FRCA Notes

Mitral Stenosis

Resources

  • Mixed mitral valve disease is more common than isolated mitral stenosis
  • Rheumatic fever remains the commonest cause
  • Calcific disease of the valve, valve ring or chordae tendinae
  • Infective endocarditis
  • Carcinoid syndrome

  • Chronic LV underfilling causes pressure- and volume-increases proximal to the mitral valve
    • The LV itself functions normally despite the poor filling
    • There is, however, low stroke volume and cardiac output
    • LV filling is optimal when the HR is low, to aid diastolic filling time

  • As valve area reduces, the pressure gradient across the valve increases
    • This leads to LA dilation and usually AF
    • Eventually there'll be raised pulmonary artery pressures and pulmonary HTN
    • Subsequent RV hypertrophy and failure ensues


Grade Valve area Pressure gradient
Normal 4 - 6cm2
Mild MS 1.6 - 2cm2 <5mmHg
Moderate MS 1.0 - 1.5cm2 6 - 10mmHg
Severe MS <1cm2 >10mmHg


  • Generally well tolerated and there may be a long asymptomatic period
  • Thereafter:
    • Worsening dyspnoea
    • Fatigue
    • LRTI
    • Pulmonary oedema

  • Patients are often in AF (up to 40%)

Medical

  • β-blockade or calcium channel blockers to maintain a low-normal heart rate
  • Diuretics or long-acting nitrates to help dyspnoea
  • Anticoagulation for AF, to reduce risk of LA thrombus generation

Surgical

  • Percutaneous mitral valve balloon valvuloplasty
  • Open mitral valve repair
  • Transcatheter mitral valve repair

Perioperative management of the patient with mitral stenosis


  • History and examination as standard, focusing on:
    • Symptoms of dyspnoea, fatigue, and a history of frequent lower respiratory tract symptoms
    • Presence of symptoms/signs of right heart failure e.g. peripheral oedema, raised JVP
    • Presence of AF

Investigations

  • ECG; may show p-mitrale, or AF
  • CXR
  • TTE; need to assess right heart function and degree of pulmonary hypertension
  • CPET - consider valve repair if <4 METs undergoing elective surgery

Monitoring and access

  • AAGBI
  • A-line
  • ±CVC
  • ±TOE

Haemodynamic goals

  • Similar to that of AS
  • Neuraxial techniques relatively contra-indicated
  • In cardiac surgery to repair the valve, the chronically underfilled ventricle may fail to cope with the sudden increase in preload that occurs when the valve is repaired and inotropic support may be required
Cardiovascular feature Goal of management Rationale
Heart rate Avoid tachycardia (HR <90bpm)
Avoid bradycardia (HR >60bpm)		 Tachycardia reduces diastolic time and LV filling
However CO is heart-rate dependent due to fixed stroke volume
Heart rhythm Maintain sinus rhythm with rapid treatment of arrhythmia Adequate atrial systole is vital for cardiac output
Afterload Maintain LV afterload
Avoid excessive RV afterload
Contractility Avoid negative inotropy ± provide inotropic support Especially in late stage disease, to manage RV failure
Preload Cautious balance Excess fluid risks pulmonary oedema but need enough volume for adequate preload

  • Cardiac HDU care
  • Avoid fluid boluses for hypotension; use positive inotropy to aid both right heart and LV, which is being asked to pump a suddenly higher volume