Mechanics of Balloon and Stent Angioplasty in Congenital Heart Interventions.

Transcatheter treatment of vascular obstruction, including balloon angioplasty and stent implantation, is central to the management of congenital heart disease (CHD). The success and safety of these procedures depend on complex mechanical interactions among abnormal vessels, adjacent "normal" segments, surrounding tissues, balloons, and stents. However, these biomechanical relationships have not been comprehensively reviewed for congenital interventional cardiologists. This review summarizes the mechanical principles most relevant to catheter-based therapy in CHD. First, we outline the biomechanical behavior of normal large vessels, especially the aorta and pulmonary arteries, including wall structure, anisotropy, nonlinear stress-strain behavior, residual stress, compliance and stress concentrations at bifurcations and curved segments. We then examine how congenital, postoperative, and acquired vascular abnormalities alter these properties and influence procedural response. Next, we review balloon mechanics, including compliance, inflation dynamics, balloon-vessel interaction, and the relationship among balloon diameter, pressure, lesion geometry, and vessel injury. Finally, we discuss the mechanics of balloon-expandable stents, including crimping, deployment, recoil, shortening, dog-boning, redilation, fracture, fatigue, and the influence of stent design and material properties on performance. Across all intervention types, clinical outcomes are shaped not only by lesion anatomy but also by local mechanical environments that remain incompletely defined and vary substantially among patients and lesions. A better understanding of these principles may improve procedural planning, device selection, risk assessment, and interpretation of acute and late outcomes after transcatheter intervention in CHD.