The mitral valve is quietly leaking, can your heart still withstand it?

Author: Zhang Haibo, Chief Physician, Beijing Anzhen Hospital, Capital Medical University

Reviewer: Wang Fang, Chief Physician, Beijing Hospital

The human body's precision machinery, the heart, has four delicate valves, among which the mitral valve plays a vital role. It is like a well-designed door that ensures that blood flows smoothly from the left atrium to the left ventricle. However, when this door cannot be completely closed, that is, when the mitral valve is insufficiency, blood will flow back, posing a threat to heart health.

1. Pathological mechanism and causes of mitral regurgitation

Imagine that in the cold winter, if the doors and windows of your house are not closed tightly, cold wind will continue to pour in. The same is true for mitral regurgitation. When the left ventricle contracts, some blood flows back to the left atrium through the incompletely closed mitral valve, causing the left atrial pressure to increase, the heart gradually expands, and then affects the right ventricle, eventually leading to a series of problems such as blood congestion in the lungs and heart failure.

Figure 1 Original copyright image, no permission to reprint

There are many causes of mitral regurgitation, which may be congenital developmental abnormalities or acquired factors. In adolescents and children, mitral regurgitation is mostly caused by congenital valve structure problems; in middle age, rheumatic valvular disease becomes a common cause, which is usually related to streptococcal infection. With age, factors such as coronary heart disease, aging and degeneration of heart valves, and rupture of chordae tendineae may also lead to mitral regurgitation. In addition, long-term heart failure and arrhythmias may also cause secondary mitral regurgitation.

Acute and chronic mitral regurgitation: different journeys, same destination

Acute mitral regurgitation is usually a serious condition, like a sudden storm, and is often caused by trauma or sudden intense physical activity, such as ruptured chordae tendineae. Because the heart does not have enough time to adapt to this sudden change, whether it is due to trauma or ischemic causes such as severe myocardial infarction, it may cause a sharp disturbance in cardiac hemodynamics. Patients may suddenly experience low blood pressure, heart failure, and even cough up pink foamy sputum.

Chronic mitral regurgitation develops more slowly, and common causes include degeneration of mitral valve tissue, valve damage caused by rheumatic diseases, etc. In the chronic stage, the heart will have a certain compensation and adaptation process, but long-term development will still lead to heart enlargement and gradual decline in heart function.

Symptoms of Mitral Regurgitation

The symptoms of mitral regurgitation are often mild in the early and middle stages, and heart murmurs can only be detected by auscultation. However, most patients may not develop obvious symptoms such as chest tightness and shortness of breath after activity until the middle and late stages, as the heart enlarges and hemodynamics change significantly. This indicates that heart function has significantly declined at this time.

The characteristic of this disease is that symptoms appear with a delay, so the timing of treatment cannot be determined solely based on symptoms, otherwise the disease may be delayed.

Figure 2 Original copyright image, no permission to reprint

Late-stage mitral regurgitation may lead to pulmonary congestion. This is because under normal circumstances, the blood in the lungs should return to the left atrium after oxygenation and enter the left ventricle through the mitral valve. However, when the mitral valve is incomplete, the blood will flow back to the left atrium, causing increased left atrial pressure, which in turn hinders the return of blood from the lungs to the left atrium. Blood accumulates in the lungs, which is pulmonary congestion.

Pulmonary congestion will affect the efficiency of blood and oxygen exchange in the lungs, manifesting as symptoms such as chest tightness and shortness of breath that worsen after activity. In severe cases, changes such as increased pulmonary blood and blurred and white lung texture can be observed through lung imaging examinations.