Discussion Although the main impact of dystrophia myotonica is usually upon skeletal muscles, in the case described the symptoms pointed to early severe heart involvement; only much later were there any complaints referable to the neuro-muscular system. It might be argued that the patient's preoccupation with the syncopal attacks explain why the comparatively minor disabilities of motor weakness and myotonia were over-looked. On the other hand, the disease may exist in the absence of symptoms, as was demonstrated by the patient's brother who, although declaring himself to be well and strong, had signs of advanced dystrophia myotonica.

Reports of such severe cardiac damage as was seen in this case are few. Brain (1951) mentions the occurrence of complete heart block and one case from a series reported by Evans (1944) had two probable Stokes-Adams attacks, a long PR interval (0 30 sec.), and atypical bundle branch block. Brou-stet (1945) describes auricular flutter with AV dissociation in the presence of an atypical myopathy; the significance of the association in this case is doubtful, however, as the patient had hypertension. Although in our case disturbance of AV conduction is undeniable, caution must be exercised in interpreting the abnormal QRS complexes as evidence of one or other type of bundle branch block. It is more likely that the variation in complexes indicated the establishment of ectopic foci of stimulation in one or other ventricle. The labile nature of the cardiographic changes in this case may, perhaps, indicate that errors of cardiac conduction in dystrophia myotonica represent functional change rather than severe myocardial disorganization.