Aortic regurgitation general approach to aortic insufficiency
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Aortic Regurgitation Microchapters |
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Chronic Aortic regurgitation |
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Raviteja Guddeti, M.B.B.S. [2]
Overview
Aortic insufficiency is defined as reverse or backward flow of blood from the aorta into the left ventricle during diastolic phase of the heart beat.
Classification
Aortic insufficiency can be acute or chronic.
Pathophysiology
Pathophysiology of acute aortic regurgitation involves sudden large regurgitant volume of blood imposed on unprepared left ventricle. There will not be any acute left ventricular enlargement as enlargement usually takes place over a period of time. The effective left ventricle stroke volume is reduced because of the reverse flow of blood from aorta. This leads to rapid increase in left ventricular end diastolic pressures. Patients tend to develop pulmonary edema because of the reversal of pressure gradients. Cardiac output is reduced and inturn blood pressure. Tachycardia can not compensate for the lowering cardiac output.
Causes
Aortic insufficiency can be caused by defects in the intrinsic valve or ascending aorta (root).
- Intrinsic Valvular:
- Degenerative / calcific aortic valve
- Endocarditis
- Bicuspid aortic valve
- Rheumatic fever
- Valvulitis
- Anorectic drugs
- Ascending aorta (root):
- Degenerative
- Type A aortic dissection
- Marfan syndrome
- Giant cell arteries
- Inflammatory:
Differentiating Aortic insufficiency from Mitral regurgitation
Natural History
Two parameters that reflect the overall outcome in patients with aortic insufficiency include:
- Ejection fraction
- End systolic diameter
After the onset of severe regurgitation it takes decades to progress to the stage of left ventricular dysfunction. This time period is longer than that for mitral regurgitation.
Lower the ejection fraction poorer the outcome. Ejection values less than 55% have a poor outcome than ≥55%.
Similarly end systolic diameter of >50 mm is associated with poorer outcome.
Diagnosis
Symptoms
Acute aortic insufficiency may present with the following symptoms:
- Sudden onset of severe breathlessness (dyspnea)
- Chest pain if aortic dissection is the cause of insufficiency.
Chronic aortic insufficiency causes:
In patients with bicuspid aortic valve if hypertension is present coarctation of aorta should be considered and similarly if chest pain is present dissection of aorta should be considered. Therefore the entire aorta should be scanned either by an magnetic resonance angiogram (MRA) or computed tomography (CT).
Physical Examination
- Bounding pulses may be present
- Head nodding (de Musset's sign) - rhythmic nodding or bobbing of the head in synchrony with the beating of the heart.
- Capillary pulsations (Quincke's sign) - pulsation of arteriolar and venous plexuses of the nail bed causing alternate blanching and flushing.
- Corrigan's pulse - rapid carotid upstroke, rapid collapse
- Duroziez's sign - 'pistol' shot sounds (audible diastolic murmur heard over the femoral artery.
- Early diastolic murmur best heard in the right second intercostal space. The murmur may be soft in acute AR.
- S3 and S4 may be heard.
Imaging
Parameters to assess on an ECHO include:
ECHO can also be used to assess the ascending aorta (root) and/or valve causes of insufficiency.
If 'mild AR' on ECHO, an aortic root injection on cath can be obtained. Echocardiographic parameters to determine severity of AR include:
- AR color jet dimension/left ventricular outflow tract diameter >60%
- Flow reversal in proximal descending thoracic aorta
- Regurgitant volume >60 ml
- Regurgitant fraction >55%
If ECHO color flow alone i staken into consideration it might underestimate or overestimate the severity of regurgitation. In such cases it is recommended to prefer cardiac catheterization as an imaging modality. If cath discrepancy is present it is recommended to do a left ventriculogram using 60 cc at 20 cc/sec to assess for severity.
- Treadmill testing in aortic regurgitation is used to get objective measurement of exercise capacity.
- Magnetic resonance angiogram (MRA) and CT are used to scan the entire aorta in case of bicuspid aortic valve.
Treatment
Acute severe Aortic insufficiency
- Urgent surgical intervention is generally indicated especially type A dissection and acute prosthetic AR.
- Nitroprusside and ionotropes can be used to maintain blood pressure.
- Treatment options that are contraindicated include:
- Intra aortic balloon pump
- Pressors
- Beta blockers
Chronic Aotic insufficiency
Vasodilator therapy for severe chronic aortic insufficiency is indicated:
- Chronic treatment for patients with symptoms and/or left ventricular ejection fraction ≤50% who are not candidates for aortic valve replacement.
- Asymptomatic patients with AR and hypertension.
Vasodilator therapy is not indicated for others with AR.
Unlike mitral regurgitation there is no need for prophylactic surgery in aortic insufficiency as the drop in ejection fraction occurs before irreversible left ventricular dysfunction occurs.