Duchenne Muscular Dystrophy (DMD) is a complex and progressive disease requiring highly specialized care, especially in emergency situations. The condition affects multiple organ systems—muscular, cardiac, and respiratory—leading to a myriad of clinical complications. When patients with DMD present in the Emergency Department (ED), an understanding of the nuanced aspects of their care is essential for optimal management. Below are key considerations based on current best practices.

Steroid Use and Ambulation

Steroids are a mainstay in DMD management, typically starting around ages 3 to 4. They are effective in delaying the loss of ambulation, although progression is inevitable. Once patients become non-ambulatory, they often develop secondary complications like lymphedema, which further complicates their care.

Cardiac Complications: A Unique Cardiomyopathy

Cardiac dysfunction in DMD differs from typical dilated cardiomyopathy. Hearts in DMD patients often have small ventricular volumes and are replaced by fatty tissue, leading to unpredictable cardiac stress responses. Importantly, while cardiac function deteriorates, the heart does not dilate, making echocardiography less reliable. MRI is preferred, particularly with late gadolinium enhancement (LGE), which helps assess scarring and the extent of remaining cardiac muscle.

For cardiac biomarkers, NT-proBNP is used instead of BNP, as valsartan and entresto can affect BNP levels. NT-proBNP values in children with DMD should be below 50, whereas levels above 125-150 in adults indicate concern. You will often observe a longitudinal trend of increasing NT-proBNP and high-sensitivity troponin levels due to ongoing “demand-based injury.” Troponin levels should ideally remain below 2.

In terms of hemodynamics, normal wedge pressures should be in single digits, with elevated values above 12-13 indicating potential cardiac dysfunction. Central venous pressure (CVP) should also stay in the single digits.

Respiratory Management: Vigilance with Hypercarbia

Respiratory failure is a critical concern in DMD. Progressive diaphragmatic weakness and fatty infiltration lead to severely diminished lung volumes, sometimes reduced to just two rib spaces. Administering oxygen alone can mask the underlying hypercarbia. Instead, prioritize non-invasive ventilation, such as BiPAP, especially for patients lying flat, which can exacerbate their respiratory insufficiency.

In cases where imaging like a CT scan is necessary, frequent blood gases should be monitored. If sedation is required, ensure careful use of BiPAP to prevent further respiratory decline.

Orthopedic Risks: Watch for Fat Embolism

DMD patients are prone to fat embolisms following fractures due to the fatty infiltration of their bone marrow. Any trauma that results in fractures should raise immediate concern for fat embolism syndrome, which can present rapidly and lead to respiratory and cardiovascular complications.

Renal and Liver Function Monitoring

Renal function is best assessed with Cystatin C rather than creatinine, as muscle mass in DMD patients is so low that creatinine levels may not accurately reflect kidney function. If an older patient presents with measurable creatinine levels, consider the possibility of acute kidney injury (AKI).

Liver function tests (AST/ALT) are usually elevated in DMD due to muscle breakdown. However, these elevations do not indicate liver dysfunction. Instead, bilirubin levels should be used to assess actual liver health.

Managing Fluids and Hemodynamics

Patients with DMD often have resting tachycardia, even before the onset of overt cardiac dysfunction. Be cautious with intravenous fluids (IVF), as patients are prone to rapid volume overload. Fluid boluses should be administered with care, as they can quickly induce cardiac failure.

In cases of hypotension, start with epinephrine, and consider milrinone if blood pressure remains low but manageable. Additional vasoactive support may be needed, including vasopressin, but only after achieving a stable blood pressure baseline. Always consider the risk of arrhythmia, which can occur despite relatively normal ECG findings.

Imaging: Prioritize MRI Over Echo

MRI is the gold standard for cardiac evaluation in DMD patients, particularly for assessing myocardial scarring and function through LGE. Echocardiograms, while frequently used, tend to overestimate cardiac function compared to MRI. DMD patients often receive yearly MRIs to monitor their cardiac health, as discrepancies between MRI and echo findings are common.

Emergency Care Plans and Advanced Directives

Many DMD patients will arrive with comprehensive emergency care plans or letters from their providers. These documents should be reviewed promptly upon presentation, as they often contain critical information about the patient’s DNR status, preferred ventilation strategies, and other key management instructions. If the patient is in an advanced stage of the disease, these care plans can guide decision-making, particularly around goals of care and interventions.

Conclusion: Holistic, Multidisciplinary Care

Emergency care for DMD patients requires a comprehensive understanding of their multi-system disease. The interplay between cardiac, respiratory, and musculoskeletal complications necessitates a highly coordinated approach. By carefully managing fluid status, ventilatory support, and orthopedic risks, and by relying on advanced imaging techniques, emergency providers can deliver the best possible care for these complex patients.

Always review the latest care plans, assess longitudinal trends in cardiac biomarkers, and consult with specialists when needed to ensure that each patient receives individualized and optimal care.

Acknowledgements

Thank you to Dr. Michelle Eckerle for the meticulous lecture notes that were the backbone of this post, and Chat GPT 4o for help with editing.

References

Crisafulli S, Sultana J, Fontana A, Salvo F, Messina S, Trifirò G. Global epidemiology of Duchenne muscular dystrophy: an updated systematic review and meta-analysis. Orphanet J Rare Dis. 2020 Jun 5;15(1):141. doi: 10.1186/s13023-020-01430-8. PMID: 32503598; PMCID: PMC7275323.

Buddhe S, Cripe L, Friedland-Little J, Kertesz N, Eghtesady P, Finder J, Hor K, Judge DP, Kinnett K, McNally EM, Raman S, Thompson WR, Wagner KR, Olson AK. Cardiac Management of the Patient With Duchenne Muscular Dystrophy. Pediatrics. 2018 Oct;142(Suppl 2):S72-S81. doi: 10.1542/peds.2018-0333I. PMID: 30275251; PMCID: PMC6566852.

Venugopal V, Pavlakis S. Duchenne Muscular Dystrophy. [Updated 2023 Jul 10]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK482346/