Mitral Regurgitation

Risk factors

• Primary MR:
• • Mitral valve prolapse (most common cause in developed countries) — myxomatous degeneration
• • Rheumatic heart disease (most common globally)
• • Infective endocarditis (acute leaflet destruction)
• • Papillary muscle rupture or dysfunction (post-MI, classically inferior MI affecting posteromedial papillary muscle — single blood supply from PDA)
• • Connective tissue disease (Marfan, Ehlers-Danlos)
• Secondary (functional) MR:
• • Ischemic cardiomyopathy
• • Non-ischemic dilated cardiomyopathy
• • Severe LV dysfunction — annular dilation, papillary muscle displacement

Pathophysiology

Regurgitant volume increases LA pressure and reduces forward stroke volume. Acute MR: no time for LA compliance to develop → flash pulmonary edema and cardiogenic shock. Chronic MR: gradual LA dilation buffers pressure; LV dilates from volume overload (eccentric hypertrophy) and initially compensates, but eventually LV systolic dysfunction develops irreversibly.

Clinical presentation

Differential diagnosis

• Tricuspid regurgitation — Holosystolic at LEFT lower sternal border; INCREASES with inspiration (Carvallo sign); prominent cv waves in JVP; pulsatile liver if severe
• Ventricular septal defect (post-MI or congenital) — Holosystolic at LSB with palpable thrill; consider post-MI VSD if days after infarct presenting with new murmur and shock
• Hypertrophic obstructive cardiomyopathy (HOCM) — Dynamic outflow murmur, LOUDER with Valsalva/standing (decreased preload), softer with squatting/handgrip — opposite maneuvers from MR
• Aortic stenosis — Crescendo-decrescendo at RUSB, radiates to CAROTIDS (not axilla); pulsus parvus et tardus; carotid murmur from radiation
• Mitral valve prolapse without significant MR — Mid-systolic click followed by late systolic murmur; click moves EARLIER and murmur LENGTHENS with decreased preload (standing, Valsalva)
• Hyperdynamic flow states (anemia, hyperthyroidism, pregnancy, fever) — Functional systolic flow murmurs; address underlying cause; murmur resolves when state corrected

Diagnostic workup

Diagnostic algorithm

Treatment

Complications

• Heart failure (acute pulmonary edema in acute MR; chronic LV failure in chronic MR)
• Atrial fibrillation (LA dilation)
• Pulmonary hypertension, right HF
• Infective endocarditis (regurgitant jet creates susceptible 'kissing' lesion on LA wall)
• LV thrombus (rare), systemic embolization
• Sudden cardiac death (more common in severe MVP with redundant leaflets)

PANCE pearls

• Murmur intensity does NOT correlate with severity — acute severe MR often has a SHORTER, softer murmur due to rapid pressure equalization with a non-compliant LA.
• Maneuvers: MVP click/murmur moves EARLIER and LENGTHENS with decreased preload (standing, Valsalva strain phase); LATER and SHORTER with increased preload (squatting, leg raise).
• Inferior MI + new holosystolic murmur + cardiogenic shock = posteromedial papillary muscle rupture. Echo confirms. Emergent surgery; bridge with IABP and afterload reduction.
• Severe acute MR with sudden hypotension after MI may have ONLY mild murmur or none — high index of suspicion.
• MVP affects ~2% of population; most asymptomatic and benign. Risk stratifiers for adverse outcome: severe MR, LV dysfunction, AFib, bileaflet involvement, prolonged QT.

References

• ACC/AHA 2020 VHD — 2020 ACC/AHA Guideline for the Management of Patients with Valvular Heart Disease (Otto et al., Circulation 2021)
• COAPT — Transcatheter Mitral-Valve Repair in Patients with Heart Failure (Stone et al., NEJM 2018)
• MITRA-FR — Percutaneous Repair or Medical Treatment for Secondary Mitral Regurgitation (Obadia et al., NEJM 2018)
• EVEREST II — Percutaneous Repair or Surgery for Mitral Regurgitation (Feldman et al., NEJM 2011)