Flail Mitral Leaflet

A flail mitral leaflet is a leaflet whose free edge or a segment of it moves into the left atrium during systole because of ruptured chordae tendineae or a ruptured papillary muscle head, so the leaflets cannot coapt and severe regurgitation results.

The commonest cause is degenerative mitral disease, either fibroelastic deficiency (older patients, single segment, usually P2) or Barlow disease (younger patients, multiple segments).

Other causes are infective endocarditis, acute myocardial infarction (papillary muscle rupture, usually 2 to 7 days after inferior infarction), blunt chest trauma, rheumatic disease, connective tissue disorders and, rarely, spontaneous rupture. The posterior leaflet is involved in about two thirds of cases.

Untreated, a flail leaflet with severe regurgitation carries a high rate of heart failure, atrial fibrillation and death over 10 years, and mortality is high in acute presentations.

Pathophysiology. Loss of coaptation allows a large regurgitant volume into a low pressure left atrium. In acute rupture the left atrium is not compliant, so left atrial and pulmonary venous pressures rise abruptly, causing pulmonary oedema, while forward output falls, causing shock.

In chronic regurgitation the atrium and ventricle dilate and compensate for years until the ventricle fails. The jet is eccentric and directed away from the flail leaflet: posterior flail gives an anteriorly directed jet along the septum and aortic root, and anterior flail gives a posteriorly directed jet.

• Acute: sudden dyspnoea, orthopnoea, pulmonary oedema, hypotension and shock. The murmur may be soft or short because left atrial pressure rises rapidly, and may radiate to the base or neck when the jet is anteriorly directed. A third heart sound and tachycardia are common. Hyperdynamic ventricular impulse with a normal sized heart.
• Chronic: exertional dyspnoea, fatigue, palpitations from atrial fibrillation, a loud apical holosystolic murmur radiating to the axilla (posterior flail) or the spine or base (anterior flail), a displaced apex, and signs of pulmonary hypertension.
• Fever, embolic signs or a preceding dental or other source suggest endocarditis. Chest pain with an inferior infarct history suggests papillary muscle rupture.

Red flags.

• Acute pulmonary oedema, hypotension or shock
• Murmur absent or short in a patient with acute severe dyspnoea
• Fever, vegetations or embolic events
• Recent myocardial infarction
• Ejection fraction of 60% or less, or end systolic diameter of 40 mm or more
• New atrial fibrillation or pulmonary systolic pressure over 50 mm Hg

• Transthoracic echocardiography. Flail segment, leaflet tip pointing into the left atrium, ruptured chordae as a mobile echo dense structure, eccentric jet direction (use colour Doppler and, when the jet is wall hugging, pulmonary vein flow), left atrial and ventricular size, ejection fraction, pulmonary pressure. A flail leaflet or ruptured papillary muscle is itself a specific sign of severe regurgitation. Further severity measures: vena contracta 7 mm or more, effective regurgitant orifice area 40 mm2 or more, regurgitant volume 60 mL or more, regurgitant fraction 50% or more, and systolic pulmonary vein flow reversal.
• Transoesophageal echocardiography with three dimensional imaging. Segment location, flail width and gap, vegetation, and repair feasibility. A flail gap under 10 mm and a flail width under 15 mm define anatomy suitable for edge-to-edge catheter repair.
• ECG, chest X-ray, natriuretic peptide, troponin (after infarction), blood cultures (3 sets) with any fever.
• Coronary assessment before surgery in men over 40 years, women over 50 years, or anyone with risk factors or symptoms. Invasive angiography or CT coronary angiography.
• Cardiac MRI to quantify regurgitation when echocardiography is discordant.

Differential diagnosis.

• Severe mitral regurgitation from prolapse without a flail segment
• Functional (secondary) mitral regurgitation from ventricular dilatation or ischaemia
• Leaflet perforation or destruction from endocarditis
• Ventricular septal rupture after infarction
• Acute severe aortic regurgitation
• Acute coronary syndrome and cardiogenic shock from other causes
• Tamponade, pulmonary embolism and acute pulmonary oedema from other causes
• Hypertrophic cardiomyopathy with systolic anterior motion
• Mitral annular disjunction without a flail leaflet

Acute severe regurgitation (shock or pulmonary oedema). Emergency.

• Admit to a cardiac intensive care unit, give oxygen to a saturation of 94 to 98%, start non-invasive ventilation for hypoxaemia, and call the heart team and the cardiac surgeon at once. Positive pressure ventilation reduces preload and helps, but intubation may precipitate collapse, so prepare vasopressors first.
• Afterload reduction when systolic pressure is over 100 mm Hg:
  • Sodium nitroprusside 0.3 microgram/kg/min intravenously, increased every 3 to 5 minutes to a usual 0.5 to 3 microgram/kg/min, maximum 10 microgram/kg/min (for no more than 10 minutes at the maximum rate). Arterial line, protect from light. Limit duration to under 48 hours, and avoid or monitor thiocyanate and acidosis in renal or liver impairment.
  • Alternative: glyceryl trinitrate 10 to 20 microgram/min intravenously, increased by 5 to 10 microgram/min every 5 to 10 minutes, usual maximum 200 microgram/min. Contraindicated with phosphodiesterase type 5 inhibitors and in hypotension.
• Furosemide 40 to 80 mg intravenously, doubled after 1 to 2 hours if the response is inadequate (maximum single dose 200 mg), with sodium, potassium and creatinine monitoring.
• Hypotension or shock: noradrenaline 0.05 microgram/kg/min intravenously, titrated to a mean pressure of 65 mm Hg, usual maximum 0.5 microgram/kg/min. Dobutamine 2.5 to 5 microgram/kg/min, maximum 20 microgram/kg/min, for low output. Intra-aortic balloon pump as a bridge, because it reduces afterload and regurgitation. Avoid beta blockers.
• Urgent surgery. Repair is preferred when anatomy allows (most posterior flails are repairable in experienced centres). Replacement with preservation of the subvalvular apparatus when repair fails. Papillary muscle rupture after infarction needs emergency replacement, and mortality is high.
• Treat endocarditis with intravenous antibiotics chosen by the organism and its sensitivities, with surgery for heart failure, abscess or large vegetation.

Chronic severe regurgitation.

• Surgery is indicated for symptoms, or for asymptomatic patients with ejection fraction of 60% or less, end systolic diameter of 40 mm or more, new atrial fibrillation, pulmonary systolic pressure over 50 mm Hg, or left atrial volume index of 60 mL/m2 or more. It is also reasonable in asymptomatic patients with a flail leaflet and normal ventricular size when a durable repair is very likely (over 95%) and operative mortality is under 1%, in a high volume valve centre.
• Transcatheter edge-to-edge repair for symptomatic patients at high or prohibitive surgical risk with suitable anatomy.
• Medical therapy does not treat the lesion. Furosemide 40 mg orally once daily in the morning, increased to 80 to 120 mg daily as needed (higher doses in renal impairment under specialist care), with sodium, potassium and creatinine monitoring, for congestion in patients who await or cannot have intervention.
• Atrial fibrillation: apixaban 5 mg orally twice daily, reduced to 2.5 mg twice daily when at least two of age 80 years or over, weight 60 kg or under and serum creatinine 133 micromol/L or over are present. Also 2.5 mg twice daily at creatinine clearance 15 to 29 mL/min, and avoided under 15 mL/min. Maximum 10 mg daily. Long term.

After surgery.

• Mechanical mitral valve: warfarin 5 mg orally once daily at the start (2 to 3 mg in older adults, liver impairment or interacting drugs), adjusted to an INR of 3.0 (2.5 to 3.5), no fixed maximum, for life. INR every 2 to 3 days at the start, weekly until stable, then every 4 to 12 weeks.
• Bioprosthesis or repair with a ring: warfarin to an INR of 2.5 (2.0 to 3.0) for 3 months, then aspirin 75 to 100 mg orally once daily long term.

Special groups. Acute severe regurgitation in pregnancy is poorly tolerated, and surgery in pregnancy is reserved for refractory heart failure. Pregnancy after repair is usually tolerated with normal ventricular function.

Monitoring. Intensive haemodynamic and urine output monitoring in the acute phase. After repair, echocardiography at 6 to 12 weeks and then yearly. In unoperated asymptomatic severe regurgitation, echocardiography every 6 months, with exercise testing and natriuretic peptide when symptoms are doubtful.

Referral and escalation. Refer to a heart team in a valve centre. Emergency for acute severe regurgitation, shock, papillary muscle rupture or endocarditis with heart failure.