Pulmonary artery enlargement, suggestive of pulmonary arterial hypertension, is very common in patients with cystic fibrosis and an independent marker of exacerbation risk, a Brisbane-based study has concluded.
Writing in a paper published in the Lancet Respiratory Medicine the international study co-authored by Professor Scott Bell and Ms Michelle Wood from the Adult Cystic Fibrosis Centre at The Prince Charles Hospital Brisbane, Brisbane, in Queensland measured the diameters of the pulmonary artery and ascending aorta in 74 patients assigned to placebo in a multinational study of the experimental drug ataluren.
The researchers discovered that the pulmonary artery (PA) was larger than the aorta (A) in exactly half the patients, and patients with a PA:A ratio >1 had a three-fold increase in the risk of exacerbations in the following year, after adjusting for sex, BMI and FEV1.
These findings were confirmed in a validation cohort, consisting of 190 patients included in the cystic fibrosis registry of The Prince Charles Hospital in Brisbane. Among those patients, 47% had an enlarged pulmonary artery and their risk of an exacerbation in the following two years was more than doubled.
“Changes on CT scans were also associated with CFTR function as determined by sweat chloride analysis, suggesting a potential pathological link between CFTR dysfunction and pulmonary artery enlargement,” the researchers said.
“The PA:A ratio could be a useful predictive biomarker of pulmonary exacerbations in cystic fibrosis.”
A PA:A ratio >1 was already known to be a robust predictor of exacerbations in COPD, outperforming traditional clinical markers of exacerbation risk. It was also superior to echocardiography for identifying pulmonary hypertension, as confirmed by invasive right heart catheterisation, in COPD.
“We hypothesised that pulmonary vascular disease detected on CT scans would also be predictive of pulmonary exacerbations in adult patients with cystic fibrosis,” they said.
Pulmonary vascular disease and pulmonary hypertension had not been well characterised in cystic fibrosis. Formal investigation of pulmonary hypertension was usually done only in patients with advanced lung disease who were being assessed for lung transplantation.
“Our findings suggest that pulmonary artery enlargement is highly prevalent, occurring in roughly 50% of adult patients with moderate airflow obstruction,” the researchers said.
“In view of the implications for morbidity and mortality, this finding highlights the need to recognise pulmonary vascular disease at all degrees of airflow obstruction.
“Measurement of the PA:A ratio could be a viable non-invasive screening tool to aid in the assessment of patients for pulmonary hypertension, in addition to its use as a prognostic
indicator for acute respiratory events.”
An editorial commented that the study provided “intriguing data” but many questions remained unanswered, including the value of routinely checking for pulmonary artery hypertension, its links with future decline in lung function, and the potential benefits of treatment in preserving lung health.