What is mitral valve stenosis, its relevant anatomy, etiology, signs, symptoms, diagnosis, management, and prognosis in a patient with a history of rheumatic fever?

Mitral Valve Stenosis: Comprehensive CVICU Overview

Definition

Mitral stenosis (MS) is an obstruction to left ventricular inflow at the mitral valve level caused by structural abnormalities of the valve apparatus that prevent proper opening during diastolic filling. 1

• The mitral valve apparatus consists of four interconnected structures: the mitral annulus, anterior and posterior leaflets, chordae tendineae, and papillary muscles—abnormalities in any component can result in stenosis 2
• The normal mitral valve area is 4.0 to 5.0 cm², and narrowing to less than 2.5 cm² typically occurs before symptom development 1

Relevant Anatomy and Physiology

Normal Valve Function

• The mitral valve normally opens widely during diastole to allow unobstructed blood flow from the left atrium to the left ventricle 1
• Normal mitral valve area ranges from 4.0 to 5.0 cm² 1

Pathological Changes

• In rheumatic MS, the pathological process causes leaflet thickening and calcification, commissural fusion, chordal fusion, or combinations of these processes 1
• The result is a funnel-shaped mitral apparatus with decreased orifice size, where interchordal fusion obliterates secondary orifices and commissural fusion narrows the principal orifice 1
• Degenerative MS results from mitral annular calcification with progressive calcium deposition, valve thickening, and chordal shortening—notably without commissural fusion 2

Hemodynamic Consequences

• With reduced valve area, blood can flow from left atrium to left ventricle only if propelled by a pressure gradient 1
• This diastolic transmitral gradient is the fundamental expression of MS and results in elevation of left atrial pressure, which reflects back into the pulmonary venous circulation 1
• Reduced mitral valve orifice area causes elevation of left atrial pressure and pulmonary artery systolic pressure 2
• Increased pressure and distension of pulmonary veins and capillaries can lead to pulmonary edema when pulmonary venous pressure exceeds plasma oncotic pressure 1
• In chronic obstruction, pulmonary arterioles may react with vasoconstriction, intimal hyperplasia, and medial hypertrophy, leading to pulmonary arterial hypertension 1

Etiology and Pathophysiology

Rheumatic MS (Most Common)

• Rheumatic carditis is the predominant cause of MS, accounting for 85% of all mitral stenosis cases worldwide 2
• Isolated MS occurs in 40% of all patients presenting with rheumatic heart disease 1
• A history of rheumatic fever can be elicited from approximately 60% of patients presenting with pure MS 1
• The ratio of women to men presenting with isolated MS is 2:1 1
• Rheumatic MS involves commissural fusion with thickening at the leaflet tips 2
• The latent phase between initial rheumatic illness and development of valve stenosis is typically measured in decades in the developed world but considerably shorter in developing countries, likely due to recurrent carditis 1

Degenerative MS (Increasingly Prevalent)

• Degenerative MS accounts for 12% of MS cases and is likely to become increasingly prevalent with an aging population 1
• Results from mitral annular calcification (MAC) with valve thickening and chordal shortening 1
• The posterior mitral valve leaflet is affected first, with relative preservation of anterior leaflet mobility 1
• Tends to present in older patients, while rheumatic MS presents in younger patients 1

Other Rare Causes

• Congenital malformation of the mitral valve occurs rarely and is observed mainly in infants and children 1
• Other acquired causes include left atrial myxoma, ball valve thrombus, mucopolysaccharidosis, and severe annular calcification 1

Progressive Pathophysiology

• Rheumatic MS is a slowly progressive disease with highly variable rates of progression 1
• In one study of 103 patients followed for 3.3±2 years, valve area decreased at 0.09 cm² per year 1
• Progressive enlargement in the right ventricle and rise in RV systolic pressure can occur even without a decrease in mitral valve area 1

Signs & Symptoms

Symptom Development

• A mitral valve area greater than 1.5 cm² usually does not produce symptoms at rest 1
• First symptoms of dyspnea in patients with mild MS are usually precipitated by exercise, emotional stress, infection, pregnancy, or atrial fibrillation with rapid ventricular response 1
• As obstruction increases, decreasing effort tolerance occurs 1
• As severity of stenosis increases, cardiac output becomes subnormal at rest 1

Clinical Presentation

• Exertional dyspnea is the primary symptom 1
• Decreased exercise tolerance develops with progression 1
• Pulmonary edema may occur when pulmonary venous pressure exceeds plasma oncotic pressure 1
• Symptoms may be precipitated by increased transmitral flow or decreased diastolic filling period 1

Physical Examination Findings

• The characteristic auscultatory sequence includes a loud first heart sound (S1), an opening snap after S2, and a low-pitched mid-diastolic rumbling murmur with presystolic accentuation, best heard at the apex with the bell of the stethoscope 3
• The opening snap occurs after S2 as the stenotic mitral valve leaflets abruptly halt their opening motion due to commissural fusion and diastolic doming 3
• An accentuated pulmonary component of S2 (P2) is commonly present, reflecting elevated pulmonary artery pressures 3
• An S4 heart sound is NOT a typical finding in mitral stenosis and should prompt consideration of alternative or coexisting pathology, as the left ventricle typically remains normal in isolated mitral stenosis 3
• In atrial fibrillation, the presystolic accentuation disappears, and the diastolic murmur becomes more uniform 3
• The intensity of auscultatory findings varies with heart rate—tachycardia shortens diastole and may make the murmur less apparent 3

Typical CVICU Presentation

Acute Decompensation Scenarios

• Patients may present with acute pulmonary edema triggered by atrial fibrillation with rapid ventricular response 1
• Fever, anemia, hyperthyroidism, or postoperative states can precipitate hemodynamic decompensation 1
• Pregnancy can trigger symptoms in previously asymptomatic patients 1
• Infection may precipitate acute symptoms 1

Post-Procedural Monitoring

• Patients admitted after percutaneous mitral balloon commissurotomy (PMBC) require monitoring for complications 2
• Post-surgical patients following mitral valve replacement need standard cardiac surgery ICU care 2

Hemodynamic Instability

• Severe pulmonary hypertension with right ventricular dysfunction may be present 1
• Elevated left atrial pressure reflected in pulmonary venous congestion 1
• Risk of atrial thrombus formation, particularly with atrial fibrillation 1

Diagnosis & Evaluation

Severity Classification

Severe MS is defined as a mitral valve area ≤1.5 cm², which usually corresponds to a transmitral mean gradient >5-10 mm Hg at normal heart rate 1

• Very severe MS is defined as mitral valve area ≤1.0 cm² with mean transmitral gradient ≥10 mmHg 2
• The mean pressure gradient is highly dependent on transvalvular flow and diastolic filling period and varies greatly with heart rate 1

Staging System

The ACC/AHA guidelines define four stages 1:

Stage A (At Risk):

• Mild valve doming during diastole
• Normal transmitral flow velocity
• No hemodynamic consequences or symptoms 1

Stage B (Progressive MS):

• Rheumatic valve changes with commissural fusion and diastolic doming
• Planimetered MVA >1.5 cm²
• Diastolic pressure half-time <150 ms
• Mild-to-moderate LA enlargement
• Normal pulmonary pressure at rest
• No symptoms 1

Stage C (Asymptomatic Severe MS):

• Planimetered MVA ≤1.5 cm²
• Diastolic pressure half-time ≥150 ms
• Severe LA enlargement
• Elevated PASP >30 mm Hg
• No symptoms 1

Stage D (Symptomatic Severe MS):

• Planimetered MVA ≤1.5 cm²
• Diastolic pressure half-time ≥150 ms
• Severe LA enlargement
• Elevated PASP >30 mm Hg
• Decreased exercise tolerance and exertional dyspnea 1

Transthoracic Echocardiography (Primary Diagnostic Tool)

TTE is indicated in patients with signs or symptoms of MS to establish diagnosis, quantify hemodynamic severity (mean pressure gradient, mitral valve area, and pulmonary artery pressure), assess concomitant valvular lesions, and demonstrate valve morphology 1

• 2D scanning from the parasternal long-axis window identifies characteristic diastolic doming of the mitral valve 1
• Short-axis scanning demonstrates commissural fusion and allows planimetry of the mitral orifice 1
• Echocardiography is the preferred method for diagnosing mitral stenosis and assessing severity, with valve area by planimetry serving as the reference measurement 2
• Planimetry must be done carefully to obtain the smallest orifice in space and the largest opening in time 1
• 3D echocardiography (TTE or TEE) may allow greater accuracy but is not yet routinely used 1

Doppler Hemodynamics

• Typically obtained from apical 4-chamber or long-axis view 1
• Should include peak and mean transvalvular gradient calculated by simplified Bernoulli equation 1
• Average from 3-5 beats in sinus rhythm and 5-10 beats in atrial fibrillation 1
• Heart rate should always be included in the report because it greatly affects transvalvular gradient 1
• Mitral pressure half-time is inversely related to mitral valve area but is also affected by left atrial and LV compliance 1
• Other methods for calculating mitral valve area include continuity method and proximal isovelocity surface area method 1

Additional Echocardiographic Assessment

• Concomitant mitral regurgitation should be sought and quantified 1
• RV systolic pressure is typically estimated by continuous wave Doppler of tricuspid regurgitation 1
• Mitral valve morphology and feasibility for PMBC or surgical commissurotomy can be assessed via the Wilkins score, which combines valve thickening, mobility, and calcification with subvalvular scarring in a 16-point scale 1
• Characterization of commissural calcification is useful 1
• Left atrial dimension, area, and volume index should be measured, with careful interrogation for possible left atrial thrombus 1

Cardiac Catheterization

• In the contemporary era, adequate assessment can be obtained in the vast majority of patients by TTE, occasionally supplemented by TEE 1
• Catheterization is indicated in patients with nondiagnostic studies or when clinical and echocardiographic findings conflict 1
• Catheterization is the only method available to directly measure left atrial pressure 1
• Critical pitfall: Pulmonary capillary wedge pressure may overestimate the transmitral gradient compared to direct left atrial pressure measurement 4

Follow-Up Imaging Intervals

Repeat TTE should be performed to re-evaluate asymptomatic patients with MS and stable clinical findings at intervals dictated by valve area 1:

• Very severe MS (MVA <1.0 cm²): every year 1
• Severe MS (MVA ≤1.5 cm²): every 1-2 years 1
• Progressive MS (MVA >1.5 cm²): every 3-5 years 1
• Asymptomatic severe mitral stenosis requires echocardiographic assessment every 2-3 years, with more frequent monitoring for very severe stenosis or borderline hemodynamics 2

Interventions/Treatments: Medical and Nursing Management

Medical Management

Diuretics provide symptom relief when edema or pulmonary congestion is present, while heart rate control is essential in patients with atrial fibrillation 2

• Medical therapy is ineffective for severe rheumatic MS as definitive treatment 5
• Heart rate control is crucial because tachycardia shortens diastolic filling time and increases transmitral gradient 1
• Beta-blockers or calcium channel blockers can be used for rate control in atrial fibrillation 2
• Anticoagulation is indicated for patients with atrial fibrillation or history of thromboembolism 2

Indications for Intervention

Intervention should be limited to patients with clinically significant (moderate to severe) mitral stenosis with valve area <1.5 cm² 2

• NYHA class II-IV symptoms with severe MS (MVA ≤1.5 cm²) warrant intervention 2
• Intervention is based on severity at which symptoms occur and at which intervention will improve symptoms 1

Percutaneous Mitral Balloon Commissurotomy (PMBC)

PMBC is the first-line intervention for symptomatic severe rheumatic MS with favorable valve morphology 2

• Appropriate for patients with suitable morphological mitral valve characteristics 5
• Procedural outcomes depend heavily on appropriate case selection 5
• Definitive imaging and interpretation are crucial for identifying appropriate candidates 5
• The Wilkins score helps assess suitability for PMBC 1
• PMBC is unsuitable for degenerative MS because there is no commissural fusion 1

Surgical Management

Mitral valve replacement should be considered as the primary surgical option for degenerative MS 2

• Surgery is indicated when PMBC is not suitable due to unfavorable valve morphology 5
• Surgical commissurotomy is an option in select cases with favorable anatomy 5
• Valve replacement is necessary when there is significant calcification or unfavorable anatomy 2

Immediate Nursing Priorities

Hemodynamic Monitoring

• Continuous cardiac monitoring for arrhythmias, particularly atrial fibrillation 1
• Monitor for signs of hemodynamic decompensation: hypotension, tachycardia, decreased urine output 1
• Assess pulmonary artery pressures if Swan-Ganz catheter is in place 1
• Monitor oxygen saturation and respiratory status closely 1

Rate Control Management

• Maintain strict heart rate control to optimize diastolic filling time 1
• Administer rate-controlling medications as ordered (beta-blockers, calcium channel blockers, digoxin) 2
• Target heart rate typically 60-80 bpm to maximize diastolic filling period 1

Fluid Management

• Careful fluid balance monitoring—avoid both volume overload and depletion 1
• Administer diuretics as ordered for pulmonary congestion 2
• Daily weights and strict intake/output monitoring 1
• Assess for signs of fluid overload: crackles, peripheral edema, jugular venous distension 1

Respiratory Support

• Position patient in semi-Fowler's or high Fowler's position to reduce pulmonary congestion 1
• Administer supplemental oxygen to maintain SpO2 >92% 1
• Monitor for signs of pulmonary edema: pink frothy sputum, severe dyspnea, crackles 1
• Prepare for non-invasive ventilation or intubation if respiratory failure develops 1

Anticoagulation Management

• Administer anticoagulation as ordered for patients with atrial fibrillation or history of thromboembolism 2
• Monitor for signs of bleeding 2
• Ensure therapeutic INR levels if on warfarin 2

Activity Modification

• Limit physical exertion to reduce cardiac workload 1
• Assist with activities of daily living to minimize oxygen demand 1
• Monitor response to activity and adjust activity level accordingly 1

Potential Complications

Atrial Fibrillation

• Common complication that can precipitate acute decompensation 1
• Rapid ventricular response shortens diastolic filling time and increases left atrial pressure 1
• Increases risk of left atrial thrombus formation 1
• Requires aggressive rate control and anticoagulation 2

Pulmonary Hypertension

• Develops from chronic elevation of left atrial pressure 1
• Pulmonary arterioles react with vasoconstriction, intimal hyperplasia, and medial hypertrophy 1
• Can lead to right ventricular dysfunction and failure 1
• Progressive enlargement of right ventricle can occur even without decrease in mitral valve area 1

Thromboembolism

• Left atrial enlargement and stasis increase risk of thrombus formation 1
• Atrial fibrillation significantly increases embolic risk 2
• Systemic embolization can cause stroke or peripheral arterial occlusion 2
• Requires careful interrogation for left atrial thrombus on echocardiography 1

Pulmonary Edema

• Occurs when pulmonary venous pressure exceeds plasma oncotic pressure 1
• Can be precipitated by increased transmitral flow or decreased diastolic filling period 1
• May not occur in chronic severe obstruction due to decreased pulmonary microvascular permeability 1

Right Heart Failure

• Results from chronic pulmonary hypertension 1
• Manifests as peripheral edema, hepatomegaly, ascites, jugular venous distension 1
• Progressive right ventricular enlargement can occur 1

Infective Endocarditis

• Stenotic valves are at increased risk for infection 2
• Requires prophylaxis for dental and certain surgical procedures 2

Relevant Red Flags & CVICU Tips

Critical Red Flags

• Sudden onset of atrial fibrillation with rapid ventricular response—can cause acute pulmonary edema and hemodynamic collapse 1
• New neurological deficits suggesting embolic stroke 2
• Pink frothy sputum indicating acute pulmonary edema 1
• Hypotension with signs of cardiogenic shock 1
• Severe dyspnea at rest with oxygen desaturation 1
• Signs of right heart failure: severe peripheral edema, hepatomegaly, elevated JVP 1

Common Pitfalls to Avoid

• Do not rely solely on pulmonary capillary wedge pressure as surrogate for left atrial pressure—it may overestimate the transmitral gradient; consider trans-septal puncture for direct measurement if discordance exists 4
• Do not assume S4 is part of mitral stenosis—its presence suggests concurrent left ventricular pathology such as hypertension, coronary artery disease, or hypertrophic cardiomyopathy 3
• Avoid aggressive diuresis that can reduce preload excessively and compromise cardiac output 1
• Do not overlook the importance of heart rate control—even mild tachycardia can significantly worsen symptoms 1, 3
• Recognize that mean pressure gradient varies greatly with heart rate and should not be used as sole criterion for severity 1
• Be aware that in atrial fibrillation, the presystolic accentuation of the murmur disappears 3
• Understand that degenerative MS has no commissural fusion, making PMBC unsuitable 1, 2

CVICU-Specific Tips

• Maintain heart rate 60-80 bpm to optimize diastolic filling time—this is more critical in MS than in most other cardiac conditions 1
• Monitor for signs of hemodynamic decompensation with any change in clinical status (fever, infection, anemia) 1
• Be prepared for rapid deterioration if atrial fibrillation develops with rapid ventricular response 1
• Recognize that tachycardia shortens diastole and may make the murmur less apparent on examination 3
• Understand that procedural outcomes for PMBC depend heavily on appropriate case selection based on valve morphology 5
• Remember that progressive right ventricular enlargement and rising RV systolic pressure can occur even without decrease in mitral valve area 1

Assessment Pearls

• Always include heart rate when reporting transvalvular gradients 1
• Planimetry of mitral orifice must capture the smallest orifice in space and largest opening in time 1
• Average Doppler measurements from 3-5 beats in sinus rhythm and 5-10 beats in atrial fibrillation 1
• Assess for concomitant mitral regurgitation and other valve lesions 1
• Carefully interrogate for left atrial thrombus, especially in atrial fibrillation 1

Expected Course and Prognostic Clues

Natural History

• Rheumatic MS is a slowly progressive disease with a prolonged latent phase between initial rheumatic illness and development of valve stenosis 1
• The latent phase is typically measured in decades in developed countries but considerably shorter in developing countries, likely due to recurrent carditis 1
• Once mild stenosis develops, further narrowing is typical, although the rate of progression is highly variable 1
• Valve area decreases at approximately 0.09 cm² per year on average, with significant interpatient variability 1
• Larger valves decrease in area more rapidly, although the same absolute decrease has greater impact in more stenotic valves 1

Prognostic Indicators

Favorable Prognostic Features:

• Mild to moderate stenosis (MVA >1.5 cm²) with no symptoms 1
• Sinus rhythm maintained 1
• Normal pulmonary artery pressures 1
• Absence of significant pulmonary hypertension 1
• Favorable valve morphology (low Wilkins score) suitable for PMBC 1, 5
• Younger age at presentation 1

Unfavorable Prognostic Features:

• Severe stenosis (MVA ≤1.5 cm²) with symptoms 1, 2
• Development of atrial fibrillation 1
• Elevated pulmonary artery systolic pressure >30 mm Hg 1
• Severe pulmonary hypertension with right ventricular dysfunction 1
• Progressive right ventricular enlargement 1
• Heavily calcified valve with unfavorable morphology 1
• Degenerative etiology in elderly patients with multiple comorbidities 1
• History of thromboembolism 2

Post-Intervention Outcomes

• PMBC provides excellent outcomes in appropriately selected patients with favorable valve morphology 5
• Long-term follow-up after PMBC shows sustained benefit in suitable candidates 5
• Surgical outcomes depend on patient age, comorbidities, and surgical expertise 1
• Degenerative MS requiring valve replacement has higher perioperative risk due to older age and comorbidities 1

Disease Trajectory

• Asymptomatic patients with severe MS may remain stable for years but require regular surveillance 1, 2
• Once symptoms develop, progressive deterioration typically occurs without intervention 1
• Development of pulmonary hypertension indicates advanced disease and worse prognosis 1
• Atrial fibrillation development often marks a turning point toward symptomatic deterioration 1
• Progressive right ventricular enlargement and rising RV systolic pressure can occur even without decrease in mitral valve area 1