Pulmonary regurgitation

Article written and reviewed by Dr Luca Moretti

Pulmonary regurgitation, or pulmonic regurgitation, is the return of blood from the pulmonary trunk to the right ventricle during diastole. A minimal, brief jet is common in a normal heart and does not constitute disease. The clinical problem arises when the valve fails to close because of abnormalities of the leaflets or outflow tract, or when pulmonary vascular pressure and dimensions dilate the orifice, generating retrograde volume capable of progressively remodeling the right ventricle.

In specialist practice, significant regurgitation is mainly a late consequence of treated congenital heart disease. Valvotomy or valvuloplasty for pulmonary valve stenosis, a transannular patch in tetralogy of Fallot, reconstruction of the outflow tract and conduit degeneration can leave the valve absent, deformed or incompetent. The initial success achieved by eliminating a dangerous pressure load can therefore evolve over time into volume overload.

The right ventricle may tolerate substantial volume overload for years, and patients often do not perceive decline because they gradually and unconsciously reduce activity. When symptoms, dilatation, dysfunction or arrhythmias become evident, part of the remodeling may be less reversible. Surveillance must therefore identify the window in which valve replacement can offer durable ventricular benefit, without waiting for heart failure but also without unnecessarily advancing implantation of a prosthesis destined to deteriorate.

Assessment requires criteria different from those used for mitral or aortic regurgitation. The anterior position limits some echocardiographic windows, low pressures make jets less conspicuous and right ventricular geometry reduces the reliability of one-dimensional estimates; echocardiography, magnetic resonance, exercise testing, rhythm and surgical history must therefore be interpreted together. Volumetric thresholds help decision-making but do not replace clinical judgment across different diagnoses and anatomies.

Mechanisms, causes and anatomical settings

Normal competence requires mobile leaflets, intact coaptation surfaces and a proportionate ventriculoarterial junction. Primary regurgitation results from a leaflet lesion: congenital malformation, fenestration, endocarditis, trauma, carcinoid disease or iatrogenic injury. Bicuspid or quadricuspid morphology may be incidental or regurgitant. Isolated prolapse is rare and must be distinguished from imaging artifacts.

Functional or secondary regurgitation develops when the annulus and pulmonary trunk dilate, especially in pulmonary hypertension. Elevated pulmonary arterial diastolic pressure increases the retrograde gradient and produces a high-frequency murmur; however, the regurgitation is often a marker of the vascular or cardiac disease that dilated the root rather than the principal determinant of prognosis. Treating the valve alone without correcting afterload would be ineffective or dangerous.

After repair of tetralogy of Fallot, a transannular patch enlarges the outflow tract across the annulus and sacrifices valve competence to a variable degree. The tract may become aneurysmal and akinetic; residual branch pulmonary artery stenosis, residual ventricular septal defect, tricuspid regurgitation, aortic dilatation and ventricular scars modify hemodynamics. There is therefore no single form of “post-Fallot” pulmonary regurgitation, but rather a constellation that must be reconstructed.

After valvuloplasty for isolated stenosis, effective separation of the commissures can create regurgitation. The ventricle does not necessarily carry the same scars or associated lesions as in tetralogy, and prognosis should not be extrapolated wholesale from the latter. Dilatation can be substantial, but timing, arrhythmic risk and intervention thresholds must be individualized according to native anatomy, residual pressure and function.

Right ventricle-to-pulmonary artery conduits and bioprostheses degenerate because of calcification, tearing, thrombosis, pannus or endocarditis. Dysfunction is often mixed: a systolic gradient coexists with diastolic backflow, imposing both pressure and volume loads. Age at implantation, growth, device type and internal diameter, previous stents and relationship to the coronary arteries determine future options.

Outflow tract geometry influences both loading and therapy. A circular rigid conduit differs from an aneurysmal pyramidal patch or a tubular tract; akinetic areas retain volume and reduce efficiency even at the same regurgitant fraction. Describing length, diameters across the cardiac cycle, calcification and motion allows the effect of the valve to be separated from that of a pathological outflow chamber.

In carcinoid disease, fibrous plaques retract the pulmonary and tricuspid leaflets, producing a combination of stenosis and regurgitation; oncologic control does not reverse established fibrosis. Endocarditis may perforate or destroy a leaflet and disseminate septic emboli to the lungs. Venous catheters, intracardiac devices, bacteremia and congenital heart disease increase suspicion, although tricuspid vegetations are more common than pulmonary valve vegetations.

The distinction between physiological and pathological regurgitation does not depend on jet size alone, but on extent, duration, origin and consequences. A thin jet confined to the immediate outflow tract without right-heart dilatation is common; a broad jet persisting through much of diastole, reaching the body of the ventricle and associated with progressive volume enlargement instead requires quantification. It should also be remembered that at very low pressures, rapid equalization may shorten the jet without implying a mild lesion.

Right ventricular overload, manifestations and arrhythmic risk

With each cycle, the ventricle receives systemic venous return plus the volume just ejected that returns from the pulmonary artery. To maintain effective output it increases total stroke volume and develops eccentric dilatation. Initially, compliance permits low filling pressures; over time, wall stress, oxygen consumption and fibrosis increase, contractility may fall and secondary tricuspid regurgitation may develop.

The amount of backflow depends not only on the orifice but also on diastolic duration, the artery-to-ventricle pressure gradient, chamber compliance, pulmonary vascular resistance and distal obstructions. Residual stenosis limits retrograde volume but increases pressure load; relieving it may make regurgitation appear more severe. Asymmetric pulmonary branches and differences in resistance produce unequal backflow that measurement in the main pulmonary artery must integrate.

As the right ventricle dilates, the mechanical relationship between the two ventricles also changes. The septum may flatten in diastole, left ventricular filling may decrease and left ventricular function may be affected by ventricular interdependence and dyssynchrony; after tetralogy repair, right bundle branch block and scars also prolong the QRS and make ejection less efficient. Valve replacement reduces volume overload but does not erase fibrosis and electrical abnormalities that developed over decades.

The first signs are often a silent reduction in reserve or palpitations. Later, exercise intolerance, dyspnea, fatigue, edema, abdominal distension and syncope appear. Chest pain may reflect ventricular demand or arrhythmia. A patient who reports feeling well but has stopped sports and taking stairs is not truly asymptomatic; cardiopulmonary exercise testing makes the trajectory visible.

On auscultation, P2 may be reduced or absent after surgery and the typical finding in regurgitation is an early diastolic decrescendo murmur along the upper left sternal border, more evident with inspiration. At low pressures the murmur tends to be brief and soft, whereas in pulmonary hypertension it becomes higher-pitched and more prolonged; a systolic component instead suggests increased flow or associated obstruction. A parasternal impulse, hepatomegaly and jugular venous distension indicate more advanced consequences.

Atrial arrhythmias are promoted by dilatation and tricuspid regurgitation; ventricular arrhythmias also depend on ventriculotomy scars, anatomical isthmuses and fibrosis. In repaired tetralogy, sustained ventricular tachycardia and sudden death are not explained by regurgitation alone. A wide or progressively widening QRS, biventricular dysfunction, documented arrhythmias and extensive scar require electrophysiological assessment independent of the valve strategy.

Pregnancy increases blood volume and heart rate. Isolated regurgitation with preserved function is often tolerated; right ventricular dysfunction, obstruction, arrhythmias or pulmonary hypertension increase risk. Preconception counseling also considers heritability of the heart defect, anticoagulation and prostheses. During pregnancy, physiological changes in volume should not be interpreted as permanent progression without postpartum comparison.

Echocardiography, magnetic resonance and integrated assessment

Echocardiography should clarify the mechanism of regurgitation, describe the jet and identify associated lesions. Color Doppler is acquired in parasternal short-axis, RVOT and subcostal views with an appropriate scale; a jet broad at its origin and capable of occupying the outflow tract supports greater severity. Continuous-wave Doppler assesses density and deceleration, pulsed-wave Doppler looks for diastolic flow reversal in the trunk and branches, whereas color jet area, which is highly dependent on gain and pressure, should not be used as a stand-alone measure.

A multiparametric assessment includes vena contracta width, jet/RVOT ratio, duration of backflow, branch pulmonary artery pattern, regurgitant volume when calculable and ventricular response. Echocardiographic thresholds are less well validated than for aortic or mitral regurgitation. A free jet in a very wide outflow tract may have low velocity and blurred contours; the report should state limitations and discordance.

Right-heart dimensions are measured from dedicated views and indexed to body surface area. TAPSE and S′ describe longitudinal motion, fractional area change a two-dimensional projection, while free-wall strain and 3D add information. Complex geometry and loading conditions modify every index. After replacement, ejection fraction may fail to increase despite improved effective output because the fraction ejected backward into a low-impedance pathway disappears.

Cardiac magnetic resonance is the reference standard for right ventricular volumes, mass and function. Contouring cine stacks yields indexed end-diastolic and end-systolic volumes and ejection fraction; phase-contrast imaging orthogonal to the pulmonary trunk measures forward and reverse flow. Regurgitant fraction is reverse/forward flow, whereas regurgitant volume expresses the absolute load: both should be interpreted together with chamber dimensions and net output.

Phase-contrast magnetic resonance is sensitive to plane errors, aliasing, vessel motion, respiration and stent artifacts, so the result should be checked through the balance between pulmonary and aortic output, stroke volumes and shunts. An apparently moderate regurgitant fraction may correspond to a high absolute volume in a high-output ventricle, whereas a high fraction with a small volume does not impose the same load. Here too, numerical categories are meaningful only when consistent with the rest of the examination.

Magnetic resonance also shows outflow aneurysm, scars with late gadolinium enhancement, pulmonary branches, differential flow and left ventricular function. CT is preferred for calcification, stents, coronary arteries and transcatheter planning. Segmentations through systole and diastole define a dynamic landing zone; a single measurement in an aneurysmal native outflow tract is insufficient.

Cardiopulmonary exercise testing records peak oxygen consumption, threshold, chronotropic response, ventilation and oxygen saturation. An unexplained serial decline may precede symptoms. ECG, Holter or longer monitoring looks for arrhythmias in the presence of palpitations, syncope or a high-risk substrate. Catheterization measures pressures and resistances when noninvasive data are discordant and allows angiography or preintervention assessment.

Functional capacity does not always parallel volumes: training status, left ventricular function, chronotropism, lung disease and obesity can dissociate oxygen consumption from right-heart dimensions. The value of exercise testing is mainly serial and interpretive. Reproducible deterioration strengthens the indication when it coincides with remodeling, whereas stable performance does not negate a progressive rise in end-systolic volume or a high-risk arrhythmic substrate.

The complete diagnosis provides a synthesis: cause, severity, any stenosis, biventricular volumes and function, exercise capacity, rhythm, pressures, tricuspid valve, pulmonary branches and procedural anatomy. The word “severe” applied to the jet does not automatically equal an indication; similarly, a non-extreme regurgitant fraction does not exclude treatment if the ventricle is worsening because of a mixed load or other correctable lesions are present.

Timing of replacement and choice of procedure

Pulmonary valve replacement is indicated when at least moderate regurgitation accompanies attributable symptoms. In asymptomatic patients it is considered if volumes or function worsen, objective exercise capacity declines, right-sided pressure is elevated or arrhythmias and lesions requiring intervention are present. The principle is to prevent irreversible damage while avoiding premature prosthesis implantation and subsequent reinterventions.

In repaired tetralogy, commonly used warning signs include an indexed right ventricular end-diastolic volume around or above 160 mL/m² and end-systolic volume around or above 80 mL/m², progressive dysfunction, right ventricular systolic pressure at least two thirds of systemic pressure and declining exercise capacity. These values are neither automatic nor universal thresholds for regurgitation after isolated stenosis: they must be integrated with sex, method, scar burden and trajectory.

Surgery allows combined correction: resection or remodeling of an aneurysmal outflow tract, tricuspid repair, enlargement of pulmonary branches, closure of residual defects and cryoablation of arrhythmic isthmuses. It requires sternotomy and cardiopulmonary bypass, but may be preferable when several problems share the same therapeutic window. A bioprosthesis is sized to optimize hemodynamics and future valve-in-valve treatment.

Transcatheter replacement was initially developed for conduits and bioprostheses that provided a cylindrical anchoring site. Preparation and prestenting can create an adequate landing zone, treat any stenosis and reduce fracture risk; balloon-expandable prostheses are used in compatible diameters, whereas dedicated self-expanding systems have extended treatment to some large native outflow tracts. Not every large RVOT is suitable, however, and selection requires CT and anatomical simulation.

The risk of coronary compression is specifically investigated. Proximity of a coronary artery to the conduit can turn expansion into fatal ischemia; when necessary, a balloon is inflated at the intended site while coronary angiography is performed. Aortic compression, conduit rupture, migration, venous access and interference with branches or the tricuspid valve are also assessed. An equivocal test contraindicates implantation.

Complications include bleeding, perforation, embolization, thrombosis, paravalvular regurgitation, stent fracture, obstruction and arrhythmias. Prosthetic endocarditis is a late concern for both surgical and transcatheter devices; risk and comparative durability depend on device, population and follow-up. Oral hygiene, education about fever and surveillance cannot be replaced by antibiotic prophylaxis alone.

Technical feasibility is not the same as clinical indication. An outflow tract compatible with a transcatheter device does not justify replacement if the ventricle is stable, just as a clear indication should not be deferred merely because no percutaneous prosthesis fits the anatomy: in the latter case, surgery remains the reference. Discussion with the patient should also include uncertainty about durability and access for future reinterventions.

If sustained ventricular tachycardia or a high-risk isthmus is present, ablation can be performed before or during replacement. A prosthesis may make the substrate less accessible and electrophysiological planning should not automatically be postponed. The decision regarding a defibrillator follows overall risk; correcting volume overload removes one hemodynamic stimulus but does not eliminate scars and predisposition.

Follow-up before and after replacement

In patients not yet meeting criteria for intervention, the interval depends on severity, volumes and trajectory. Follow-up looks for changes in activity and palpitations; echocardiography monitors regurgitation, gradient, tricuspid valve and pressures; magnetic resonance is repeated often enough to distinguish true progression from variability. Measurements should use consistent protocols and indexing, preferably at the same expert center.

A single volume above a threshold does not mandate intervention, but a concordant trend of increasing end-diastolic and end-systolic volumes, declining function or exercise capacity and worsening electrical markers reduces the advantage of waiting. Conversely, small differences between readers or scanners are not progression. Direct image comparison and repeat testing when a finding is unexpected prevent irreversible decisions based on noise.

After replacement, a baseline examination records gradient, regurgitation, function and rhythm. Over subsequent months the ventricle should decrease in size, but the degree of normalization depends on timing and scar burden. Persistent exercise intolerance requires assessment for left ventricular dysfunction, chronotropic incompetence, arrhythmias, branch pulmonary artery stenosis, pulmonary disease or deconditioning, without assuming prosthetic failure.

Prosthetic follow-up monitors for rising gradient, new regurgitation, leaflet mobility, thrombosis and endocarditis. CT can identify hypoattenuated leaflet thickening or stent abnormalities; blood cultures should precede antibiotics when possible and safe. Initial and long-term antithrombotic therapy is selected according to device, rhythm, bleeding risk and center protocols, not by uncritical analogy with TAVI.

Every prosthesis has limited durability, but a surgical bioprosthesis may later serve as a site for valve-in-valve, and a transcatheter valve may itself receive another device in selected cases. Accumulating layers reduces the orifice and may eventually require surgery; therefore the diameter and position of the first prosthesis are long-term decisions. Growth magnifies this issue in children.

After stabilization, physical activity, work and pregnancy should also be reassessed because a well-functioning prosthesis does not necessarily mean a normal heart in the presence of scars, arrhythmias or residual dysfunction. Regular guided exercise can improve functional capacity, whereas competitive sports require specific risk stratification. Pregnancy after replacement also requires monitoring of cardiac function and the device, in addition to management of any anticoagulants.

The optimal clinical outcome combines a competent valve, low gradient, a less dilated ventricle, good effective output and controlled arrhythmic risk. None of these goals guarantees the others. Lifelong congenital heart disease follow-up preserves anatomical documentation and allows intervention on the dominant problem at the appropriate time, avoiding both waiting until heart failure and an excessively early sequence of prostheses.