Study of Spontaneous Congestive Heart Failure in the Dog

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Abstract
Spontaneous cardiovascular disease has been found in dogs from the Savannah River Valley area, predominantly in the male house pet and hunting dog. The causes have been Dirofilariasis, chronic mitral valvular disease, and congenital cardiovascular defects. Cardiac stress in these dogs caused marked salt and water retention, increased blood volume, increased central venous and right heart pressures, and cardiac dilation and hypertrophy. These compensatory mechanisms were similar to those in man. Cardiac dilation was more pronounced in spontaneous failure than in experimental failure. Regression of cardiac dilation was very slow even after apparent compensation and clinical improvement. Plasma protein concentrations were decreased, but total extracellular protein mass was markedly increased. Sodium and potassium plasma concentrations were within normal range. Hyponatremia was occasionally observed in dogs as in man.20 Dirofilariasis was characterized by marked pulmonary hypertension, caused primarily by pulmonary vascular changes rather than mechanical blockage. There was massive hypertrophy of the right ventricular myocardium. Heartworm dogs in congestive failure have a similar range of right heart pressure to experimental pulmonic stenosis dogs in failure.21 Cage rest was of little therapeutic value in these dogs in congestive failure. Clinical response and physiological changes were remarkable with the use of saltabsorbing resin or digitalis compounds causing negative sodium balance. Digitalization of the dog required vigorous individual treatment controlled by clinical symptoms and P-R interval of the electrocardiogram. Acquired tolerance to digitalis required increased dosage levels every few months. The veterinary practitioner who recognizes the necessity of individual digitalization and the importance of detection and removal of thoracic fluid will be rewarded with improved clinical therapy of congestive heart failure. Experimental dogs during periods of severe cardiac stress can benefit from adequate digitalization. The similarity of biochemical and physiological changes in spontaneous heart disease, as it occurs in man and in dogs, affords an avenue for clinical research. This applicability to man is enhanced because the dog can be more comprehensively studied.