Aortic sclerosis natural history

Overview
Calcification of the aortic valve is common among the elderly population and shares epidemiologic and histopathologic similarities to atherosclerosis. Progressive thickening and calcification of the aortic valve subsequently causes left ventricular stiffness resulting in left ventricular outflow tract obstruction, thereby leading to aortic stenosis. Prognostically, it is known that aortic stenosis is clearly associated with adverse cardiovascular outcomes; however, it is unclear whether aortic sclerosis independently increases the risk of cardiovascular events or progression of aortic sclerosis to aortic stenosis increases the risk, including mortality.

Progression to Aortic Stenosis

 * Echocardiographic indicators of progression of aortic sclerosis to aortic stenosis include:
 * Restricted leaflet mobility
 * Increased echogenicity suggestive of increase leaflet calcification
 * Increase in jet flow velocity across the valve


 * Based on a database study from 1987 to 1993, that evaluated 2131 cases of aortic valve thickening with minimum 1-year echocardiographic follow-up, reported the development of aortic stenosis in 15.9% cases, of which 10.5% developed mild AS, 2.9% had moderate AS and 2.5% had severe AS. Thus, this study demonstrated the prevalence of benign aortic valve thickening with the progression to significant aortic stenosis.


 * Another large population-based cohort reported an ~9% of subjects with aortic sclerosis progressed to aortic stenosis over a 5-year echocardiographic follow-up. Additionally, no association was observed between C-reactive protein levels and the presence of calcific aortic-valve disease or incidental aortic stenosis. However, if C-reactive protein was present it was a poor predictor of subclinical calcific aortic-valve disease.

Risk of Microembolism
Spontaneous calcific embolization has been associated with calcific aortic valve disease; however, Boon et al and Kizer et al, demonstrated no significant increase in the risk of stroke in aortic sclerosis patients with or without aortic stenosis.

Prognosis

 * Prognostically, it is known that aortic stenosis is clearly associated with adverse cardiovascular outcomes; however, it is unclear whether aortic sclerosis independently increases the risk of cardiovascular events or progression of aortic sclerosis to aortic stenosis increases the risk, including mortality. One of the possible explanation, could be that aortic sclerosis serves as a inflammatory marker for coronary artery disease;   however, Novaro et al demonstrated no association between C-reactive protein levels and the presence of calcific aortic-valve disease or incidental aortic stenosis.


 * Population-based prospective study, evaluated baseline echocardiograms obtained from 5621 men and women 65 years of age or older, off which 70% had normal aortic valve, 29% had aortic sclerosis without outflow obstruction and only 2% had aortic stenosis. During a mean 5-year follow-up, a stepwise significant increase in mortality was observed in patients with increasing aortic-valve abnormality. Thus, the study concluded an ~50% increase in the risk of death from cardiovascular causes and the risk of myocardial infarction in patients with aortic sclerosis, even in the absence of hemodynamically significant obstruction of left ventricular outflow.


 * Similar association between aortic sclerosis and the incidence of new coronary events were reported in multiple prospective studies and was independent of co-existing cardiovascular disease or traditional cardiovascular risk factors.