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The Section on Cardiology and Cardiac Surgery appreciates the comments of Dr Rein in response to the American Academy of Pediatrics clinical report "Cardiovascular Health Supervision for Individuals Affected by Duchenne or Becker Muscular Dystrophy."1 We believe the report is not "overly nihilistic" but provides cautious optimism to a group of patients who experience significant morbidity and mortality from the cardiomyopathy associated with their disease.
As stated, the report provides "recommendations for optimal cardiovascular evaluation to health care specialists caring" for those with muscular dystrophy.1 The intent of the report was to alert the health care community to the need for earlier diagnosis and treatment and to provide minimum guidelines for cardiovascular care. Unfortunately, in many areas of this country, patients with Duchenne muscular dystrophy (DMD)/Becker muscular dystrophy (BMD) do not come to the attention of the cardiologist until they are approaching end-stage cardiomyopathy. At that point, traditional heart failure therapies are used although this approach has failed to alter the natural history of the disease.
Until a cure is found, we are optimistic that early recognition can change DMD from a fatal to a chronic disease. The challenge lies in finding sensitive and specific markers to detect early cardiac dysfunction. Unfortunately, studies have not shown brain natriuretic peptide (BNP) elevation in DMD to meet the criteria as an early screening test. BNP levels become elevated in DMD relatively late in the disease process. In the article by Mori et al2 (cited by Rein), BNP elevation was minimal, with a shortening fraction as low as 15%. Individuals with shortening fractions <15% did have dramatic increases in BNP. Demachi et al3 compared BNP levels between subjects with DMD/BMD and idiopathic dilated cardiomyopathy and ejection fraction <50%. The study revealed dramatically lower BNP levels in subjects with DMD/BMD for a similar degree of dysfunction, leading the authors to conclude that "plasma BNP may underestimate the degree of systolic dysfunction in patients with muscular dystrophy."4 This suggests that BNP is unlikely to be an ideal screening test for the presence of cardiac dysfunction in DMD/BMD.
It is interesting to note that cardiovascular risk is inferred on the basis of genetic diagnosis, potentially allowing treatment to be initiated before the onset of clinical symptoms. In the absence of adequate clinical trials, cardiologists and families are left with only a handful of cited case series and reports to direct therapy. Although angiotensin-converting enzyme (ACE) inhibitor use is gaining attention in the presymptomatic patient with DMD/BMD, no multicenter prospective clinical trial exists regarding its efficacy at this time.4,5
Given the number of patients followed at each center in this country, a nationwide collaborative effort is required to obtain suitable evidence for inclusion of other therapies into official guidelines. A clinical report such as this leading to improved awareness is the first step to early cardiovascular evaluation and, ultimately, treatment.
REFERENCES
Related articles in Pediatrics:
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