Duchenne muscular dystrophy (DMD) causes progressive skeletal myopathy and the worsening of cardiac function, leading to heart failure. In later stages of DMD, heart failure is a leading cause of death. 

A little known fact about DMD is that its first description in the early 19th century by Italian physicians was in part due to the observation of cardiomyopathy. The physicians reported the case of 2 brothers experiencing progressive muscle weakness while facing paradoxical hypertrophy. One of the brothers lost the ability to ambulate, while the other died of an enlarged heart. Over the years, other physicians would go on to build on their observations and characterize the features of DMD more clearly. 

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The last few decades have seen vast improvements in pulmonary and neuromuscular care. The effect of this is twofold: life expectancy of DMD patients has extended, but the extended life expectancy has allowed cardiomyopathy to progress to heart failure in more patients, highlighting the severity of the issue. 

Today, approximately 30% to 50% of deaths among DMD patients are related to cardiac disease. In Pediatric Cardiology, Villa and colleagues wrote, “These mortality rates have led to sequential consensus guidelines discussing the evolving outcomes, diagnostic protocols, and approaches to medical therapy.”

Tools for Early Detection and Monitoring

We now recognize that the early diagnosis and treatment of cardiomyopathy in DMD patients can lead to better outcomes. The 2018 DMD Care Considerations issued by the Centers for Disease Control and Prevention (CDC) affirmed cardiac monitoring and care as an essential element of DMD management. They recommended that cardiac assessment be carried out—without exception—upon diagnosis. 

“This initial cardiac visit should include a past and present cardiac medical and family history,” Buddhe and colleagues wrote in Pediatrics. ”In addition, the clinician should perform a physical examination, electrocardiogram, and noninvasive imaging with either an echocardiogram or cardiac [magnetic resonance imaging (MRI)] on the basis of the child’s age and ability to cooperate.”

For monitoring cardiac functional decline, echocardiography is a particularly useful tool. Studies have indicated that pediatric patients aged about 9 to 10 years may experience a drop in ejection fraction to less than 50%. As the disease progresses, the ejection fraction may drop to as low as 25% to 30%. 

Cardiac MRI is beneficial in detecting declining myocardial strain—an index of cardiac dysfunction—before a notable decrease in ejection fraction occurs. It can also detect fibrotic scarring of the heart, another early warning sign of cardiac dysfunction. Cardiac dysfunction in DMD patients often leads to dilated cardiomyopathy, which explains the death of one of the brothers by an enlarged heart mentioned earlier. 

Improving Cardiac Care in Patients With DMD

Physicians are rightly viewing the improvement of cardiac care is an important step to ensuring quality of life and better survival rates for patients with DMD. The Advanced Cardiac Therapies Improving Outcomes Network (ACTION) formed a committee in 2019 with the stated intention to improve cardiac outcomes in these patients. This network consists of 50 international institutions committed to improving clinical outcomes in young patients with heart failure. 

ACTION conducted an online survey to understand current diagnostic and management approaches to DMD cardiac care. They recruited 31 cardiology providers involved in providing DMD care from 22 medical centers. 

Among the key findings of the study were: 

  • 90% of participants responded that patients were seen by a cardiologist upon diagnosis with DMD. The most common time frame for follow-up was once a year. 
  • The majority of providers conducted cardiac MRI as part of their clinical evaluation, with gadolinium typically used in each study. 
  • The majority of providers routinely employed Holter monitoring, although responses on its indication and frequency differed. 
  • All providers used angiotensin-converting enzyme inhibitors and angiotensin receptor blockers as routine components of DMD management. 
  • All providers utilized beta-blockers as a routine component of DMD management when systolic dysfunction developed. 
  • The majority of providers routinely used aldosterone antagonists as a component of DMD care. 
  • 55% of respondents have placed an implantable cardioverter defibrillator in at least one patient with DMD. 
  • 74% of respondents would consider ventricular assist devices as destination therapies.  

This study demonstrated that, encouragingly, significant consensus was found regarding cardiac management in DMD patients. This is notable because diagnostic and treatment guidelines do not necessarily translate into routine clinical practice. 

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Cardiology, like all medical disciplines, is an evolving field, and the need for improvement remains. “Creating the infrastructure for tracking medical therapy, understanding these factors, and creating a system for intervention and dissemination is especially important in the era of rapidly evolving medical therapy for non-DMD heart failure that will likely be employed in DMD as well,” the research team wrote. 

Viewed from a historical perspective, our understanding of DMD cardiomyopathy and our ability to treat it has improved drastically over the past few years, nearly 2 centuries after DMD was first described. The continuous advancement in the field of DMD cardiac care may yet turn the tide in our fight against this disease. 

References

Villa C, Auerbach SR, Bansal N, et al. Current practices in treating cardiomyopathy and heart failure in Duchenne muscular dystrophy (DMD): understanding care practices in order to optimize DMD heart failure through ACTIONPediatr Cardiol. 2022;1-9. doi:10.1007/s00246-021-02807-7

Buddhe S, Cripe L, Friedland-Little J, et al. Cardiac management of the patient with Duchenne muscular dystrophyPediatrics. 2018;142(Suppl 2):S72-S81. doi:10.1542/peds.2018-0333I

Meyers TA, Townsend D. Cardiac pathophysiology and the future of cardiac therapies in Duchenne muscular dystrophyInt J Mol Sci. 2019;20(17):4098. doi:10.3390/ijms20174098