Cardiac tissue velocities and strain rate in the early detection of myocardial dysfunction of asymptomatic boys with Duchenne’s muscular dystrophy: relationship to clinical outcome

Duchenne’s muscular dystrophy (DMD) is one of the most common neuromuscular disorders. Boys with DMD lose independent ambulation by the age of 12 and die of respiratory failure or cardiomyopathy in their late teens or early 20s.1 Histological changes in the heart include fibrosis, degeneration and fatty infiltration starting from the left ventricular posterior wall, which is a specific finding for DMD.2 The posterior wall can be more sensitive in identifying impaired myocardial function. Recent consensus guidelines on the early cardiac follow up and for the treatment of asymptomatic dysfunction have been proposed.3 An unresolved issue is, however, the timing of introducing treatment. Some authors have proposed that, in view of the almost invariable development of dilated cardiomyopathy (DCM), treatment should be started even in the absence of echocardiographic signs of dysfunction. It is therefore important to be able to identify early changes that precede DCM.3 We hypothesised that strain rate (SR) can identify early myocardial dysfunction in young asymptomatic boys with DMD without conventional echocardiographic signs of DCM. We related SR to the development of cardiomyopathy over a three-year follow up. Fifty six consecutive asymptomatic boys with DMD (mean age 8.8 (2.85) years) were enrolled. Diagnosis was confirmed by DNA analysis, unequivocal findings in muscle biopsy, or positive family history. The patients were not taking any cardiac drugs and had normal ECGs and routine echocardiograms (fractional shortening > 29%). Twenty two healthy volunteers (mean age 9 (SD 2.96) years) were recruited from the children’s outpatient department. We used the HDI 5000 (Phillips Medical Systems) machine equipped with a P4-2 transducer for conventional and tissue Doppler imaging echocardiographic studies. The conventional study included two dimensional and Doppler blood flow velocity measurements …