Electrocardiographic curves have given us exact and conclusive graphic records of many and varied types of cardiac arrhythmias. They have also offered some evidence, as yet inconclusive, regarding the presence of right and left ventricular hypertrophies. Furthermore, electrocardiograms have been of aid in diagnosing main branch lesions of the auriculoventricular conduction system; in isolated instances, the electrocardiographic diagnosis has been supported by pathologic examination of the heart. Because of the importance and clinical significance of myocardial disease, attempts are constantly being made to interpret the condition of the myocardium from the electrocardiogram.
In an electrocardiographic study of a series of patients with valvular, and with myocardial disease,1 I have observed a characteristic which seems of importance in the diagnosis of myocarditis, namely, the abnormal width of the main deviation of the ventricular complex, commonly called the R-wave or the first ventricular spike. The width of the normal R-wave has been