Widening of the pulmonary artery in PH is common: Large-scale study

Dilation not associated with increased mortality risk, researchers say

Steve Bryson, PhD avatar

by Steve Bryson, PhD |

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Pulmonary arterial dilatation — the abnormal widening of the main pulmonary artery leading from the heart — was a common feature among people with pulmonary hypertension (PH) in a large-scale study.

The clinical characteristics related to a dilated pulmonary artery, such as heart function and blood flow parameters, varied widely among the types of PH, but dilation wasn’t associated with an increased mortality risk, according to “Pulmonary artery dilatation in different causes of pulmonary hypertension,” which was published in Pulmonary Circulation.

The hallmark feature of PH is high blood pressure in the pulmonary arteries, the blood vessels that carry blood from the heart through the lungs to be oxygenated.

PH is classified into different types based on the underlying cause and symptoms. Two types are pulmonary arterial hypertension (PAH), caused by the narrowing of the smaller arteries in the lungs, and chronic thromboembolic pulmonary hypertension (CTEPH), the result of blood clots.

A dilated pulmonary artery is a long-term consequence of chronic PH and several studies have investigated the relationship between it and different PH causes and clinical factors. However, the results have been inconsistent, mostly due to the small number of participants involved, according to researchers in China who examined PA dilatation in 1,018 PH patients, ages 13-80, 699 (68.7%) of whom were women.

“As far as we know, the present study uses the biggest sample size to clarify the association between clinical features and PA dilatation in patients with various [causes] of PH,” the researchers said.

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Dilatation differences among PH types

Among the PH types, 22.1% were diagnosed with CTEPH, 39.2% with PAH with an unknown cause (idiopathic PAH or IPAH), 27.6% with PAH associated with congenital heart disease, and 11.1% with PAH due to connective tissue disease. The patients had been having PH symptoms for a mean of 5.6 years.

Dilatation was measured by the PA ratio, defined as the diameter of the pulmonary trunk (PA diameter) divided by the diameter of the adjacent aorta, the large artery connected to the heart that supplies oxygenated blood to the body. Nearly all the participants (88.8%) had a PA ratio greater than 1.0, a sign of PA dilatation, and 27.2% had a PA ratio greater than 1.5.

PAH patients with congenital heart defects had the largest PA diameter and PA ratio. CTEPH patients had the second-largest diameter, but the lowest PA ratio due to an enlarged aorta. There were no differences in systolic blood pressure (during a heartbeat) or resistance to blood flow (pulmonary vascular resistance) across all the groups.

The highest PA ratios were in those with PAH caused by atrial septal defect, a congenital defect marked by a hole in the wall between the upper chambers of the heart.

Among those with CTEPH, a larger PA diameter and PA ratio strongly correlated with a longer symptom duration. In this group, a larger PA diameter was significantly related to a shorter distance walked in six minutes and a broader diameter across the right heart ventricle (lower chamber) measured after a heartbeat (right ventricular end-diastolic dimension, or RVED).

IPAH patients who had PH symptoms longer also had a significantly larger PA diameter and PA ratio. Also, a wider PA diameter correlated with a larger RVED and worse blood flow parameters, including pulmonary blood pressure, pulmonary circulation volume, and cardiac index, a measure of heart function.

“It is interesting to note that only IPAH patients showed a correlation between PA diameter or PA ratio and PA pressure when we looked at different PH groups,” the researchers wrote.

A larger PA diameter only correlated with pulmonary circulation volume in PAH patients with congenital heart defects, and RVED in those with PAH related to connective tissue disease.

During a follow-up that ranged from three to 109 months (about nine years), 70 (6.9%) patients died. After adjustments for factors that may influence the results, the only significant factor independently linked to a higher mortality risk was a shorter distance walked during the six-minute walking test. PA dilatation was not related to mortality risk by any cause.

“PA dilatation is frequently observed in PH patients,” and “clinical features of PA dilatation vary greatly between PH types,” the researchers said.

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