Aortic Valve Pathology and Surgery

The aortic valve guards the outflow from the left ventricle into the aorta, and its disease takes two main forms: aortic stenosis, a narrowing that obstructs ejection, and aortic regurgitation, an incompetence that allows blood to leak back into the ventricle in diastole. This topic covers the pathology of these lesions and the surgical and transcatheter procedures used to treat them, a field reshaped over the past two decades by transcatheter aortic valve replacement.

Definition

Aortic valve pathology comprises the structural and functional disorders of the aortic valve — principally stenosis and regurgitation — and the surgical or transcatheter procedures used to relieve obstruction or restore competence of the valve.

Scope

The entry addresses aortic valve structure including the bicuspid variant, the mechanisms of stenosis and regurgitation, the ventricular consequences of pressure and volume overload, and the spectrum of treatment from surgical replacement to transcatheter implantation. It is an anatomical and methodological reference and does not give indications or thresholds for operating on an individual patient.

Core questions

• What causes calcific and bicuspid aortic stenosis and how do they differ?
• How do pressure overload from stenosis and volume overload from regurgitation affect the left ventricle?
• When is surgical replacement preferred over transcatheter implantation, and vice versa?

Key concepts

• Aortic stenosis
• Aortic regurgitation
• Calcific (degenerative) aortic valve disease
• Bicuspid aortic valve
• Pressure overload and concentric hypertrophy
• Surgical aortic valve replacement
• Transcatheter aortic valve replacement (TAVR/TAVI)

Mechanisms

Aortic stenosis most often arises from an active, atherosclerosis-like process of leaflet calcification that progressively stiffens and narrows the valve; a congenitally bicuspid valve, present in a small percentage of the population, accelerates this process and tends to bring patients to operation earlier. The resulting outflow obstruction imposes a chronic pressure overload that drives concentric left-ventricular hypertrophy. Aortic regurgitation, by contrast, arises from leaflet disease or from dilatation of the aortic root and ascending aorta that prevents leaflet coaptation; the regurgitant volume imposes a combined pressure-and-volume overload that dilates the ventricle. Both lesions are well tolerated for years before symptoms or ventricular decompensation appear, which is why their natural history and the timing of intervention are central themes. Treatment replaces or, less often, repairs the valve — surgically with a prosthesis or, increasingly, by seating a prosthesis through a catheter (transcatheter aortic valve replacement).

Clinical relevance

Calcific aortic stenosis is among the most common valve lesions in ageing populations, and the introduction of transcatheter replacement has broadened the population that can be treated, including patients once considered inoperable. This entry describes the disease and the evidence base for reference; it does not provide operative timing or recommend a specific treatment for an individual, which are matters for current guidelines and the heart team.

Epidemiology

Calcific aortic stenosis becomes increasingly prevalent with age and is a leading indication for valve intervention in older adults. The bicuspid aortic valve is the most common congenital cardiac malformation and predisposes to earlier stenosis or regurgitation and to associated aortopathy. Randomised trials have progressively extended transcatheter replacement from high- and intermediate-risk to selected low-risk patients.

History

Surgical aortic valve replacement became feasible with cardiopulmonary bypass and the first prosthetic valves around 1960 and was for decades the only effective treatment for severe disease. The first human transcatheter aortic valve implantation in 2002 opened an alternative route, and a sequence of randomised trials through the 2010s extended transcatheter replacement from inoperable patients to high-, intermediate-, and selected low-risk patients.

Debates

Surgical versus transcatheter aortic valve replacement across risk strata

Randomised trials have shown transcatheter replacement to be a reasonable alternative to surgery in high- and intermediate-risk patients and, in selected low-risk patients, comparable on early endpoints; the long-term durability of transcatheter valves and the optimal choice in younger, lower-risk patients remain under study.

Key figures

• Catherine Otto
• Michael Reardon
• Martin Leon

Seminal works

• reardon-2017
• mack-2019
• siu-2010

Frequently asked questions

What is a bicuspid aortic valve?

It is a congenital variant in which the aortic valve has two leaflets instead of the usual three. It is the most common congenital cardiac malformation, tends to calcify and become stenotic earlier than a normal three-leaflet valve, and is associated with disease of the aorta.

What is transcatheter aortic valve replacement?

It is a procedure in which a prosthetic valve is delivered through a catheter — usually via an artery in the leg — and seated within the diseased native valve, without surgically removing it or opening the chest. It has become an established alternative to surgery for many patients with aortic stenosis.