Mitral Regurgitation

1. Natural History

a) Etiology

i) Acute

a) Papillary muscle/chordae tendinae dysfunction 2°

(1) myocardial ischaemia/infarct

(a) Papillary muscles very vulnerable to ischaemia

(b) 40% patients with post septal MI

(c) 20% patients with ant septal MI

(2) Trauma

(3) Endocarditis

ii) Chronic

a) Barlow syndrome

(1) 1° MVP

(a) 10% total pop;

(i) 5% of 10% clinically significant

b) Rheumatic

c) Ventricular dilatation

(1) Hypertension

(2) Ischaemia/infacrtion

(3) Valvular

(4) Shunts

2. Symptoms

a) Presence of symptoms is ominous - have < 5 years life expectancy

b) left ventricular failure

i) In the early stages of MR the heart maintains normal circulatory function by increasing left ventricular end diastolic volume

ii) Marked degrees of MR may be well tolerated by compensatory measures before patient is aware of having a heart disease Beyond critical stages, heart cannot keep up with work demand

c) Pulmonary oedema

i) reduced net movement of blood from left atrium into left ventricle

Þ increased blood volume in left atrium

Þ increase in left atrial pressures

Þ increased pulmonary capillary pressures

Þ pulmonary oedema

d) Pulmonary hypertension

i) increased pulmonary capillary pressures

Þ damming of blood in pulmonary artery

Þ pulmonary oedema

Þ intense pulmonary arteriolar constriction

Þ pulmonary artery hypertension

Þ hypertrophy right heart

Þ RHF

e) Atrial fibrillation

i) increased blood volume in left atrium

Þ enlargement of left atrium

Þ increases electrical pathway conduction distance

Þ development of circus movements

Þ atrial fibrillation

Þ Source of left atrial thrombi

a) systemic emboli

3. Pressure-volume loops

a) In chronic MR, the LVEDP may remain normal until terminal stages of disease

b) See major increases in LVEDV & LVESV

c) Eccentric hypertrophy allows maintenance of forward stroke volume by increasing total stroke volume

1. Gross Anatomy

§ Enlarged dilated left atrium

§ Enlarged dilated left ventricle

§ Right ventricular hypertrophy & dilatation

§ Ruptured chordae tendineae

§ Pulmonary fibrosis

1. Pathophysiology