Allan Goldblatt

Studies on Cardiac Dimensions in Intact, Unanesthetized Man

A method is described which permits measurement of relative changes in the external dimensions of individual cardiac chambers throughout the cardiac cycle in intact, unanesthetized man. It consists of suturing multiple radiopaque silver-tantalum clips to the surface of the heart at the time of cardiac operations. In the postoperative period, cine-radiograms are obtained and the distances between clips are measured on each individual frame. This technique has been found to be safe and has been employed in 68 patients without any complications. As a result of studies in eight patients utilizing biplane serial exposures, the effects of rotation of the heart in the sagittal plane during the cardiac and respiratory cycles were determined precisely. If clips were properly placed on the heart, the possible errors resulting from such rotation were found to be quite small. During inspiration right ventricular dimensions increased, while the opposite occurred during expiration and during the Valsalva maneuver. Left ventricular dimensions exhibited little change during normal respiration. During deep, slow inspiration, the changes in dimensions of the left ventricle lagged behind those of the right ventricle by one to five (generally two or three) cardiac cycles; the magnitude of the changes in the dimensions of the left ventricle was smaller than that which occurred in the right ventricle. The effects on ventricular dimensions of light muscular exercise performed in the supine position were studied in nine patients. The end-diastolic dimensions decreased by an average of 6.0% of control in the right ventricle, and by an average of 5.1% in the left ventricle. End-systolic dimensions decreased by an average of 5.6% of control in the right ventricle and by an average of 6.5% in the left ventricle. These decreases are considered to approximate one-half of the resting stroke volume. In the four patients in whom the rate of right ventricular pressure rise was determined continuously, exercise resulted in an elevation of dp/dt while ventricular end-diastolic dimensions decreased. These data are interpreted to indicate that an increase in myocardial contractility occurs during muscular exercise in man.

Serum Digoxin Concentrations in the Human Fetus, Neonate and Infant

Abstract The correlation between digoxin dosage and serum digoxin concentration measured by radioimmunoassay was investigated in seven neonates (three to 30 days of age) and 10 infants (one to 12 months of age) with congenital heart disease. The results were compared with those from 21 adult patients. Digoxin dosages commonly used in the neonates and infants were substantially larger than those used in adults on a basis of milligrams per kilogram of body weight or milligrams per square meter of body-surface area. This higher dosage schedule produced a mean serum digoxin concentration five to eight hours after the last maintenance dose of 2.0 ± 0.9 (± S.D.)ng per milliliter in children, a value significantly higher than that of the adults (1.3 ± 0.4) (p less than 0.005). Despite the higher concentration, which ranged up to 4.3 ng per milliliter, no case of cardiac-rhythm disturbance suggesting digoxin intoxication was observed. In each of seven women who received digitalis during pregnancy, fetal umbilical...

THE EFFECTS OF ACUTE HYPOXIA ON THE SYSTEMIC VENOUS AND ARTERIAL SYSTEMS AND ON MYOCARDIAL CONTRACTILE FORCE

The circulatory changes that occur during acutely induced hypoxia have been of interest for many years (1-6). It now seems clear that many of the observed responses to this stimulus result from a complex interaction of its direct effects on the heart and the vascular bed and of its indirect effects mediated through nervous, or humoral mechanisms, or both. The present investigation was designed to study the circulatory effects of hypoxia in an experimental preparation in which the responses of the systemic venous bed, the heart, and the systemic arterial bed could be separated. Particular attention was directed to determining the effects of hypoxia on the total systemic venous bed. The potential importance of any changes in venous tone are apparent when it is considered that this segment of the circulation contains the major portion of the systemic blood volume (7). Small changes in the diameter of the veins might be expected to produce large changes in the volume of the venous bed and in the magnitude of the venous return to the heart; any such changes could, in turn, modify the cardiac output and, therefore, the arterial pressure (8-11 ). In the present investigation the activity of the chemoreceptors, the adrenal glands, and the spleen was also studied, since these organs have been implicated in the circulatory responses to hypoxia (1218).

The krypton85 inhalation test for the detection of left-to-right shunts.

One of the primary reasons for performing cardiac catheterization in patients known to have, or suspected of having, congenital heart disease is to determine whether a left-to-right shunt is present and the site at which it enters the right side of the heart. Although a variety of techniques for the detection of such shunts has been developed (Wood et al., 1957, 1958; Zimmerman, 1959; Braunwald and Morrow, 1960) relatively little specific information regarding their reliability has been published. The inhalation of an inert foreign gas and the determination of its concentration in blood sampled from the right side of the heart and the systemic arterial bed forms the basis of a sensitive test for the determination of left-to-right circulatory shunts (Morrow et al., 1958; Sanders et al., 1959; Braunwald et al., 1960). Radioactive krypton (Kr85) has been found to provide substantial advantages over other gases and it has therefore been employed routinely in this laboratory for the past several years (Sanders and Morrow, 1959; Braunwald et al., 1960). It is the purpose of this communication to analyse the results obtained from the application of the Kr85 inhalation test in 323 patients, in all of whom the specific cardiac diagnosis was subsequently established. In this analysis particular emphasis was placed upon: (1) an evaluation of the reliability of the Kr85 inhalation test in the detection of left-to-right shunts, (2) the establishment of specific criteria for the interpretation of the results of the test, (3) an evaluation of the ability of the test to localize the site of entry of a left-to-right shunt, and (4) the usefulness of the test in detecting multiple left-to-right shunts.

The Cyanotic Infant — Heart Disease or Lung Disease

Abstract To determine whether differential diagnosis in infants with cyanosis of uncertain etiology may be facilitated without requiring cardiac catheterization, the Pao2, Paco2, pH and bicarbonate of aortic blood were measured in 28 cyanotic infants. Measurements were made 10 to 15 minutes after the infant has breathed oxygen at a concentration of 0.9 to 1.0 at atmospheric pressure, and again 10 to 15 minutes after breathing the same concentration of oxygen under a positive end-expiratory pressure of 8 to 10 cm of water. In seven with subsequently proved cardiac disease, Pao2 fell 33 mm Hg on the average, whereas Paco2 rose 9 mm Hg. In 21 infants with subsequently proved lung disease, Pao2 rose an average of 141 mm Hg, whereas Paco2 did not change. Thus, a simple procedure is available to help differentiate cyanosis of cardiac from that of pulmonary causation; it permits earlier diagnosis of the former and avoids the risks of cardiac catheterization in the latter.

Delay in the onset of right ventricular contraction in patients with surgically induced disturbance of right ventricular conduction

Abstract In this study, we attempted to elucidate the mechanism responsible for the electrocardiographic evidence of right ventricular conduction disturbance which develops in patients after surgical closure of ventricular septal defects and repair of the tetralogy of Fallot. The time intervals between the onset of ventricular depolarization and of right ventricular contraction were determined both before and after operation in 17 patients who developed this electrocardiographic abnormality. In 11 of the 17 patients the time interval increased by 0.02 to 0.06 sec.; in 3 patients it increased by 0.01 sec., and it remained unchanged in the other 3 patients. We have concluded that the mechanical delay in the onset of right ventricular contraction which develops in the majority of patients after closure of ventricular septal defects and complete correction of the tetralogy of Fallot results from interruption of, or other trauma to, the right bundle branch.

Combined congenital pulmonic and mitral stenosis.

IN an occasional patient with rheumatic mitral stenosis tricuspid stenosis is present as well. In the combined lesion the usual symptoms and signs of mitral stenosis may be absent since the obstruc...

Left-superior-vena-cava steal syndrome.

TRICUSPID atresia constitutes approximately 3 per cent of autopsied cases of cyanotic congenital heart disease and 3 per cent of clinically diagnosed congenital heart lesions in patients under 14 y...