Mitral Stenosis¶

Chapter 274 | Part 6: Disorders of the Cardiovascular System · Part 6 – Cardiovascular Disorders · Chapter 274

Key Clinical Points¶

Rheumatic fever is the leading cause of mitral stenosis (MS); incidence is high in low-income countries.
Severe MS is defined by a mitral valve area (MVA) <1.5 cm²; critical stenosis is <1.0 cm².
The opening snap (OS) follows aortic valve closure (A2) by 0.05–0.12 s; the interval varies inversely with MS severity.
Percutaneous mitral balloon commissurotomy (PMBC) is preferred for symptomatic patients with pliable valves, no significant MR, and no thrombus.
Vitamin K antagonists (INR 2–3) are recommended for MS patients with AF or history of thromboembolism; DOACs are not recommended for rheumatic MS.
Chronic severe MR is defined by regurgitant volume (RVol) ≥60 mL/beat, regurgitant fraction (RF) ≥50%, and effective regurgitant orifice area (ERO) ≥0.40 cm².
Acute severe MR may present with reduced arterial pressure, narrow pulse pressure, and prominent pulmonary congestion.
Mitral annular calcification (MAC) can involve both primary and secondary MR components as the disease process may encroach on the leaflets.
Systemic embolization in MS occurs more frequently in patients with AF, age >65 years, and reduced cardiac output (CO).
Surgical mitral valve replacement (MVR) is necessary for MS with significant associated MR or severe distortion by previous manipulation.

DEFINITION & OVERVIEW¶

• Mitral Stenosis (MS): Valvular heart disease characterized by obstruction of left ventricular inflow due to narrowing of the mitral valve orifice. • Mitral Regurgitation (MR): Backflow of blood from the left ventricle into the left atrium during systole. • Primary (Degenerative) MR: Resulting from an abnormality in the leaflets and/or chordae tendineae. • Secondary (Functional) MR: Resulting from LV and/or LA remodeling, annular dilation, papillary muscle displacement, dysynchrony, leaflet tethering, or a combination thereof; leaflets and chordae are 'innocent bystanders'.

Mitral Stenosis Classification¶

• Severe MS: MVA <1.5 cm². • Critical Stenosis: MVA <1.0 cm².

EPIDEMIOLOGY¶

• Rheumatic Fever Impact: Primary cause of MS; incidence has declined in temperate climates but remains high in low-income countries (sub-Saharan Africa, India, Southeast Asia, and Oceania). • Prevalence: Pure or predominant MS occurs in ~40% of all patients with rheumatic heart disease. • Clinical Course: In temperate climates, the period between initial rheumatic carditis and symptomatic MS is typically 2 decades; most patients begin to experience disability in the fourth decade.

ETIOLOGY & PATHOPHYSIOLOGY¶

• MS Pathophysiology: - Chronic inflammation leads to tissue thickening, formation of fibrous tissue, and calcific deposits. - Result: Fusion of mitral commissures and chordae tendineae; leaflets become rigid, leading to a 'fish-mouth' valve shape. - Hemodynamics: MVA <2 cm² requires elevated LA pressure; MVA <1.5 cm² (severe) requires ~25 mmHg to maintain normal cardiac output (CO). - Complications: Pulmonary venous hypertension leads to pulmonary edema, hemoptysis, and potential for pulmonary infections. • MR Pathophysiology: - Reduced LV afterload leads to LV decompression into the LA during ejection. - Compensation: Initial complete LV emptying; later, LV volume increases as regurgitation worsens. - Hemodynamics: Regurgitant volume varies directly with LV systolic pressure and orifice size. In pure severe MR, a rapid y descent occurs due to fast flow across a normal-sized mitral orifice.

Table 274-1: Major Causes of Mitral Stenosis¶

• Rheumatic fever • Congenital (parachute valve, cor triatriatum) • Severe mitral annular calcification with leaflet involvement • SLE, RA • Myxoma • IE with large vegetations

Table 275-1: Major Causes of Mitral Regurgitation (MR)¶

• Acute: IE, Papillary muscle rupture (post-MI), Chordal rupture/leaflet flail (MVP, IE), Blunt trauma. • Chronic Primary: Myxomatous (MVP, Barlow's, forme fruste), Rheumatic fever, Congenital (cleft, AV canal), Radiation. • Secondary: Ischemic cardiomyopathy, Dilated cardiomyopathy, HOCM (with SAM), AF with LA enlargement and annular dilation, Mitral annular calcification.

CLINICAL FEATURES¶

• General Signs: Malar flush, pinched/blue facies; prominent a waves in S2 if pulmonary hypertension is present. A parasternal lift signifies an enlarged RV. • Mitral Stenosis Findings: - S1: Accented and slightly delayed in early stages. - S2: Pulmonary component (P2) accentuated; components closely split. - Opening Snap (OS): Follows A2 by 0.05–0.12 s; interval inversely proportional to severity. - Murmur: Low-pitched, rumbling diastolic murmur at the apex; presystolic accentuation in sinus rhythm. - Graham Steell Murmur: High-pitched, diastolic decrescendo blowing murmur along the left sternal border (indicates pulmonary hypertension). • Mitral Regurgitation Findings: - S1: Absent, soft, or buried in holosystolic murmur. - S3: Occurs 0.12–0.17 s after A2; may indicate ventricular dysfunction in cardiomyopathy. - Murmur: Holosystolic (usually), loudest at apex and radiating to axilla. Decrescendo quality in acute MR.

Key Clinical Distinctions¶

• S1/S2 Differences: In MS, S1 is accentuated; in severe MR, S1 is often absent or buried. • Murmur Timing: MS features a diastolic rumble; MR features a systolic murmur.

DIFFERENTIAL DIAGNOSIS¶

• Mitral Stenosis Differentials: - Atrial Septal Defect (ASD): Distinguished by absence of LA enlargement and presence of fixed split S2 with mid-systolic murmur. - Left Atrial Myxoma: Presents with similar symptoms/murmurs but associated with systemic features (weight loss, fever) and distinct echo appearance. • Mitral Regurgitation Differentials: - Austin Flint Murmur: Mid-diastolic murmur from severe AR; not intensified in pre-systole and softens with vasodilators. - Tricuspid Stenosis (TS): May mask MS features; murmur increases with inspiration; delayed y descent.

Key Distinctions¶

• MS vs. MR: In isolated MR, the diastolic murmur starts later and is accompanied by clear LV enlargement. • MS vs. ASD: ASD lacks LA enlargement and Kerley B lines; shows fixed S2 split.

DIAGNOSTIC APPROACH¶

Echocardiogram (TTE):
MS: Measure MVA, transvalvular gradients, and presence of MR; assess leaflet calcification/restriction.
MR: Assess mechanism, severity (V_c geq 0.7 ext{ cm}, mL geq 50, RVol geq 60, EF leq 50%, ERO geq 0.40 ext{ cm}^2), and LV function.
Transesophageal Echocardiography (TEE):
Used when TTE is inadequate or to exclude LA thrombus before PMBC.
Chest X-Ray:
MS: Look for enlarged LA, prominent PAs, and Kerley B lines (present if mean LA pressure > 20 mmHg).
MR: Identify LV/LA enlargement; look for asymmetric pulmonary edema in acute MR.

ECG Findings¶

• MS: P wave suggests LA enlargement; RV hypertrophy and right axis deviation if pulmonary hypertension is present. - Note: S1 is usually accentuated in early MS.

MANAGEMENT & TREATMENT¶

• General Measures: Sodium restriction, diuretics, and rate control (Beta blockers, CCBs, Digoxin) for AF. • Anticoagulation: - Vitamin K antagonists (INR 2–3) for MS with AF, history of embolism, or LA thrombus. - DOACs are NOT recommended for rheumatic MS.

Management of Rheumatic Mitral Stenosis¶

Cardioversion:
Indicated if AF is recent and MS is not severe enough for PMBC/Surgery.
Requires 3 weeks of anticoagulation; TEE to rule out thrombus if urgent.
Mitral Commissurotomy (PMBC):
Criteria: Symptomatic (NYHA II–IV), isolated severe MS, MVA ≤ 1.5 cm², mean gradient ≤ 50 mmHg (rest) or >60 mmHg (exercise).
Exclusion: Not for patients with significant MR or extensive calcification.
Surgical Intervention (MVR):
Required if: Significant associated MR, severe tissue distortion, or non-surgical candidate with high risk.

Management of Primary Mitral Regurgitation¶

Identify Severity: V_c geq 0.7 ext{ cm}, mL geq 50, RVol geq 60, EF leq 50%, and ERO geq 0.40 ext{ cm}^2.
Determine Strategy based on LV Function:
LV Dysfunction (C2): (LVEF leq 60% or ESD geq 40 ext{ mm}).
Normal LV Function (C1): (LVEF > 60% or ESD < 40 ext{ mm}).
Decision Tree:
High Surgical Risk: → Transcatheter edge-to-edge repair (2).
Low/Moderate Risk: → MV surgery (1) → Degenerative? (Yes → Surgery at primary/secondary; No → Rheumatic? Yes → Repair at CVC).
Asymptomatic (Stage E) with Normal LV Function:
If Expected surgical mortality >95% likelihood of success is No AND Progressive increase in LV size over 3 years is No → MV repair or replacement (2).

Management of Secondary Mitral Regurgitation¶

Initial Step: Initiate GDMT supervised by a HF specialist.
Surgical Decision: Recommended for patients with LVEF > 50%.
Transcatheter Option: Reasonable in selected patients after GDMT/AF Rx optimization.
Synergy: If concurrent need for revascularization → Undergoing CABG.

PROGNOSIS & COMPLICATIONS¶

• Mitral Stenosis: - Pulmonary hypertension → Right heart failure. - Systemic embolization (higher risk in AF, age >65, reduced CO). - Pulmonary infections (bronchitis, pneumonia) especially in winter. • Mitral Regurgitation: - Chronic severe MR leads to LV dilation and eventually systolic dysfunction. - Acute severe MR can lead to rapid pulmonary edema.

Table 275-2: Mortality Rates After Mitral Valve Surgery¶

• MVR (isolated): 4.5% mortality. • MVRp (Repair): 1.2% mortality. • Note: Surgical mitral valve commissurotomy cases are included in the repair procedures.

KEY PEARLS & HIGH-YIELD POINTS¶

• MS Severity: MVA <1.5 ext{ cm}^2 is the threshold for 'Severe'. • Opening Snap: The interval between A2 and OS decreases as MS severity increases. • MR Distinction: Primary (valve problem) vs. Secondary (heart muscle/anatomy problem). • Transcatheter Edge-to-Edge Repair (TEER): Preferred for high surgical risk in primary MR; used for specific criteria in secondary MR. • Surgical Choice: MV surgery is preferred over replacement when repair is feasible for primary MR.

Reference Tables¶

TABLE 274-1 Major Causes of Mitral Stenosis Etiologies Rheumatic fever Congenital (parachute valve, cor triatriatum)…¶

Harrison's 22e, p.2048

Etiologies
Rheumatic fever
Congenital (parachute valve, cor triatriatum)
Severe mitral annular calcification with leaflet involvement
SLE, RA
Myxoma
IE with large vegetations

TABLE 275-1 Major Causes of Mitral Regurgitation (MR) Etiologies Acute¶

Harrison's 22e, p.2052

Etiologies

Acute
IE
Papillary muscle rupture (post-MI)
Chordal rupture/leaflet flail (MVP, IE)
Blunt trauma
Chronic
Primary (affecting leaflets, chordae)
Myxomatous (MVP, Barlow’s, forme fruste)
Rheumatic fever
IE (healed)
Congenital (cleft, AV canal)
Radiation
Secondary (leaflets, chordae are “innocent bystanders”)
Ischemic cardiomyopathy
Dilated cardiomyopathy
HOCM (with SAM)
AF with LA enlargement and annular dilation (atrial functional MR)
Mitral annular calcificationa

275

Mitral Regurgitation
Patrick T. O’Gara, Joseph Loscalzo

TABLE 275-2 Mortality Rates After Mitral Valve Surgery a¶

Harrison's 22e, p.2055

OPERATION	NUMBER	UNADJUSTED OPERATIVE MORTALITY (%)
MVR (isolated)	10,699	4.5
	3509
MVRp	12,424	1.2
	4093
Mitral anato LV EF 2 LV ESD PASP ≤7	my favorable 0–50% ≤70 mm 0 mm Hg
Transcatheter edge-to- edge MV repair (2a)	MV surgery (2b)	MV surgery* (2a)