Stentitis and Infected Coronary Pseudoaneurysm Post-PTCA and Role of FDG-PET : A Case Report

INTRODUCTION

Coronary pseudoaneurysms and stent infections (stentitis) are exceedingly rare complications of PTCA, often associated with high mortality due to rupture or uncontrolled infection.^[1,2] Major causative factors include procedural arterial injury, bacterial seeding, and immunosuppression.^[2] Clinical presentations are nonspecific, typically involving chest pain and fever, and may mimic ischemia or stent thrombosis. Multimodality imaging, including coronary angiography (CAG) and FDG PET/CT, is critical for diagnosis.^[3,4] We present a case of a 39-year-old male with a history of ACS who developed an infected pseudoaneurysm and stentitis post-PTCA, detected on FDG PET-CT scan, who unfortunately had a fatal outcome due to hemorrhage.

CASE REPORT

A 39-year-old-male with a history of ACS underwent PTCA with drug-eluting stent placement to the obtuse marginal (OM) artery. After two months, he presented with chest pain. CAG revealed in-stent stenosis. Patient underwent stent placement and drug-coated balloon (DCB) to OM1. However, a few days later, the patient was again admitted with symptoms of unstable angina and fever. Repeat angiography showed a patent OM1 stent, but showed a pseudoaneurysm, raising suspicion of stentitis. The patient was referred to us for an FDG PET-CT scan to detect and localise infection sites. A PET scan was performed with pre-preparation on a high-fat, low-carbohydrate diet and prolonged fasting to suppress physiological myocardial uptake. The scan revealed a large, partially thrombosed pseudoaneurysm in OM1 (9.3 × 6.4 cm in axial dimensions, and 8.5 cm superoinferiorly) with eccentric contrast filling and abnormal increased peripheral FDG uptake (SUVmax 8.1), with the OM1 stent coursing through the aneurysm also exhibiting abnormal increased FDG uptake, suggesting an infected OM1 stent with mycotic pseudoaneurysm [Fig 1]. Two-dimensional echocardiography showed RWMA involving the mid-basal inferior and lateral walls, with type II LV diastolic dysfunction. Blood cultures grew Pseudomonas aeruginosa, and intravenous (IV) antibiotics were initiated. The patient continued on antibiotics and was planned for surgical intervention. Unfortunately, he succumbed to uncontrolled hemorrhage from the infected pseudoaneurysm of the circumflex artery secondary to stent infection.

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Fig 1

(a) FDG PET/CT maximum intensity projection (MIP) image, (b) axial CT, (c) axial fused PET/CT, (d) coronal CT, and (e) coronal fused PET/CT images showing a large, partially thrombosed pseudoaneurysm in OM1 with eccentric contrast filling and abnormal increased peripheral FDG uptake (yellow arrows in b–e). The OM1 stent coursing through the aneurysm demonstrates abnormal FDG uptake (green arrows in b–e).

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DISCUSSION

Coronary artery pseudoaneurysms are rare and often result from atherosclerosis, procedural trauma, or infection.^[1,2,4]

Coronary mycotic/infected pseudoaneurysms are localized dilatations of coronary arteries due to vascular wall destruction, more commonly by invasive organisms like Staphylococcus aureus and Pseudomonas aeruginosa.^[4] The incidence of coronary artery pseudoaneurysm ranges from 0.3% to 0.6% following PCI and presents unique challenges in both diagnosis and management.^[4]

Restrepo et al. proposed a “two-hit” hypothesis to describe its pathogenesis.^[5] The first insult involves compromise of vascular wall integrity, which may result from atherosclerosis, trauma, or interventional procedures, use of oversized balloons/stents, and high-pressure balloon inflations. The second insult involves microbial infiltration of the already weakened vascular segment, either through direct extension, hematogenous dissemination, or embolic seeding.^[4]

Drug-eluting stents, such as the one used in our patient, contain an antiproliferative agent (e.g., sirolimus), which is associated with a higher risk of pseudoaneurysm formation because it not only inhibits neointimal hyperplasia and prevents restenosis but also impairs local host defenses and delays endothelialization. This creates a fertile ground for microbes to survive and multiply in susceptible individuals.^[6]

A high suspicion of stent infection was raised in our patient in view of the clinical presentation of fever and unstable angina post-recent coronary intervention, positive blood cultures, and pseudoaneurysm detected on coronary angiogram, as per the Dieter criteria.^[7]

FDG PET-CT imaging has high sensitivity for detecting and localising sources/sites of infection^[8], and, similarly, in our patient, it helped localise the infection to the stent and pseudoaneurysm.

Management of infected coronary pseudoaneurysms, however, is challenging due to the risk of rupture with mortality as high as 25-40%, and limited guidelines are available.^[9] Isolation of an organism enables targeted therapy, thereby improving outcomes. Surgical options, including aneurysm resection and coronary artery bypass grafting, are preferred for symptomatic cases but carry significant risk.^[2,4]

Our patient received IV antibiotics targeting Pseudomonas aeruginosa isolated on blood cultures, and was planned for aneurysm closure surgery. However, the patient succumbed to a fatal hemorrhagic outcome, highlighting the aggressive nature of infected pseudoaneurysms.

Therefore, an FDG PET-CT scan can help in early diagnosis and guide surgical planning. Early recognition, along with aggressive antimicrobial therapy and timely surgical intervention, is therefore essential in managing these rare but life-threatening complications.

CONCLUSION

Our case highlights the role of FDG PET-CT scan in detecting and localising mycotic coronary pseudoaneurysm and stentitis, which are rare life-threatening complications of PTCA that require early diagnosis and timely intervention to avert potential catastrophic outcomes.