Diagnosis of tricuspid regurgitation and stenosis
When assessing the severity of tricuspid regurgitation, the direction of blood flow is a critical criterion. If retrograde (reverse) flow is detected in the inferior vena cava, the regurgitation is definitively graded as severe.
Interestingly, the peak regurgitant jet velocity, measured using Continuous Wave Doppler, is not used to grade the severity of regurgitation itself. However, this parameter is critical for another purpose: using the modified Bernoulli equation, it allows the calculation of the peak systolic pressure in the right ventricle (RV) and pulmonary artery (PA). This is necessary to assess the hemodynamic impact of various left heart pathologies and myocardial diseases.
In tricuspid stenosis, echocardiography visualizes thickened valve leaflets with significantly restricted mobility. Doppler ultrasound makes it possible to clearly visualize and measure the transvalvular blood flow jet.
The role of MRI in assessing the right heart
Cardiac magnetic resonance imaging (MRI) provides additional capabilities for visualization. In particular, SSFP cine sequences (steady-state free-precession) are used, which are excellent for determining abnormal valve morphology. This is especially relevant in conditions such as Ebstein's anomaly or carcinoid heart disease.
There is an important imaging feature: the signal void from tricuspid regurgitation in the right atrium appears less pronounced than the analogous process in mitral regurgitation. This is explained by lower blood flow velocity and less pronounced turbulence in the right chambers.
To quantify the regurgitant volume, a combination of methods is used: phase-contrast blood flow measurements at the pulmonary valve are compared with the right ventricular stroke volume.
Aortic stenosis: concomitant pathology
Aortic stenosis (AS) is frequently considered in the comprehensive evaluation of valvular heart disease. In Western countries, its main cause is degenerative calcific disease affecting middle-aged and elderly patients. Calcium deposits on initially normal leaflets, leading to obstruction (rheumatic etiology is rarely seen today). Clinically, this manifests as dyspnea, chest pain, and syncope, and ECG reveals signs of left ventricular hypertrophy (LVH).
Chest radiography may reveal rounding of the cardiac apex (a sign of LVH) and bulging of the ascending aorta along the right contour due to post-stenotic dilatation. In elderly patients, the entire thoracic aorta may be dilated due to atherosclerosis. The lateral view is most informative for detecting valve calcification itself.
Echocardiography and calculation of aortic valve parameters
Transthoracic echocardiography is the first-line method. It allows assessment of the number of leaflets, their thickening, mobility, and the degree of calcification (which correlates with the severity of stenosis and its progression). Using Doppler ultrasound, stenosis is evaluated by three parameters:
- Peak flow velocity.
- Pressure gradient (calculated using the modified Bernoulli equation: Δp = 4v²).
- Aortic valve area (AVA).
It is important to understand the difference between areas. The anatomical orifice area (AOA) is not equal to the effective orifice area (EOA). EOA reflects the cross-section of the blood jet itself and is usually smaller than the anatomical area due to the vena contracta effect below the valve orifice.
The continuity equation is used for calculation: EOA = SV / VTI_Ao. This principle is based on the fact that, in the absence of shunts, blood flow in the left ventricular outflow tract must equal blood flow at the leaflet level.
Assessment of left and right ventricular function
In the presence of a poor acoustic window, transesophageal echocardiography is used for planimetric measurement of the orifice at maximum opening (in mid-systole). Furthermore, 3D echocardiography is preferred because it eliminates off-axis errors in 2D measurements at the leaflet tips, which could lead to a false overestimation of the area.
Echocardiography must include an assessment of left ventricular (LV) function. A reduced ejection fraction (EF < 50%) is an indication for surgery even in asymptomatic patients. The low-flow, low-gradient AS phenomenon requires special attention, where severe stenosis is masked by low velocity and a low gradient due to reduced cardiac output in the setting of LV dysfunction. Assessment of right ventricular function is also critically important, especially in cases of severe aortic stenosis and combined valvular lesions (e.g., mitral stenosis or regurgitation).
Briefly: answers to topical questions
What etiological factors cause tricuspid stenosis?
Tricuspid stenosis is caused by organic and functional factors leading to obstruction of the right atrioventricular orifice.
- Rheumatic fever is the leading cause of organic disease, causing sclerosis of the leaflets, fibrous ring, chordae tendineae, and papillary muscles.
- Congenital heart defects (CHD) are anomalies characterized by increased blood return to the right atrium.
- Increased circulating blood volume (CBV) — diseases accompanied by this condition.
- Orifice obstruction — presence of a space-occupying lesion or foreign body.
Rare causes in post-illness patients are also mentioned.
What specific ECG criteria indicate left ventricular hypertrophy in aortic stenosis?
In aortic stenosis, ECG signs of left ventricular hypertrophy (LVH) are detected. Sources do not single out specific criteria exclusively for aortic stenosis, but general ECG criteria for LVH include:
- Sokolow–Lyon index — SV1 + RV5-6 > 35 mm.
- R-wave amplitude — in lead aVL ≥ 11 mm.
- Cornell voltage index — > 28 mm for men and > 20 mm for women.
- Cornell product — > 2440 mm × ms.
Additionally, initial changes (T-wave inversion in left precordial leads) and advanced changes (high R wave with downsloping ST-segment depression) are distinguished.
What are the grades of severity of tricuspid regurgitation and their echocardiographic criteria?
Several stages of tricuspid valve regurgitation with characteristic echocardiographic criteria are distinguished.
| Severity | Regurgitant jet area | Vena contracta width | Hepatic venous flow |
|---|---|---|---|
| Initial | < 5.0 cm² | impossible to measure | predominantly systolic flow |
| Moderate (Stage B 2) | 5.0–10.0 cm² | < 0.70 cm | blunted systolic flow |
| Severe (Stage C) | > 10.0 cm² | > 0.70 cm | systolic reversal flow |
An additional criterion for severe tricuspid regurgitation is the presence of retrograde blood flow in the inferior vena cava.
Class and exam questions
How to reliably determine severe tricuspid regurgitation?
The severity is graded as severe if retrograde (reverse) blood flow is detected in the inferior vena cava during ultrasound examination.
Why measure peak velocity in regurgitation if it does not determine its severity?
The peak flow velocity is used in the modified Bernoulli equation to calculate right ventricular and pulmonary artery systolic pressure, which is important for hemodynamic assessment.
What is the difference between anatomical orifice area (AOA) and effective orifice area (EOA)?
The effective area reflects the actual cross-section of the blood flow jet. It is always smaller than the anatomical area due to the physiological constriction (contraction) of the flow immediately after passing through the leaflets.
In which cases is surgical treatment indicated for asymptomatic aortic stenosis?
Surgical or interventional correction is indicated in asymptomatic patients if echocardiography reveals a left ventricular ejection fraction of less than 50%.
What else to study on this topic
- Pathophysiology of Ebstein's anomaly and carcinoid heart disease
- Application of phase-contrast MRI for quantitative blood flow volume calculation
- Diagnostic features of low-flow, low-gradient states in aortic stenosis
- Advantages of 3D echocardiography over standard 2D imaging in leaflet assessment
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