Unmasking Coronary Microvascular Dysfunction in Hypertrophic Cardiomyopathy: Multimodality Imaging With Stress Cardiac MRI and Coronary CT Angiography.

Coronary microvascular dysfunction (CMD) is a hallmark feature in hypertrophic cardiomyopathy (HCM), linked to significant clinical challenges including myocardial ischemia, fibrosis, and an elevated risk of heart failure and sudden cardiac death. In this case, a 21-year-old female presented with intermittent lower extremity edema, exertional dyspnea, and persistent fatigue. Imaging studies were pivotal in identifying the underlying CMD and confirming the HCM diagnosis. Transthoracic echocardiography revealed mild left ventricular hypertrophy with hyperdynamic function, reduced global longitudinal strain, and mildly increased LVOT gradients. Cardiac magnetic resonance imaging (CMR) provided more definitive findings: severe asymmetrical left ventricular hypertrophy, most pronounced in the apical inferoseptal wall, alongside subendocardial perfusion defects identified during regadenoson stress perfusion imaging. These perfusion abnormalities involved multiple myocardial segments and did not conform to a single epicardial coronary artery distribution, supporting a microvascular pattern of ischemia and strongly implicating CMD as the underlying cause of myocardial ischemia. The absence of late gadolinium enhancement, coupled with elevated native T1 and extracellular volume values, suggested early interstitial expansion without extensive fibrosis. Coronary computed tomography angiography confirmed the absence of significant epicardial coronary artery disease, further substantiating that the ischemia was driven by microvascular dysfunction rather than large-vessel obstruction. Structural abnormalities in the coronary microvasculature, such as intimal and medial hyperplasia, reduced lumen size, and impaired vasodilatory capacity, were likely contributors to the CMD observed in this patient. In summary, this case highlights the crucial role of advanced imaging techniques, such as CMR stress perfusion and T1 mapping, in diagnosing CMD within the context of HCM. These findings underscore the need for tailored management strategies targeting CMD to mitigate its impact on clinical outcomes in HCM patients.