Great progress has taken place in the interpretation of electrocardiograms since their introduction. The evolution of the understanding of the significance of the Q R S complex, the R T and S T segments and the T wave has undergone many rapid strides, particularly during recent years, so that the recognition of pathologic variations from the usual normal appearance has become of considerable importance in detecting myocardial damage and abnormalities of the site of impulse production and of conduction and in the localization of cardiac infarction. Detailed attention to the description of the form and contour of the waves has yielded considerable information.
The variation to be described involves the terminal portion of the S wave in lead III.Of approximately 8,000 serial records, taken from the cardiographic laboratory of the Jewish Hospital of Brooklyn, 320 revealed a positive finding. Of the latter, the data in 50 are herewith
KATZ SM, SLATER SR. THE SECOND POSITIVE WAVE OF THE Q R S COMPLEX. Arch Intern Med (Chic). 1935;55(1):86-99. doi:10.1001/archinte.1935.00160190089008