Acute Severe Aortic Regurgitation

Acute severe aortic regurgitation is sudden backflow from the aorta into a left ventricle of normal size that cannot accommodate the regurgitant volume. It causes elevated end diastolic pressure, pulmonary oedema and low forward output.

Epidemiology. It is uncommon. Infective endocarditis and type A aortic dissection are the commonest causes. Mortality is high without surgery.

Causes and associations.

• Infective endocarditis (leaflet destruction, perforation, root abscess).
• Type A aortic dissection (loss of commissural support, leaflet prolapse).
• Chest trauma, iatrogenic injury (balloon valvuloplasty, transcatheter valve procedures), prosthetic valve failure or dehiscence.
• Rarely connective tissue disease, aortitis and cusp rupture in bicuspid valves.

Pathophysiology. The normal sized left ventricle receives a large regurgitant volume on top of left atrial inflow, so end diastolic pressure rises rapidly. Mitral valve closes early. Forward stroke volume falls and compensatory tachycardia shortens diastole. Coronary perfusion falls with low diastolic pressure and high end diastolic pressure, causing ischaemia.

Presentation is severe dyspnoea, pulmonary oedema, hypotension and shock, with tachycardia, narrow pulse pressure (compared with the wide pulse pressure of chronic disease), soft or short diastolic murmur, soft first heart sound, third heart sound and an Austin Flint murmur. Peripheral signs of chronic regurgitation are absent. Fever, embolic phenomena and heart block suggest endocarditis with abscess.

Red flags.

• Pulmonary oedema or shock with a new diastolic murmur.
• Tearing chest pain (dissection) or fever (endocarditis).
• PR interval prolongation (root abscess).

Transthoracic echocardiography (severity: premature mitral closure, short pressure half time under 200 ms, holodiastolic flow reversal in the descending aorta, vena contracta over 6 mm), then transoesophageal echocardiography for the mechanism, vegetations and root abscess. CT angiography of the aorta if dissection is suspected. Blood cultures (three sets before antibiotics), ECG, chest radiograph, troponin, natriuretic peptide and lactate. Avoid coronary angiography if there are aortic vegetations or dissection of the root.

Differential diagnosis. Acute mitral regurgitation, aortic stenosis with heart failure, myocardial infarction, tamponade and acute pulmonary oedema of other cause.

Urgent surgery is the definitive treatment. Medical therapy is a short bridge.

Contraindicated or harmful. Intra-aortic balloon pump (diastolic augmentation increases regurgitation), beta blockers (blunt compensatory tachycardia, and prolong diastole) and drugs that slow the heart rate.

Stabilisation.

• Oxygen, non-invasive ventilation or intubation.
• Vasodilator: nitroprusside 0.3 to 0.5 microgram/kg/min (maximum 10 microgram/kg/min, short term, with thiocyanate monitoring) to reduce afterload and regurgitant fraction, only when systolic pressure allows.
• Inotrope: dobutamine 2.5 to 10 microgram/kg/min, with noradrenaline for hypotension.
• Furosemide 40 to 80 mg IV.
• Keep the heart rate fast, and do not use pacing to slow it. Temporary pacing at 90 to 100 beats/min may shorten regurgitant time in selected cases with bradycardia.

Endocarditis. Take cultures first. Then give vancomycin 25 to 30 mg/kg IV loading dose then 15 to 20 mg/kg every 8 to 12 hours (adjusted to levels and renal function), plus gentamicin 3 mg/kg IV daily. For prosthetic valves add rifampicin 300 mg orally or IV every 8 hours (started 3 to 5 days after the other drugs). Continue 6 weeks, adjusted to organism.

Dissection. Emergency surgery (aortic root and ascending aorta replacement). Control heart rate and pressure only with careful vasodilator use, avoiding drugs that worsen regurgitation.

Surgery. Aortic valve replacement or repair and root procedures. Do not delay surgery for infection to settle when there is shock or pulmonary oedema.

Monitoring. Arterial pressure, ECG (PR interval), lactate, urine output, echocardiography and renal function.

Referral and escalation. Cardiac surgery, cardiology and cardiac intensive care at once.

Special groups. In pregnancy, plan with cardiology and obstetrics. In renal failure, adjust gentamicin and avoid nitroprusside accumulation.