Ask the Doctors by Eve Glazier, M.D. and Elizabeth Ko, M.D

Study Links Gut Microbiome With Pulmonary Arterial Hypertension

Dear Doctor: It seems like gut microbes are part of every kind of health issue now. I just read that having the wrong bacteria causes pulmonary hypertension, which is something our dad had before he died. Is that really true? How can it be fixed?

Dear Reader: We’re right there with you in being amazed by the breadth and depth of the role of the gut microbiome in health and well-being. The emerging research these days is fascinating, and it continues to shape and expand our understanding of how the body functions. In your question, you’re referring to the results of research published last February in the American Heart Association’s journal Hypertension. According to the study, researchers found that a specific assortment of gut bacteria may not only contribute to a certain type of pulmonary hypertension, but also may be useful in predicting its onset.

Let’s start by talking about the condition itself. When someone has pulmonary hypertension, it means that something has caused high blood pressure in the arteries of their lungs. This is in contrast to general hypertension, which is high blood pressure in the arteries throughout the body. The study that you’re asking about focuses on a specific subset of the disease, known as pulmonary arterial hypertension, or PAH. That’s when progressive scarring damages the walls of the small arteries within the lungs, which makes them stiff and narrow and slows down blood flow. As blood pressure rises, the right side of the heart has to work harder. Over time, this extra workload taxes the heart and causes it to become enlarged and weakened, which leads to a new set of problems.

Symptoms of PAH include fatigue, shortness of breath, heart arrhythmias, and swelling in the feet, legs, abdomen and neck. Although the condition can arise on its own, it has been associated with congenital heart disease, COPD, chronic liver disease and drug use.

PAH is a serious and progressive disease, and there is no known cure at this time. Because the symptoms are common to many conditions, it can be hard to diagnose in its earliest stages. When PAH is suspected, diagnosis begins with blood tests, chest X-rays, scans of the heart and lungs, and endurance tests. The condition is confirmed with a procedure known as right heart catheterization, which allows a direct measurement of blood pressure within the main pulmonary arteries. Treatment focuses on managing symptoms with blood thinners, diuretics and supplemental oxygen.

The new PAH findings hint at a radical new approach to the disease. In the study, researchers analyzed stool samples from 18 PAH patients and 12 people with no history of cardiopulmonary disease. They were surprised to find the PAH patients’ microbiomes harbored a specific collection of bacteria that were absent in the stool of the healthy test subjects. According to the study results, the presence of those specific bacteria predicted a diagnosis of PAH with 83% accuracy. It’s a small study, and many questions remain. But if the results are corroborated in future research, this new direction holds promise for new avenues in PAH diagnosis and therapy.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)