A 62-year-old female with a historyof hypertension presented at 07:00 on November 1, 2025, with typical chest discomfort.She denied a history of diabetes mellitus, dyslipidemia, smoking,alcohol consumption, or any family history ofcardiovascular disease. Physical examination was unremarkable

Electrocardiogramdemonstrated ST elevation in leads II, III, and aVF, with Q waves in lead III,indicating acute inferior myocardial infarction. Chestradiographshowed borderline cardiomegaly and mild pulmonary congestion

Coronaryangiography revealed a diffuse, calcified lesion with 77% stenosis in the midleft anterior descending artery (LAD), and 57% stenosis in the mid leftcircumflex artery (LCx). Theposterolateral ventricular (PLV) branch showed critical stenosis with TIMI-1flow. Collateral circulation from the left coronary artery (LCA) to the distalright coronary artery (RCA) segment or posterior descending artery (PDA)was faintlyvisible



LCA angiography with collateral.mp4
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Dualaccess via right radial and right femoral arteries was established. A 7Fr SAL1.0 guiding catheter was used for the RCA, and a diagnostic catheter forcontralateral injection of the LCA. Based on ECG and clinical findings, initialpercutaneous transluminal coronary angioplasty (PTCA) was performed on the PLVbranch using a 2.0 mm semi-compliant balloon, restoring TIMI-3 flow.Despiteexhaustive review of the RCA angiogram, the PDA ostium remained elusive. Toaddress this, a real-time intravascular ultrasound (IVUS)-guided technique wasemployed to systematically identify all side branches, ultimately pinpointingthe PDA ostium with precision. A Finecross microcatheter and UB3 guidewire wereused to create an entry into the PDA, overcoming mild resistance. The UB3guidewire successfully established the entry, and a runthrough guidewire wasadvanced through the chronic total occlusion (CTO) lesion.Serialballoon dilations were performed with 2.0 mm and 2.5 mm semi-compliantballoons. IVUS assessment indicated vessel diameter between 2.0–2.5 mm. A 2.5mm B.Braun Sequent Please Neo drug-coated balloon was used to treat the targetlesion, resulting in an excellent angiographic outcome.



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Thiscase highlights the importance of identifying and treating the often-overlookedPDA in inferior STEMI. Conventional angiography may miss subtle lesions, butcontralateral angiography for collateral from the LCA and real-time IVUSguidance provide crucial clues and definitive localization. Though technicallystraightforward, this case underscores the need for careful assessment ofcoronary anatomy and the wise use of available tools. Real-time IVUS improvessafety and efficacy, and helps clinicians address challenging lesions. Overall,this case is an instructive example with ongoing educational value forinterventional cardiologists.