Eko Health | What is Mitral Stenosis?

Summary: Mitral stenosis causes obstruction to blood flow from the left atrium to the left ventricle. This results in a backlog of blood before the valve, leading to symptoms such as atrial enlargement (which can cause atrial fibrillation and embolism), lung congestion (resulting in cough and dyspnea), and in severe cases, pulmonary edema. It's most commonly caused by rheumatic heart disease. Treatment for severe or symptomatic cases often involves balloon valvuloplasty or transcatheter/surgical valve replacement.

Etiology

Rheumatic heart disease (RHD), a continuously progressive lifelong disease, is the most common cause of mitral stenosis and remains a major health concern in resource-limited countries.^1,2

Other causes include:

Mitral annular calcification^3,4
Radiation associated valve disease^5,6
Congenital (rare)⁴

Pathophysiology

RHD is an exaggerated immune response to untreated or inadequately treated streptococcal infection. Inflammation and fibrosis of the mitral valve leaflets leads to thickening, calcification, and fusion of the commissures and chordae tendineae.^7,8 Over time, the valve opening becomes narrowed, restricting blood flow from the left atrium to the left ventricle.

95% of mitral stenosis cases are caused by rheumatic fever in developing countries (shown in green).⁹

Symptoms/Clinical Presentation

Duration of the asymptomatic phase varies widely, with more rapid progression in resource-limited countries. In addition, even in cases of severe disease, physical exam findings can be subtle or non-specific.

Common symptoms include¹⁰:	-Exertional dyspnea -Decreased exercise tolerance
Less common symptoms include:	-Fatigue -Hemoptysis -Chest pain
Symptoms may be precipitated by¹¹:	-Physical exertion -Emotional stress -Fever -Atrial fibrillation (AFib) -Pregnancy
Complications:	-Right heart failure (ascites, lower extremity edema) -AFib^12,13 -Thromboembolic events (e.g., stroke) -Hoarseness -Infective endocarditis (rare)¹⁴

Diagnostics

Due to the slow progressive nature of mitral stenosis, a careful patient history and physical exam are required. Below is a non-exhaustive list of diagnostic methods:

1. Auscultation:

Loud first heart sound (S1) due to stiff leaflet motion
Intensity of second heart sound (S2) is initially normal, but increases with pulmonary hypertension
When AFib present, possible pre-systolic crescendo
Low-pitched decrescendo mid-diastolic or pre-systolic murmur (“rumble”), often with opening “snap” (indicative of preserved leaflet mobility)

Tip! → Best heard with stethoscope bell at the apex in left lateral decubitus position
Tip! → Duration of murmur correlates with severity of disease

Exemplary PCG: Mitral stenosis is a low-pitched, mid-diastolic or pre-systolic murmur that begins with an opening snap in early diastole as the mitral valve is forced open.

Sound recorded by Eko digital stethoscope technology:

2. ECG: There are no pathognomonic ECG changes, but there are common findings from the downstream effects on the heart.

The physical dilation of the left atrium causes a left atrial abnormality, seen as a prolonged and bifid P wave in lead II (sometimes referred to as “P mitrale”) and a broader and deeper inverted component of the P wave in lead V1.
However, for the many MS patients who develop atrial fibrillation, no P waves will be seen, and irregularly spaced QRS complexes will be observed instead.

3. Echocardiography: For grading (e.g., trace, mild, moderate, severe), as well as determination of possible concomitant valve disease.

4. Chest X-ray: Enlarged left atrium, signs of pulmonary congestion, right ventricular hypertrophy.

Therapy

Asymptomatic patients: Conservative treatment and regular check-ups.
For patients with heart failure symptoms or atrial fibrillation, medical management (e.g., diuretics, beta blockers, anti-arrhythmics, anticoagulants).
For patients with advanced/concomitant heart disease: surgical or interventional options (e.g., balloon valvuloplasty, MitraClip, TMVR, surgical commissurotomy).

References

1. Olson, Lyle J., et al. “Surgical pathology of the mitral valve: A study of 712 cases spanning 21 years.” Mayo Clinic Proceedings, vol. 62, no. 1, Jan. 1987, pp. 22–34.

2. Horstkotte, D., et al. “Pathomorphological aspects, Aetiology and natural history of acquired mitral valve stenosis.” European Heart Journal, vol. 12, no. suppl B, 2 July 1991, pp. 55–60.

3. Kato, Nahoko, et al. “The natural history of severe calcific mitral stenosis.” Journal of the American College of Cardiology, vol. 75, no. 24, June 2020, pp. 3048–3057.

4. Otto, Catherine M., et al. “2020 ACC/AHA guideline for the management of patients with valvular heart disease: A report of the American College of Cardiology/American Heart Association joint committee on clinical practice guidelines.” Circulation, vol. 143, no. 5, 2 Feb. 2021.

5. Adabag, A. Selcuk, et al. “Critical stenosis of aortic and mitral valves after mediastinal irradiation.” Catheterization and Cardiovascular Interventions, vol. 63, no. 2, 23 Sept. 2004, pp. 247–250.

6. Hull, Matthew C. “Valvular dysfunction and carotid, subclavian, and coronary artery disease in survivors of hodgkin lymphoma treated with radiation therapy.” JAMA, vol. 290, no. 21, 3 Dec. 2003, p. 2831.

7. Carapetis, Jonathan R, et al. “Acute rheumatic fever.” The Lancet, vol. 366, no. 9480, July 2005, pp. 155–168.

8. Rajamannan, Nalini M., et al. “Calcified rheumatic valve Neoangiogenesis is associated with vascular endothelial growth factor expression and osteoblast-like bone formation.” Circulation, vol. 111, no. 24, 21 June 2005, pp. 3296–3301.

9. Chang, Christopher. “Cutting edge issues in rheumatic fever.” Clinical Reviews in Allergy & Immunology, vol. 42, no. 2, 20 May 2011, pp. 213–237.

10. Chandrashekhar, Y, et al. “Mitral stenosis.” The Lancet, vol. 374, no. 9697, Oct. 2009, pp. 1271–1283.

11. Van Hagen, Iris M., et al. “Pregnancy outcomes in women with rheumatic mitral valve disease.” Circulation, vol. 137, no. 8, 20 Feb. 2018, pp. 806–816.

12. Diker, Erdem, et al. “Prevalence and predictors of atrial fibrillation in rheumatic valvular heart disease.” The American Journal of Cardiology, vol. 77, no. 1, Jan. 1996, pp. 96–98.

13. Karthikeyan, Ganesan. “Stroke risk in rheumatic heart disease.” Heart, vol. 107, no. 9, 18 Jan. 2021, pp. 694–696.

14. Zühlke, Liesl, et al. “Characteristics, complications, and gaps in evidence-based interventions in rheumatic heart disease: The Global Rheumatic Heart Disease Registry (the remedy study).” European Heart Journal, vol. 36, no. 18, 26 Nov. 2014, pp. 1115–1122.

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