Valvular Heart Disease: Overview

Valvular heart diseases are disorders affecting the heart valves, which are complex structures that separate the cardiac chambers and regulate blood flow between the atria, ventricles, and great vessels. Under physiological conditions, the valves open and close in synchrony with the cardiac cycle, ensuring unidirectional blood flow without regurgitation. Structural or functional alterations in these valves compromise this mechanism, causing abnormal hemodynamic loads on the cardiac chambers and negatively affecting systemic and/or pulmonary circulation.

The left ventricle is separated from the left atrium by the mitral valve complex, which includes the fibrous annulus, valve leaflets, chordae tendineae, and papillary muscles. During diastole, the mitral valve opens to allow ventricular filling; during systole, it closes tightly, preventing blood from flowing back into the left atrium during ventricular contraction. Any defect that impairs leaflet coaptation or opening dynamics may result in mitral stenosis or regurgitation.

Similarly, the aortic valve regulates blood flow from the left ventricle into the aorta. It is a semilunar valve composed of three cusps: during diastole, it remains closed to prevent blood reflux from the aorta into the ventricle; during systole, it opens under pressure to allow blood ejection into the systemic circulation. Dysfunction of this valve may increase afterload, leading to pressure overload and subsequent ventricular remodeling.

On the right side of the heart, the tricuspid valve separates the right atrium from the right ventricle. It also opens during diastole to allow ventricular filling and closes during systole to prevent regurgitation into the atrium. Its morphology is similar to that of the mitral valve, but adapted to the lower pressures of the systemic venous circuit.

Lastly, the pulmonary valve, also semilunar and composed of three cusps, is located between the right ventricle and the pulmonary artery. It closes during diastole to prevent reflux from the pulmonary circulation and opens during systole to allow oxygen-depleted blood to be ejected toward the lungs.

Each of these structures may be affected by congenital or acquired diseases that alter their anatomy or function.

Valvular heart diseases are traditionally classified into two major categories:

• Stenosis: anatomical narrowing of the valve orifice that hinders forward flow and causes increased pressure in the upstream chamber;
• Regurgitation (or insufficiency): defective leaflet coaptation that allows blood to flow backward in the opposite direction of normal physiology.

In clinical practice, a single valve may exhibit only one of these defects or a combination of stenosis and regurgitation, resulting in so-called mixed lesions. Furthermore, multiple valves may be involved simultaneously, especially in systemic pathological conditions such as connective tissue diseases or rheumatic heart disease.

From a pathophysiological standpoint, the changes induced by valvular disease directly affect the workload of the cardiac chambers. Stenosis creates an obstacle to forward flow, increasing pressure in the chamber upstream of the stenotic valve. This pressure overload triggers an adaptive response that may be hypertrophic (especially in the ventricles) or dilative (in the atria) to maintain adequate output. In contrast, valvular regurgitation causes volume overload in the downstream chamber, which dilates to accommodate the increased diastolic volume. These compensatory mechanisms are effective in the early stages but become progressively inadequate, leading to contractile dysfunction and heart failure.

Valvular diseases may present in acute or chronic forms. Acute forms, such as mitral or aortic regurgitation due to chordal rupture or prosthetic valve dysfunction, arise suddenly and often overwhelm compensatory responses, rapidly resulting in acute pulmonary edema or cardiogenic shock. Chronic forms develop slowly over time, allowing gradual activation of compensatory mechanisms. Chamber dilation and/or hypertrophy enable hemodynamic function to be preserved even in the presence of severe valve defects, at least until overt heart failure occurs.

Clinically, the symptomatic manifestations of valvular diseases vary depending on the type of defect (stenosis vs regurgitation) and the valve involved.

However, three common pathogenic mechanisms contribute to symptom development:

• Reduced cardiac output: manifests as fatigue, exercise intolerance, hypotension, syncope, or near-syncope in severe cases;
• Pulmonary hypertension: due to retrograde pressure overload, especially in left-sided valvular disease, leading to dyspnea, orthopnea, and bendopnea;
• Systemic venous congestion: more pronounced in right-sided defects, but also present in advanced left-sided disease, with jugular venous distention, peripheral edema, congestive hepatomegaly, and ascites.

The most characteristic physical finding is the presence of heart murmurs, caused by turbulent blood flow across stenotic or incompetent valves. These murmurs are heard over auscultation areas corresponding to the affected valve: systolic murmurs are typical of aortic stenosis and mitral regurgitation; diastolic murmurs occur in mitral stenosis and aortic regurgitation. These may be accompanied by abnormal heart sounds such as splitting, opening snaps (typical of mitral stenosis), or muffled sounds in the case of associated pericardial effusion.

The electrocardiogram (ECG), though not specific, provides useful information on secondary structural adaptations, such as atrial enlargement (P mitrale or P pulmonale), axis deviations, ventricular hypertrophy (widened QRS), and repolarization abnormalities. It may also detect arrhythmias, particularly atrial fibrillation in mitral valve disease.

Chest X-ray is useful for a global assessment of cardiac silhouette and pulmonary circulation. It may show cardiac enlargement due to atrial or ventricular chamber dilation, prominence of the aortic arch or pulmonary artery, and signs of pulmonary venous hypertension such as Kerley B lines or alveolar edema.

Transthoracic echocardiography is the cornerstone test for diagnosing valvular heart disease. Doppler imaging allows precise assessment of valve morphology, orifice size, presence of regurgitation, and estimation of transvalvular gradients. Transesophageal echocardiography is used in complex cases or for better preoperative anatomical definition. Three-dimensional echocardiography has further enhanced valvular assessment, particularly for the mitral valve.

Finally, cardiac catheterization, though now reserved for selected cases, provides comprehensive hemodynamic evaluation, including direct measurement of pressure gradients and intracavitary pressures. It is indicated in ambiguous cases, in patients with concomitant coronary artery disease, or in planning surgical or percutaneous valve correction.

Clinical, auscultatory, and imaging findings vary significantly depending on the valve involved and the nature of the defect, and will be analyzed in detail in the dedicated sections for each specific valvular disease.

References
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