Diuretics, BNP Levels Predict Survival in Late-stage DMD: Study
Reduced heart function is associated with a higher rate of mortality among people with Duchenne muscular dystrophy (DMD), a new study reports.
Results, however, did not suggest that reduced heart function is an independent predictor of survival for DMD patients. Instead, analyses indicated patients who took diuretics or who had higher levels of a protein called BNP in their blood had a higher mortality risk, regardless of heart function.
“Our results suggest that diuretic use and BNP levels are independent predictors for clinical outcomes irrespective of” heart function, the researchers wrote.
Despite advances in care, heart disease remains a leading cause of death among people with DMD, and predicting long-term outcomes in DMD patients remains a challenge for clinicians. Scientists in Korea reported long-term outcomes for 116 people with DMD, ages 16 and older, who received care at their facility between 2006 and 2017.
“In this study, we investigated the association between cardiac involvement and long-term clinical outcomes in patients with late-stage DMD,” the research team wrote.
The researchers divided the 116 patients based on whether they had heart disease at an initial assessment. Patients were separated based on left ventricle ejection fraction (LVEF), which is the proportion of blood in heart’s left ventricle that gets pumped out to the body when the heart contracts. Normally, LVEF is about 50% to 70%.
Here, 32 patients with LVEF up to 40% were categorized as “reduced LVEF,” while the remaining 84 were categorized as “preserved LVEF.” Overall, the mean patient age was just over 20, and follow-up time was slightly less than five years. Most participants (86.2%) were not able to walk.
Results showed the overall survival rate after six years was significantly lower in the reduced LVEF group, compared to the preserved LVEF group (81.3% vs. 98.8%). A separate analysis that assessed rates of survival in addition to not being hospitalized due to heart-related health problems also found lower rates in the reduced LVEF group (65.6% vs. 86.9%).
However, in an additional analysis (called a multivariate analysis) that accounted for other differences between the two groups, reduced LVEF was not a significant predictor of survival. Instead, results showed survival rates were lower among patients with higher blood levels of BNP — a protein marker of heart failure — and among those who take diuretics (medicines that prompt the body to excrete more water and salt in urine).
“As expected, patients with DMD and [heart] dysfunction had higher mortality and more cardiovascular events than those without [heart] dysfunction. However, in the multivariate analysis, diuretic use and BNP level rather than reduced [heart] function were independent predictors of survival and cardiovascular events,” the scientists concluded.
The research team noted this was a retrospective analysis conducted at a single center, and the findings are not generalizable to the younger DMD population. They also emphasized more research is needed to validate and expand on their findings.