Robert A. Helm

An accurate lead system for spatial vectorcardiography

Abstract A description is given of the placement of two large saline-containing sponge electrodes and five small conventional electrodes for recording three orthogonal leads which possess relatively uniform vector properties for all portions of the heart. Each of the three leads is assigned a vector magnitude of 2√2 or 2.83 mv./Ma.-cm. Experimental evidence is cited to justify the substitution of the convenient sponge electrodes for networks of small electrodes joined through resistors.

The Pseudo P Pulmonale

IT HAS BEEN generally accepted that the electrocardiographic pattern of a tall and peaked P wave with a normal duration in leads II, III, or aVF is characteristic of right atrial enlargement.1-3 Such a P wave is called the P pulmonale in contrast to a wide and notched P wave, usually best seen in leads I and II, due to left atrial enlargement, the P mitrale. During the course of interpretation of the routine electrocardiograms in a general hospital, the authors were impressed by the frequent appearance of such a P-pulmonale pattern in patients whose clinical diagnoses did not suggest the presence of right atrial enlargement. The purpose of the present study was to determine the specificity of such a P-pulmonale pattern by clinical correlation. Vectorcardiographic analysis of the P waves was done in many of the patients in an attempt to obtain additional useful information.

The Electrocardiographic Pattern of Right Ventricular Hypertrophy in Chronic Cor Pulmonale

The electrocardiographic patterns encountered in 28 patients with pulmonary hypertension secondary to chronic lung disease have been studied. Thirteen had neither right ventricular hypertrophy nor right bundle-branch block; eight had either right ventricular hypertrophy alone or right ventricular hypertrophy and right bundle-branch block (complete or incomplete); and seven had incomplete right bundle-branch block. A statistical comparison is made between these various groups of the means of the following physiologic measurements: mean pulmonary artery pressure, total pulmonary resistance, arterial oxygen saturation, right ventricular work, arterial carbon dioxide content, and cardiac index. The significance of the pattern of right ventricular hypertrophy is discussed.

The Spatial QRS Loop in Right Ventricular Hypertrophy with Special Reference to the Initial Component

Spatial vectorcardiograms were recorded from 18 subjects with normal electrocardiograms and from 14 subjects with electrocardiograms indicative of right ventricular hypertrophy. In the latter group there was a significant incidence of deviation of the initial portion of the QRS loop from the normal direction of inscription, suggesting that activation of the interventricular septum oftenproceeds in an abnormal manner in right ventricular hypertrophy. A statistically significant difference in the direction of rotation of the entire QRS loop in the transverse and sagittal planes was noted in the two groups. The relationship between the direction of inscription of the QRS loop in the transverse plane and the timing of the intrinsicoid deflections of precordial leads is discussed.

Right Ventricular Hypertrophy I. Correlation of Isolated Right Ventricular Hypertrophy at Autopsy with the Electrocardiographic Findings

The electrocardiograms of 22 cases showing isolated right ventricular hypertrophy at autopsy were examined for changes suggestive of right ventricular hypertrophy. Only 5 of 22 cases fulfilled at least one of the criteria of Sokolow and Lyon and only three could be diagnosed as having right ventricular hypertrophy by the criteria of Myers, Klein and Stofer. Factors contributing to the development of electrocardiographic changes of right ventricular hypertrophy are discussed.

Theory of vectorcardiography: A review of fundamental concepts

Abstract Five factors which determine the accuracy of representing the electrical field of the heart by means of a spatial vectorcardiogram are: 1. 1. The validity of representing multiple dipole centers within the heart as a single resultant dipole. 2. 2. The variability of the location of the assumed single resultant dipole center during the cardiac cycle. 3. 3. The degree of eccentricity of the assumed single resultant dipole center. 4. 4. The lack of electrical homogeneity of tissues forming the volume conductor. 5. 5. The irregularity of the limiting boundary of the volume conductor. The last three factors influence the validity of utilizing reference frames devised according to anatomic considerations but can be eliminated by the use of reference frames, the electrical properties of which are determined experimentally and expressed in terms of the lead vector concept. The latter has been explained and illustrated in a detailed manner. The first factor involves an assumption which becomes increasingly tenous, the more closely one or more electrodes forming a lead approach the heart. Various methods, reviewed in detail, have been devised to assess the validity of this assumption. Such studies have indicated limitations of applying the concept of a single resultant dipole to precordial leads, although, in general, it would appear that such limitations are not as stringent as would be predicted from anatomic considerations. A possible explanation for this is discussed. The second factor, migration of the assumed single resultant dipole center during the cardiac cycle, is related to and, from a practical standpoint, inseparable from, the first factor. It contributes to the shortcomings involved in applying the single resultant dipole concept to any electrocardiographic lead and is involved in the experimental evaluation of the validity of this concept. A method is suggested for devising a spatial reference frame formed by remote leads which may obviate the last three factors and reduce to a minimum the influence of the first two. In view of the limitations inherent in the single resultant dipole concept, alternate methods of representing the manner in which the electromotive forces arising in the heart influence an electrocardiographic lead are discussed. These comprise a mathematical representation consisting of multiple lead vectors, one for each point in the myocardium generating an electromotive force, and its physical counterpart consisting of “flow lines” or “tubes of influence” to depict the electrical characteristics of the lead field at each myocardial point. A method is outlined in Appendix II for the application of the multiple lead vector concept to the experimental determination of the relative extent to which various portions of the heart contribute potentials to precordial leads.

Right Ventricular Hypertrophy II. Correlation of Electrocardiographic Right Ventricular Hypertrophy with the Anatomic Findings

Twelve cases whose electrocardiograms fulfilled at least one criterion of Sokolow and Lyon for right ventricular hypertrophy were examined at autopsy. Eight of the 12 demonstrated right ventricular hypertrophy anatomically. Eleven of the 12 cases had diseases usually associated with increased pressure in the right ventricle and pulmonary artery and with increased total pulmonary resistance. It is likely that factors other than muscle mass contribute significantly to the electrocardiographic pattern of right ventricular hypertrophy.

The lead vectors of multiple dipoles located on an electrically homogeneous circular lamina.

1. 1. The uniformity of the magnitudes and directions of the lead vectors of various leads calculated for multiple dipoles located on an electrically homogeneous circular lamina has been investigated by graphic and by statistical methods. 2. 2. The results of this study strongly support the contention of Johnston and associates that, under certain circumstances, a lead recorded between two networks of points is greatly superior, from a vectorcardiographic standpoint, to a lead recorded between two single points. 3. 3. On the basis of these findings a reference frame is suggested for investigation gation as to its possible superiority to those currently used in vectorcardiography. Methods of evaluating such a frame are outlined. 4. 4. A statistical expression (Equation 4) involving the concept of the co-efficient of variation has been developed to estimate the degree to which a given lead varies from an ideal vectorcardiographic lead. The wide field of application of this expression to the evaluation of data collected from the study of the distribution of dipole currents in models is pointed out.

Studies on the QRS-T angle☆

Abstract 1. 1. A trigonometric method is used for the calculation of the angle between any two spatial vectors, given the angular positions of their projections on two mutually perpendicular planes. The necessary formulas and their derivations are given in the appendix. 2. 2. A method is described for estimating the angle between the mean spatial QRS and T vectors from a 12 lead electrocardiogram. This method permits a determination of the angular positions of the projections of the mean spatial QRS and T vectors on the transverse, as well as on the frontal plane; from these measurements the spatial angle may be calculated trigonometrically. 3. 3. The determination of the angles between the mean QRS and T vectors from 12 lead electrocardiograms of twenty normal individuals, age 18 to 57, suggests that the upper limit of normal previously given for this determination is too low. Some of the possible reasons for this discrepancy are discussed. 4. 4. Statistical study of the vectorcardiographic data indicates that there was a significant difference in the mean of the angles between the largest spatial and frontal QRS and T vectors obtained with the cube and tetrahedral reference frames. A significant association, as determined by regression, could not be demonstrated for either the spatial or the two planar angles obtained with these two systems. While these findings do not prove conclusively that a significant association might not exist if more cases were studied, it suggests that there would be difficulty in translating from one system to another in a given patient.

Severe hyperbilirubinemia and coma in chronic congestive heart failure.

A 64-year-old man developed severe hyperbilirubinemia of predominantly conjugated fraction in 1978, eight years after a myocardial infarction and development of congestive heart failure. In 1975, he was admitted elsewhere for symptoms suggestive of chronic hepatitis, but liver biopsy revealed replacement of hepatocytes by red blood cells which was interpreted as a result of left-sided cardiac failure. In 1978, liver biopsy showed congestive liver disease with cardiac sclerosis. Despite initial improvement, his condition deteriorated, he became encephalopathic, and died in a coma. This case is reported to illustrate that chronic congestive heart failure can present with severe jaundice and terminate in hepatic coma.