Drug delivery at the aortic valve tissues of healthy domestic pigs with a Paclitaxel-eluting valvuloplasty balloon

Uncoupling the Vicious Cycle of Mechanical Stress and Inflammation in Calcific Aortic Valve Disease

Calcific aortic valve disease (CAVD) is a common acquired valvulopathy, which carries a high burden of mortality. Chronic inflammation has been postulated as the predominant pathophysiological process underlying CAVD. So far, no effective medical therapies exist to halt the progression of CAVD. This review aims to outline the known pathways of inflammation and calcification in CAVD, focussing on the critical roles of mechanical stress and mechanosensing in the perpetuation of valvular inflammation. Following initiation of valvular inflammation, dysregulation of proinflammatory and osteoregulatory signalling pathways stimulates endothelial-mesenchymal transition of valvular endothelial cells (VECs) and differentiation of valvular interstitial cells (VICs) into active myofibroblastic and osteoblastic phenotypes, which in turn mediate valvular extracellular matrix remodelling and calcification. Mechanosensitive signalling pathways convert mechanical forces experienced by valve leaflets and circulating cells into biochemical signals and may provide the positive feedback loop that promotes acceleration of disease progression in the advanced stages of CAVD. Mechanosensing is implicated in multiple aspects of CAVD pathophysiology. The mechanosensitive RhoA/ROCK and YAP/TAZ systems are implicated in aortic valve leaflet mineralisation in response to increased substrate stiffness. Exposure of aortic valve leaflets, endothelial cells and platelets to high shear stress results in increased expression of mediators of VIC differentiation. Upregulation of the Piezo1 mechanoreceptor has been demonstrated to promote inflammation in CAVD, which normalises following transcatheter valve replacement. Genetic variants and inhibition of Notch signalling accentuate VIC responses to altered mechanical stresses. The study of mechanosensing pathways has revealed promising insights into the mechanisms that perpetuate inflammation and calcification in CAVD. Mechanotransduction of altered mechanical stresses may provide the sought-after coupling link that drives a vicious cycle of chronic inflammation in CAVD. Mechanosensing pathways may yield promising targets for therapeutic interventions and prognostic biomarkers with the potential to improve the management of CAVD.

Pathophysiologic mechanisms of calcific aortic stenosis

Calcific aortic stenosis (CAS) comprises the leading indication for valve replacement in the Western world. Until recently, progressive calcification was considered to be a passive process. Emerging evidence, however, suggests that degenerative aortic stenosis constitutes an active process involving stimulation of several pathophysiologic pathways such as inflammation and osteogenesis. In addition, CAS and atherosclerosis share common features regarding histopathology of lesions. These novel data raise a new perspective on the prevention and treatment of disease. The current article reviews the most important pathophysiologic mechanisms of senile aortic stenosis.

Balloon Aortic Valvuloplasty in the Transcatheter Aortic Valve Replacement Era

Initial enthusiasm for balloon aortic valvuloplasty (BAV) as an alternative to surgical aortic valve replacement waned because of the perceived failure of the procedure to alter the natural history of calcific severe aortic valve stenosis (AS) and significant initial procedural morbidity. Despite technical and procedural advances, BAV has been reserved as a palliative procedure for patients who cannot undergo valve replacement or as a bridge to surgery in hemodynamically unstable patients. This article reviews the indications, technical aspects, and outcomes of BAV for calcific AS and discusses the current role of BAV in the era of transcatheter aortic valve replacement.

The Pathogenesis and treatment of the valvulopathy of aortic stenosis: Beyond the SEAS

Fibrocalcific aortic stenosis (AS) results from an active process similar to atherosclerosis that involves basement membrane disruption, lipid deposition, inflammatory cell infiltration, and calcification. Consequently, 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) have been extensively studied as potential therapeutic agents capable of slowing the progression of AS. However, two randomized trials, SALTIRE and the SEAS study, showed no benefit with statin therapy for AS. These results have shed doubt over the efficacy of statin therapy for AS, although their potential efficacy at early stages of aortic valve disease remains possible. In this article, we review the pathophysiology of fibrocalcific AS and discuss future directions for its nonsurgical management in the post-SEAS era.