Aortic Insufficiiency (or regurgitation, incompetence, "leaky valve"), occurs when the leaflets do not close completely in diastole, letting blood leak backward across the valve. This could include the presence of acute or chronic backwards or retrograde flow of blood across a closed cardiac valve causes an increase of blood volume within the chamber behind it.
ETIOLOGIES:
1. Leaflet Abnormalities
- Congenital
- Bicuspid - diastolic redundancy
- Acquired
- Calcific or Rheumatic AS
- Infective Endocarditis
- Bacterial infection enters the bloodstream, attacking the endothelial layer of the heart and valves resulting in perforations.
- Myxomatous degeneration
- Build up of fluid within the leaflet tips, inability to sustain high pressure during diastole, makes the leaflets thick, heavy and weak, this is a precursor to AoV prolapse.
- AoV prolapse is the abnormal apical displacement of one or more of the aortic cusps below the annulus.
- Radiation Induced
Aortic valve prolapse is seen predominantly
2. Aortic Root Abnormalities
- Annular dilation
- Systemic hypertension
- Marfan's syndrome
- Aortic aneurysm/dissection
- Post-stenotic dilation
- Systemic Lupus Erythematosus
Acute vs. Chronic Insufficiency
- Acute
- Causes: Infective Endocarditis, Aortic dissection or trauma.
- Normal LV size and function
- Elevated LV end diastolic pressures
- Increased LA and pulmonary pressures
- Surgical emergency requiring replacement or repair
- Early diastolic closure of the MV and opening of AoV
- Chronic
- Causes: Calcific, Rheumatic AS, Bicuspid AoV, Hypertension, Marfans
- LV volume overload, dilation and remodeling (eccentric hypertrophy)
- LV dysfunction with initial forward flow maintained due to Frank Starling mechanism.
- LA dilation and enlargement (compensation for regurgitant flow)
- Normal to small increase in LV end diastolic pressure and increase in LA pressure.
Findings of Aortic Regurgitation:
- M-mode
- Aortic Valve: diastolic flutter, premature systolic opening with high LVEDP (acute setting).
- Mitral Valve: increased EPSS, decreased D-E point of AMVL, and IVS/AMVL fluttering in diastole.
- Colour flow Doppler
- High velocity laminar jet at the vena contracta.
- Post-jet disturbance due to turbulent retrograde flow.
- Assess multiple views for spatial distribution, number of jets and direction.
- Spectral Analysis
- Use apical 5 or 3 chamber view with aligned parallel flow for CW Doppler.
CW flow - AI Pressure Half-time (P1/2):
- The loss/decay of pressure correlates with severity
- Mild AI - slow equalization of Ao-LV pressure resulting in a flatter slope (increased P1/2).
- Severe AI - fast equalization of Ao-LV pressure resulting in a steeper slow (decreased P1/2)
Quantification of AI severity by diastolic flow reversal (DFR):
- Descending Aorta:
- Presence of some DFR suggests normal/mild AI
- Prescence of HDFR suggests moderate to severe AI
- Proximal Abdominal Aorta:
- Presence of HDFR would be highly sensitive for severe AI
