Intracoronary imaging demonstrating vasculitis as a rare cause of myocardial infarction: a case report.

Background: Proteinase 3 (PR3)-positive anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis, most associated with granulomatosis with polyangiitis (GPA-'Wegener's), is a rare, systemic autoimmune disorder. In this report, we describe an uncommon case of thrombus formation in ANCA vasculitis. Case summary: A 20-year-old male with well-controlled type 1 diabetes presented with the sudden onset of chest pain. The patient had a recent diagnosis of ANCA-associated vasculitis with multisystemic involvement and had completed induction rituximab therapy and pulse of methylprednisolone, before starting moderate dose oral prednisolone and avacopan in the week prior. Electrocardiogram demonstrated inferolateral ST-elevation myocardial infarction; an initial computed tomography aortogram excluded aortic dissection and illustrated mural thickening and luminal irregularity involving the left anterior descending artery. Coronary angiography confirmed distal left circumflex artery occlusion. Given age, stenosis location, vessel size and underlying vasculitis diagnosis, the lesion was prepared with semi-compliant balloon dilatation and then treated with drug-coated balloon angioplasty. Follow-up imaging 4-days later revealed residual left circumflex coronary artery thrombus and vessel wall inflammation, along with inflammation in the left anterior descending artery. Additional intravascular imaging at 6-months showed ongoing intimal thickening. Discussion: PR3-positive disease presenting as a myocardial infarction is an exceedingly rare cardiac manifestation of small vessel vasculitis. This case highlights the role of intracoronary imaging in assessing ANCA-associated vasculitis, which has not, to our knowledge, been previously detailed in the literature. Importantly, this case underscores the importance of characterising the underlying pathology to treat reversible causes and demonstrates the novel use of using drug coated balloons in such cases.