(From the March 2014 Issue of PediatricsOnline)
About half of all patients with cystic fibrosis develop mild pulmonary hypertension (PH), a condition where the blood pressure on the right side of the heart is elevated. But what impact, if any, the combined conditions have on survival after lung transplant has been poorly understood. Now, a study by clinician scientists at Nationwide Children’s Hospital of nearly 1,200 cystic fibrosis (CF) patients who received lung transplants suggests that the presence of PH doesn’t negatively impact survival after surgery.
There are five types of PH, which is defined as having a mean pulmonary artery pressure of 25 mmHg or higher; the normal pulmonary artery pressure is between 8 and 20 mmHg. The most common types are usually caused by underlying disease of the heart, blood or lungs — including CF. A diagnosis of PH in patients awaiting lung transplant can impact patients’ lung allocation score, one of many factors used to determine patients’ status on the United Network for Organ Sharing (UNOS) transplant list.
To better understand the condition in patients with CF, a team of researchers examined the records of patients on the UNOS lung transplant list over a six-year period who had both CF and PH. The findings, published in a recent issue of the Journal of Cystic Fibrosis, were led by clinician scientists from Nationwide Children’s Hospital, including Karen S. McCoy, MD, chief of Pulmonary Medicine; Don Hayes, MD, medical director of the Advanced Lung Disease Program and the Lung and Heart-Lung Transplant Program; and Stephen E. Kirkby, clinical director of the Lung and Heart-Lung Transplant Program.
“We treat both CF and PH with lung transplant,” says Dr. Hayes, lead author of the study. “With this population having both, we looked at UNOS data to see if the two together affected outcomes after transplant.”
When the researchers compared survival rates of CF patients with PH to patients without CF, they found that patients with both conditions actually had a slightly higher survival rate post-lung transplant. Although the findings weren’t statistically significant, they did raise some interesting questions.
“We speculate that this trend in improved survival seen in our cohort could be due to the benefit of treating two potentiating co-morbidities — CF and PH — with lung transplant,” says Dr. Hayes, who also is an associate professor of pediatrics and internal medicine at The Ohio State University College of Medicine. “We cannot determine the exact mechanism for our findings with a retrospective study, but our findings clearly support the need for further research in this area. We are continuing to review the national database to determine the impact of PH prior to lung transplant, which is an even more important question to answer.”
A barrier to doing such studies is that the test used to diagnose PH — right heart catheterization — is invasive and comes with increased risks to patients. To address that issue, Dr. Hayes is pursuing a new project to identify alternative ways to diagnose PH, the first step toward another study that could explore the question of increased survival rates in patients who have both CF and PH.
With support from a Davis/Bremer Pilot Award from The Ohio State University Center for Clinical and Translational Science, Dr. Hayes is now conducting a study to measure the effectiveness of CT scans in diagnosing PH.
“Echocardiography is our common method of testing that is non-invasive, but it is not a good test in the setting of lung disease because the diseased lungs interfere with the sound waves of echo so the images are limited,” Dr. Hayes says. “We’d like to develop a less-invasive and more sensitive test that would help us identify PH earlier, allowing us to better study it.”
Collaborators on the Davis/Bremer Pilot Award project include Dr. Kirkby; Curt Daniels, MD, director of the Adolescent and Adult Congenital Heart Disease Program at The Heart Center at Nationwide Children’s; and Richard White, MD, chair of radiology, and Subha Raman, MD, professor of cardiovascular medicine, both at The Ohio State University College of Medicine.
Hayes D, Higgins RS, Kirkby S, McCoy KS, Wehr AM, Lehman AM, Whitson BA. Impact of pulmonary hypertension on survival in patients with cystic fibrosis undergoing lung transplantation: An analysis of the UNOS registry. Journal of Cystic Fibrosis. 2013 Dec 30. pii: S1569-1993(13)00230-0. [Epub ahead of print].