Hole between upper heart chambers can worsen CF outcomes
Hole fails to close naturally after birth for 25% of people, usually to no ill effects
People with cystic fibrosis (CF) experience a more severe disease course when they continue to have a small hole between the heart’s upper chambers that fails to close naturally after birth, a study suggests.
The hole, called patent foramen ovale (PFO), in CF patients was linked to more pulmonary exacerbations requiring in-patient hospitalizations, and the benefits of CFTR modulator treatments did not affect associations between PFO and low blood oxygen or pulmonary exacerbations.
Moreover, those with CF and PFO are more likely to need supplemental oxygen at disproportionately higher lung function.
The study, “Patent Foramen Ovale and Oxygenation in Patients with Cystic Fibrosis,” was published in the journal Respiration.
During fetal development, the lungs aren’t working yet, so there’s no need to pump blood to the lungs. Instead, the fetus receives oxygen-rich blood from the mother via the placenta and the umbilical cord. As a result, blood is pumped through an opening called the foramen ovale, which sits between the upper heart chambers.
Although the hole typically closes during infancy, it does not for 25% of the population.
PFO-related CF complications include blood clots, stroke, reduced lung function
Case studies have reported PFO-associated complications in people with CF, including blood clots, stroke, and reduced lung function. Other reports suggest the closure of the PFO can substantially improve pulmonary function.
Now, University of Utah researchers investigated the impact of PFOs in people diagnosed with CF because little is known about their relationship with clinical outcomes.
One method to detect PFO is a saline contrast study, also called a bubble study. During a standard echocardiogram, a salt solution containing tiny bubbles is infused into the bloodstream, traveling to the right side of the heart. With PFO, some bubbles will appear on the left side of the heart, indicating a hole between the upper chambers.
Among 157 individuals who underwent at least one echocardiogram with a bubble study, 64 were CF patients, and 93 were people who did not have CF and were matched by age and sex (controls). Bubble studies were conducted to investigate unexplained low blood oxygen (hypoxemia) or shortness of breath (dyspnea).
Results showed PFO incidence was similar between CF patients and controls without hypoxemia. In contrast, for unexplained hypoxemia, PFO was five times more common in CF than in controls, suggesting hypoxemia is more likely to be associated with a PFO in CF than in the general population, the team noted.
PFO in CF patients found to be more severe on average
PFO in the patients was more severe on average than in the control group. Other measures showed CF patients with PFO had a higher mean pulmonary artery pressure (PAP), or higher blood pressure in the blood vessels that supply the lungs. They also had a reduced (abnormal) tricuspid annular plane systolic excursion (TAPSE), a measure of the function of the heart’s right ventricle.
Certain factors were similar among CF patients with or without PFO, including sex, reasons for echocardiogram, and lung function. Still, those with PFO were younger by an average of 7.9 years, and PFO was associated with an average decrease in oxygen saturation (a measure of oxygen levels in the blood) of 2.47%.
The researchers then investigated the impact of oxygen supplementation on the relationships between oxygen saturation and lung function, as assessed by forced expiratory volume in one second, or FEV1, which measures how much air can be exhaled after a deep breath.
When oxygen saturation dropped to 89%, which qualified them for oxygen supplementation, the average FEV1 was significantly lower among CF patients with PFO than those without (42.3% vs. 64.8%), reflecting an average difference of 22.5% in FEV1. In other words, oxygen supplementation was needed in PFO patients with better lung function.
CF patients with PFO also had experienced nearly twice as many exacerbations requiring hospitalization in the year before the echocardiogram than those who did not have PFO. During five years of follow-up, most CF patients (87.5%) were hospitalized for pulmonary exacerbations.
There were 32 deaths and four lung transplants (56%) among CF patients, of whom 21 (58%) had PFO. Still, there was no association between PFO and the time to death or transplant after adjusting for age, sex, FEV1, and prior-year exacerbations. Also, associations between PFO and hypoxemia or exacerbations were unrelated to PAP, TAPSE, and/or CFTR modulator therapies.
“Our findings suggest an association of PFO with a more severe disease course characterized by more frequent pulmonary exacerbations,” the researchers concluded. “We recommend that [CF patients] requiring supplemental oxygen despite unexpectedly high FEV1% should undergo echocardiographic bubble studies.”
About the Author
