Mitral Regurgitation Overview

Mitral Regurgitation (MR)

• Mitral regurgitation (MR) can arise from abnormalities affecting mitral valve components (leaflets, annulus, chordae tendineae, papillary muscles, and myocardium).
• Acute MR can result from acute myocardial infarction (MI) with papillary muscle rupture, blunt chest trauma, or infective endocarditis (IE). The posteromedial papillary muscle is more commonly affected in acute MI than the anterolateral one.
• Transient acute MR can occur during angina pectoris episodes.
• Chronic MR can be primary (degenerative) or secondary (functional). Primary MR involves abnormal leaflet or chordae tendineae function, while secondary MR is caused by LV remodeling, annular dilation, papillary muscle displacement, dyssynchrony, or posterior leaflet tethering.
• Rheumatic fever can cause valve rigidity, deformity, retraction, and commissural fusion, along with chordae shortening and fusion.
• Congenital MR can occur, often involving endocardial cushion defects; a cleft anterior leaflet can accompany an ostium primum atrial septal defect.
• Radiation exposure can lead to leaflet thickening, retraction, and calcification, often with annular and chordal involvement, and sometimes mitral stenosis.
• Post-MI MR is common and linked to changes in LV size, shape, and function.
• Non-ischemic dilated cardiomyopathy, once LV end-diastolic dimension reaches 6 cm, often leads to MR due to similar annular dilation and ventricular remodeling mechanisms.
• Hypertrophic obstructive cardiomyopathy (HOCM) often causes dynamic MR dependent on systolic anterior mitral valve leaflet motion.
• Chronic persistent atrial fibrillation (AF) can lead to atrial remodeling, annular dilation and MR due to inadequate leaflet lengthening
• Annular calcification, especially prevalent in older women with hypertension and diabetes and advanced renal disease, can cause MR.
• Irrespective of cause, severe chronic MR tends to progress because LA enlargement strains the posterior leaflet, exacerbating dysfunction.

Pathophysiology of MR

• LV afterload is decreased in MR patients, causing LV decompression into the LA during ejection and a rapid drop in LV tension.
• Initial MR compensation involves more complete LV emptying.
• LV volume progressively increases with MR severity and declining LV function.
• Increased LV volume is often associated with reduced cardiac output (CO).
• LV compliance frequently increases.
• Regurgitant volume directly correlates with LV systolic pressure and regurgitant orifice size.

Management of MR

• Chronic severe MR management depends on the cause.
• Anticoagulation (warfarin or direct oral anticoagulants) is necessary with atrial fibrillation, guided by CHA2DS2-VASc risk score.
• Direct oral anticoagulants should be avoided with moderate-to-severe rheumatic mitral stenosis or mechanical prosthetic valves.
• Cardioversion can be considered.
• Vasodilators aren't definitively supported for chronic isolated severe MR with preserved LV function without hypertension.
• GDMT (including diuretics, beta-blockers, ACE inhibitors/ARBs, angiotensin-neprilysin inhibitors, mineralocorticoid receptor antagonists, SGLT2 inhibitors, and CRT) may improve secondary MR, especially in ischemic or dilated cardiomyopathy.
• Antibiotic prophylaxis for IE is warranted for MR patients with prior IE.
• Isometric exercise should be avoided by asymptomatic MR patients with normal LV size and function in sinus rhythm.
• Acute severe MR necessitates urgent stabilization and surgical preparation.

Surgical Treatment of MR

• For chronic severe primary MR, surgery is indicated when symptoms appear, especially if repair is feasible.
• Surgery is also indicated for asymptomatic patients with LV dysfunction (EF ≤60% or LV ESD ≥40 mm).
• Progressive LVEF decline or increasing LV ESD on serial imaging also warrants consideration.
• Repair, rather than replacement, is preferred, because it avoids thromboembolic/hemorrhagic complications associated with mechanical prostheses, and late valve failure requiring re-replacement in the case of bioprostheses.
• Repair preserves LV function better than replacement.

Explore the various aspects of mitral regurgitation (MR), including its causes, types, and pathological mechanisms. This quiz covers both acute and chronic forms of MR and the underlying abnormalities affecting the mitral valve. Test your knowledge on this important cardiac condition and its implications.