R. Curtis Ellison

Myocardial Force-Velocity Relationships in Clinical Heart Disease

Myocardial force-velocity relationships were studied in 33 children and young people with varying heart lesions. From analysis of left ventricular pressures and consideration of left ventricular geometry, measured from biplane angiocardiograms, maximal contractile element velocity (Vmax) was determined by extrapolation of a stress-velocity plot to zero stress. The value of Vmax in each patient was compared with the assessment of cardiac function by usual hemodynamic criteria (left ventricular end-diastolic pressure [LVEDP], volume [LVEDV], and ejection fraction [EF]).In general, patients with normal LVEDP, LVEDV, and EF had values for Vmax above 3 circumferences/sec. Patients with elevated LVEDP or LVEDV or with EF below 0.5 had lower values for Vmax. Three patients whose usual catheterization data suggested normal ventricular function were found to have low Vmax. In all three, other evidence for myocardial abnormality was found. Several patients with excessive afterloads had impaired function by conventional criteria, yet had normal Vmax.Evaluation of myocardial mechanics in man with measurement of Vmax appears to aid significantly in evaluating patients with heart disease by giving an index to the state of the myocardium not available from routine catheterization data.

General index for the assessment of cardiac function

Abstract The concept of a “normalized velocity” was employed to provide a uniform approach for the assessment of cardiac function. In particular, the quantities [(dp/dt/)/p]max, [(dV/dt/)/V]max and [t(dl/dt/)/l]max were applied to data taken from 89 studies in 71 infants, children and young adult patients. Here p represented the total left ventricular pressure, V the instantaneous ventricular volume and I the instantaneous outward displacement as recorded from an apex cardiogram at time t from the onset of displacement. Results were as follows: (1) The contractility index [(dp/dt)/p]max appeared to relate to myocardial function assessed clinically and to be more consistent with the clinical findings in the clear-cut situations than Vmax based on total pressure, Vmax based on developed pressure and [(dP/dt)/P] at P = 40 mm Hg developed pressure where P = total pressure minus end-diastolic pressure. (2) The ejection velocity [(dV/dt)/V]max was found to reflect hemodynamic function and correlated with the ejection fraction ( r = 0.80). (3) The index [t(dl/dt)/l]max as obtained from the apex cardiogram related well to [(dp/dt)/p]max ( r = 0.72). These studies suggest that values for “normalized velocity” obtained from direct or indirect methods, give reliable guides to myocardial function and allow for meaningful comparisons among patients.

Assessment of myocardial contractility in children and young adults from ventricular pressure recordings

Abstract The index V pm (the actual or physiologic maximal shortening velocity of the contractile element) has been obtained from the analysis of left ventricular pressure recordings and then applied to the assessment of myocardial contractility in man. Pressures during the isovolumic period of ventricular systole were recorded during routine catheterization of 46 patients with a variety of cardiac lesions. The quantity V pm , that is (dp/dt/kp) max , was compared with the hemodynamic evaluation of each patient based on the left ventricular end-diastolic pressure, ejection fraction and left ventricular end-diastolic volume. V pm was selected for this study since it appeared to be largely independent of load and does not require biplane angiocardiography and extrapolation analyses. Preliminary results suggest that a value of V pm greater than 1.6 sec −1 indicates normal myocardial function; lower values indicate abnormal function. In several instances this index was not in agreement with the hemodynamic measures, but in most cases the clinical assessment supported the conclusion drawn from V pm . This study suggests that reliable guides to myocardial contractility can readily be obtained from high fidelity pressure recordings alone.

Spatial voltages in the assessment of left ventricular hypertrophy (Frank system)

Summary The existence of a relationship between surface potentials in the QRS complex on one hand, and left ventricular weight and wall thickness on the other was demonstrated in 150 individuals studied by orthogonal electrocardiography (Frank lead system) and biplane angiocardiography. Equations for the estimation of left ventricular weight and wall thickness were derived from data on that same series. They were based on two simple spatial voltage criteria together with the subjects age and weight. It was shown that the simple voltage criteria provide rather reliable means of detecting conditions of left ventricular overload. With a cut-off point corresponding to a 5% false positive rate, one of the two criteria had a false negative rate of only 33 % for left ventricular overload. Moreover, only a minority of these false negative subjects had left ventricular hypertrophy in terms of heart weight as a fraction of body weight.

Use of the Dipole Moment in the Assessment of Left Ventricular Hypertrophy

A multi-electrode grid lead system, suited for the measurement of the total outward electromotive force of the heart expressed as a dipole moment, was tested in 64 subjects without heart disease and in 44 patients with left ventricular overload. The normal group showed the maximum dipole moment to the left (L-MDM) to be proportional to body weight, and by inference to left ventricular weight. For the patients with heart disease, the degree of hypertrophy was assessed in terms of LV weight derived from biplane angiocardiograms; for these patients, L-MDM was found to be proportional to LV weight (r = 0.85). The grid allowed for a more accurate assessment of LV weight than parameters obtained from the Frank lead system in the same patients.A substantially improved estimation of LV weight was achieved with both systems when body weight was considered in addition to the electrocardiographic measurements.Among the reasons for the better performance of the grid system are surface potential integration instead of sampling, consideration of individual torso dimensions, and as a result of distributed multiple electrodes, absence of distortion in the local field.

Application of Fiberoptic Dye-Dilution Technic to the Assessment of Myocardial Function I. Description of Technic and Results in 100 Patients with Congenital or Acquired Heart Disease*

Abstract Indicator-dilution curves were recorded by means of the fiberoptic hemoreflection system in 100 patients. The technic involves left ventricular injection of indocyanine green and central aortic sampling. Stroke volume, ejection fraction, end-diastolic and end-systolic volumes were all derived from the same density curve. Multiple curves were recorded in all instances. There were 19 patients with valvar aortic stenosis, 15 with idiopathic hypertrophic subaortic stenosis, 15 with aortic regurgitation, 9 with mitral regurgitation and 6 with chronic myocarditis of varying severity. Eight patients had a ventricular septal defect, 9 an atrial septal defect and 6 had valvar pulmonic stenosis. The remainder of the patients had diverse disorders. The results were expressed as milliliters per kilogram of body weight and as milliliters per square meter of body surface area. Since there was close similarity among the data describing the 40 patients with obstructive lesions, their data were collected into a group. Stroke volume was 1.5 ml./kg. body weight, ± 0.42; ejection fraction was 0.577, S.D. ± 0.08; end-diastolic volume 2.7 ml./kg. body weight, S.D. ± 0.76; end-systolic volume was 1.2 ml./kg. body weight, S.D. ± 0.49. These data correspond closely to those of normal subjects reported by other investigators. In contrast, in regurgitant lesions, end-diastolic volume was high, stroke volume normal and ejection fraction depressed, reflecting the severity of the regurgitation. Still lower ejection fractions and higher end-diastolic volumes were found in myocarditis. Conversely, high ejection fraction and high end-diastolic volume with high stroke volume were seen in ventricular septal defects. While a linear correlation between end-diastolic volume and stroke volume existed in the group with obstructive lesions, no such clear relation could be determined in the remaining lesions. The variability in the interrelation of these factors is stressed, as well as the need for their determination in the proper assessment of the total hemodynamic state of the individual lesion.

Quantitation of ventricular hypertrophy and hemodynamic load with vectrocardiogram

Abstract Studies in 540 children with congenital heart disease have shown correlations between the orthogonal electrocardiogram and the hemodynamic load placed on the right and left ventricles. Using the Frank lead system, the maximum spatial voltage directed to the left has been shown to reflect the degree of pressure or volume overload of the left ventricle in patients with aortic stenosis and septal defects and even in the cyanotic lesions tetralogy of Fallot and complete transposition of the great arteries. The maximum spatial voltage directed to the right has been found to correlate well with pressure overload of the right ventricle in patients with pulmonic stenosis and septal defects. The direction of rotation of the vectorcardiographic loop in the horizontal plane has been shown to reflect well the relative hemodynamic loads on the two ventricles, and thus presumably the relative degrees of left and right ventricular hypertrophy present. In certain lesions, the electrocardiographic-hemodynamic correlations are close enough to allow the Frank electrocardiogram to be of significant help in the clinical management of children with congenital heart disease.

The Frank electrocardiogram in complete transposition of the great arteries: Its use in assessment of left ventricular pressure

Abstract Frank ECGs were obtained in one hundred children with transposition of the great arteries and related to the hemodynamic state, especially the left ventricular pressure, measured at cardiac catheterization. Abnormal degrees of right ventricular hypertrophy were seen in almost all children above 2 months of age. Associated left ventricular hypertrophy, detected by a counterclockwise or figure-of-eight horizontal loop and usually increased leftward voltages, was found to relate to the level of the left ventricular systolic pressure. Provided the hematocrit was not excessively elevated, a counterclockwise loop in the horizontal plane was associated with a high left ventricular pressure (> 70 per cent of the right ventricular pressure), whereas a clockwise horizontal loop indicated a left ventricular pressure less than 70 per cent of the right ventricular pressure. In individual patients, changes in the level of left ventricular pressure were reflected by changes in the Frank ECG. Thus the Frank ECG is useful in the clinical evaluation of patients with transposition of the great arteries, especially in assessing the level of the left ventricular pressure.

The Frank scalar atrial vectorcardiogram in normal children

Abstract High-gain recordings of the Frank scalar atrial vectorcardiogram were obtained with conventional vectorcardiographic apparatus in 115 normal subjects. Forty measurements of time intervals, scalar voltages, and spatial voltages, which were expected to most likely reflect patterns of depolarization found in the experimental laboratory, were selected for analysis. The atrial vectorcardiogram was found to relate well to patterns of right and left atrial depolarization previously described in dogs. Right atrial activity was reflected in leftward, inferior, and anterior forces, while left atrial depolarization began later and was reflected in leftward, inferior, and more posterior forces. Normal values of selected parameters are presented. The study indicates that high-gain recordings of the scalar atrial vectorcardiogram can be easily obtained as a part of a routine vectorcardiographic procedure. Readily determined parameters reflect differential depolarization of the right atrium and of the left atrium.