9 mg/L, rheumatoid factor < 15 IU/mL, and negative anti-nuclear antibodies, anti-neutrophil cytoplasmic antibodies, and extractable nuclear antigen antibodies. Echocardiogram demonstrated normal left and right ventricular size and function with no significant valvular disease. Coronary angiogram revealed a massive, 65mm x 60mm RCA aneurysm with swirling of contrast and no clear thrombosis. Distal to the aneurysm, vasculature was patent with minimal coronary disease, though difficult to visualize. The distal left main artery was moderately ectatic while the left anterior descending and circumflex arteries had mild irregularities.
The patient’s case was discussed at multidisciplinary heart team rounds and it was ultimately decided to pursue surgical ligation of the RCA aneurysm proximally and distally, with bypass grafting to the posterior descending artery. The patient underwent this procedure successfully. Pathology of the specimen revealed fibromuscular tissue in keeping with vascular wall and no evidence of inflammation.
The patient was discharged post-operatively without significant complications. At two-month follow-up she was recovering well with increasing functional capacity in the absence of symptoms. She is awaiting brain MRI to rule out associated intracranial aneurysm.
Management Challenges: Coronary artery aneurysms (CAAs) are dilations of a coronary artery segment greater than 1.5 times the size of adjacent vessel. Rarely, (0.02%) they can grow large enough to be classified as giant coronary artery aneurysms (GCAAs). The gold standard diagnostic test is coronary angiography, though debate exists for follow-up of asymptomatic aneurysms including choice of imaging modality and size/ rate of growth necessitating intervention. CAAs are most often present in the RCA (40%) and risk factors include: male sex, hyperlipidemia, hypertension, smoking, and cocaine use.
Mechanism of CAA formation is uncertain though atherosclerosis is common, linked to 50% of cases. Chronic transmural inflammation, characteristic of atherosclerosis, leads to weaking of the vessel wall allowing distention. Genetic predisposition exists for altered vascular remodelling resulting in aneurysmal dilation of other important arteries such as the abdominal aorta and intercranial vasculature. Pathogenic associations include certain vascular and connective tissue diseases. Local wall injury following infections and intracoronary manipulation with angioplasty, stenting or brachytherapy have also been connected. Our patient had evidence of only mild atherosclerosis but did have positive risk factors of treated hyperlipidemia, hypertension, and remote smoking. Serology did not indicate a rheumatological etiology nor did she have history of connective tissue disease. However, family history of multiple relatives with aneurysmal dilations is concerning for a genetic component of her GCAA.
Most often, CAAs are clinically silent and incidentally discovered but can present as angina, acute coronary syndrome or dyspnea. Giant coronary artery aneurysms are more likely to be symptomatic due to mass effect and can mimic a cardiac or mediastinal mass. Registry data shows CAAs rarely have catastrophic consequences including rupture, dissection, and tamponade but have been associated with thrombosis, due to abnormal blood flow, leading to secondary myocardial infarction or distal embolization. This risk is highest when aneurysm diameter is greater than 5mm. Despite being asymptomatic, our patient’s aneurysm exceeded 6 cm in diameter and demonstrated mass effect, raising concern for hemodynamic compromise or thromboembolic events.
Apart from disease specific therapy for vascular and connective tissue diseases, medical management of CAAs is unclear. Risk factor modification with statins, angiotensin-converting enzyme inhibitors, and beta blockers are sometimes prescribed. Ongoing debate exists for the use of single vs dual antiplatelet therapy. Considerations include CAA z-score, rate of growth, size relative to patient size, sluggish flow on angiography, previous myocardial infarction, length and proximity as well as additional risk factors for thrombosis such as smoking. Vitamin K antagonists are often reserved for therapy of intra-aneurysmal thrombus to reduce distal embolization, and use has been associated with significant reduction in major adverse cardiac events. Vasodilators should be avoided as they may induce further dilation. Our patient was managed with statin and aspirin monotherapy.
Percutaneous coronary intervention with exclusion of the aneurysm using stenting or coil embolization have demonstrated long-term safety and efficacy in symptomatic CAA. Conversely, a surgical approach is favoured for GCAAs as well as patients with mechanical complications. The options for surgical intervention include aneurysmal resection, ligation or marsupialisation with interposition grafts. The most common surgical technique is opening the CAA, suturing both afferent and efferent vessels and bypass grafting if necessary. For our patient, surgical approach was preferred due to the long distance between the proximal entry to the aneurysm and distal exit vessel resulting in technical difficulty with selectively wiring the distal RCA, stent sizing, and the requirement for extensive long stenting strategy.
Current guidelines indicate need for clarification of ideal timing for intervention and approach to management while recognizing the lack of adequate clinical data. In the case of asymptomatic incidentally found GCAA, the decision to treat is challenging. Ongoing debate exists for medical and interventional management as well as follow-up of asymptomatic aneurysms. Given the absence of definitive guidelines, management of asymptomatic GCAA should be individualized through a multidisciplinary approach. This case illustrates the rationale for pre-emptive surgical intervention to mitigate risk of rupture, thrombosis, and mass effect related complications.
