Pulmonary Valve

The pulmonary valve is one of four heart valves – and one that receives little attention in everyday life until it causes problems. Its task: to control the blood flow from the right ventricle to the lungs. It sits precisely between the right ventricle and the pulmonary trunk (pulmonary artery). During systole, i.e. when the heart contracts, it opens and allows blood to flow towards the lungs. In diastole, the relaxation phase, it closes again – so that no blood flows back from the pulmonary artery into the ventricle.

Function of the Pulmonary Valve

Basically, the pulmonary valve has a simple but vital job: to pass oxygen-poor blood from the right ventricle into the lungs, where it is freshly loaded with oxygen. It opens as soon as the blood pressure in the right ventricle rises sufficiently during systole – and closes again when the ventricle relaxes and the pressure in the pulmonary trunk prevails.

1. Opening of the valve: During contraction of the right ventricle, oxygen-poor blood is pumped through the pulmonary valve into the pulmonary artery and from there further into the lungs.
2. Closing of the valve: In diastole, the pulmonary valve closes to prevent backflow of blood from the pulmonary artery into the right ventricle.

Diseases of the Pulmonary Valve

Several diseases can impair the function of the pulmonary valve. The two most common ones that vets encounter in dogs are pulmonary stenosis and pulmonary valve insufficiency – both with very different courses.

Pulmonary Stenosis

• Pulmonary stenosis is usually a congenital disease in which the pulmonary valve is narrowed. The consequence: blood flow from the right ventricle into the pulmonary artery is slowed down, the heart has to exert more force – and the right ventricle can thicken in response (hypertrophy).
• Symptoms: Affected dogs show weakness, shortness of breath or fainting spells; in advanced cases, ascites due to fluid accumulation can also occur. With severe manifestation, heart failure is threatened.
• Diagnosis: The method of choice is echocardiography (heart ultrasound), which provides information on the structure and function of the valve. Additionally, X-rays and ECG can help to better assess the effects of the stenosis on the heart.
• Treatment: Mild cases are initially monitored regularly without immediate intervention. In severe stenosis, balloon valvuloplasty is often used – a balloon catheter is inserted into the narrowed valve and dilated. Open surgical correction is only necessary in rare exceptional cases.

Pulmonary Valve Insufficiency

• Pulmonary valve insufficiency occurs when the pulmonary valve no longer closes completely – blood then flows back from the pulmonary artery into the right ventricle. Causes can be valve damage, an infection or a congenital defect.
• Symptoms: Often, the complaints are initially milder than with pulmonary stenosis. Some dogs show breathing difficulties, heart murmurs or reduced exercise tolerance. In severe courses, right-sided heart failure can develop.
• Diagnosis: Here too, echocardiography is the central tool – it allows the severity of the insufficiency to be assessed and the blood flow to be examined in detail.
• Treatment: Mild insufficiencies are often only monitored. If heart failure is already present, medications can be used to support heart function and reduce excess fluid.

Diagnosis of Pulmonary Valve Diseases

In practice, the investigation of a pulmonary valve disease relies on several methods that complement each other:

1. Auscultation: Even when listening with a stethoscope, the vet can hear characteristic heart murmurs that indicate a valve problem.
2. Echocardiography: The heart ultrasound provides detailed images of the pulmonary valve and shows what blood flow and valve function actually look like.
3. X-rays: The chest X-ray can reveal enlarged heart chambers or fluid in the lungs as signs of heart failure.
4. Electrocardiogram (ECG): The ECG detects arrhythmias that may indicate an underlying heart disease.

Treatment options

What ultimately constitutes the right treatment depends heavily on the severity and the specific symptoms of the dog. Some animals initially need nothing more than regular check-ups – others require medical or even surgical interventions.

In mild pulmonary stenosis or pulmonary valve insufficiency, heart medications can be prescribed to support heart function, regulate blood pressure and reduce fluid accumulation. Diuretics are added if the dog is already suffering from the consequences of heart failure.

In severe pulmonary stenosis, balloon valvuloplasty is often the method of choice: a small balloon catheter is inserted into the narrowed valve, inflated and thus dilates it – a minimally invasive procedure with often good results.

In very severe cases where other measures are insufficient, surgical correction of the pulmonary valve may become necessary.

Prognosis

The long-term outcome for a dog with pulmonary valve disease depends largely on the type and severity of the diagnosis:

• Dogs with mild pulmonary stenosis or pulmonary valve insufficiency often lead a largely normal life – provided the condition is regularly monitored and treated if necessary.
• Severe courses, particularly with existing heart failure, have a less favourable prognosis. However, targeted therapy can often significantly improve quality of life and slow the progression of the disease.