Pathogenesis and forms
Depending on the rate of development, acute and chronic mitral regurgitation (MR) are distinguished. Hemodynamically, the body attempts to compensate for the defect by increasing the stroke volume and ejection fraction of the left ventricle (LV).
- Acute MR: occurs suddenly, for example, in infective endocarditis or chordal rupture. The left atrium (LA) does not have time to dilate (it is non-compliant), and the pressure within it rises sharply, leading to the rapid development of pulmonary edema.
- Chronic MR: develops gradually against the background of cardiomyopathies, rheumatic disease, or chordal pathology. In response to volume overload, the LA and LV expand (dilate), acting as a reservoir. This restrains the rise in pulmonary vascular pressure in the early stages, but over time the effective stroke volume drops, causing decompensation and heart failure.
Mitral valve prolapse (MVP)
MVP syndrome is a leading cause of severe non-ischemic regurgitation. In this pathology, during systole, the valve leaflet bulges (prolapses) into the atrial cavity by more than 2 mm relative to the plane of the fibrous annulus.
MVP features:
- Localization: the middle segment of the posterior leaflet is most commonly affected.
- Causes: myxomatous degeneration of the leaflets and elongation of the chordae tendineae. It occurs both isolated and in Marfan syndrome or atrial septal defect.
- Clinical presentation: may present with chest pain and ECG changes, mimicking coronary artery disease.
Instrumental diagnostics
To confirm the diagnosis and assess valve anatomy, a number of imaging methods are used:
- Echocardiography (EchoCG): the baseline method. It allows visualization of LA dilatation, leaflet prolapse (e.g., parasternal long-axis view). Color Doppler visualizes the regurgitant jet, while pulsed- and continuous-wave Doppler assess its volume and velocity.
- Cardiac MRI: cine-MRI shows the jet as a dark flow due to turbulence. The method allows precise calculation of the regurgitant volume and fraction from the difference in ventricular stroke volumes or using phase-contrast scanning.
- X-ray: in acute MR, heart size is usually normal, but alveolar pulmonary edema is visible. In the chronic form, enlargement of the LV and LA appendage is noticeable.
- CT: useful for assessing calcification, searching for small vegetations and ruptured chords.
Functional regurgitation
Occurs in dilated cardiomyopathy and ischemic heart disease. In this case, the mitral valve itself is structurally unchanged. Regurgitation occurs due to external factors:
- Dilatation of the LV or the valve fibrous annulus.
- Impaired contractility of individual myocardial wall segments.
- Pathological tension of the chordae tendineae.
Such dysfunction is often severe in nature and complicates the course of the underlying disease.
Briefly: answers to topical questions
What causes acute mitral regurgitation to develop?
Acute mitral regurgitation is caused by infectious and ischemic lesions, as well as structural disorders of the valve apparatus.
- Infective endocarditis — causes damage to valve structures.
- Rupture of chordae tendineae (chordae tendineae) — can be complete or partial.
- Papillary muscle rupture — most commonly the posteromedial muscle due to specific blood supply features.
- Ischemia and papillary muscle dysfunction — occurs in acute coronary syndrome.
- Papillary muscle infarction — leads to impaired valve function.
- Left ventricular dilatation — chamber expansion leads to dilatation of the mitral annulus without muscle rupture.
What echocardiographic parameters must be measured to assess the severity of mitral regurgitation?
To assess the severity of mitral regurgitation, a number of quantitative and semi-quantitative echocardiographic parameters must be measured.
- Penetration depth and jet area — assessed in the left atrium using pulsed-wave Doppler.
- Regurgitant volume — a value greater than 60 mL is a criterion for severity.
- Effective regurgitant orifice area (EROA) — an effective orifice area greater than 0.4 cm² indicates severe regurgitation.
- Proximal isovelocity surface area (PISA) — used to calculate jet volume and area.
Additionally, left atrial dilatation and increased emptying volume are assessed.
What ECG changes may be observed in mitral valve prolapse?
In mitral valve prolapse, exact electrocardiographic parameters are not detailed in sources. It is only noted that the resulting ECG changes can mimic coronary artery disease. This condition may also be accompanied by chest pain, which, combined with the electrocardiographic picture, requires differential diagnosis with ischemic myocardial injury.
What specific radiographic symptoms are characteristic of alveolar pulmonary edema?
Alveolar pulmonary edema is characterized by the appearance of bilateral symmetrical consolidation zones and nodular opacities in the air spaces.
- Bat-wing sign (perihilar bat's wing) — bilateral perihilar consolidation, with the apices, bases, and peripheral regions remaining intact.
- Air bronchograms (air bronchograms) — visualization of bronchi against the background of dense lung tissue consolidation.
- White-out pattern (white-out) — occurs when opacities merge as edema progresses.
- Kerley B lines (Kerley B lines) — thickening of the interlobular septa.
Pleural effusion and varying tissue density from mildly decreased transparency to dense consolidation are also observed.
Comprehensive MRI assessment of MR includes the three "A" rule: Anatomy (of the valve), Adaptation (of the LV to overload), and Analysis (quantitative volume calculation).
Class and exam questions
Why is the heart size often normal on chest X-ray in acute mitral regurgitation?
In acute development of the defect, the left atrium does not have time to stretch (it is non-compliant). Acute congestion in the pulmonary circulation with pulmonary edema occurs, but chamber dilatation has not yet had time to form.
What are the quantitative criteria for severe mitral regurgitation on MRI?
Severe grade is established if the regurgitant volume exceeds 60 mL per beat and the regurgitant fraction is greater than 50%.
What is a flail leaflet?
This is a pathological condition occurring upon rupture of chordae tendineae, when the valve leaflet loses support and flails freely in the blood flow, causing severe regurgitation.
What else to study on this topic
- Limitations of various Doppler modes in eccentric regurgitant jets
- Formulas for calculating regurgitant volume and fraction on MRI
- Differential diagnosis with mitral stenosis
- The role of CT in assessing valvular and subvalvular calcification
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