Systolic time intervals in patients with progressive muscular dystrophy of the Duchenne type

Systolic time intervals (STIs) were measured in 57 patients with progressive muscular dystrophy (PMD) of the Duchenne type, and were correlated with the stages of physical disability. The total electromechanical systole (Q-A2), pre-ejection period (PEP), and left ventricular ejection time (LVET) were corrected for heart rate using the linear regression equations calculated from 91 normal subjects. Each systolic time interval index (STII), i.e. corrected STI, was analyzed. In 15 ambulatory patients (Group P-1), the STIIs did not differ significantly from those in normal controls. In 37 patients who were unable to walk (Group P-2) and 5 patients who were confined to bed (Group P-3), there was a significant increase (p less than 0.001) in the PEP index (PEPI), a decrease (p less than 0.001) in the LVET index (LVETI), and an increase (p less than 0.001) in the PEP/LVET compared with those in controls. The PEPI (p less than 0.001), LVETI (p less than 0.025), and PEP/LVET (p less than 0.001) in Group P-2 differed significantly from those in Group P-1. In Group P-3, the PEPI (p less than 0.005), LVET (p less than 0.001), and PEP/LVET (p less than 0.001) were significantly changed in comparison with those in Group P-2. Remarkable myocardial histopathologic changes suggestive of dystrophy were revealed in autopsies of 3 patients who had been in the severely disabled stage and had shown impaired STIs. It is suggested that cardiac function in patients with moderate to advanced PMD of the Duchenne type is deteriorated in proportion to the disability stages, i.e. the severity of changes in the skeletal muscles.