A 71-year-old male presented with progressive dyspnea and chest tightness on exertion for 2 months, FC II > FC III. He reported no orthopnea, paroxysmal nocturnal dyspnea (PND), edema, or chest pain. Physical examination revealed a regular heart rate, parasternal heaving, normal S1, and a loud P2. Additionally, a grade II pansystolic murmur was auscultated at the left lower parasternal border.

An EKG showed normal sinus rhythm, with tall R waves in V1 to V3 and T wave inversion in V1 to V6. A chest X-ray indicated cardiomegaly and an enlarged pulmonary artery, without congestion. An echocardiogram revealed normal biventricular systolic function, a dilated right atrium and right ventricle, moderate tricuspid regurgitation (TR), and a high probability of pulmonary hypertension.

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A coronary angiogram revealed severe ostial left main (LM) stenosis, while the other parts of the coronary arteries were normal and plaque-free. External compression was suspected. Intravascular ultrasound (IVUS) confirmed severe stenosis with dynamic external compression, with the intima being free of plaque. Right heart catheterization showed pre-capillary pulmonary hypertension with a MPAP of 44 mmHg, a PCWP of 7 mmHg, and a PVR of 6.28 Wood units (WU).
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A CTA coronary artery scan showed compression of the left main coronary artery from an enlarged pulmonary artery. The heart team recommended undergoing PCI for the left main stenosis. A Guiding JL3.5 6F catheter was engaged to the left main, and a Sion Blue guidewire was passed to the distal LAD. IVUS was used to mark the left main ostium, and a floating wire was deployed to assist in the LM PCI. Direct stenting was performed using an Everolimus-eluting stent, sized 4.00 x 15 mm, at 12 atm. Post-dilatation was done with a non-compliant balloon, 5.0 mm, at 14 atm. The final angiogram showed good stent expansion, and IVUS confirmed good apposition with minimal stent protrusion.

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His symptoms improved after the LM PCI. He was prescribed dual antiplatelet therapy for 6 months and a pulmonary vasodilator for the treatment of pre-capillary hypertension. This case demonstrated an unusual occurrence of left main stenosis due to an enlarged pulmonary artery, which was successfully treated with LM stenting.