Mitral Regurgitation (MR)

Question 1

Definition of MR

Answer 1

• Systolic leakage of blood from the LV into the LA
• Results in HF

Question 2

Aetiology of MR

Answer 2

• Acute MR
  
  • Infective endocarditis
  • Ischaemic papillary muscle dysfunction or rupture
  • Rheumatic fever
  • Acute dilatation of the LV due to myocarditis or ischaemia
• Chronic AR
  
  • As above
  • Degeneration of the mitral leaflets or chordae tendineae
  • Mitral valve prolapse
  • Mitral annular enlargement

Question 3

Signs and Symptoms of MR

Answer 3

• Pan-systolic, high pitched ‘whistling/blowing’ murmur that radiates to the left axilla and may have a 3rd heart sound.
• Signs/symptoms include dyspnoea on exertion, lower extremity oedema, fatigue and displaced point of maximal impulse.
• Risk factors include mitral valve prolapse, Hx of rheumatic heart disease, infective endocarditis, Hx of cardiac trauma, Hx of MI/IHD, congenital heart disease, LVSD, hypertrophic cardiomyopathy and anorectic/dopaminergic drugs.

Question 4

Pathophysiology of MR

Answer 4

• Progression leads to cardiac hypertrophy and elongation of the myocardial fibres and increased LV end diastolic volume.
• This allows increase in stroke volume to maintain cardiac output
• LV and LA enlargement accommodate the volume at a lower filling pressure to prevent pulmonary congestion
• Eventually, prolonged volume overload leads to LV dysfunction and increased LV end systolic diameter
• Also leads to pulmonary HTN, secondary right heart dilatation and AF

Question 5

Investigation of MR

Answer 5

• ECHO
  
  • Presence and severity of MR
• ECG
  
  • May show underlying arrhythmia