The committee's first report, published in Circulation for June 1953, recommended a terminology and certain conventions for recording ballistocardiograms of the type then in use. However, it soon became apparent that the committee's work was far from complete.Increasing knowledge of ballistic theory soon began to throw light on the relations of records secured by various instruments to one another, and a rapid advance in instrumentation began to provide records related to, but often not identical with, those which had been provided with a standard terminology by the committee in its first report. Accordingly, the committee has continued its labors to provide the rapidly advancing field with a uniform terminology.While they were thus engaged, attention was called to the fact that the designation of spatial axes previously recommended for vector ballistocardiograms differed from that which had been recommended for electrocardiograms by another committee of the American Heart Association. The advantages of a common system for designating spatial axes were obvious to all. Accordingly, as the electrocardiographic usage had priority and as little had been published in the field of ballistocardiographic vectors the committee voted to withdraw their original recommendation and substitute one conforming to that in use by electrocardiographers. In the present communication this new convention is also set forth.All members of the committee have shared in the deliberations and taken part in the decisions which form the basis of this report; but so much of the larger proportion of the actual work fell on Dr. Scarborough and Dr. Talbot that it was agreed without dissenting vote that only their names should appear as authors. This report has the endorsement of the committee as a whole, and the terminology it suggests is recommended as the official terminology of the American Heart Association.

Thirty-four patients were studied by electrocardiogram for electrical position of the heart, and by x-ray and angiocardiogram for anatomic position of the heart. A significant association between electrocardiographic and anatomic positions of the heart was found insofar as rotation about the anteroposterior and longitudinal axes is concerned. No association between electrocardiographic and anatomic positions was found with regard to rotation about the transverse axis.T HE HEART may rotate about three anatomic axes: anteroposterior, becoming horizontal or vertical in position; longitudinal, becoming clockwise or counterclockwise in position as viewed from the apex; and transverse, causing the apex to move forward or backward. This is illustrated in figures 1, 2, and 3. This study was undertaken in order to ascertain whether or not the rotation of the heart about its three axes can be estimated from ordinary unipolar electrocardiographic leads.In 1942, Master1 presented a detailed study concerning the effect of change in heart position upon the configuration of the standard leads of the electrocardiogram. In the same year Wilson2 described six positions of the heart from the electrocardiographic standpoint: horizontal, semihorizontal, vertical, semivertical, intermediate, and indeterminate. These positions were determined from a study of the relationship between the unipolar extremity leads and the unipolar precordial leads, and were concerned with rotation around the anteroposterior axis only. In 1943, Gardberg and Ashman,3 and in 1946, Ashman4 described forty-five electrocardiographic positions of the heart in the three standard leads produced by rotation of the heart about three axes: anteroposterior, transverse, and longitudinal. In the most recent edition of his monograph, Gold-

The autocorrelation function of the ventricular electrocardiogram was calculated on an IBM-650 computer. The resulting function can lie fitted by an exponential-cosine function. This result is typical for a mixture of periodic and unperiodic events. For different patients, various degrees of periodicity were put in evidence by this method on a quantitative basis; the ventricular response was never completely irregular. In all cases investigated so far, the period that corresponds to the periodic component of the autocorrelation function was more rapid than the average rate of ventricular conduction.

No abstract

Experimental cardiac tamponade was produced in open-chest dogs. Left and right ventricular systolic pressures fell when intrapericardial pressure was increased only a few millimeters of mercury. Negative diastolic transmural pressures of 1 to 6 mm. Hg developed in the left ventricle and negative diastolic transmural pressures of 2 to 8.5 mm. Hg developed in the right ventricle. In some instances the period of right ventricular systolic ejection was greatly abbreviated at higher levels of intrapericardial pressure.