The vectorcardiogram in Duchenne's progressive muscular dystrophy

Abstract

This study represents a Frank system vectorcardiographic analysis of 34 patients with classic rapidly progressive X-linked recessive Duchenne's muscular dystrophy. The data add to the scanty body of descriptive vectorcardiographic information in this myopathic disorder. In addition the VCG was shown to be a useful supplement to the scalar ECG, and in the context of this analysis sheds light on the mechanisms responsible for the distinctive, uniform electrocardiographic-vectorcardiographic patterns in Duchenne's dystrophy. The characteristic electrocardiographic changes reside in the QRS; conduction abnormalities and rhythm disturbances—except sinus tachycardia—are of incidental importance. Previous studies have shown that the distinctive QRS patterns are not due to thoracic deformity, thoracic muscle atrophy, right ventricular hypertension, or coexisting coronary arteriopathy. The present study confirms that the patterns are not those of right ventricular hypertrophy or abnormal right ventricular conduction, and casts serious doubt on the idea that the essential explanation lies in persistence of the electrocardiographic-vectorcardiographic pattern of infancy and early childhood. The electrophysiologic abnormality may instead represent a genetically determined pattern that stems from disordered electrical activity of a particular zone of left ventricular myocardium.