Mitral Stenosis and Mitral Regurgitation¶
Chapter 274 | Part 6: Disorders of the Cardiovascular System
KEY CLINICAL POINTS¶
- Mitral stenosis (MS) is primarily caused by rheumatic fever, with congenital anomalies and calcification as less common causes.
- Severe MS (valve area <1.5 cm²) leads to elevated left atrial (LA) pressures, pulmonary hypertension, and right heart failure.
- Mitral regurgitation (MR) can be primary (degenerative) or secondary (LV remodeling), with ischemic cardiomyopathy and MVP as common causes.
- Diagnosis relies on echocardiography, Doppler flow studies, and clinical findings like diastolic murmurs and pulmonary congestion.
- Treatment options include percutaneous balloon commissurotomy, surgical repair/replacement, and anticoagulation for AF.
1. DEFINITION & OVERVIEW¶
Mitral stenosis (MS) is a narrowing of the mitral valve orifice, leading to impaired left atrial (LA) to left ventricular (LV) flow. Mitral regurgitation (MR) is the backward flow of blood from LV to LA during systole. Both conditions are critical valvular disorders with distinct pathophysiology and management.
Table 274-1: Major Causes of Mitral Stenosis¶
| 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)¶
1.1 Mitral Stenosis¶
Defined by reduced mitral valve area (<1.5 cm²), leading to elevated LA pressures and pulmonary hypertension. Rheumatic fever is the leading cause, with congenital anomalies and calcification as alternative etiologies.
1.2 Mitral Regurgitation¶
Caused by structural valve abnormalities (primary) or LV dysfunction (secondary). Primary MR includes MVP, degenerative disease, and IE; secondary MR arises from LV remodeling in ischemic or dilated cardiomyopathy.
2. EPIDEMIOLOGY¶
MS is declining in temperate regions due to reduced rheumatic fever, but remains prevalent in low-income countries. MR is more common in older adults, with ischemic cardiomyopathy and MVP as leading causes. Risk factors include rheumatic heart disease, congenital anomalies, and systemic inflammation.
2.1 MS Demographics¶
Incidence has declined globally, but persists in sub-Saharan Africa, India, and Southeast Asia. Most patients develop symptoms in their 4th decade of life.
2.2 MR Demographics¶
Common in elderly with ischemic heart disease or dilated cardiomyopathy. Secondary MR is more prevalent than primary in adults.
3. ETIOLOGY & PATHOPHYSIOLOGY¶
MS results from valve fibrosis, calcification, or structural abnormalities. MR arises from leaflet dysfunction, chordal rupture, or LV remodeling. Both conditions lead to LA hypertension, pulmonary congestion, and right heart failure.
3.1 MS Pathophysiology¶
Chronic inflammation from rheumatic fever causes valve fibrosis and calcification. Severe MS leads to elevated LA pressures, pulmonary hypertension, and right ventricular (RV) dilation.
3.2 MR Pathophysiology¶
Primary MR involves leaflet/annular pathology; secondary MR results from LV dilation and dysfunction. Both cause volume overload, LA enlargement, and progressive heart failure.
4. CLINICAL FEATURES¶
MS presents with dyspnea, fatigue, and pulmonary congestion. MR manifests as exertional dyspnea, palpitations, and signs of LV dysfunction. Both conditions may present with hemoptysis, embolic events, or systemic symptoms.
4.1 MS Symptoms¶
Dyspnea on exertion, orthopnea, paroxysmal nocturnal dyspnea, and fatigue. Hemoptysis may occur with pulmonary hypertension.
5. DIFFERENTIAL DIAGNOSIS¶
Distinguish MS from atrial septal defect (ASD) and MR from aortic regurgitation (AR). Key differentiators include LA enlargement, pulmonary venous congestion, and specific auscultatory findings (e.g., Graham Steell murmur for MS vs. Austin Flint murmur for AR).
6. INVESTIGATIONS & DIAGNOSIS¶
Echocardiography (TTE/TEE) is the gold standard for assessing valve anatomy and function. Doppler studies quantify regurgitant volume and valve area. ECG findings include LA enlargement and pulmonary hypertension. Cardiac catheterization may confirm hemodynamic severity.
6.1 Diagnostic Criteria¶
MS: Mitral valve area <1.5 cm², elevated LA pressures, and pulmonary hypertension. MR: Regurgitant volume ≥ 60 mL/beat, effective regurgitant orifice ≥ 0.40 cm², and LV dysfunction.
6.2 Imaging Techniques¶
TTE provides valve area, regurgitant jet width, and LV function. TEE is used for LA thrombus detection and detailed valve assessment. CMR and cardiac catheterization are adjuncts for complex cases.
7. MANAGEMENT & TREATMENT¶
Medical management includes diuretics, rate control for AF, and anticoagulation. Surgical options include mitral valve repair (preferred), commissurotomy, or replacement. Transcatheter edge-to-edge repair (TEER) is used in high-risk patients.
Table 275-2: Mortality Rates After Mitral Valve Surgery¶
| Operation | Number | Unadjusted Operative Mortality (%) |
|---|---|---|
| MVR (isolated) | 10,699 | 4.5 |
| MVR + CAB | 3,509 | 9.6 |
| MVRp | 12,424 | 1.2 |
| MVRp + CAB | 4,093 | 5.4 |
7.1 Medical Therapy¶
Diuretics for congestion, beta-blockers for rate control, and anticoagulation (warfarin) for AF. ACE inhibitors/ARBs for LV remodeling.
7.2 Surgical Options¶
Mitral valve repair (preferred for primary MR), commissurotomy for MS, and replacement for severe dysfunction. TEER is used in high-risk patients with suitable anatomy.
8. PROGNOSIS & COMPLICATIONS¶
Severe MS without treatment leads to progressive heart failure and death within 2–5 years. MR complications include LV dilation, AF, and embolic events. Prognosis improves with early intervention and management of comorbidities.
8.1 MS Prognosis¶
Untreated severe MS results in 2–5 year mortality. Early intervention (balloon commissurotomy or surgery) improves survival.
8.2 MR Prognosis¶
Secondary MR has worse outcomes than primary MR. Long-term survival is improved with guideline-directed medical therapy (GDMT) and surgical repair.
9. SPECIAL CONSIDERATIONS¶
Pregnancy in MS requires close monitoring due to risk of pulmonary hypertension. Pediatric MS is rare but may present with congenital anomalies. Elderly patients with MR require careful management of comorbidities and anticoagulation risks.
10. KEY POINTS & CLINICAL PEARLS¶
- MS is primarily rheumatic, while MR is often secondary to LV dysfunction.
- Echocardiography is essential for diagnosis and severity assessment.
- Surgical repair is preferred over replacement for primary MR.
- Anticoagulation is critical for AF in MS and MR.
- TEER is a viable option for high-risk patients with suitable anatomy.