摘要:

Myocardial contractile force in five areas of the left ventricle was measured in 14 dogs under chloralose anesthesia prior to and following segmental chemical epicardiectomy. Electrical stimulation of the stellate ganglia was performed before and after each segment of epicardium was destroyed, and records of myocardial contractile response to stimulation were obtained. Epicardiectomy resulted in ablation of contractile response in specific areas of the left ventricle. In a recent publication from our laboratory (Circulation Res. 22: 315, 1968), the predominance of an epicardial distribution of sympathetic fibers was demonstrated. As an extension of that work, this study demonstrates the projection of fibers from both left and right stellate ganglia and the innervation of both anterior and posterior surfaces of the left ventricle. The major projections of sympathetic fibers are oriented along an axis passing from base to apex and can be interrupted by epicardial destruction in the area of the cephalad portion of the anterior descending coronary artery and adjacent to the origin of the left marginal artery.

ISSN:0009-7330    

出版商:OVID    

年代:1968

数据来源: OVID

摘要:

The prevalence rate for cardiovascular malformations in dogs presented to a large university veterinary clinic was 6.8 per 1000. Patent ductus arteriosus, as in man, was found predominantly in females. Breed-specific prevalence rates were significantly greater in purebred dogs than in mongrels, and the breed distributions of patent ductus arteriosus, pulmonic stenosis, subaortic stenosis, persistent right aortic arch, and tetralogy of Fallot were significantly different than would be expected if all breeds were equally susceptible to each type of malformation. On the basis of these observations, two hypotheses were made: (1) Genetic factors are determinants of certain types of congenital heart disease in the dog. (2) These genetic factors have specific effects on cardiac morphogenesis, resulting in specific types of cardiovascular malformations. Preliminary genetic studies confirmed the specific hereditary transmission of valvular pulmonic stenosis in beagles, persistent right aortic arch in German shepherds, and conal septal defects (including ventricular septal defects and tetralogy of Fallot) in keeshonden. The pattern of inheritance of these defects was not consistent with any simple genetic hypothesis. Patent ductus arteriosus in dogs of poodle ancestry and fibrous subaortic stenosis in Newfoundlands were shown provisionally to be transmitted in a manner consistent with autosomal dominant inheritance. The significance of these findings is considered in relation to present and future understanding of the etiology and pathogenesis of congenital heart disease.

ISSN:0009-7330    

出版商:OVID    

年代:1968

数据来源: OVID

摘要:

Simulation by a digital computer of propagated excitation in the ventricular myocardium has been accomplished. Experience with the program in normal conduction and in one example of abnormal conduction, an extrasystole, is presented. Results of the simulation process were in harmony with observations in animal experiments. This justifies attempts to apply this scheme to the analysis of abnormal ventricular excitation caused by other disturbances.A crucial role of the Purkinje network in determining the course of excitation spread was recognized in the simulated process of both normal beats and extrasystoles. New knowledge is expected from this scheme when applied to other types of abnormal excitation.The possibility of combining the scheme with a method of reconstruction of QRS complexes by means of “transfer impedance” values was pointed out.

ISSN:0009-7330    

出版商:OVID    

年代:1968

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:1968

数据来源: OVID

摘要:

Multiple measurements of left ventricular volumes, ejection fractions, and circulatory pressures were made under conditions of varied outflow resistance in five intact anesthetized dogs by using a biplane videoangiographic recording system which displays simultaneously two roentgen images on the same television screen, records the images on video tape, and requires low radiation levels and small amounts of contrast medium. Aortic pressure was controlled by intra-aortic infusion of angiotensin or acetylcholine. With spontaneous sinus rhythm and normal aortic pressure, end-diastolic volume averaged 35 ml (2.3 ml/kg), and ejection fraction averaged 47% of end-diastolic volume. When aortic pressure was increased, average end-diastolic volumes increased to 53 ml and ejection fractions decreased to 29%. Conversely, when aortic pressure was decreased, average ejection fraction increased to 73%, although changes in stroke volume were usually not large under these conditions. Concomitant large changes in the shape of the left ventricular cavity were also observed. Similar changes were observed when heart rate was maintained constant by electrical pacing of the atria and ventricles with a constant atrial-ventricular stimulus interval. The variability in left ventricular volume and ejection fraction observed in the same animal during different circulatory states may account in part for the differences in values for these variables reported by different investigators.

ISSN:0009-7330    

出版商:OVID    

年代:1968

数据来源: OVID

摘要:

The role of the carotid sinus reflex in control of the blood flow in the left circumflex coronary artery was studied in nine open-chest dogs anesthetized with chloralose. Flow was measured with an electromagnetic flowmeter. The effects of bilateral common carotid occlusion were examined in a three-part experiment in each dog. (1) Under vagotomy (control) conditions, occlusion of both common carotid arteries resulted in tachycardia, increased blood pressure, and a decrease in coronary artery resistance. (2) After beta-receptor blockade with propranolol, 1.0 mg/kg, carotid sinus hypotension still resulted in increased blood pressure but the tachycardia was blocked, and coronary artery resistance increased. (3) Following rapid cardiac sympathectomy, carotid sinus hypotension still resulted in a reflex rise in systemic blood pressure but coronary resistance remained steady. This demonstrated the reflex nature of the increased coronary resistance observed after beta-receptor blockade. It is concluded that the coronary circulation is under reflex control and that sympathetic coronary artery vasomotion is a part of a carotid sinus reflex.

ISSN:0009-7330    

出版商:OVID    

年代:1968

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:1968

数据来源: OVID

摘要:

Dilatation of collateral blood vessels was studied following occlusion of the femoral artery in anesthetized dogs. This was achieved by measuring pressure and flow in the anterior tibial artery distal to the occlusion and pressure in the femoral artery proximal to the occlusion. Dilatation of the collateral vessels to the anterior tibial artery was estimated by the increase in the conductance of the collaterals from the minimum value measured 8 to 10 seconds following onset of the occlusion. Conductance rose 277 ± 67 (SEM)% during the first 70 seconds following occlusion and an additional 178 ± 66% during the ensuing hour. When the femoral artery was reopened after a 2-minute period of occlusion, the collaterals reconstricted to their preocclusion size in 12 to 14 minutes. Elimination of circulatory reflexes by total spinal anesthesia did not alter the course of collateral vasodilatation. However, when systemic arterial pressure was lowered to approximately 45 mm Hg for 8 minutes prior to occlusion, the collaterals dilated almost completely even before the occlusion was instituted, indicating that tissue ischemia is in some way related to collateral vasodilatation.

ISSN:0009-7330    

出版商:OVID    

年代:1968

数据来源: OVID

摘要:

The effects of stellate ganglion stimulation on idioventricular automaticity were studied in anesthetized dogs. An idioventricular rhythm was obtained in one series of animals by ligating the His bundle and in the other by stimulating the vagus. On isolation of the left stellate ganglion, the idioventricular rate fell by 5 beats/min which is compatible with a rate of “tonic” discharge of about 3 impulses/sec. On stimulation of the stellate ganglia at increasingly higher frequencies, the idioventricular rate accelerated progressively and the frequency-response curve was sigmoid. When the stimulation frequency was increased above 10 to 15 pulses/sec, there was no further enhancement of ventricular automaticity. The ventricular rates attained during sympathetic stimulation rarely exceeded 70/min. The interval between the initiation of sympathetic stimulation and the maximal ventricular acceleration was shorter at higher stimulation frequencies. The effects of right and left stellate stimulation on the rate of idioventricular pacemakers were comparable. Reflex vagal inhibition had little influence on the acceleratory action of the sympathetic nerves on the idioventricular pacemakers since in dogs with atrioventricular block the results before and after vagotomy were similar. Furthermore, the idioventricular rhythm during vagally induced block increased on sympathetic stimulation to values comparable to those obtained in dogs with surgically induced block.

ISSN:0009-7330    

出版商:OVID    

年代:1968

数据来源: OVID

摘要:

In 13 canine hearts, 158 disappearance curves for133Xe and antipyrine-1125I, given by intra-arterial slug injection, were recorded at a wide range of perfusion rates. Flow rates (ml/100 g/min) calculated from these curves by a variety of methods were compared with measured flow rates (Fa) per weight of perfused tissue. Perfusion of isolated, supported hearts and of anterior descending coronary arteries in open-chest dogs provided similar data. The semilogarithmic slope of curves from apex or whole heart decreased with time, particularly at high flow rates. There was a small, consistent difference in shape between antipyrine and xenon curves, suggesting that radioactivity in fat contributed somewhat to this tailing. Estimation of flow rate from the steepest semilog slope yielded an average value of 1.1 Fafor all rates; estimation from slope at 30% of peak radioactivity gave 0.9Fa. The curves were closely described by a two-exponential equation which gave flow estimates of 0.95Fawhen collimation limited the observations to the heart apex, and lower values when the whole heart was observed. Peak height/area methods gave values of approximately 0.75Fain spite of various compensations for the impossibility of recording the curve until radioactivity = 0.

ISSN:0009-7330    

出版商:OVID    

年代:1968

数据来源: OVID