Why is there venous blood in the pulmonary artery?
Aug 27, 2025
Source: Cainiu Health
Dr. Liu Feng
Introduction
Under normal circumstances, the main reasons for venous blood in the pulmonary artery include the physiological pathway of the pulmonary circulation, the need for oxygen-poor blood to be transported before oxygenation, atrial septal defect, ventricular septal defect, chronic pulmonary heart disease, and others. If symptoms such as chest tightness, shortness of breath, and fatigue occur, it is recommended to seek timely consultation at the cardiology or respiratory department of a reputable hospital. A detailed analysis is as follows:
Under normal circumstances, the main reasons why venous blood is present in the pulmonary artery include the physiological pathway of pulmonary circulation, the need for venous blood to be transported before oxygenation, atrial septal defect, ventricular septal defect, and chronic pulmonary heart disease. If symptoms such as chest tightness, shortness of breath, or fatigue occur, it is recommended to visit the cardiology or respiratory department at a formal hospital promptly. Detailed explanations are as follows:
1. Physiological Pathway of Pulmonary Circulation
After systemic circulation, venous blood with low oxygen content and high carbon dioxide concentration returns to the right atrium and is then pumped into the pulmonary artery through the contraction of the right ventricle. This is the normal starting process of pulmonary circulation in the human body, aimed at delivering venous blood to the lungs for oxygenation. It is important to avoid excessive fatigue and strenuous exercise in daily life.
2. Venous Blood Transport Needs Before Oxygenation
Blood must first reach the pulmonary capillaries through the pulmonary artery and complete gas exchange with oxygen in the alveoli before becoming arterial blood. Therefore, prior to oxygenation, the pulmonary artery necessarily carries venous blood. Maintaining a clear airway and avoiding prolonged stays in enclosed, oxygen-deficient environments are recommended in daily life.
3. Atrial Septal Defect
This is a mild form of congenital heart disease caused by an abnormal defect between the left and right atria. Arterial blood from the left atrium shunts into the right atrium, increasing the proportion of venous blood entering the pulmonary artery. Patients with mild symptoms can take medications such as spironolactone tablets, furosemide tablets, and hydrochlorothiazide tablets under a doctor's guidance to reduce cardiac load.
4. Ventricular Septal Defect
Compared to atrial septal defect, this condition more easily affects hemodynamics. Arterial blood from the left ventricle flows into the right ventricle through the defect, further increasing the proportion of venous blood in the pulmonary artery. Long-term effects may impair heart function. Patients can take medications such as captopril tablets, enalapril tablets, and metoprolol tartrate tablets under a doctor's guidance to protect heart function.
5. Chronic Pulmonary Heart Disease
This condition often develops from chronic bronchitis and emphysema. Lung lesions lead to increased pulmonary vascular resistance, causing compensatory thickening of the right heart. Venous blood pumped into the pulmonary artery cannot be effectively oxygenated, and blood stasis exacerbates the characteristics of venous blood. Patients can take medications such as aminophylline tablets, salbutamol aerosol, and budesonide-formoterol powder inhaler under a doctor's guidance to relieve airway spasms. Patients with severe conditions may need lung volume reduction surgery to improve pulmonary ventilation and perfusion matching.
In daily life, avoid smoking and exposure to secondhand smoke to reduce lung damage; keep warm and prevent respiratory infections; maintain a balanced diet and reduce intake of high-salt and high-fat foods; and undergo regular cardiopulmonary function examinations, such as chest X-rays and electrocardiograms, to monitor cardiopulmonary health.
