USMLE Guide: Cardiology of Valvular Heart Disease

Introduction

Valvular heart disease refers to the dysfunction of one or more heart valves, leading to impaired blood flow within the heart. This USMLE guide aims to provide a comprehensive overview of the cardiology aspect of valvular heart disease, including the etiology, pathophysiology, clinical presentation, diagnosis, and management.

Table of Contents

1. Etiology
2. Pathophysiology
3. Clinical Presentation
4. Diagnosis
5. Management

1. Etiology

Valvular heart disease can have various etiologies, including:

• Congenital abnormalities
• Rheumatic heart disease
• Infective endocarditis
• Degenerative changes (calcification, fibrosis)
• Connective tissue disorders (Marfan syndrome, Ehlers-Danlos syndrome)
• Radiation therapy

2. Pathophysiology

The pathophysiology of valvular heart disease involves the impairment in valve function, leading to either stenosis (narrowing) or regurgitation (leakage) of blood flow across the affected valve. The specific mechanisms vary depending on the valve involved.

• Aortic stenosis: Calcification and fibrosis of the aortic valve leaflets result in reduced valve opening, causing increased pressure load on the left ventricle during systole.
• Aortic regurgitation: Incompetence of the aortic valve allows backward flow of blood from the aorta into the left ventricle during diastole, leading to volume overload and left ventricular dilation.
• Mitral stenosis: Thickening and fusion of the mitral valve leaflets restrict the flow of blood from the left atrium to the left ventricle, resulting in increased left atrial pressure and pulmonary congestion.
• Mitral regurgitation: Incomplete closure of the mitral valve during systole causes backflow of blood from the left ventricle to the left atrium, leading to volume overload and left ventricular dilation.
• Tricuspid stenosis/regurgitation: Similar to mitral valve abnormalities, but affecting the right side of the heart.
• Pulmonary stenosis/regurgitation: Similar to aortic valve abnormalities, but affecting the pulmonary valve.

3. Clinical Presentation

The clinical presentation of valvular heart disease depends on the severity and chronicity of the valvular dysfunction. Common signs and symptoms include:

• Dyspnea: especially on exertion, due to pulmonary congestion.
• Fatigue: resulting from reduced cardiac output.
• Chest pain: angina may occur in aortic stenosis due to increased myocardial oxygen demand.
• Syncope: episodes of loss of consciousness may occur in severe aortic stenosis or aortic regurgitation.
• Murmurs: abnormal heart sounds heard upon auscultation, specific to the affected valve.

4. Diagnosis

The diagnosis of valvular heart disease involves a combination of clinical assessment, imaging studies, and specialized tests. Key diagnostic modalities include:

• Echocardiography: Provides detailed information regarding valve anatomy, function, and severity of dysfunction.
• Electrocardiography (ECG): Detects conduction abnormalities, arrhythmias, and signs of ventricular hypertrophy.
• Chest X-ray: Assesses for signs of cardiac enlargement, pulmonary congestion, or calcifications.
• Cardiac catheterization: Invasive procedure used to measure pressures within the heart chambers and assess coronary artery disease.

5. Management

The management of valvular heart disease depends on the severity of symptoms and the impact on cardiac function. Treatment options include:

• Medical therapy: Symptomatic relief with medications such as diuretics, beta-blockers, and vasodilators.
• Valve repair or replacement: Surgical intervention to restore valve function in cases of severe dysfunction.
• Antibiotic prophylaxis: Administered prior to dental or surgical procedures in patients with certain valvular abnormalities to prevent infective endocarditis.
• Lifestyle modifications: Encouraging healthy habits, including regular exercise, a balanced diet, and smoking cessation.

Conclusion

Valvular heart disease encompasses a wide range of conditions affecting the heart valves. Understanding the etiology, pathophysiology, clinical presentation, diagnosis, and management is essential for healthcare professionals. This USMLE guide provides a concise overview to assist in your preparation for the examination.