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CASE 2.1 MITRAL VALVE STENOSIS

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Patient Presentation

During a scheduled prenatal visit, a 34-year-old in the 24th week of her first pregnancy complains of shortness of breath and fatigue. During a couple of recent exercise sessions she noticed that her heart was "racing." During one of these episodes, she noticed a small amount of blood in her saliva.

Relevant Clinical Findings History

This patient emigrated from India to the United States 10 years ago. She indicates that there is no family history of cardiovascular or respiratory disease. She does not have records for childhood immunizations and illnesses. To date, her pregnancy has been unremarkable.

Physical Examination

Noteworthy vital signs:

  • Pulse: 122 bpm

    Adult resting rate: 60–100 bpm

  • Fetal pulse: 143 bpm

    Baseline fetal rate: 110–160 bpm

Results of physical examination:

  • Auscultation over the heart apex with the patient in left decubitus position reveals a mid-diastolic murmur and a systolic "snap."

  • Crackles are detected in all lung lobes.

Imaging Studies
  • Echocardiography reveals calcification in both leaflets of the mitral valve, doming of the anterior leaflet, and thickened and shortened chordae tendineae. The left atrium is enlarged.

Electrocardiogram
  • Atrial fibrillation

Clinical Problems to Consider

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LEARNING OBJECTIVES

  1. Describe the anatomy of the left atrioventricular (mitral) valve.

  2. Correlate the normal electrocardiogram (ECG) with events of the cardiac cycle.

  3. Explain the anatomical basis for the signs and symptoms associated with this case.

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RELEVANT ANATOMY

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Left Atrioventricular (Mitral) Valve
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A system of one-way valves guards the entry and exit channels of the ventricles of the heart (Fig. 2.1.1). These valves are divided into those that lie at the junction of each atrium with its respective ventricle (atrioventricular valves) and those that are located in the root of the large vessel exiting each ventricle (pulmonary and aortic valves). The cusps for each heart valve are composed of a fibrous core that is coated with endocardium. All cusps are anchored to the cardiac skeleton, a fibrous ring that insulates atrial from that of the ventricular myocardium.

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Figure 2.1.1

(A) Anterior view of the interior of the heart in a frontal section. The pulmonary trunk and arteries are sectioned in this view. (B) View of the left atrium and ventricle showing the left atrioventricular (mitral) valve.

Graphic Jump Location
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The left atrioventricular (mitral or bicuspid) valve lies at the junction of the left atrium and ventricle (Fig. 2.1.1). Its two cusps are termed anterior and posterior and the two papillary muscles of the left ventricle have the same distinctions. The area of the anterior cusp is approximately twice that of the posterior cusp. Chordae tendineae from each papillary muscle extend to both valve cusps. This arrangement is most important during ...

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