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Structure

Cardiac valves

Not medically reviewed · Content last updated · 2 min read ·

This is the date the draft was written, not a medical review date.

Four valves maintain one-way blood flow through the heart: the tricuspid and mitral (atrioventricular) valves and the pulmonary and aortic (semilunar) valves. They are anchored in the fibrous skeleton of the heart.

Terminologia Anatomica (Latin): Valvae cordis · Open in the 3D atlas

Location

Surface projections on the chest wall: pulmonary behind the left third costal cartilage, aortic behind the left sternal edge at the third space, mitral behind the left fourth costal cartilage, tricuspid behind the sternum at the fourth and fifth spaces. Auscultation sites differ from these projections because sound follows blood flow.

Structure

The tricuspid valve has three leaflets (anterior, posterior, septal); the mitral (bicuspid) valve has two (anterior and posterior). Both are tethered by chordae tendineae to papillary muscles. The pulmonary and aortic valves each have three semilunar cusps without chordae; the aortic cusps are right, left and non-coronary, and the coronary arteries arise from the right and left aortic sinuses.

Blood supply

The leaflets are largely avascular and are nourished by diffusion from the blood passing over them; small vessels are found only near the valve base (annulus).

Innervation

Sparse sensory and autonomic fibres are found mainly at the base of the leaflets and in the papillary muscles and chordae; valve function is mechanical and driven by pressure gradients.

Function

Atrioventricular valve closure produces the first heart sound (S1) and semilunar closure the second (S2). The semilunar valves close passively as ventricular pressure falls, and the atrioventricular valves are prevented from prolapsing by papillary muscle contraction.

Clinical correlations

Stenosis (narrowing) and regurgitation (incompetence) are the two basic lesions. Rheumatic disease classically affects the mitral valve, calcific degeneration the aortic valve of older adults, and a congenital bicuspid aortic valve is present in about 1 to 2% of people. Infective endocarditis and mitral valve prolapse are other common conditions; management follows local guidelines.

Common exam points

  • Auscultation areas: aortic, right second intercostal space at the sternal edge; pulmonary, left second intercostal space; tricuspid, left lower sternal edge; mitral, cardiac apex (left fifth intercostal space, midclavicular line).
  • Mitral valve is bicuspid (anterior and posterior leaflets); tricuspid has anterior, posterior and septal leaflets.
  • Atrioventricular valves have chordae tendineae and papillary muscles; semilunar valves do not.
  • Coronary arteries arise from the right and left aortic sinuses; the third cusp is non-coronary.
  • S1 is closure of the mitral then tricuspid valve; S2 is closure of the aortic then pulmonary valve (physiological splitting on inspiration).
  • Mitral stenosis is nearly always rheumatic; calcific aortic stenosis and bicuspid aortic valve are classic associations.

References

  1. Drake RL, Vogl AW, Mitchell AWM. Gray's Anatomy for Students. Elsevier — Tier 3 (textbook)
  2. Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy. Wolters Kluwer, 8th edition (2018) — Tier 3 (textbook)
  3. Bickley LS. Bates' Guide to Physical Examination and History Taking (Bickley). Wolters Kluwer, 13th edition (2020) — Tier 3 (textbook)
  4. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. Elsevier, 12th edition (2022) — Tier 3 (textbook)

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