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Electrophysiological studies of verapamil on isolated cardiac tissue show its effects to occur during Phase 2 and Phase 4 of the cardiac action potential and to be a result of blocking the slow inward Ca 2+ current. It is important to know if verapamil effects the transmembrane movement of ions other than Ca 2+ . By studying uptake and efflux of 42 K by canine cardiac Purkinje fibres in the presence and absence of verapamil (1.1 × 10 −6 M–4.4 × 10 −6 M). it was found that the drug inhibits both 42 K uptake (15%) and efflux (30%).

Summary A modified technique for transseptal angiography of the left side of the heart is described. Ten left-sided angiocardiograms, three left ventricular injections and seven left atrial injections were done in the course of sixty-five transseptal left heart catheterisations.

Severe intravascular hemolysis is described as a complication of implantation of an aortic Starr-Edwards ball-valve prosthesis and insertion of a Teflon patch in the ascending aorta in a 9-year-old boy with severe aortic valvar stenosis. This progressive hemolysis of delayed onset was the sole indicator of extreme degeneration of the silicone rubber ball of the prosthetic aortic valve, a potentially lethal condition requiring surgical intervention. The phonocardiographic signs of aortic ball variance were not present, and there was no overt valvar incompetence. A lesser but noteworthy aspect in this case was the occurrence of an "aplastic crisis" superimposed on the severe hemolysis. This transient bone marrow, red cell aplasia, which was unrelated to drugs, precipitated an acutely severe anemia which accounted for the presenting symptoms of the patient and required transfusion.

The vectorcardiographic (VCG) and electrocardiographic (ECG) features in nine cases of ventricular inversion with two functioning ventricles (congenital corrected transposition of the great arteries) and associated cardiac malformations were correlated related with their hemodynamic states. All three cases with low venous ventricular pressure showed a similar VCG pattern with a posterior and completely counter-clockwise horizontal QRS loop. The ECG showed a leftward QRS axis, QS complexes in V 1 , and RS complexes in V 6 . These findings are normal for ventricular inversion without major associated defects. Three patients with isolated pressure or volume overload of the venous ventricle showed large leftward and posterior initial QRS forces, followed by a predominantly clockwise and rightward horizontal QRS loop. The ECG showed right axis deviation, qR complexes in V 1 , and rS complexes in V 6 . These findings are considered to represent venous ventricular hypertrophy. Three patients with hemodynamic situations which would be expected to result in biventricular overload demonstrated varying degrees of anterior displacement of the horizontal QRS loop, two with counter-clockwise inscription and one predominantly clockwise. The initial QRS forces, although leftward and superior as in the other groups, were anterior in each case. The ECG demonstrated normal or rightward QRS axis, no precordial q waves, and large biphasic RS complexes in the midprecordial leads. These findings are considered to represent biventricular hypertrophy. One patient had serial tracings which revealed progressive ECG-VCG changes due to increasing venous ventricular hypertension secondary to increasing pulmonic stenosis. These findings indicate that the ECG-VCG accurately reflect the anatomy and hemodynamics in ventricular inversion.

Two pathological specimens are presented in which the morphological left ventricle contains the right atrioventricular ostium, completely or in its major portion and, totally, the left atrioventricular ostium. It is suggested from a consideration of these cases and of the pathological material available in the literature that this constitutes an entity that can be usefully separated from the heterogeneous group of single ventricle with which it has previously been classified. The entity is called double-inlet left ventricle and is defined as existing when two separate atrioventricular ostia open in a morphological left ventricle. An ontogenetic explanation is presented based on the study of normal human embryos. These cases resemble the heart of the embryo during the horizons XIII to XVI of Streeter. It is suggested that there has been a partial arrest in the widening of the atrioventricular canal and the changing relation of the atria with the ventricles at these stages. It is noted that both atria open into the morphological left ventricle whether situated to the left or to the right. This is an expected finding, since the left ventricle is derived from the primitive ventricle and the primitive ventricle is always connected with both atria during the early stages of embryological development. Other malformations include transposition of the great arteries in both cases and ventricular inversion in one.

Summary A case of ventricular parasystole is presented which appeared in an otherwise healthy newborn infant. The dysrhythmia persisted until 10 months of age. In contrast to its occurrence in adults, this rare dysrhythmia appears not to be associated with primary cardiac disease in children.

Surgically induced complete heart block (CHB) occurred in 40 (9 percent) of 425 infants and children who underwent intracardiac repair of congenital heart disease. Thirteen patients died in the immediate postoperative period from causes other than CHB, and there was one late death following a Stokes-Adams attack. Among the 26 survivors, 18 reverted to a sinus rhythm and eight patients required permanent cardiac pacing. The complications of permanent cardiac pacing were numerous; yet all eight patients survived and enjoyed normal activities up to five years after surgery. A new method of managing postoperative CHB in infants and children has been presented.

The authors report the development and evaluation of a computer program for analysis of pediatric scalar electrocardiograms. The program is an extension of the existing IBM 5890 ECG Analysis Program. It includes extensive age-dependent criteria and tables of limits for ECG parameters. Special pediatric correlative statements are incorporated to direct physician attention to combinations of electrocardiographic findings which may indicate congenital abnormality. The program permits the use of alternate precordial leads V4R, V3R, and V7 in addition to the standard V1 to V6. The evaluation shows the program to be 96.8% sensitive and 88.3% specific in detecting abnormal rhythms; a sensitivity of 99.8% and specificity of 96.0% were obtained for detection of abnormalities affecting ECG contour. Program performance is apparently insensitive to choice of precordial leads, but dependent on patient age, improving as age increases.