Pulmonary Regurgitation (Pulmonic Regurgitation) Workup

Pulmonary or pulmonic regurgitation (PR) should be considered in patients with an early diastolic murmur and in patients with right ventricular (RV) enlargement. PR should also be considered in patients who have a history of valvotomy/valvectomy, balloon pulmonary valvuloplasty performed for RV outflow tract obstruction, and in patients with repaired tetralogy of Fallot. When PR is suspected, echocardiography generally confirms the diagnosis and provides an evaluation of its cause and severity. For moderate or severe PR, cardiovascular magnetic resonance imaging (CMRI) is reasonable to provide quantitative assessment of the PR and of RV size and function.

Computed tomography (CT) scanning can be used to evaluate the right heart size and function, but it is generally not used unless there is a contraindication to CMRI, such as the presence of an implanted cardiac device.

Japanese investigators suggest that evels of plasma brain natriuretic peptide (BNP) have the potential to be useful for postsurgical long-term monitoring of patients with tetralogy of Fallot who are under consideration for pulmonary valve replacement to correct PR or RV dysfunction. ^[19]  In their study of 33 patients who underwent repair of tetralogy of Fallot, significantly higher plasma BNP levels were found not only in patients with moderate-severe PR compared to those with insignificant or mild PR (P = 0.013.) but also in patients with cardiac symptoms compared to asymptomatic patients (P = 0.005). Following pulmonary valve replacement, there was a significant reduction in mean BNP levels, and the plasma BNP level correlated with the RV end-diastolic pressure. ^[19]  The investigators reported 32.15 pg/mL was the optimal BNP cut-off level for considering pulmonary valve replacement.

Exercise testing may provide prognostic information and assist in deciding the timing of valve replacement in symptomatic patients. It is also reasonable in selected asymptomatic severe patients with valvular heart disease (VHD) to confirm the absence of symptoms, to assess the hemodynamic response to exercise, or to determine prognosis. ^[1]

2014 American Heart Association and American College of Cardiology (AHA/ACC) recommendations

The AHA/ACC recommends the following for diagnosis and follow-up in those VHD (all class I) ^[1] :

• Transthoracic echocardiography (TTE) for the initial evaluation of patients with known or suspected VHD for confirmation of the diagnosis, establishment of the cause, determination of the severity and prognosis, and assessment of hemodynamic consequences and timing of interventions
• TTE for patients with known VHD and any changes in symptoms of physical examination findings
• Periodic TTE monitoring in asymptomatic patients with known VHD at intervals based on the valve lesion, severity, and ventricular size and function
• Cardiac catherization for hemodynamic assessment in symptomatic patients in the setting of inconclusive findings with noninvasive studies or in the presence of a discrepancy between results of noninvasive testing and physical examination regarding severity of the valve lesion
•  

With severe pulmonary or pulmonic regurgitation (PR), patients may have dilatation of the pulmonary trunk and central pulmonary arteries. Prominent central pulmonary arteries with enlarged hilar vessels and loss of vascularity in the peripheral lung fields ("pruning") suggests severe pulmonary hypertension. In addition, the right ventricle is usually enlarged.

Cardiac catheterization is usually not necessary for the diagnosis of pulmonary or pulmonic regurgitation (PR), but it may be helpful in determining the underlying etiology and for determining coexisting conditions that may influence treatment and/or repair decisions.

Pulmonary artery angiography may reveal evidence of multiple pulmonary emboli as a cause of pulmonary hypertension when the degree of clinical suspicion is high. Ventilation/perfusion scanning or computed tomography angiography is more commonly performed in most hospitals. Pulmonary emboli must be excluded before the diagnosis of primary pulmonary hypertension is possible.

If pressure measurements are performed, the pulmonary artery and right ventricular pressure curves equalize in late diastole in individuals with severe PR.

Two-dimensional echocardiography (2DE) and M-mode echocardiography can reveal right ventricular (RV) hypertrophy and dilatation. RV volume overload may induce a characteristic abnormal septal wall motion, which appears as flattening of the septum during diastole. Conversely, RV pressure overload usually appears as flattening of the septum during systole. The lack of a pulmonic valve or valve deformities can be noted with 2DE, but the pulmonic valve apparatus typically appears unremarkable. In some cases, pulmonic ring dilatation with poor valve leaflet coaptation may be observed.

Doppler techniques can visualize the regurgitant flow. These techniques are useful to directly visualize regurgitant jets, measure the flow velocities of the regurgitant jets, and accurately estimate pulmonary pressures. Regurgitation that persists throughout diastole suggests the presence of pulmonary hypertension, whereas regurgitation that diminishes earlier in diastole suggests more normal pulmonary arterial pressures. Normally, peak flow velocity across the pulmonic valve is achieved within 140 milliseconds of systole. With pulmonary hypertension, the peak flow velocity is reached faster. The shortening of the interval within which the peak velocity is reached (acceleration time) is linearly inversely proportional to the severity of the pulmonary hypertension.

Color flow Doppler echocardiography is the mainstay for identifying pulmonary or pulmonic regurgitation (PR). In trivial-to-mild PR, the jet is central and narrow. In moderate-to-severe PR, the width of the jet increases, as does the penetration of the jet into the RV outflow tract. In free or open PR (usually due to congenitally absent pulmonic valve), color Doppler can miss the jet altogether due to the brisk and laminar regurgitant flow.

Using pulsed-wave and continuous-wave Doppler, pulmonary artery systolic and diastolic pressures can be calculated. Pulmonary artery systolic pressure can be estimated (using continuous-wave Doppler) in the presence of tricuspid regurgitation by measuring the peak regurgitant flow velocity across the tricuspid valve, converting it to a pressure gradient (by use of the modified Bernoulli equation), and then adding the gradient to an estimate of the right atrial pressure.

Pulmonary artery diastolic pressure can be estimated by measuring the end-diastolic regurgitant flow velocity across the pulmonic valve (at the QRS complex on the electrocardiogram), converting it to a pressure gradient, and then adding the gradient to the estimated right atrial pressure. Both pulmonary artery systolic pressure and diastolic pressure are predictors of cardiac status and outcome. ^{[20, 21]}

Pulmonary arterial mean pressure can also be estimated by converting the early diastolic regurgitation velocity to a pressure gradient, and then adding it to the estimated right atrial pressure.

In a study that evaluated the utility of pulmonary arterial end-diastolic forward flow (EDFF) late after repair of tetralogy of Fallot in 399 patients to predict a restrictive RV, Kutty et al noted that while EDFF was common in this group, its presence and extent varied between  echocardiography and cardiac magnetic resonance imaging (CMRI), and it had an association with greater PR and larger RV size but no relationship with markers of poor RV compliance (eg, right atrial enlargement). ^[22]  The investigators suggested that additional mechanisms beyond RV compliance have a role in EDFF.

Cardiac magnetic resonance imaging (CMRI) has shown promise based on studies of pulmonary or pulmonic regurgitation (PR). CMRI has excellent temporal and spacial resolution and can provide an accurate estimation of the severity of the regurgitation, the mechanism of the regurgitation, and right ventricular (RV) size and function. However, size and time constraints limit the use of CMRI in clinical practice.

In a retrospective study (2000-2015) of 63 patients with postintervention native valve PR and two or more CMRIs, El-Harasis et al noted clinical characteristics of a low-risk group for rapid progression of RV enlargement included those with PR without an RV end-diastolic volume index (RVEDVi) above 130 mL/m² and/or without moderate or more severe tricuspid regurgitation. ^[23]  The investigators indicated that this subgroup of patients may be appropriate for clinical and echocardiographic follow-up, with potentially infrequent CMRI follow-up.

Electrocardiography (ECG) may demonstrate findings of right ventricular (RV) dilatation (occurs either while in a compensated volume overload state or in a decompensated pressure overload state), including incomplete right bundle branch block and right axis deviation. RV hypertrophy may be present by ECG criteria.

In the presence of RV hypertrophy (representing a compensated state of pressure overload), the following may be present:

• Tall R wave in V₁ or qR in V₁

• R wave greater than S wave in V₁

• R wave progression reversal in the precordial leads

• Inverted T wave in the anterior precordial leads

• Right axis deviation

• Right atrial enlargement

Mild-to-moderate pulmonary or pulmonic regurgitation (PR) on echocardiography does not require any follow-up or intervention if the patient is asymptomatic with normal right ventricular (RV) size and function.

For severe PR, the valve anatomy is distorted or has absent leaflets, and annular dilatation is present. In addition, the valve hemodynamics include color jet filling the RV outflow tract, as well as the presence of a continuous wave jet density and contour in addition to dense laminar flow with a steep deceleration slope that may terminate abruptly. ^{[1, 24]} Hemodynamic consequences include paradoxical septal motion and RV enlargement. Symptoms include none or variable, and they depend on the cause of the PR and RV function. ^{[1, 24]}