Hypoattenuated Leaflet Thickening: Pathophysiology, Clinical Implications, and Its Role in Structural Valve Longevity

The expansion of transcatheter aortic valve replacement (TAVR) into younger and lower-risk populations has heightened attention toward long-term valve durability. Hypoattenuated leaflet thickening (HALT), a subclinical imaging finding identified on multidetector computed tomography, has emerged as a relatively common occurrence following TAVR. It is characterized by low-attenuation, often meniscal-shaped thickening of bioprosthetic valve leaflets and may be present with or without associated reduced leaflet motion. Although frequently asymptomatic, HALT is increasingly recognized as part of a broader spectrum of leaflet thrombosis that may progress to clinically significant valve dysfunction.