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Cardiomyopathy in duchenne, becker, and sarcoglycanopathies: a role for coronary dysfunction?
T Gnecchi-Ruscone1, J Taylor, E Mercuri
1MRC Cyclotron Unit, Imperial College School of Medicine, Hammersmith Hospital, Du Cane Road, London W12 ONN, UK.
Insights
Dilated cardiomyopathy in Duchenne and sarcoglycanopathy patients shows impaired coronary vasodilator reserve due to increased baseline blood flow. This finding offers insights into muscular dystrophy cardiac complications.
Area of Science:
- Cardiology
- Neurology
- Genetics
Background:
- Dilated cardiomyopathy is a known complication of Duchenne muscular dystrophy (DMD), Becker muscular dystrophy (BMD), and sarcoglycanopathies.
- The underlying mechanisms of cardiomyopathy in these muscular dystrophies remain poorly understood.
- Coronary smooth muscle dysfunction is implicated in myotonic dystrophy cardiomyopathy.
Purpose of the Study:
- To investigate myocardial blood flow and coronary vasodilator reserve in patients with Duchenne muscular dystrophy, Becker muscular dystrophy, and sarcoglycanopathies.
- To elucidate the role of coronary circulation in the pathogenesis of cardiomyopathy in these genetic disorders.
Main Methods:
- Positron emission tomography (PET) was utilized to assess myocardial blood flow and coronary vasodilator reserve.
- Measurements were taken at baseline and during hyperemia in patients with Duchenne muscular dystrophy (n=7), Becker muscular dystrophy (n=8), and sarcoglycanopathies (n=5).
Main Results:
- All Becker muscular dystrophy patients exhibited normal findings.
- Duchenne muscular dystrophy and sarcoglycanopathy patients displayed increased baseline myocardial blood flow and blunted coronary vasodilator reserve.
- The diminished coronary vasodilator reserve was attributed to elevated baseline myocardial blood flow.
- After adjusting for cardiac workload, coronary vasodilator reserve normalized in Duchenne muscular dystrophy but remained abnormal in sarcoglycanopathies.
Conclusions:
- Coronary vasodilator reserve is impaired in Duchenne muscular dystrophy and sarcoglycanopathies, independent of hyperemic flow.
- In Duchenne muscular dystrophy, the impairment appears related to cardiac workload, while vascular smooth muscle dysfunction may contribute in sarcoglycanopathies.
Abstract:
Dilated cardiomyopathy is a feature of Duchenne and Becker muscular dystrophies and occasionally of sarcoglycanopathies. Its pathogenesis is unknown. Patients with myotonic dystrophy have an impairment of coronary smooth muscle and this could contribute to their cardiomyopathy. We used positron emission tomography (PET) to study myocardial blood flow and coronary vasodilator reserve at baseline and during hyperemia in 7 Duchenne, 8 Becker, and 5 sarcoglycanopathy patients. The study was normal in all Becker patients. In contrast, baseline myocardial blood flow was increased and coronary vasodilator reserve blunted in Duchenne and sarcoglycanopathy patients despite normal hyperemic myocardial blood flow. The reduction of coronary vasodilator reserve was due to an increased baseline myocardial blood flow. In Duchenne dystrophy, but not in sarcoglycanopathies, correction for cardiac workload normalized the coronary vasodilator reserve. In the latter patients, abnormal baseline myocardial blood flow could be due to vascular smooth muscle dysfunction.