by Phyllis Hanlon, Contributing Writer

Scientists continue to explore the origins and effects of WHO Group 4 PH (CTEPH, chronic thromboembolic pulmonary hypertension), but much more research needs to be conducted before the disease is fully understood. A study published in the European Respiratory Review ( reported that CTEPH is thought to occur as a result of acute pulmonary embolism (PE) after a patient has a venous thromboembolism (VTE), i.e., a blood clot in a vein usually in the legs. In an effort to learn more about the causes and effects of CTEPH, as well as how often the disease occurs, a team of German researchers conducted an extensive literature review and database search for information.

The study focused on publications, databases and other sources specific to the United States, Europe and Japan. During the data review, the authors looked at how often PE was diagnosed in the U.S. and Europe; they also reviewed the number of pulmonary endarterectomies (PEA) that had been performed. This surgery for some people with CTEPH can potentially cure the disease.

For the Japanese population, the authors reviewed patients registered in the Intractable Disease Survey (, and looked at how many patients had PE and how many patients with CTEPH also had record/memory/etc. of a PE.

After analyzing the data, the authors calculated estimated numbers of diagnosed and potential undiagnosed CTEPH and found that the United States and Europe both had between three and five cases annually for every 100,000 individuals; in Japan, the rate was 1.94 for every 100,000 persons. The reason for the lower rate in Japan might have to do with genetics, lifestyle, population characteristics, or possibly the fact that only severe cases are reported, the authors suggested. Also, differences in the diagnostic methods used in various parts of the world may make it more difficult to make an accurate CTEPH diagnosis.

Based on their findings, the authors estimated that CTEPH diagnoses might increase by 20 percent during the next 20 years in Europe and the U.S. due to increases in disease awareness. They concluded that Japan would have a much higher increases, since the current rates are below the U.S. and Europe, of 35 percent over 15 years, or 2.33 percent every year.

The authors also evaluated treatment options for CTEPH. To date, riociguat is the only medication approved for patients who have inoperable or latent. A new treatment procedure, percutaneous balloon pulmonary angioplasty (BPA), widens the pulmonary arteries but is only performed at specialist centers. The role of BPA and which patients should receive this treatment is still under investigation. PEA, however, is still considered the “gold standard treatment for CTEPH,” but not all patients receive it, according to the authors. They noted that between 24 and 37 percent of patients do not qualify for the surgery and only about 85 percent of patients who fit the criteria for PEA will undergo the operation. To improve survival, the authors emphasize the importance of evaluating all patients with CTEPH for PEA, as recommended by the 2015 European Respiratory Society/European Society of Cardiology (ERS/ESC) guidelines for treating pulmonary hypertension (

The authors of this study indicated that, although nonresolution of acute PE is the most common cause of CTEPH, it’s unknown how many patients who have PE will develop CTEPH, but the Follow-Up after Acute Pulmonary Embolism (FOCUS) study ( should provide some answers.

After examining all the statistics and compiling their findings, the authors determined that CTEPH continues to be under-diagnosed. They “…suggested that there may be a need for increased education, awareness of guidelines and/or availability of resources to improve CTEPH diagnosis rates worldwide.”

Each PH patient is different. It is essential that you talk to your own doctor about what treatment options are best for you. For more information on finding a doctor or an accredited care center, visit