A method is described for the production of chronic atrioventricular block in dogs, by incision of the region of the bundle of His through the open right atrium during temporary caval occlusion. Exercise tolerances, chest x-ray films, electrocardiograms, phonocardiograms, cardiac outputs, intracardiac pressures, femoral pressures, and left ventricular coronary flows were obtained preoperatively and from 1 to 10 months postoperatively. The majority of the animals developed clinical, laboratory, and pathological evidence of congestive heart failure. All animals had generalized myocardial hypertrophy.D ESPITE the inherent limitations of itransferring data on experimental [heart disease from animals to man, it is possible, after surgical production of lesions in animals, to make controlled analyses of various syndromes which are analogous to human disease entities. In a contemporary study in dogs' the acute effect of surgically induced complete heart block on cardiocirculatory function was reported. The present communication is concerned with a study of the chronic effects of complete heart block in dogs, as well as with a more detailed description of the operative procedure.During the study, the majority of the animals with chronic complete heart block developed right and left sided heart failure, either spontaneously or after several weeks of daily exercise. Because of the current interest in developinig experimental means of producing congestive heart failure, the events and details of decompensation have been

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A study has been conducted immediately and up to 18 (lays after the surgical production of complete heart block in dogs. Immediately Ju1ly, 19.55

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ANGIOCARDIOGRAPHY and cineangiocardiography are employed with increasing frequency for the diagnosis of cardiovascular diseases. These commonplace technics of cardiovascular radiology depend upon the rapid injection of radiopaque materials into the heart or central circulation. A wide variety of substances are in use, but all are hypertonic and some are considerably more viscous than blood. A variety of studies are available to indicate that the hemodynamic effects can be related to chemical structure, -3 but as newer and safer agents have become available it seems clear that the pharmacodynamic effects are related most importantly to the hypertonicity of these compounds. The effects of the injection of oontrast media can therefore be considered to be the effects of hypertonicity on the circulation, and the study of these effects assumes considerable practical importance.Numerous reports are available that deal with the effects of hypertonic (and radiopaque) materials injected into the right heart and pulmonary circulation in animals,4-10 but comparable systematic studies in man are not available. The hemodynamic consequences associated with the injection of radiopaque ma-From the

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The indicator-dilution principle has been employed to study coronary blood flow and the venous drainage into the coronary sinus ( CS) in the dog. Nine open-chest dogs were prepared to allow separate perfusion and flow measurement of the right and left coronary arteries ( RCAand LCA) as well as simultaneous sampling at two sites in the CS. By injecting indicator at various sites in the arterial tree, it has been demonstrated that the posterior circumflex artery drains chiefly to the CS near the CS ostium; the left anterior descending drains chiefly to the area of the CS far upstream from the CS ostium, and the RCA does not drain to the CS. These drainage data have been used to help determine the adequacy of mixing of dye and blood, and to measure LCA flow. Adequate mixing of dye and blood was frequently achieved by the criteria established, but LCA flow was accurately measured with only a minority of injections. It is likely that pecularities of the anatomy of the coronary vascular bed account for the discrepancies.