Reversing the Reverse: Nitrate-Enhanced Tc-99m MIBI MPS Unmasking Microvascular Dysfunction in Takayasu Arteritis

Takayasu Arteritis (TA) is a large vessel vasculitis involving the aorta and its major branches, which could be complicated by significant cardiovascular manifestations. A woman with TA, severe aortic regurgitation, and mild global left ventricular hypokinesis underwent Technetium-99m (Tc-99m) sestamibi (MIBI) myocardial perfusion scintigraphy (MPS). Stress imaging revealed mild apical hypoperfusion (SSS: 5); however, resting imaging demonstrated a markedly larger and more pronounced defect (SRS: 12), characterizing a reverse redistribution pattern. Importantly, subsequent nitrate-enhanced resting acquisition resulted in a significant reduction of the defect (N-SRS: 6). Invasive coronary angiography was normal. This pronounced reversal of resting hypoperfusion following a potent vasodilator suggests coronary microvascular dysfunction (CMD) mediated by microvascular vasoconstriction, highlighting the silent but prognostic ischemic involvement in Takayasu arteritis.