Comparison of right atrium incision and right ventricular outflow incision for surgical repair of membranous ventricular septal defect using cardiopulmonary bypass in dogs.

OBJECTIVE: To compare right atrium incision (RAI) and right ventricular outflow incisions (RVI) for surgical repair of membranous ventricular septal defect (VSD) facilitated by cardiopulmonary bypass (CPB). STUDY DESIGN: Retrospective study. ANIMALS: Dogs (n=10) with VSD. METHODS: Medical records of dogs that had VSD repair were reviewed. Membranous VSD without any malformation and abnormality was confirmed on several clinical examinations and by angiocardiography. RAI (5 dogs) and RVI (5 dogs) was used for VSD access and repair facilitated by CPB. Procedure comparison was by surgical duration, postoperative recovery period, and occurrence of postoperative arrhythmia. RESULTS: Duration of surgery was similar for RAI and RVI; however, postoperative recovery time was significantly reduced with RAI. Significant moderate operative damage occurred with right atrium incision. CONCLUSIONS: Right atrium incision was more effective than RVI for repair of membranous VSD using CPB. CLINICAL RELEVANCE: RAI should be considered in preference to RVI for repair of membranous VSD using CPB.

The effect of differing rates and injection sites on the amount of protamine delivered before detection of hemodynamic alterations in dogs.

OBJECTIVES: To determine the effect of the route and rate of protamine administration on the amount of protamine that could be delivered before a hemodynamic reaction occurred in dogs. STUDY DESIGN: Prospective randomized experimental study. ANIMALS: Twenty adult mixed-breed dogs weighing 25.1+/-2.5 kg. METHODS: Before vascular surgery, the dogs were heparinized to reach an activated clotting time (ACT) of 300 seconds. After completion of the vascular surgery, protamine was administered intravenously until a hemodynamic reaction was recorded. The 4 groups of dogs were given protamine at 5 mg/min (slow) or 10 mg/min (fast) via the cephalic or the jugular veins. Systemic and pulmonary arterial pressures, central venous pressure (CVP), and pulmonary arterial occlusion pressure (PAOP) were recorded before and after protamine administration. The dose of protamine was recorded when a reaction occurred, which was defined as mean arterial pressure (MAP) <60 mm Hg or mean pulmonary arterial pressure (MPAP) >20 mm Hg or more than double the baseline value. RESULTS: Significant decreases in systolic arterial pressure (SAP), MAP, and diastolic arterial pressure (DAP) and significant increases in systolic (SPAP), mean (MPAP), and diastolic (DPAP) pulmonary arterial pressures were recorded after protamine administration. The cephalic slow group had significantly fewer protamine reactions than other groups (chi-square = 8.57, P = .03, df = 3). Significantly more protamine could be delivered from the cephalic vein (52.5+/-14.5 mg) compared with the jugular vein (37.6+/-16 mg) before a reaction occurred (P = .048). CONCLUSION: The rate of administration did not have an effect on the amount of protamine delivered. Adverse reactions were minimized when protamine was administered via the cephalic vein at a slow rate. CLINICAL RELEVANCE: We would recommend delivering protamine after cardiopulmonary bypass or vascular surgery through a peripheral venous route.

Pontes de miocárdio em cäes. II. Topologia / Myocardial bridges in dogs. II. Topology

Estudou-se em 134 coraçöes de cäes de diferentes raças a localizaçäo das pontes de miocárdio, mediante dissecaçäo das artérias coronárias injetadas com soluçäo de gelatina ou Neoprene Látex. Verificou-se que as pontes de miocárdio ocorrem em 90,43 por cento nos ramos da a. coronária esquerda e em 9,57 por cento nos ramos da a. coronária direita. Sua posiçäo foi assinalada em 37,23 por cento na porçäo dorsal do ventrículo, em 28,72 por cento na média, em 21,28 por cento na ventral, em 7,45 por cento no ápice e simultaneamente nas porçöes dorsal e média em 3,19 por cento e nas porçöes média e ventral em 2,13 por cento. Näo foram notadas diferenças estatisticamente significativas em relaçäo ao sexo

Microscopic study of myocardial bridges over the coronary arteries of pigs

Foram estudados 5 coraçöes de suínos resultantes do cruzamento das raças Landrace e Large White com o objetivo de analisar microscopicamente as pontes de miocárdio sobre as artérias coronárias e seus ramos estabelecendo possíveis correlaçöes morfofuncionais. Retiramos destes coraçöes blocos dos segmentos pré, pós e pontino, os quais foram submetidos a cortes seriados e corados pelos métodos de AZAN e WEIGERT-van GIESON. Com a metodologia empregada foram observadas que as pontes de miocárdio eram constituídas por fibras musculares da camada superficial do miocárdio, näo havendo espessamento nem alteraçöes patológicas na túnica íntima das artérias coronárias estudadas. Foram observadas intersecçöes tendíneas de natureza elástica no trajeto dos feixes de fibras musculares da ponte de miocárdio, e ainda feixes de fibras colágenas e elásticas interligando a adventícia das artérias com os feixes de fibras musculares tanto da ponte como do resto do miocárdio. Estas estruturas assim como a presença do tecido adiposo em torno da artéria poderiam suavizar os possíveis efeitos compressivos da contraçäo sistólica

Cardiovascular effects of dibutyryl cyclic AMP and milrinone under right heart bypass in anesthetized dogs.

To compare the cardiovascular effects of dibutyryl cyclic AMP (DBcAMP) and milrinone, we used the right heart bypass method in intact anesthetized dogs. The preload of the left ventricle was maintained constant throughout the experiment. Therefore, the effects of DBcAMP and milrinone on cardiac contractility and afterload of the left ventricle were investigated respectively without preload influence. DBcAMP and milrinone exhibited marked positive chronotropic-, positive inotropic-, vasodilative- and diuretic-activity. DBcAMP expressed these effects gradually and continuously, whereas milrinone expressed its pharmacological actions rapidly, but for a short duration of time. Both the afterload-reducing and the cardiac contractile force-enhancing activities of DBcAMP were longer lasting than those of milrinone. Mean arterial pressure was not altered by DBcAMP infusion, whereas it was increased significantly (p < 0.05) by milrinone infusion. The results of this study suggested that DBcAMP appeared to be indicated when there is a need to increase cardiac output by reducing afterload and increasing cardiac contractile force gradually and continuously. On the other hand, milrinone would seem to be indicated when the goal is to raise blood pressure rapidly and to increase cardiac output simultaneously.

Ocorrência de pontes do miocárdio em suínos / Incident of myocardial bridges in pigs

Estudou-se em 60 coraçöes de suínos sem raça definida, a frequência, a largura, a posiçäo, a topografia e a vasculotopia das pontes de miocárdio, mediante injeçäo das artérias coronárias com soluçäo de Neoprene látex - 450 -, fixaçäo em soluçäo aquosa de formol e dissecçäo. Os resultados obtidos permitiram concluir que: -as pontes de miocárdio ocorrem em 36,36 por cento das peças, em número de 1 a 3, tendo sido identificadas num total de 32; -a largura das pontes variou de 0,2cm a 1,9cm com média de 0,75 cm; -a topografia mais frequentemente observada foi na porçäo média (36,66 por cento), dorsal (31,25 por cento) e ventral (31,25 por cento); -as pontes de miocárdio ocorrem com maior frequência sobre os ramos da artéria coronária direita (65,62 por cento), do que sobre os ramos da artéria coronária esquerda (34,37 por cento)