Pulmonary Veno-Occlusive Disease: Causes, Symptoms, Treatment, Prognosis, Pathophysiology, Epidemiology
Pulmonary veno-occlusive disease is a very rare condition in which pulmonary hypertension takes place. This leads to obstructed blood flow within the small pulmonary veins thereby causing high blood pressure in the pulmonary arteries. Pulmonary veno-occlusive disease is progressive and life threatening.
What is Pulmonary Veno-occlusive Disease?
Veno-occlusive diseases or VOD occur when the veins get congested leading to obstruction and tissue necrosis. This progressively leads to failure of the organ of the affected region or subsequent death. Veno-occlusive diseases or VOD is classified into two categories hepatic veno-occlusive disease and pulmonary veno-occlusive disease. In case of hepatic Veno-occlusive diseases, the portal veins associated with liver undergo portal hypertension; whereas in case of pulmonary veno-occlusive disease, the pulmonary veins get congested and suffer from pulmonary hypertension.
Pulmonary veno-occlusive disease is characterized by the occurrence of fibrosis within the small pulmonary veins and capillaries, leading to accumulation of the pulmonary interstitial fluid. This further increases the pulmonary vascular resistance and occurrence of pulmonary edema. The pulmonary arteries which are directly connected to the right ventricle have high pressure built in due to the increase in pulmonary vascular resistance which leads to impairment of the right ventricle. With advancement of age, the condition gets worse accompanied by narrowed pulmonary veins with congestion, swelling of lungs and pulmonary artery hypertension.
Symptoms of Pulmonary Veno-occlusive Disease
Common symptoms that prevail due to pulmonary veno-occlusive disease are:
- Difficulty in catching of breath is one of the symptoms of pulmonary veno-occlusive disease
- Increased tendency to faint is also a symptoms of pulmonary veno-occlusive disease
- Pain in the chest
- Cyanosis or bluish colored skin due inadequate supply of oxygenated blood to the body.
Epidemiology of Pulmonary Veno-occlusive Disease
The incidence rate for Pulmonary Veno-occlusive Disease is one in five million with around ten percent cases suffering from pulmonary artery hypertension and around twenty percent cases arise due to hereditary factors.
Prognosis of Pulmonary Veno-occlusive Disease
The prognosis or outlook for pulmonary veno-occlusive disease is very poor with most patient dying within two years of diagnosis. In case of infants the survival is only up to a few weeks.
Causes of Pulmonary Veno-occlusive Disease
The primary causes that contribute to pulmonary veno-occlusive diseases or VOD are:
- Narrowing of pulmonary veins
- Pulmonary artery hypertension can cause pulmonary veno-occlusive disease
- Inflammation and congestion of lungs
- Hematopoietic cell transplantation
- Presence of the disorder within the family can also be a cause for pulmonary veno-occlusive disease
Pathophysiology of Pulmonary Veno-occlusive Disease
The prime mechanism of the injury to the pulmonary sinusoids is due to contraction and obstruction of the pulmonary veins and venules. The onset of this occlusion and constriction begins with accumulation of fluid within the pulmonary tissues which progressively become thick and dense sclerotic fibrous tissue. In addition to this, these tissues form an intimal thickening on the walls of the veins and venules which causes narrowing of the pulmonary veins, but this never occurs in the large veins. Apart from constriction of the pulmonary veins, dilation of the lymphatic capillaries also occurs which contributes to pulmonary veno-occlusive disease.
Risk Factors of Pulmonary Veno-occlusive Disease
The major risk factors that pose a threat of pulmonary veno-occlusive disease are:
- Genetic Risk Factors for Pulmonary Veno-occlusive Disease: Though pulmonary veno-occlusive disease is rare in occurrence but the probability of it happening in the same family is greater due to the genetic factors.
- Toxic Exposure as a Risk Factor for Pulmonary Veno-occlusive Disease: Chemotherapy and bone marrow transplants pave way to exposure of several toxins to the body like Mitomycin, Carmustine, Bleomycin etc. which when metabolized by the body contribute to inflammation, thrombosis and fibrosis. Also, increased usage of drugs like cocaine and Fenfluramine pose as a risk factor for pulmonary veno-occlusive disease.
- Autoimmune Disorders Posing a Risk for Pulmonary Veno-occlusive Disorder: Autoimmune disorders contribute to the destruction of the pulmonary venules through an onset of a health condition which may be primary or secondary, trailed by fibrosis with or without thrombosis. The health condition may be myopathy, rheumatoid arthritis, alopecia, lupus syndrome, positive antinuclear antibodies and Raynaud's phenomena.
- Thrombotic Diathesis Leading to Pulmonary Veno-occlusive Disease: It is a condition where hypercoagulability exists within the individual which contributes to the thrombotic occlusion of the pulmonary veins.
Complications of Pulmonary Veno-occlusive Disease
The possible complications of pulmonary veno-occlusive disease are:
- Progressive dyspnea
- Failure of right side of the heart
- Hemoptysis or coughing out blood
- Hypoxemia or low levels of oxygen in blood
- Chronic coughing
- Pleural effusions or fluid accumulation in between the chest cavity and lungs is one of the possible complications of pulmonary veno-occlusive disease
- Raynaud's Phenomena
- Sudden death
Diagnosis of Pulmonary Veno-occlusive Disease
Pulmonary veno-occlusive disease can be diagnosed through below procedures:
- Radiographic Analysis for Pulmonary Veno-occlusive Disease: The radiographic analysis of the chest is done to determine the presence of pulmonary edema, pulmonary hypertension and pressure due to pulmonary artery occlusion.
- Diagnosing Pulmonary Veno-occlusive Disease with Lung Biopsy: It is a conclusive procedure which involves surgical removal of the tissue from the lungs to check for pulmonary artery occlusion and edema.
Treatment of Pulmonary Veno-occlusive Disease
There are certain treatments available to treat pulmonary veno-occlusive disease as well as it's up surging complications but the effects of them are not up to the expected levels. Some such treatments are:
- Vasodilators to Treat Pulmonary Veno-occlusive Disease: Calcium channel blockers and Epoprostenol are certain pulmonary vasodilators that check the pulmonary hypertension.
- Anticoagulants as a Treatment for Pulmonary Veno-occlusive Disease: Anticoagulants are suggested to control hypercoagulability which is one of the contributing factors for occlusion of the pulmonary veins.
- Immunosuppressant Used to Treat Pulmonary Veno-occlusive Disease: Immunosuppressive medications are given to the patient to check for the autoimmune disorders. Such medications include antimetabolites and glucocorticoids.
- Oxygen Therapy for Managing Pulmonary Veno-occlusive Disease: It is a long term treatment which delivers higher levels of oxygen flow within the blood to maintain the oxygen level in the body as the lungs are unable to do this.
- Lung Transplant to Treat Pulmonary Veno-occlusive Disease: Amongst all, lung transplantation is the sole treatment which significantly helps in prolonging the life of the patient. The transplant can be done for single as well as both the lungs. The risk that lies with lung transplant is the waiting time for the donor organ exceeding the life expectancy of the patient and post-surgical bronchiolitis causing morbidity and mortality amongst the recipients.
Pulmonary veno-occlusive disorder is a condition about which not much is known. It is a condition that arises due to several critical factors which cause occlusion of the pulmonary veins. The condition is usually misdiagnosed or diagnosed at a later stage. This leads to high mortality rate amongst the patients. The only treatment that promises a prolonged life to the patient is the lung transplantation but that too is shadowed by the long waiting time for the organ donation.