From the Guidelines
In mitral regurgitation, the fluid that accumulates in the lungs is pulmonary edema, which consists primarily of serous fluid that has leaked from pulmonary capillaries into the alveolar spaces and interstitial tissue. This fluid is essentially a filtrate of blood plasma containing water, electrolytes (mainly sodium and chloride), and small amounts of protein. The accumulation occurs because mitral regurgitation causes blood to flow backward from the left ventricle into the left atrium during systole, increasing left atrial pressure. According to a systematic review of clinical practice guidelines and recommendations for mitral regurgitation management 1, this elevated pressure is transmitted backward to the pulmonary veins and capillaries, increasing hydrostatic pressure and forcing fluid out of the vasculature into the lung tissue. Key points to consider include:
- The severity of the valve regurgitation and the myocardial response to volume overload determine patient symptoms and outcomes
- Mitral regurgitation is associated with morbidity and mortality, particularly if left untreated, as noted in the European Heart Journal study 1
- The optimal timing of intervention is not always clear, especially in multivalve disease, but the primary goal is to prevent or reduce pulmonary edema and its consequences on morbidity, mortality, and quality of life. In severe or acute mitral regurgitation, this process happens rapidly, overwhelming the lymphatic drainage system that normally removes excess fluid from the lungs. The resulting pulmonary edema impairs gas exchange by creating a barrier between inhaled air and pulmonary capillaries, leading to symptoms like shortness of breath, coughing, and in severe cases, pink frothy sputum due to the mixture of air, edema fluid, and sometimes small amounts of blood.
From the Research
Composition of Fluid in Lungs in Mitral Regurgitation
The fluid in the lungs in mitral regurgitation is primarily composed of:
- Pulmonary edema, which is a buildup of fluid in the lungs due to the heart's inability to pump blood efficiently 2
- Fluid accumulation in the lungs can be caused by the increased pressure in the left atrium, which is a result of the mitral valve not closing properly 3
- The fluid can also be a result of the heart's inability to pump blood forward, causing blood to back up into the lungs 4
Pathophysiology of Mitral Regurgitation
The pathophysiology of mitral regurgitation involves:
- The mitral valve not closing properly, allowing blood to flow backward into the left atrium 3
- The increased pressure in the left atrium can cause fluid to build up in the lungs 2
- The heart's inability to pump blood forward can also cause fluid to accumulate in the lungs 4
Treatment of Mitral Regurgitation
The treatment of mitral regurgitation involves:
- Medications such as nitrates, which can help to reduce the pressure in the left atrium and alleviate symptoms 2
- Surgical intervention, such as mitral valve repair or replacement, may be necessary in severe cases 4, 3
- The use of enoximone or dobutamine and nitroglycerin can also help to reduce pulmonary arterial pressure and improve cardiac output 5