Pulmonary Arterial Hypertension

By | 8 April 2021

Pulmonary Arterial Hypertension (PAH)

Pulmonary hypertension; is an increase in blood pressure in the veins (pulmonary arteries) that bring the blood circulating in the body to be oxygenated from the heart to the lungs. There are dozens of diseases that can cause pulmonary hypertension. Pulmonary Arterial Hypertension, which is a group among these; can progress quickly and be life-threatening.

Under normal circumstances, the right side of the heart (right atrium and right ventricle) sends contaminated blood to the lungs to be cleaned (oxygenated) via the pulmonary arteries. When pulmonary hypertension develops, the pulmonary arteries narrow. Trying to pump blood into the narrowed pulmonary arteries begins to strain, and the right side of the heart expands.

Pulmonary hypertension is a type of high blood pressure affecting the right side of the heart and pulmonary arteries.

The increased pressure causes the heart’s right ventricle to use more power to pump blood to the lungs, which over time causes weakness and insufficiency of the heart muscle2.

Normal pulmonary artery pressure is 14 ± 3 mmHg at rest, and its upper normal limit is 20 mmHg³.

In pulmonary hypertension, mean pulmonary artery pressure, PAP is ⩾25 mmHg³.

It refers to a group of PH patients defined by pulmonary artery end pressure PAWB ≤15 mmHg and PVD> 3 Wood units (WU), without other causes of precapillary PH such as pulmonary arterial hypertension (PAH), lung diseases, CTEPH, or rare diseases.

EPIDEMIOLOGY

There is insufficient data on the incidence of PH in the literature.

The epidemiology of PAH is defined in various registry studies. The lowest estimated prevalence of PAH and idiopathic PAH (IPAH) in the adult population is 15/1 million and 5.9 / 1 million cases, respectively.

The lowest PAH incidence estimate is 2.4 / 1 million cases per year in the adult population.

In Europe, the prevalence and incidence of PAH are in the range of 15-60 / 1 million patients and 5-10 / 1 million cases per year, respectively.

CLASSIFICATION

  • Group 1: Pulmonary arterial hypertension
  • Group 2: Pulmonary hypertension caused by left heart disease
  • Group 3: Pulmonary hypertension caused by lung disease and/or hypoxia
  • Group 4: Pulmonary hypertension caused by chronic pulmonary embolism
  • Group 5: Unknown/multifactorial Pulmonary hypertension

SYMPTOMS

  • In the early stages of the disease, the disease is difficult to detect because the symptoms are nonspecific.
  • Shortness of breath (initially when exercising and when at rest)
  • Tiredness
  • Dizziness or fainting spells (syncope)
  • Chest pressure or chest pain
  • Swelling (edema) in your ankles, legs and eventually in the abdomen
  • Bluish color of the lips and skin (cyanosis)
  • Palpitation

DIAGNOSIS

The diagnosis of PH requires clinical suspicion based on symptoms and physical examination. This requires a series of examinations. A few of them are listed below:

  • ECG (Electrocardiography)
  • Lung X-ray
  • Respiratory function tests and arterial blood gases
  • Echocardiography
  • Ventilation-perfusion scintigraphy
  • High resolution IT
  • Contrast-enhanced CT and pulmonary angiography
  • Cardiac MR
  • Right heart catheterization (CCT) and vasoreactivity
  • Genetic tests

TREATMENT

The diagnosis and treatment of pulmonary hypertension vary according to the place of the disease-causing it in the PAH classification. Since it is a disease that concerns many specialties, PAH patients should be examined with a multidisciplinary approach, and their treatment and follow-up should be done by experienced specialists in PAH centers.

The general treatment goal in PAH patients;

  • To put the patient in a low-risk group by improving exercise capacity, quality of life, right ventricular function, and decreasing mortality,
  • Bringing the patient to WHO-FC II whenever possible and/or keeping it here,
  • It is to make 6DYM normal or close to normal.
    – A threshold value of 6DYM> 440 m is adopted.

The current treatment strategy for PAH patients can be divided into three main steps:

  • The initial approach includes general precautions, supportive therapy (oral anticoagulants, diuretics, O2, digoxin), referral to specialized centers, and acute vasoreactivity testing for chronic CCB treatment indication.
  • The second step is to administer high-dose CCB in vasoactive patients as initial therapy, and drugs approved for PAH in non-vasoactive patients, according to the patient’s prognostic risk and the degree of recommendation and level of evidence available for each product or combinations of products.
  • The third step concerns the response to the initial treatment strategy; If the response is insufficient, use of approved drug combinations and lung transplantation is recommended.

With PAH treatment, the rate of clinical deterioration of the disease can be slowed down and survival can be partially prolonged. Unfortunately, PAH is still a controllable disease, not a fully curable disease. The goals of PAH treatment are to improve the functional stage of the patient, stop or improve clinical deterioration, improve quality of life and prolong survival.

New drugs have been developed for the pathophysiology of PAH. These are endothelial receptor antagonists (oral bosentan, ambrisentan, sitaxentan); prostanoids (inhaler iloprost, subcutaneous / iv treprostinil, and iv epoprostenol), and phosphodiesterase inhibitors (oral sildenafil, tadalafil, vardenafil). With randomized controlled studies conducted with these drugs, evidence and levels of evidence on the efficacy and safety of drugs at each functional stage have been defined. In the treatment guidelines, recommended medications for each functional stage patient are shown according to their level of evidence kanıt.

Every patient in whom PAH treatment is initiated should be monitored every 3 months in terms of response to treatment. If the targeted response is not achieved with single-drug treatment, it should be switched to “combination” therapy, which can be given two or three drugs together.

Balloon atrial septostomy (BAS) or lung or heart-lung transplantation should be applied to prevent mortality in patients with advanced PAH who have failed or insufficient drug therapy and occasionally have syncope.

Pregnancy should be prevented in patients with PAH, and if they do, pregnancy should be terminated.