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How can Aortic dissection cause Acute Aortic Regurgitation

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"Aortic Dissection"[MeSH Terms] AND "Aortic Valve Insufficiency"[MeSH Terms]

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acute aortic regurgitation mechanism aortic dissection aortic root commissures

In a Stanford type A aortic dissection, the intimal tear involves the ascending aorta and may extend into the aortic root, just above the aortic valve.
Blood entering the false lumen can cause acute AR by:
  1. Separating or displacing a valve commissure
    The dissection splits the aortic root wall and can pull apart the points where the valve cusps are anchored. The cusps then cannot meet properly in diastole.
  2. Acutely dilating/distorting the aortic annulus or root
    The disrupted root enlarges or loses its normal circular shape. Even structurally normal cusps cannot coapt if their supporting ring is suddenly widened or distorted.
  3. Prolapsing an intimal flap into the valve
    The dissected intimal flap can interfere mechanically with cusp closure, creating a regurgitant gap.
Result: during diastole, blood rapidly leaks from the high-pressure aorta back into the left ventricle.
Because this occurs abruptly, the LV has not had time to dilate or adapt. LV end-diastolic pressure rises sharply, causing pulmonary edema, hypotension, and possibly cardiogenic shock. This is why acute AR from proximal aortic dissection is a surgical emergency. Textbook sources describe acute AR as a major complication of aortic dissection, particularly with proximal involvement (Textbook of Clinical Echocardiography, Complications of Aortic Dissection; MSD overview).
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