Pulmonary Regurgitation

Pulmonary regurgitation is a valvular disorder characterized by the retrograde flow of blood from the pulmonary artery into the right ventricle during diastole, caused by incompetence of the pulmonary valve. This backward flow occurs when the valve leaflets fail to maintain complete and coapted closure during ventricular relaxation.

A distinction is made between a physiological form, present in a significant portion of the healthy population and generally of no clinical relevance, and a pathological form, secondary to diseases that cause dilation of the valve annulus or structural alterations of the leaflets.

Regurgitation may be primary, when directly caused by valvular lesions (e.g., endocarditis, rheumatic disease), or secondary to annular dilation in the setting of pulmonary hypertension or right ventricular outflow tract disease.

Etiology, Pathogenesis, and Pathophysiology

The main causes of pulmonary regurgitation include:

• Pulmonary arterial hypertension: the most common cause of significant pulmonary regurgitation. Dilation of the pulmonary artery displaces the valvular commissures, preventing proper leaflet coaptation.
• Infective endocarditis: may cause destruction of the valve leaflets with subsequent acute insufficiency.
• Rheumatic disease: rare at the level of the pulmonary valve, but possible, particularly in association with mitral or aortic lesions.
• Operated congenital heart disease: particularly Tetralogy of Fallot after surgical repair, is frequently associated with pulmonary regurgitation due to iatrogenic valve damage or resection of the right ventricular outflow tract.
• Idiopathic dilation of the right outflow tract or pulmonary artery, rare and often asymptomatic.
• Thoracic trauma and invasive maneuvers (e.g., cardiac catheterization).

Loss of leaflet coaptation results in a retrograde diastolic flow from the pulmonary artery to the right ventricle. This leads to an increase in right ventricular end-diastolic volume, resulting in dilation and eccentric hypertrophy in an attempt to maintain effective stroke volume.

Over time, progressive right ventricular dilation may impair contractile function, ultimately leading to right heart failure. The elevated right-sided intracavitary pressures retrogradely affect the systemic venous system, causing hepatic congestion, ascites, peripheral edema, and jugular venous distention.

In cases of acute regurgitation, such as infectious or traumatic forms, the right ventricle does not have time to compensate, leading to rapid development of systemic hypoperfusion and venous congestion.

Clinical Manifestations

Pulmonary regurgitation tends to remain clinically silent for a long time, especially when mild or moderate. This initial apparent benignity is due to the low pressure in the pulmonary circulation and the high adaptability of the right ventricle, which can tolerate volume overload for years without producing evident symptoms.

However, over time, progressive regurgitation leads to eccentric remodeling of the right ventricle, which dilates to accommodate the regurgitant volume during diastole. When compensatory mechanisms fail, right ventricular systolic dysfunction develops, with increased right atrial pressure and subsequent signs and symptoms of systemic congestion.

The onset of symptoms therefore marks an advanced stage of the disease and should prompt a more thorough clinical and instrumental reassessment.

Main symptoms include:

• Exertional dyspnea, initially during intense activity, later even during mild exertion
• Asthenia and easy fatigue, due to reduced cardiac output
• Peripheral edema, especially in the lower limbs
• Ascites and abdominal distension, due to hepatic-portal venous stasis
• Congestive hepatomegaly, often painful on palpation
• Jugular venous distension with positive hepatojugular reflux, indicating elevated right atrial pressure
• Palpitations, with or without supraventricular arrhythmias (frequent in patients with atrial dilation)

On physical examination, the most characteristic finding, though not always present, is a low-frequency diastolic murmur, often described as a “soft murmur”, heard along the left sternal border, typically accentuated by deep inspiration (Carvallo’s sign). This intensification is due to the increased diastolic return flow during inspiration. In mild or moderate forms, however, the murmur may be faint or absent.

In more advanced cases, a right-sided gallop rhythm may be appreciated, indicating right ventricular dysfunction, and a displaced apical impulse toward the epigastrium due to progressive right ventricular dilation.

Diagnosis

The clinical suspicion of pulmonary regurgitation arises from the presence of signs and symptoms of right-sided heart failure, especially in patients with a history of pulmonary hypertension or congenital heart disease.

The electrocardiogram (ECG) may show signs of right atrial dilation (P pulmonale) and right ventricular hypertrophy (right axis deviation, dominant R waves in V1). Supraventricular arrhythmias, particularly atrial flutter or fibrillation, may also be present.

The chest X-ray: may reveal dilation of the pulmonary artery and right-sided heart chambers, with a widened right cardiac silhouette and signs of systemic congestion such as diaphragmatic elevation and ascitic fluid.

Echocardiography: is the reference examination for diagnosis and morphological and functional assessment of the pulmonary valve. The transthoracic approach is usually sufficient, but transesophageal echo may be helpful in complex cases.

Integration with Doppler allows for regurgitation quantification:

• The retrograde diastolic signal in the pulmonary artery is the most direct finding.
• The regurgitant jet can be assessed in terms of extension and density with color Doppler.
• A vena contracta > 0.5 cm and markedly reduced pulmonary diastolic pressure are indicative of severe regurgitation.

Cardiac Magnetic Resonance Imaging (CMR) is useful in patients with complex congenital heart disease or unclear echocardiographic findings. It provides a precise quantification of regurgitation (regurgitant fraction > 40% = severe) and of biventricular function.

Cardiac catheterization: rarely necessary for diagnosis, it is indicated when pulmonary pressures need to be quantified, anatomy defined preoperatively, or operability assessed in the setting of cardiac surgery.

Treatment and Prognosis

In most cases, mild or moderate pulmonary regurgitation does not require specific treatment. Management consists of periodic clinical and instrumental monitoring to detect early signs of right ventricular dysfunction.

Treatment focuses primarily on the underlying disease (e.g., control of pulmonary hypertension with specific vasodilator drugs, treatment of infective endocarditis, congenital heart disease surgery). In overt right heart failure, the following are used:

• Loop diuretics to reduce systemic venous congestion
• Antiarrhythmics for supraventricular arrhythmias
• Anticoagulants in the presence of atrial fibrillation

Valve surgery is indicated only in symptomatic severe cases or in patients undergoing surgery for congenital heart disease with significant regurgitation:

• Pulmonary valvuloplasty or valve replacement with biological or mechanical prostheses, depending on clinical context and age.
• In selected patients, percutaneous pulmonary valve implantation (Melody, Sapien) may be considered, especially in those with degenerated surgical conduits between the right ventricle and pulmonary artery.

Prognosis strongly depends on the underlying disease and right ventricular function. If well-controlled, pulmonary regurgitation may remain stable for a long time. In postoperative congenital heart disease patients (e.g., Tetralogy of Fallot), progression of valve regurgitation is a critical factor for ventricular dysfunction and arrhythmic risk.

Complications

Untreated pulmonary regurgitation may lead to:

• Progressive right ventricular dysfunction
• Refractory right heart failure
• Atrial fibrillation and other supraventricular arrhythmias
• Deep vein thrombosis due to systemic venous stasis
• Reduced exercise tolerance and impaired quality of life

Thus, regular follow-up is essential, especially in patients with operated congenital heart disease, to monitor regurgitation progression and determine the optimal timing for surgical or percutaneous intervention.

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