Makindo Medical Notes

Mitral regurgitation (MR) occurs when the mitral valve fails to close properly during systole, allowing blood to flow backward from the left ventricle (LV) into the left atrium (LA). This leads to volume overload in the LA and potentially progressive heart failure if not managed effectively.

About

• Definition: Retrograde systolic flow of blood from the LV into the LA due to incomplete mitral valve closure.
• Over time, chronic MR allows the LA to dilate and adapt, reducing the rise in LA pressure, whereas acute MR (e.g., post-myocardial infarction) can precipitate pulmonary oedema due to a sudden increase in LA and pulmonary pressures.

Pathophysiology

• Volume Overload: The regurgitant flow increases LA volume, and over time, the LV also enlarges (eccentric hypertrophy) to accommodate the extra volume, potentially leading to heart failure.
• Acute vs. Chronic MR:
  • Acute MR: Sudden onset leads to pulmonary oedema and acute heart failure symptoms.
  • Chronic MR: Gradual onset allows compensatory LA enlargement and less acute pulmonary congestion but can eventually progress to LV dysfunction and symptomatic heart failure.

Causes

Clinical Features

• Symptoms: Palpitations (often due to AF), dyspnoea, fatigue, and signs of heart failure. In severe cases, patients may present with orthopnoea or paroxysmal nocturnal dyspnoea.
• Signs Suggesting Severity:
  • Small pulse volume
  • Displaced, diffuse apex beat
  • S3 heart sound due to increased LV filling
  • Pansystolic murmur (PSM) best heard at the apex, radiating to the axilla
  • Early diastolic rumble indicating significant regurgitant volume
  • Soft S1, loud P2 with pulmonary hypertension, and evidence of enlarged LV or LA on examination.

Investigations

• Blood Tests: FBC, U&E, raised CRP (suggestive of endocarditis or inflammation).
• ECG: May show atrial fibrillation, P mitrale (LA enlargement), or LV hypertrophy.
• CXR: LA enlargement, cardiomegaly, pulmonary oedema, or mitral valve calcification.
• Echocardiography: Key investigation. Shows LV and LA size, LV function, regurgitant jet on Doppler, valve anatomy, and signs of pulmonary hypertension. Transoesophageal echo (TOE) provides better anatomical detail.
• Cardiac Catheterization: Confirms MR by showing a regurgitant jet during LV contrast injection and a prominent V wave on the pulmonary capillary wedge pressure trace.

Management