Valvular Heart Disease: Aortic Stenosis, Mitral Regurgitation, and Prosthetic Valves

Valvular heart disease encompasses structural or functional abnormalities of cardiac valves that impede forward flow or allow regurgitant flow. The most clinically significant lesions include aortic stenosis (AS) and mitral regurgitation (MR).

[KEY_CONCEPT] Aortic stenosis is characterized by narrowing of the aortic valve orifice, creating obstruction to left ventricular outflow. The normal aortic valve area is 3.0-4.0 cm². AS is classified as:

• Mild: Valve area 1.5-2.0 cm²
• Moderate: Valve area 1.0-1.5 cm²
• Severe: Valve area <1.0 cm²
• Critical: Valve area <0.6 cm²

Mitral regurgitation involves retrograde flow from the left ventricle to the left atrium during systole. MR can be primary (organic valve disease) or secondary/functional (normal valve with ventricular dysfunction).

Epidemiology

Aortic stenosis affects 2-7% of adults >65 years, with bicuspid aortic valve being the most common congenital heart defect (1-2% of population). Degenerative calcific AS is the predominant form in developed countries, while rheumatic AS remains common in developing regions.

Mitral regurgitation is the second most common valvular lesion in developed countries. Primary MR commonly results from mitral valve prolapse (2-3% prevalence), while secondary MR often accompanies heart failure with reduced ejection fraction.

[CLINICAL_PEARL] The prevalence of severe AS doubles every decade after age 65, making it a major cause of cardiac morbidity in the elderly population.

Aortic Stenosis Clinical Manifestations

[HIGH_YIELD] The classic triad of severe symptomatic AS includes:

1. Exertional dyspnea and heart failure symptoms
2. Angina pectoris (even without coronary disease)
3. Syncope or presyncope with exertion

Physical Examination Findings:

• Harsh systolic ejection murmur at right sternal border, radiating to carotids
• Pulsus parvus et tardus: Delayed, weak carotid upstroke
• Paradoxical splitting of S2 (if severe)
• Sustained apical impulse (left ventricular hypertrophy)

Mitral Regurgitation Clinical Features

Acute MR presents with:

• Acute pulmonary edema and cardiogenic shock
• Soft systolic murmur (due to rapid equalization of LA/LV pressures)
• Signs of hemodynamic instability

Chronic MR manifests as:

• Progressive exertional dyspnea and fatigue
• Holosystolic murmur at apex, radiating to axilla
• Laterally displaced apical impulse (LV dilatation)
• S3 gallop and signs of heart failure

[KEY_CONCEPT] Secondary MR often presents with heart failure symptoms disproportionate to the degree of regurgitation, as the underlying cardiomyopathy drives symptomatology.

Prosthetic Valve Complications

Early complications (<60 days):

• Paravalvular leak and hemolysis
• Thromboembolism and bleeding (anticoagulation-related)
• Infection (prosthetic valve endocarditis)

Late complications (>60 days):

• Structural valve deterioration (bioprosthetic)
• Pannus formation and thrombosis (mechanical)
• Chronic anticoagulation complications

[CLINICAL_PEARL] New neurological symptoms in prosthetic valve patients should raise suspicion for thromboembolism, while new fever warrants evaluation for prosthetic valve endocarditis.

Echocardiographic Assessment

[HIGH_YIELD] Transthoracic echocardiography (TTE) is the primary diagnostic modality for valvular heart disease assessment.

Aortic Stenosis Severity Criteria

Mitral Regurgitation Assessment

Qualitative Parameters:

• Color Doppler jet area and penetration into LA
• Vena contracta width: >7 mm suggests severe MR
• Pulmonary vein flow reversal

Quantitative Parameters:

• Regurgitant volume: ≥60 mL (severe)
• Regurgitant fraction: ≥50% (severe)
• Effective regurgitant orifice area (EROA): ≥40 mm² (severe)

Advanced Imaging

Transesophageal Echocardiography (TEE) is indicated for:

• Prosthetic valve assessment and suspected endocarditis
• Intraoperative monitoring during valve repair
• Poor transthoracic windows

Cardiac Catheterization is performed when:

• Discordant clinical and echo findings
• Coronary angiography needed pre-operatively (age >40, risk factors)
• Hemodynamic assessment in complex cases

Low-Flow, Low-Gradient AS Evaluation

[KEY_CONCEPT] Dobutamine stress echocardiography differentiates true severe AS from pseudo-severe AS:

Dobutamine Stress Echo Protocol: ↓ Baseline: Low gradient, small valve area ↓ Dobutamine infusion (up to 20 mcg/kg/min) ↓ True Severe AS: Valve area remains <1.0 cm², gradient increases ↓ Pseudo-severe AS: Valve area increases >1.0 cm², gradient normalizes

[CLINICAL_PEARL] BNP or NT-proBNP elevation in asymptomatic severe AS may indicate subclinical LV dysfunction and warrants closer monitoring for symptom development.

Aortic Stenosis Management

Treatment Algorithm for Aortic Stenosis

Severe Aortic Stenosis Diagnosed ↓ Symptomatic? (Dyspnea, angina, syncope) ├─ YES → INTERVENTION INDICATED │ ├─ Low surgical risk → SAVR (Class I) │ ├─ Intermediate risk → SAVR or TAVR (Class IIa) │ └─ High/prohibitive risk → TAVR (Class I) └─ NO (Asymptomatic) ├─ LVEF <50% → INTERVENTION (Class I) ├─ Abnormal stress test → INTERVENTION (Class IIa) ├─ Very severe AS (Vmax >5 m/s) → Consider intervention └─ Otherwise → Serial monitoring q6-12 months

[HIGH_YIELD] Surgical Aortic Valve Replacement (SAVR) remains the gold standard for low-risk patients, while Transcatheter Aortic Valve Replacement (TAVR) is preferred for high-risk or inoperable patients.

Medical Management:

• No proven medical therapy delays progression
• Avoid vasodilators (ACE inhibitors, nitrates) in severe AS
• Cautious diuretic use for heart failure symptoms
• Statin therapy may slow progression (controversial)

Mitral Regurgitation Management

Primary (Organic) MR Treatment

Surgical Indications (Class I):

• Symptomatic severe MR with LVEF >30%
• Asymptomatic severe MR with LV dysfunction (LVEF 30-60% or LVESD ≥40 mm)
• Asymptomatic severe MR with pulmonary hypertension (PASP >50 mmHg)

Mitral valve repair is preferred over replacement when feasible (lower operative mortality, preservation of LV function).

Secondary (Functional) MR Treatment

[KEY_CONCEPT] Treatment focuses on optimizing heart failure therapy per guideline-directed medical therapy:

1. ACE inhibitors/ARBs or ARNI (sacubitril/valsartan)
2. Beta-blockers (carvedilol, metoprolol succinate, bisoprolol)
3. Aldosterone antagonists (spironolactone, eplerenone)
4. SGLT2 inhibitors (dapagliflozin, empagliflozin) per DAPA-HF trial

Surgical intervention for secondary MR remains controversial, with cardiac resynchronization therapy (CRT) often preferred.

Prosthetic Valve Management

Anticoagulation Strategies

[CLINICAL_PEARL] Direct oral anticoagulants (DOACs) are contraindicated in mechanical prosthetic valves but may be considered in bioprosthetic valves after the initial 3-month warfarin period.

Surveillance Protocol:

• Annual TTE for prosthetic valve function
• Serial imaging if gradient elevation or new symptoms
• Endocarditis prophylaxis for high-risk procedures

Aortic Stenosis Complications

Natural History Landmarks:

• Asymptomatic severe AS: 1-2% annual mortality
• Symptomatic severe AS: 25% annual mortality without intervention
• Average survival after symptom onset: 2-3 years

[HIGH_YIELD] Sudden cardiac death risk in asymptomatic severe AS is <1% annually, but increases significantly with symptom development.

Procedural Complications:

• TAVR-specific: Paravalvular leak, conduction abnormalities (15-30% pacemaker rate), stroke (2-4%)
• SAVR-specific: Bleeding, infection, longer recovery time

Mitral Regurgitation Complications

Primary MR Natural History:

• Asymptomatic severe MR: 6-7% annual progression to symptoms or LV dysfunction
• LV remodeling occurs progressively, often irreversible if delayed

Secondary MR Impact:

• Increased mortality in heart failure patients independent of LVEF
• Recurrent heart failure hospitalizations
• Reduced exercise capacity and quality of life

[KEY_CONCEPT] Effective regurgitant orifice area (EROA) ≥20 mm² in secondary MR is associated with increased mortality despite optimal medical therapy.

Prosthetic Valve Complications

Early Complications (0-60 days)

Paravalvular Leak:

• Hemodynamically significant: Requires intervention
• Chronic hemolysis: Monitor haptoglobin, LDH, bilirubin
• Surgical repair vs. percutaneous closure options

Prosthetic Valve Endocarditis (PVE):

• Early PVE: Usually Staphylococcus epidermidis, S. aureus
• Late PVE: Streptococcus viridans, Enterococcus
• High mortality (20-40%), often requires surgical intervention

Late Complications (>60 days)

Structural Valve Deterioration:

• Bioprosthetic valves: 10-20% at 10 years, age-dependent
• Valve-in-valve TAVR emerging option for failed bioprosthetic valves

Thromboembolism:

• Annual stroke risk: 1-2% with adequate anticoagulation
• Subclinical leaflet thrombosis: Detected on CT, clinical significance unclear

Monitoring Protocols

Asymptomatic Severe AS:

• Clinical evaluation every 6 months
• Echocardiography annually or if symptom development
• Exercise stress testing if symptoms equivocal

Post-Valve Intervention:

• Baseline TTE at discharge and 30 days
• Annual surveillance imaging
• Anticoagulation monitoring per INR targets

[CLINICAL_PEARL] B-type natriuretic peptide (BNP) elevation >3× upper limit normal in asymptomatic severe AS may predict symptom development and guide intervention timing.

Long-term Outcomes

Aortic Stenosis Prognosis

Post-SAVR Outcomes:

• Operative mortality: 1-3% for isolated SAVR in low-risk patients
• 10-year survival: 75-85% in patients <70 years
• Excellent functional recovery in most patients

Post-TAVR Outcomes:

• 30-day mortality: 2-5% in contemporary series
• Equivalent survival to SAVR in intermediate and high-risk patients
• Improved outcomes in low-risk patients per recent trials

[HIGH_YIELD] Transcatheter valve durability appears excellent through 5-8 years of follow-up, with ongoing studies evaluating long-term outcomes.

Mitral Regurgitation Prognosis

Primary MR Post-Surgery:

• Repair vs. Replacement: Repair associated with better long-term survival and LV function preservation
• Repair durability: >90% freedom from reoperation at 10 years for degenerative MR
• Optimal timing: Intervention before LVEF <60% or LVESD >40 mm

Secondary MR:

• Medical therapy optimization improves outcomes per PARADIGM-HF and DAPA-HF trials
• Surgical intervention benefit remains controversial
• Percutaneous mitral repair (MitraClip) shows symptom improvement but limited survival benefit

Risk Stratification Tools

STS Risk Score for cardiac surgery:

• Low risk: <4%
• Intermediate risk: 4-8%
• High risk: >8%

EuroSCORE II provides alternative risk assessment for European populations.

[KEY_CONCEPT] Frailty assessment increasingly important in valve intervention decisions, particularly for elderly TAVR candidates.

Follow-up Protocols

Post-Intervention Surveillance

Immediate Post-operative (0-30 days):

• Clinical assessment for complications
• Baseline echocardiography to establish new hemodynamic parameters
• Anticoagulation optimization per valve type

Long-term Follow-up:

• Annual clinical visits with focused cardiac examination
• Annual TTE to assess valve function and ventricular recovery
• Endocarditis prophylaxis education for high-risk procedures

Special Populations

Pregnancy Considerations:

• Mechanical valves: High-risk due to anticoagulation challenges
• Bioprosthetic valves: Preferred for women of childbearing age
• Multidisciplinary management with maternal-fetal medicine

Elderly Patients:

• Quality of life considerations paramount
• Cognitive assessment pre-intervention
• Rehabilitation programs improve outcomes

[CLINICAL_PEARL] LV function recovery after mitral valve surgery for MR is dependent on pre-operative LV dimensions and function, emphasizing the importance of optimal intervention timing.

Prevention Strategies

• Rheumatic heart disease prevention: Group A streptococcal infection treatment
• Endocarditis prophylaxis for high-risk procedures in prosthetic valve patients
• Cardiovascular risk factor modification to slow AS progression
• Regular surveillance in bicuspid aortic valve patients