pulmonary hypertension in cats (PH) is considered a complex syndrome characterized by a increased blood pressure inside the structures that make up the vascular network of the lungs. In the veterinary clinic, PH includes various clinical manifestations and is usually classified according to its etiology (identification of the cause) and its pathophysiological mechanism (behavior and evolution in the organism).
Although this pathology has a low incidence in the young population, it can appear with some frequency in elderly felines, whether they are mestizo or of a defined breed. Of course, we must highlight the importance of going to a trusted vet when observing any change in the appearance or behavior of your cat.
However, in this article on our site, we explain the main symptoms, causes and risk factors of Hypertension lung disease in cats, to help you recognize early the signs of this disease in your feline.
What is pulmonary hypertension?
The lungs of felines have a high-capacity vascular network, but with low pressure and resistance, which participates directly in the process of respiration and oxygenation of the tissues of your body. To establish a comparison, the resistance of the cardiac (systemic) vascular network can be up to 10 times greater than that of the lungs in he althy individuals. As a consequence, the cardiac structures are prepared to withstand a much higher pressure than the network of pulmonary arteries and veins.
However, the presence of some diseases, malformations or risk factors can cause an increase in pressure and resistance of pulmonary vascular structures. This pulmonary hypertension usually directly affects the lung tissues and the functioning of the cardiac structures, impairing the oxygenation mechanism of the body's tissues.
Precisely for this reason, pulmonary hypertension in cats is considered a complex syndrome and its effects are worrying, as they can have repercussions negatively in practically all the organs that need to receive correct oxygenation to guarantee their optimal functioning.
Symptoms of pulmonary hypertension in cats
Feline pulmonary hypertension encompasses various clinical manifestations, but the most frequent symptoms of pulmonary hypertension in cats are:
- Exertional dyspnea: it is generally characterized by shortness of breath and difficulty in recovering on exertion of any kind. However, in more severe cases, shortness of breath can be permanent, even at rest.
- Constant Exhaustion: Felines with pulmonary hypertension may be constantly tired and demonstrate constant exhaustion. Due to the loss of respiratory capacity and fatigue, cats may lose interest in playing and performing daily activities, such as eating or drinking water. In more severe cases, the animal may also urinate and defecate outside the litter box.
- Cough, which may be accompanied by blood in the more advanced stages of the disease.
- Exercise intolerance.
- Fainting or syncope.
- Loss of appetite and weight.
- Dehydration.
- Cardiac arrhythmia.
- Abnormal lung sounds (mainly in PH associated with respiratory diseases).
Here's a cat with pulmonary hypertension and polycythemia suffering from syncope, from @hockeyken10 on YouTube:
Causes and risk factors of pulmonary hypertension in cats
In human medicine, pulmonary hypertension may be idiopathic (also formerly known as "primary") orsecondary , depending on its aetiology. Idiopathic conditions are those that appear "alone", that is, they are not related to an underlying cause. However, idiopathic PH are rarely seen in the veterinary clinic.
Pulmonary hypertension in cats usually develops from another disease, so it is often considered a symptom of a more complex clinical picture. Secondary PH is usually associated with various causes and can affect the pulmonary arteries and veins.
Although there is still no consensus in Veterinary Medicine on the classification of PH, the predominant tendency is to accept and adopt the same classification applied in humans. Below, we explain the main differences, the causes and the pathophysiological processes of idiopathic and secondary PH in cats.
Idiopathic pulmonary hypertension in cats
In certain cases, the detailed diagnostic process is unable to reveal a specific cause for PH. When this happens, it is very likely that we are dealing with a case of idiopathic pulmonary arterial hypertension (previously also known as "primary").
In idiopathic PAH, there is a dysfunction in the endothelium (walls of blood capillaries) of neuroendocrine origin that affects the vascular network of the lungs, leading to a predisposition to vasoconstriction and thrombosis. This condition begins in the small-caliber pulmonary vessels, which are affected by the formation of small clots (thrombi). As a consequence, the loss of many pulmonary vessels and an increase in vascular pressure in the lungs can be observed.
Although there are many discussions about the possible causes of idiopathic PAH in felines, aging and obesity appear as factors of risk, since they favor the wear of the cardiac and pulmonary vascular structures. Currently, research is also being carried out on the relevance of the genetic factor in the predisposition to idiopathic PH in cats.
Secondary Pulmonary Hypertension in Cats
According to the cause and pathophysiological mechanism, secondary PH in cats is usually divided into 4 main "types". Below, we summarize the main characteristics of each subtype of secondary pulmonary hypertension in cats:
- PAH secondary to pulmonary hypercirculation: in these cases, an increase in blood pressure is observed inside the pulmonary arteries, derived from a picture of hypercirculation. That is to say: the blood flow in the pulmonary arteries has a very high frequency and intensity, which increases the pressure inside these vascular structures. The most common causes are congenital heart disease that causes deviations in blood circulation, such as patent ductus arteriosus (PDA) and interatrial septum. In general, this type of PAH is more commonly diagnosed in young cats with malformations in the cardiovascular structure.
- Pulmonary hypertension due to respiratory diseases: Some respiratory diseases can generate hypoxia and increase the risk of pulmonary vasoconstriction. As a consequence, the pulmonary vascular structure may suffer deformation and dysfunction, leading to an increase in pulmonary pressure. Secondary PH associated with chronic respiratory problems with hypoxia can also cause dilation and dysfunction in the right ventricle of the heart, a clinical condition known as cor pulmonale. Among the most frequent causes in cats, we find feline pneumonia, pulmonary fibrosis and obstructive tracheobronchial disease.
- PH associated with pulmonary thromboembolism: Thromboembolism is a complex clinical picture characterized by the formation of multiple clots (thrombi) in the vascular network of the lung (mainly in the pulmonary arteries) and on the right side of the heart. One of the consequences of pulmonary thromboembolism is the obstruction of the arteries and the consequent persistent increase in pulmonary pressure. In general, heartworm disease appears as the main cause of this type of PH. However, there are other possible causes, such as: systemic diseases that lead to hypercoagulability, neoplasms, glomerular disease, sepsis, hyperadrenocorticism, etc.
- HP caused by alterations in the left atrium of the heart: when the left atrium presents a chronic elevation of pressure, the drainage of the pulmonary veins is impaired. As a consequence, pulmonary venous hypertension may be observed, which is usually mild or moderate. However, when this picture is added to respiratory diseases or thromboembolism, pulmonary hypertension can become severe. Among the main causes of this increase in blood pressure, we find dilated cardiomyopathy, congenital mitral dysplasia and degenerative valve disease (DVE) that most commonly affects the mitral valve.
Diagnosis of Pulmonary Hypertension in Cats
When observing any of the symptoms mentioned in your cat, do not hesitate to go quickly to the veterinary clinic. Pulmonary hypertension in cats requires a very detailed differential diagnosis to identify the underlying cause and subsequent specific treatment.
After performing a physical examination and analyzing the patient's history, the veterinarian may request an electrocardiogram (ECG), somethoracic x-rays and clinical analyzes (blood, urine, feces), to verify the state of he alth of the feline and verify the evolution of the disease in your body. Suspicion of PH will usually also need to be confirmed by a Doppler echocardiography
Here is a color Doppler echocardiogram:
Feline Pulmonary Hypertension Treatment
Treatment of pulmonary hypertension in cats will depend on identifying the underlying cause and the individual patient's he alth status. In general, the veterinarian adopts as basic therapy the controlled administration of some drugs with inhibitory action on pulmonary vasoconstriction. In addition, medications that contribute to strengthening the walls of the pulmonary blood capillaries can also be used, to slow down the progression of endothelial dysfunction.
When the presence of clots (thrombi) is diagnosed, drug therapy is also usually added anticoagulants On the other hand, in some cases of congenital heart malformations with deviations, surgical intervention may be studied as a viable treatment option for patients with a more stable state of he alth.
Is it possible to prevent pulmonary hypertension in cats?
The prevention of pulmonary hypertension consists fundamentally in offering adequate preventive medicine to the feline throughout his life. To do this, it is essential to make regular visits to the veterinary every 6 months, respect the feline vaccination schedule and the cat deworming schedule. It is also essential to offer a balanced diet of excellent quality to your cat, and provide him with toys, scratchers and other accessories that allow him to exercise his body and mind on a daily basis.
