Sequential changes of orthogonal electrocardiograms in progressive muscular dystrophy of the Duchenne type

Sequential changes of orthogonal electrocardiograms in 70 patients with progressive dystrophy of the Duchenne type (PMD) were investigated. The patients were classified into eight stages from the mildest, S(1), to the severest, S(8), according to Swinyard-Deaver's criteria. The most prominent finding was a progressive reduction in R wave amplitude in Lead X (Rx) with advancing severity. It was considered that loss of electrical activity in the left ventricular free wall might be mainly responsible for the reduction in the Rx amplitude. An abnormal Q wave was frequently observed in each stage. Its occurrence remained essentially unchanged with the progression of PMD. Thus, the presence of a deep Q wave cannot serve as an index for assessing the heart involvement, but rather, we conclude that a reduction of the Rx amplitude can be a useful criterion for estimating the extent of cardiac involvement in PMD.