Heart Care in Duchenne: Why Monitoring Starts Early

DMD cardiac care is one of the quietest revolutions in Duchenne medicine. As respiratory care has improved and patients live longer, the heart has become the leading cause of death in Duchenne muscular dystrophy. The international care standards now recommend cardiac assessment at the time of diagnosis, regular imaging on an age-graded schedule, and cardio-protective drugs started before measurable dysfunction appears. (Birnkrant et al., Lancet Neurology 2018 Part 2)

This post explains why monitoring starts early, what it looks like in practice, and which questions families can usefully bring to a care team.

Why the heart is affected

Dystrophin is not only in skeletal muscle. It is also expressed in cardiac muscle, where its absence causes progressive myocardial damage through the same membrane-instability mechanism that drives skeletal muscle loss. Over years this typically manifests as a dilated cardiomyopathy: the left ventricle enlarges, the wall thins, and contractile function falls. Fibrotic scarring accumulates and conduction abnormalities can appear. (MedlinePlus Genetics, Duchenne and Becker muscular dystrophy)

The clinical implication is straightforward. The heart muscle is being affected from a young age, often long before any symptoms or imaging abnormalities appear. Waiting for symptoms before screening means missing the window where treatment can preserve function.

Female carriers can also develop cardiomyopathy, typically later in life and more variably than affected boys. The genetic and biological reason is the same: insufficient functional dystrophin in the heart wall, in the carrier’s case driven by skewed X-inactivation patterns over time. Carrier mothers therefore have their own cardiac monitoring recommendations.

When monitoring should begin

The 2018 international care considerations recommend a baseline cardiac evaluation at the time of diagnosis, even in young children before any symptoms or imaging abnormalities are detectable. Subsequent monitoring follows an age-graded schedule, with frequency increasing as the child grows. From around age 10, annual imaging is the consensus default for most patients. (Birnkrant et al., Lancet Neurology 2018 Part 2)

For families just receiving a diagnosis, this can feel premature. A toddler with normal energy and a normal heart on imaging does not look like a cardiac patient. The point of baseline assessment is to document a starting point, not to find disease. Without baseline numbers, later changes cannot be interpreted with confidence.

Baseline assessment also matters for treatment decisions that affect the heart. Corticosteroid therapy, which is started in many boys between ages four and six, has known cardiovascular effects that should be tracked from a documented starting point.

What monitoring looks like in practice

Three tools dominate routine DMD cardiac care:

• Echocardiogram. The workhorse for measuring left ventricular size, ejection fraction, and global function. Most clinics start here.
• Cardiac MRI. Increasingly used in older children and adolescents because it detects fibrosis before functional decline appears on echo. It also gives more precise measures of left ventricular volume and ejection fraction. The 2018 care considerations specifically endorse incorporating cardiac MRI in routine surveillance from a certain age, depending on the patient and the centre. (Birnkrant et al., Lancet Neurology 2018 Part 2)
• Electrocardiogram (ECG). Routine in most visits. Looks for conduction abnormalities, arrhythmias, and baseline electrical changes.

Practical reality varies. Not every clinic has easy access to cardiac MRI in young patients, and not every patient tolerates the procedure without sedation. Families often hear different schedules in different centres. That is not a sign of bad care; it reflects the gap between consensus recommendations and local resources.

Cardio-protective treatment

A central principle of current DMD cardiac care is that medication can begin before measurable dysfunction, not only after it. The most commonly prescribed agents are angiotensin-converting enzyme (ACE) inhibitors, sometimes paired with angiotensin receptor blockers, and beta blockers when arrhythmias or further functional decline appear. The aim is to slow the progression of cardiac remodelling, not to wait for clinical heart failure. (Birnkrant et al., Lancet Neurology 2018 Part 2)

The optimal age to start these drugs in fully asymptomatic patients is not perfectly settled. Some teams treat earlier, others wait for first signs of remodelling on imaging. Both approaches are within current evidence; the choice is individualised. What is agreed is that waiting for clinical heart failure to develop before acting is no longer the standard.

Corticosteroids, while having their own well-known side-effect profile, have also been associated with delayed onset of cardiomyopathy in observational studies. They are now considered cardioprotective among their other effects. The full risk-benefit conversation is the cardiologist’s and neurologist’s joint territory, and varies per patient.

What families can ask their care team

A few starting questions, all with the goal of understanding the plan rather than directing it:

• When did the baseline cardiac assessment happen, and what did it show?
• What imaging is planned going forward, on what schedule, and with which modality?
• Are cardio-protective drugs appropriate now, or only when function changes?
• How does the cardiac plan coordinate with corticosteroid and respiratory plans? Who is the lead clinician across all three?
• What signs should trigger contact with the team between scheduled visits?

These are not prescriptions. They are points around which a productive conversation can happen with the clinicians who know the child’s full picture.

What is still uncertain

Several questions remain open and are actively being studied:

• The optimal start time for cardio-protective therapy in fully asymptomatic patients.
• The role of cardiac MRI frequency in changing treatment decisions, rather than only confirming what echocardiography already suggests.
• The effect of newer disease-modifying therapies (exon skipping, gene therapy) on cardiac muscle specifically, since most pivotal trials have used skeletal endpoints.
• Cardiac care models for adult DMD patients, a population that has grown rapidly as survival has improved.

Patient registries and longitudinal cohort studies continue to refine these answers. Families should expect cardiac care guidance to keep updating as evidence accumulates.

Where to learn more

• The 2018 international care considerations Part 2, on respiratory and cardiac care, at the PubMed abstract.
• MedlinePlus genetics on DMD for a general overview that includes cardiac involvement.
• On this site: DMD standards of care for the wider multidisciplinary framework, and the DMD diagnosis pathway for what happens before cardiac monitoring begins.

Disclaimer: This post is informational and does not constitute medical advice. Decisions about diagnosis or treatment must be made with a qualified care team.