An award of $465,000 from the National Institutes of Health was recently granted to a physical therapy researcher from the IU School of Health and Rehabilitation Services at Indiana University-Purdue University Indianapolis. The grant will be used to assess aerobic exercise training for pulmonary arterial hypertension patients, a strategy that could be used to reduce the mortality and morbidity in patients suffering with the disease.
According to Mary Beth Brown, an assistant professor in the Department of Physical Therapy, traditionally, PH patients were not encouraged to exercise.
“It’s only in the last decade that the first evidence came out that exercise may be okay and may even be beneficial,” Brown said. “Because it is such a relatively new potential therapy there is a lot of work that needs to be done to optimize it, just like with any other new therapy.”
Pulmonary hypertension (PH) is a rare lung disorder in which the arteries that carry blood from the heart to the lungs become narrowed, making it difficult for blood to flow through the vessels. As a result, the blood pressure in these arteries — called pulmonary arteries — rises far above normal levels. This abnormally high pressure strains the right ventricle of the heart, causing it to expand in size. Overworked and enlarged, the right ventricle gradually becomes weaker and loses its ability to pump enough blood to the lungs. This could lead to the development of right heart failure.
According to Brown, while exercise is thought to be beneficial for patients with PH, the best exercise strategy for reducing risks while maximizing health benefits in pulmonary hypertension patients remains unclear.
“Patients with pulmonary hypertension can get extremely high pulmonary pressures during exercise,” she said. “So you have to wonder what the implications of that are.”
As Brown notes, PH progressively worsens patients’ capacity to tolerate exercise, with evidence suggesting that the progression of the disease leads to heart and skeletal muscle metabolism to stop producing energy.
Brown noted that exercise reverses or improves the inefficient energy metabolism of other diseases, and could also be the case in PH.
“If we can find an exercise protocol that will improve blood pressure in the lungs, and thus the load on the right heart, in addition to promoting improvement in skeletal muscle and heart metabolism, we could actually slow the progression of the disease,” Brown said.
In a mild form PH rat model, Brown’s team used high intensity interval training, alternating with short periods of intense exercise with less-intense recovery periods. Results from the experiment revealed an improvement in the lungs’ blood pressure during exercise and also at rest. The researchers also observed an enlargement in the right ventricle size.
“We’ve never seen reversal of the right heart hypertrophy,” she said. “My first thought was this can’t be right, so the experiment was repeated, but we got the same results again.”
With the NIH award, the team is planning to conduct a study in severe PH rat models with intensity interval training to understand see if there is as much or more benefit as occurred with a mild form of the disease.
To measure pulmonary pressures during exercise, Brown’s team will use implantable telemetry over the course of disease development and treatment.
“That’s important because patients don’t always have problems when they are just resting. They have them when they are walking across the room or going up a flight of stairs,” Brown said. “We need to understand the hemodynamics during physical exertion so we can better optimize exercise protocols.”
Results from a previous study have shown reduction in pulmonary pressure to normal levels for a period of time in animals that underwent a single exercise session. Brown’s new research aims at determining which is the best exercise protocol to normalized pulmonary pressures.
“That in itself could potentially produce a huge benefit,” Brown said. “Patients who exercised daily would have more of these post-exercise windows of lower pressure, and less load on the heart.”
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