Less Oxygen Uptake With Exercise a Risk for PAS-PH Patients

Researchers used CPET to assess prognosis in cases of PAS-associated PH

Margarida Maia, PhD avatar

by Margarida Maia, PhD |

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Less oxygen uptake during exercise increases the risk of clinical worsening in people with pulmonary hypertension (PH) due to a heart defect called pulmonary artery stenosis (PAS), a study shows.

Data also showed the chance of recovery was generally poor for this subgroup of patients and it was common for them to have exercise intolerance, which occurs when the demands of physical activities are unable to be met.

These parameters were measured by cardiopulmonary exercise testing (CPET), a noninvasive way to assess heart and lung performance at rest or during exercise (exercise capacity). The findings highlight CPET as “a vital component of routine examinations and risk assessment for PAS-PH,” the researchers wrote.

The study, “Exercise feature and predictor of prognosis in patients with pulmonary artery stenosis-associated pulmonary hypertension,” was published in ESC Heart Failure.

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PAS is characterized by the narrowing of the large blood vessel that takes blood from the heart to the lungs. This obstruction can increase pressure in the blood vessels supplying blood from the heart to the lungs (pulmonary arteries) and promote thickening and stiffening of their walls.

Since the right side of the heart needs to work harder to pump blood through the artery due to PH, it becomes weaker over time and may fail to work when it should.

Symptoms of PH can include shortness of breath, fatigue, and dizziness or fainting. These often get worse during exercise, which can limit patients’ ability to take part in physical activities.

People who develop PAS-associated PH (PAS-PH) are known to have a poor prognosis, but what puts them at risk is not known.

Assessing PAS-associated PH prognosis

Since CPET can help predict the likely disease course of other types of PH, researchers in China set out to evaluate whether it could identify PAS-PH patients at higher risk of clinical worsening.

The study included 72 PAS-PH patients who participated in a larger study (NCT02061787) to assess PH patients’ heart and lung performance by CPET before and after medication or balloon pulmonary angioplasty, a procedure that uses a balloon to open a narrowed blood vessel.

Patients’ mean age was 49 and 54 (75%) were women. More than half (51.4%) belonged to the World Health Organization functional classification III or IV, meaning their symptoms were severe enough to limit their ability to carry out some or any physical activity.

At the study’s start, 38 (52.8%) patients were taking PH-targeted medication only; 15 (20.8%) had a balloon pulmonary angioplasty in addition to taking medication; and six (8.3%) underwent balloon pulmonary angioplasty alone.

During a median follow-up of 1.8 years, 18 patients (25%) had clinical worsening, including four deaths and 14 new hospital admissions for heart failure or PH symptom worsening.

The percentage who remained free of clinical worsening was 92.5% after one year. This decreased to 81.7% after three years and to 62.7% after five years, highlighting that “the prognosis is poor in patients with PAS-PH,” the researchers wrote.

Compared with those who didn’t have clinical worsening, those who did had on average a significantly larger right ventricle (29 vs. 33.4 mm in diameter) and a higher mean pulmonary arterial pressure (42.1 vs. 53 mm of mercury). The right ventricle is the heart’s chamber responsible for pumping oxygen-depleted blood to the lungs.

Patients showing clinical worsening also had significantly worse exercise capacity, or the maximum amount of physical exertion a person can sustain, as assessed with CPET.

This was reflected by a significantly lower oxygen uptake at peak exercise, lower peak oxygen pulse, or less oxygen consumed per heartbeat during exercise peak, and a lower oxygen uptake efficiency slope.

After adjusting for several potential influencing factors, peak oxygen pulse was shown to be the best of the CPET parameters at predicting clinical worsening. Patients with a peak oxygen pulse of 5.85 mL per beat or less had a significantly worse prognosis than those with a greater peak oxygen pulse.

Moreover, a lower peak oxygen pulse was significantly associated with more severe disease.

According to the 2015 ESC/ERS PH risk stratification, there were 34 (47.2%) patients in the low-risk group, 36 (50%) in the intermediate-risk group, and two (2.8%) in the high-risk group.

While this type of risk stratification strategy is a significant predictor of clinical worsening, “a significant improvement in accuracy was observed when including peak [oxygen] pulse in the risk stratification,” the researchers wrote. “A low peak [oxygen] pulse identified patients at high risk of clinical deterioration and served for risk stratification of PAS-PH.”

The researchers noted their findings underscore peak oxygen pulse as “a powerful and independent prognostic marker of clinical worsening in PAS-PH” and said, to their knowledge, the study was the first to explore the noninvasive CPET predictors of prognosis in patients with PAS-PH.

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