chronic mitral regurgitation (MR)

Classification

• mild
  • vena contracta < 0.30 cm
  • regurgitant oriface area < 0.20 cm2
  • regurgitant volume < 30 mL
  • regurgitant fraction < 30%
• moderate
  • vena contracta 0.30-0.69 cm
  • regurgitant oriface area 0.20-0.39 cm2
  • regurgitant volume 30-59 mL
  • regurgitant fraction 30-49%
• severe
  • vena contracta >- 0.7 cm
  • regurgitant oriface area >= 0.40 cm2
  • regurgitant volume >= 60 mL
  • regurgitant fraction >= 50%

* primary: involves mitral annulus only

* secondary: involves causes other than mitral annulus (ventricular dysfunction)

Etiology

• mitral valve prolapse (most common)
• myxomatous degeneration of the mitral valve (common)
• rheumatic heart disease
• calcification of the mitral valve annulus
• coronary artery disease associated with papillary muscle dysfunction
• infective endocarditis
• connective tissue diseases
  • Marfan's syndrome
  • Ehlers-Danlos syndrome
• secondary phenomenon associated with left ventricular dilation
• hypertrophic cardiomyopathy

Epidemiology

• young adult with history of rheumatic fever
• 9.3% of elderly (> 75 years)

Pathology

• left ventricular volume overload
• marked ventricular dysfunction generally occurs prior to a significant decline in LV ejection fraction (LVEF)
• decrease left ventricular ejection fraction (LVEF) with progression of disease
• left atrial enlargement with progression of disease
• atrial fibrillation with left atrial enlargement
• mitral regurgitation increases markedly with exercise in 32% of patients

Clinical manifestations

• apical holosystolic or late systolic murmur
  • murmur best heard at the apex
  • usual murmur is crescendo-decrescendo
  • rheumatic MR is usually plateau
  • murmur may be decreased with diminished cardiac output
  • radiates to left axilla or base if posterior leaflet is involved
  • Valsalva maneuver moves onset of murmur closer to S1
  • handgrip increases intensity of murmur
  • no change in murmur after extra-systole
• systolic click in mitral valve prolapse
• displaced & enlarged point of maximum impulse (PMI)
• decreased S1, widely split S2, S3 audible, increased P2
• preserved carotid pulsations
• orthopnea, paroxysmal nocturnal dyspnea, edema

Diagnostic procedures

• electrocardiogram is generally abnormal
  • left atrial enlargement is common
  • atrial fibrillation may occur
  • left ventricular hypertrophy with or without ST-T wave changes
• echocardiography is indicated for all holosystolic murmurs
  • doppler
    • doppler difficult to not feasible in obese patient
  • transesophageal echocardiogram (TEE)
    • if visualization inadequate with transthoracic echocardiogram (TTE)
      • doppler inadequate with TTE
      • obese patients (initial evaluation)
    • alternative is cardiac magnetic resonance imaging
  • severe mitral regurgitation: regurgitant orifice area >= 0.4 cm2, regurgitant fraction >50%
  • unfavorable surgical outcomes suggested by:
    • left ventricular end diastolic volume of > 7.0 cm
    • left ventricular end systolic volume of > 4.5 cm
    • left ventricular ejection fraction of < 60%
  • frequency of serial evaluation
    • every 1-2 years for moderate mitral regurgitation (regurgitant fraction <50%)
    • every 6-12 months for severe mitral regurgitation (regurgitant fraction >50%)
  • repeat echocardiography indicated when there is a change in clinical status (even if most recent echocardiogram was 3-4 months prior)
• cardiac catheterization
  • standard for assessing severity of MR
  • required for evaluating patient for mitral valve replacement (MVR)
• exercise stress testing may be useful for identifying asymptomatic patients at risk

Radiology

• cardiac magnetic resonance imaging
  • alternative to transesophageal echocardiogram (TEE) when
    • visualization is inadequate with transthoracic echocardiogram (TTE)
    • assessment from TTE disrepant from clinical assessment from symptoms

Differential diagnosis

• aortic stenosis
  • murmur of aortic stenosis is louder & longer after extra-systole in contrast to MR
• mitral valve prolapse
• infectious endocarditis
• hypertrophic cardiomyopathy
• ischemic heart disease
• ventricular dilation
• Marfan's disease
• use of appetite suppressants (fenfluramine-phentermine)

Management

• Medical therapy for secondary mitral regurgitation
  • prophylaxis for infective endocarditis
    • previously indicated
    • no longer recommended
  • anticoagulation
    • atrial fibrillation
      • ref recommends continued warfarin even in the absence of evidence of further atrial fibrillation after surgical repair
    • left atrial enlargement
    • previous embolic event
    • incidence of thromboembolic events is less than that for mitral stenosis
  • atrial fibrillation
    • cardioversion (see atrial fibrillation)
      • 3 weeks of anticoagulation indicated prior to elective cardioversion
      • rhythm control unlikely to be sustainable in a patient with left atrial enlargement
    • ventricular rate control
      • verapamil, diltiazem
      • beta-blocker
  • vasodilators have not been shown to reduce progression of LV dysfunction
    • decrease systemic vascular resistance (SVR)
      • nitroprusside
      • ACE inhibitor or angiotensin receptor blocker (ARB)
      • hydralazine
    • used primarily in patients with contraindication(s) to surgery
  • beta-blocker may improve LV dysfunction
  • diuretics useful for treating congestive symptoms
    • loop diuretic
    • spironolactone may be useful
  • digoxin may be useful if LV systolic dysfunction
  • nitrates reduce:
    • preload
    • left ventricular end diastolic volume
    • severity of mitral regurgitation
• Surgery:
  • indications
    • moderate to severe disease
      • symptomatic despite optimized medical management
      • LV dilation
      • left ventricular ejection fraction (LVEF) >40%
        • LVEF 30-60% (indicates moderate LV dysfunction)
      • early surgical repair is associated with reduced late cardiac mortality & cardiac events in asymptomatic patients with severe mitral stenosis
      • mitral valve repair for moderate MR during CABG reduces MR at 12 months, but does not improve reverse LV remodeling or improve survival or quality of life
    • minimal to mild symptoms
      • mitral valve replacement (MVR) or repair when
        • LV dilatation: LV end-systolic dimension > 40-45 mm
        • decreasing LVEF with LVEF 30-60%
        • pulmonary artery systolic pressure > 50 mm Hg
        • exercise-induced increase in pulmonary artery pressures of >= 25 mm Hg
        • new onset atrial fibrillation
      • mitral valve surgery NOT indicated if LVEF < 30%
      • surgery for regurgitant orifice of > 40 mm2
        • close monitoring for regurgitant orifice of 20-40 mm2
      • moderate to severe mitral regurgitation in patients undergoing cardiac surgery for other reasons
      • new-onset atrial fibrillation
      • advanced age NOT a contraindication
        • operative mortality 5-15% (mitral valve replacement)
  • mitral valve repair, when feasible, preferable to mitral valve replacement
    • bioprosthetic valve preferred over mechanical valve
    • outcomes similar at 1 year for mitral valve replacement vs mitral valve repair for mitral regurgitation secondary to ischemic heart disease
    • transcatheter mitral valve repair improves survival in high surgical risk patients
    • no difference in survival at 2 years for repair vs replacement, but recurrence of mitral regurgitation more common with repair
    • 15-year recurrence after mitral valve repair is 13%
      • older age, residual mild MR in the operating room, bileaflet or anterior leaflet prolapse, & absence of ring annuloplasty predict recurrent MR
  • MitraClip, a transcatheter system for mitral valve repair in patients with high surgical risk
    • similar 5 year outcomes to surgery in patients with severe mitral regurgitation (5 year survival 40%)
    • 1,100 reports of patient deaths
    • MitraClip system (illustration)
• follow-up
  • mild:
    • clinical evaluation yearly
    • echocardiography only if symptomatic
  • moderate
    • clinical evaluation yearly
    • echocardiography every 1-2 years
  • severe
    • clinical evaluation every 6-12 months
    • echocardiography every 6-12 months

More general terms

• mitral regurgitation (MR)
• chronic heart disease

Additional terms

• heart murmur
• mitral valve