A 10-year follow-up study by orthogonal Frank lead ECG on patients with progressive muscular dystrophy of the Duchenne type

Abstract

A 10-year follow-up study by orthogonal Frank lead electrocardiography was performed on 25 patients with progressive muscular dystrophy of the Duchenne type (DMD). With advancing age, no apparent changes were observed in the duration and amplitude of the P wave or in the PR interval, whereas the duration of the QRS complex tended to increase. The amplitudes of the R wave in lead X (Rx) and lead Y (Ry) tended to decrease from 1.75 +/- 0.90 and 1.96 +/- 0.59 mV to 0.80 +/- 0.63 and 1.39 +/- 0.62 mV (p < 0.01), whereas the amplitude of the S wave in lead X tended to increase from 0.24 +/- 0.23 mV to 0.53 +/- 0.36 mV in 10 years after initiation of the study (p < 0.01). It is noteworthy that the Ry amplitude began to decrease markedly from the seventh year after the initiation of this study, whereas the Rx amplitude showed a gradual and unceasing decline through the 10-year period. Observation of the sequential changes of the QRS loops in three planes clearly demonstrated that the electrical force tended to decrease in the leftward and inferior directions and increase in the rightward direction. It is of interest that the frequency of occurrence of the deep Q wave was found to be quite high even in the early stages of DMD and that it did not display a direct relation to the sequential evolution of this disease. It can be concluded that observation of the sequential changes in the QRS complex allows estimation of the extent and direction of myocardial involvement in DMD.