bluuebunny/crossref_metadata_2025_split huggingface dataset:
Diagnosis in adolescents and adults with congenital heart disease. Prospective assessment of individual and combined roles of magnetic resonance imaging and transesophageal echocardiography.
Authors: Hirsch R , Kilner P J , Connelly M S , Redington A N , St John Sutton M G , Somerville J 
Published: June 2012

BACKGROUND
The inability to obtain complete diagnoses with transthoracic echocardiography in many adults with congenital heart disease provided the incentive to evaluate prospectively the individual and combined roles of magnetic resonance imaging (MRI) and transesophageal echocardiography (TEE) as "second-line" techniques for unresolved diagnostic problems.

METHODS AND RESULTS
Eighty-five patients were studied; 81 had MRI with a 0.5-T magnet to obtain spin-echo images, cine-MRI, and flow-velocity maps. Seventy-nine patients had TEE (37 biplane). A simple score (range, 0 to 1) was used for quantification of the results of MRI and TEE alone, for their comparison (in the 75 patients who had both), and for assessment of their combination. MRI, TEE, or their combination achieved a score of at least 0.75 in 18 of 25 diagnostic categories. A summary of the scores showed that for intracardiac anatomy. MRI scored 0.34, TEE scored 0.71 (P < .0001), and MRI plus TEE scored 0.84 (P < .003); for extracardiac anatomy, MRI scored 0.76, TEE scored 0.23 (P < .0001), and MRI plus TEE scored 0.84 (P = NS); and for hemodynamics and function, MRI scored 0.58, TEE scored 0.41 (P < .05), and MRI plus TEE scored 0.67 (P = NS). Total scores were MRI, 0.52; TEE, 0.50 (P = NS); and MRI plus TEE, 0.80 (P < .0001). MRI and TEE were inadequate for collateral and coronary arteries and pulmonary vascular resistance. Cine-MRI and flow-velocity maps comprised 43% of the MRI scores. Biplane TEE was better than single plane (scores of 0.59 versus 0.42, P < .0001).

CONCLUSIONS
MRI and TEE are important and complementary "second-line" investigations for congenital heart disease. Analysis of their performance in a wide range of diagnostic categories provides guidelines for their judicious application. Where both are available, diagnostic catheterizations are either obviated or simplified.
Plasma thromboxane B2 concentration in pulmonary hypertension associated with congenital heart disease.
Authors: Fuse S , Kamiya T 
Published: June 2012

BACKGROUND
We investigated the plasma concentration of thromboxane B2 (TXB2), a stable metabolite of thromboxane A2 (TXA2), to assess platelet activation in 78 patients who had pulmonary hypertension associated with congenital heart disease (PH group) and 16 patients with almost normal hemodynamics (control group).

METHODS AND RESULTS
The PH group was divided into two subgroups: pulmonary vascular resistance (Rp) < or = 10 U/m2 (Rp < or = 10 group) and > 10 U/m2 (Rp > 10 group). In addition, the Rp < or = 10 group was divided on the basis of clinical symptoms into groups with dyspnea (dyspnea[+] group) and without dyspnea (dyspnea[-] group). Plasma TXB2 levels were measured by radioimmunoassay. Plasma TXB2 levels in the three groups (control, Rp < or = 10, and Rp > 10) were significantly different (P < .005); the TXB2 levels in the Rp < or = 10 group were significantly higher than the others. Among the Rp < or = 10 patients, the plasma TXB2 levels were significantly higher in the dyspnea(+) group than in the dyspnea(-) group (P < .0001). In addition, the pulmonary-to-systemic flow ratio and pulmonary blood flow divided by body surface area were significantly higher in the dyspnea(+) group than in the dyspnea(-) group (P < .02 and P < .002, respectively).

CONCLUSIONS
These findings suggest that platelet activation led to increased TXA2 release in patients with pulmonary hypertension, especially those with dyspnea and Rp < or = 10. TXA2 release from platelets probably caused constriction of the pulmonary arterioles and the bronchi, thus worsening pulmonary hypertension and dyspnea in these patients. In the patients with high Rp values, it was considered that the number of pulmonary arterioles where platelets could be activated had been reduced.
Anterior septal coronary artery infarction in the canine: a model of ventricular tachycardia with a subendocardial origin. Ablation and activation sequence mapping.
Authors: Tweddell J S , Rokkas C K , Harada A , Pirolo J S , Branham B H , Schuessler R B , Boineau J P , Cox J L 
Published: June 2012

BACKGROUND
In humans, chronic ventricular tachycardia (VT) is usually associated with myocardial infarcts that involve the interventricular septum. In an effort to more closely mimic the anatomic substrate that gives rise to chronic VT in humans, we developed a canine model of VT in which the anterior septal coronary artery was ligated. The site of earliest activation, the subsequent activation sequence, and the mechanism of VT associated with the resultant ventricular septal infarct was then evaluated to determine if this model accurately reflected the characteristics of human VT.

METHODS AND RESULTS
Seventeen dogs underwent occlusion-reperfusion ventricular septal infarcts. Four to 7 days later, electrophysiological studies were performed. VT was initiated by programmed electrical stimulation and terminated by pacing at a cycle length of 50% to 75% of the VT cycle length. Electrophysiological studies were performed using a 256-channel mapping system. A total of 15 VT morphologies were mapped in 9 animals. Fourteen of 15 morphologies had septal subendocardial sites of earliest activation and 1 had a septal midwall site of earliest activation. VT ablation was performed using a nitrous oxide cryoprobe and confirmed the site of earliest activation by subsequently rendering VT noninducible. Electrophysiological studies demonstrated four distinct VT activation sequences: (1) circular reentrant (n = 7), (2) concentric spread (n = 5), (3) figure-of-eight (n = 2), and (4) septal midwall (n = 1).

CONCLUSIONS
This canine model of ventricular septal infarction produces VTs with sites of earliest activation and activation sequences similar to those in humans. A reentrant mechanism as the basis of these arrhythmias is supported by the following observations: (1) all VT was initiated and terminated with programmed electrical stimulation; (2) VT activation sequences were consistent with reentry; and (3) precise interruption of the sequence terminated the VT and rendered it noninducible.
Pathophysiological Changes in the Lungs During Extracorporeal Circulation
Authors: Cartwright Robert S. , Lim Thomas P. K. , Luft Ulrich C. , Palich William E. 
Published: June 2012

An attempt has been made to determine the optimal method of managing the lungs during cardiopulmonary bypass. The chemical behavior (oxygen saturation, acid-base balance) of the pulmonary venous blood indicates (a) that static inflation of the lungs with either a gas mixture of high oxygen content or ambient air is sufficient to maintain a proper internal milieu for the pulmonary vasculature when the bronchial collateral flow is the sole pulmonary perfusate, and (b) that in adult human beings artificial respiration up to 2 L./min. is necessary when the pulmonary perfusate consists of the coronary venous blood in addition to the bronchial collateral flow.
The effective application of the heart-lung bypass procedure in physiological investigation is depicted by the studies on metabolic rate of the lung tissues and the measurement of bronchial flow. It is estimated that the bronchial collateral flow amounts to 8.8 ml./ min. or 0.7 per cent of the total systemic flow, and that the oxygen consumption of the lungs averages 1.6 ml./min. or 1 to 2 per cent of the total metabolic rate in the open-chest dogs. The pulmonary compliance did not change following either passive deflation or static inflation, but is transiently reduced after artificial respiration.
Hemodynamic Alterations Caused by Passive Changes in Body Position in Dogs with Chronic Atrial Septal Defects
Authors: de S. Amorim Dalmo , W. Marshall Hiram , Wolford John L. , Wood Earl H. 
Published: June 2012

The effects of passive tilting on the circulatory pressures and on the magnitude of shunts across chronic atrial septal defects were studied in 11 dogs with closed chests. These determinations were performed with the dogs in four positions: 45-degree head-up, 45-degree head-down, right lateral decubitus, and left lateral decubitus. Control values were obtained with the animals in the supine horizontal position.
The 45-degree head-up tilt position was associated with an increase in the magnitude of the right-to-left shunt detected after injections of indicator into the inferior vena cava, while change from supine to the 45-degree head-down tilt resulted in a decrease or disappearance of a pre-existing right-to-left shunt detected after similar injections. These effects on the right-to-left shunt were not demonstrable after injections of indicator into the superior vena cava, either during the head-up or head-down tilt, in spite of identical alterations in circulatory pressures. A significant interanimal correlation between the magnitude of the changes in systemic or right atrial pressures and the magnitude of the changes in right-to-left shunts could not be demonstrated. Passive changes in posture from supine to 45-degree head-up or head-down positions were not associated with demonstrable systematic effects on the magnitude of the left-to-right shunts. It is postulated that the descent of the heart and diaphragm during the head-up tilt results in a closer anatomical relation between the ostium of the inferior vena cava and the defect in the atrial septum and consequently an increase in the preferential shunting of inferior caval blood through this defect. In these animals, changing the body position from the supine to the right lateral decubitus position was consistently associated with an increase in the magnitude of the left-to-right shunts across the atrial septal defect and an increase in pulmonary blood flow. Since these animals have preferential shunting of blood from the right lung in the left-to-right direction, it is believed that the increase in blood flow through the dependent right lung is responsible for the observed increase in the left-to-right shunt. The left lateral decubitus position was not associated with appreciable effects on pulmonary blood flow or left-to-right shunting of blood across the atrial septal defect.
Effectiveness of 1-Dimethylaminoethyl-4-benzylpiperidine (IN379) in Prevention and Regression of Experimental Atherosclerosis in the Rabbit
Authors: O'Dell Thomas B. , Napoli Martha D. , Miller Lowell D. , Cavallito Chester J. 
Published: June 2012

The compound, 1-dimethylaminoethyl-4-benzylpiperidine (IN379) has been shown to possess antiatherogenic properties based on the results obtained from experimental studies in rabbits. Two methods were employed to induce the experimental atherosclerosis. One was a short-term procedure involving the use of large doses of epinephrine and thyroxine, while the other procedure consisted of feeding the animals a high cholesterol diet over a more prolonged period of time. The effectiveness of the compound both as a prophylactic measure and on the regression of the atherosclerosis has been determined using the two methods. The influence of IN379 was found to be consistently favorable, although its effect was most marked in the prophylactic experiments.
The antiatherogenic properties of this compound are not related to influences on blood cholesterol content, in fact, hypercholesterolemia is not depressed by the drug. Attempts are made to correlate the antiatherogenic activity with other findings and pertinent observations are discussed.
Cancellation of Electrocardiographic Effects During Ventricular Excitation
Authors: Abildskov J. A. , Klein Robert M. 
Published: June 2012

Theoretical and experimental estimates of the amount of cancellation of electrocardiographic effects of ventricular excitation have been carried out. The theoretical estimate was based on the excitation sequence reported by Scher and consisted of comparing the total length of excitation fronts at several moments in the activation process with a measurement of the uncanceled portions of these fronts.
Experimental estimates in 10 dogs were based on the relative areas of spatial magnitude curves during normal ventricular excitation and during stimulation of the ventricular site yielding the largest magnitude curve area. A theoretical estimate of the cancellation to be expected during ventricular stimulation was also carried out. The theoretical estimate of cancellation of electrocardiographic effects during normal ventricular activation was 71 per cent, while the experimental estimates varied from 51 per cent to 80 per cent, with an average of 66 per cent.
Electric Shock Hazards in Cardiac Catheterization
Authors: Weinberg Daniel I. , Artley John L. , Whalen Robert E. , McIntosh Henry D. 
Published: June 2012

1. These studies demonstrate that ventricular fibrillation can be produced in anesthetized, mechanically ventilated dogs by a current as low as 35 microamperes and a voltage as low as 0.06 volt.
2. Analysis of circuits of medical electronic equipment which is usually considered safe indicates that such low current levels may exist in the heart during catheterization.
3. The safety procedures established for our laboratory to minimize the hazard of electric shock are presented.
Effect of Stimulation of Hypothalamus and Reticular Activating System on Production of Cardiac Arrhythmia
Authors: ATTAR HOUSHANG J. , GUTIERREZ MARIO T. , BELLET SAMUEL , RAVENS J. R. 
Published: June 2012

Changes in blood pressure and the electrocardiogram were studied before and after the stimulation of the hypothalamus (anterior, lateral, and posterior) and the reticular formation of the pons in anesthetized cats.
The stimulation of the anterior hypothalamus produced a rise of blood pressure and usually bradycardia; tachycardia was rarely observed. Arrhythmias were not observed, and the electrocardiographic changes consisted only of slight ST elevation and deepening of the T waves. Stimulation of the lateral hypothalamus produced a rise in blood pressure of a lesser magnitude than that of the anterior hypothalamus but was associated with a transitory phase of A-V dissociation and frequent premature systoles. Stimulation of the posterolateral hypothalamus resulted in the same rise in blood pressure as that of stimulation of the lateral hypothalamus and was accompanied by nodal rhythms, aberrant ventricular conduction, and fusion beats. Stimulation of the reticular formation produced a rise in blood pressure similar to stimulation of the lateral and posterolateral hypothalamus and was associated with slight tachycardia, widening of the QRS complexes, transitory A-V dissociation with nodal escapes and ectopic beats of ventricular origin, and fusion beats.
These findings suggest that: (1) the hypothalamus serves as a pathway for cardiac neurovegetative stimuli, probably via the reticular formation, producing predominantly sinus node depression; (2) the posterolateral hypothalamus and reticular formation have similar functions in the production of cardiac arrhythmia.
Hypertension and Increased Hindlimb Vascular Reactivity in Experimental Coarctation of the Aorta
Authors: NOLLA-PANADES JUAN 
Published: June 2012

Experimental coarctation of the aorta has been produced in rats. Animals with the clip above both renal arteries have been compared with animals with the clip below both renal arteries and with dummy operated rats. The fore- and hindlimb blood pressures, heart weights and perfusion pressure, and norepinephrine responses of the isolated perfused hindquarters have been measured.
Only the animals with a clip above the renal arteries developed hypertension and hypertrophy of the heart. The increase in blood pressure was progressive, requiring about 10 days to reach hypertensive levels. Such animals showed an increase in the norepinephrine responses and in the perfusion pressure of hindlimb blood vessels when compared with either of the other two groups. The differences are statistically significant. In rats with clips above the renal arteries, there is a highly significant regression line of hindlimb norepinephrine responses on hindlimb perfusion pressure and of either of these values on heart weight.
It is considered: (a) that the hypertension in experimental coarctation of the aorta is not purely mechanical and the kidneys are essential for the development of this type of hypertension; and (b) that the increase in the norepinephrine responses and in the perfusion pressure found in the hindquarter vascular bed of rats with coarctation of the aorta above the renal arteries is not secondary to the hypertension as such, but in some way is related to the mechanism that produces the hypertension in experimental coarctation of the aorta.
Effects of Isoproterenol on Carbohydrate Metabolism of Isolated Canine Heart
Authors: WINTERSCHEID LOREN C. , BRUCE ROBERT A. , BLUMBERG JACK B. , MERENDINO K. ALVIN 
Published: June 2012

Chronotropic and inotropic effects of intraarterial infusion of isoproterenol were monitored in the isolated, metabolically supported preparations of the canine heart.
The time-dosage relationship was found to be hyperbolic over a narrow range of concentration of isoproterenol. Increasing concentration beyond the optimal range by a factor of about two produced arrhythmias and A-V conduction defects.
Oxidative metabolism increased significantly and proportionally to heart rate.
Since utilization of glucose remained the same, pyruvate utilization increased slightly and lactate was excreted; the augmented oxidative metabolism could not be accounted for by the observed changes in carbohydrate substrates.
Myocardial glycogen concentrations were insignificantly changed during this inotropic stimulation.
Murmurs Arising from Ductus Arteriosus in Normal Newborn Swine
Authors: EVANS J. R. , ROWE R. D. , DOWNIE H. G. , ROWSELL H. C. 
Published: June 2012

The natural history of murmurs arising from the ductus arteriosus was investigated in normal newborn swine and compared with observations in other animals and infants at term. Ausenltation of 206 swine examined between birth and two weeks of age revealed a high incidence of continuous murmurs in the first six hours of life, crescendo systolic murmurs in 5% to 10% of animals during the first 24 hours and early systolic murmurs in a large proportion of the animals throughout the first week. Absence of a murmur was rare one to two hours after birth but, by 24 hours, less than 50% of the swine had murmurs of any type and after one week only one of 34 animals studied had a murmur. The continuous murmur was often preceded or followed by a crescendo systolic or early systolic murmur and it is proposed that all three murmurs arise from the ductus arteriosus under different conditions.
Internal sound recordings with a phonocatheter in the thoracic aorta demonstrated a systolic murmur loudest at the orifice of the ductus arteriosus in all swine in the first six hours of life and in a decreasing proportion of animals thereafter. Evidence is presented to suggest that this murmur is closely linked to patency of the ductus arteriosus but is different in origin from the murmur normally heard on auscultation of the chest. In four animals under six hours of age the phonocatheter passed through the ductus into the pulmonary artery and a continuous murmur was recorded. In two older swine the phono-catheter traversed the ductus but in these cases the murmur in the main pulmonary artery was confined to systole.
Since the occurrence of the different murmurs could not be satisfatorily explained on the basis of the systolic pressure gradient across the ductus nor on the basis of the anatomical size of the ductus at necropsy, it is postulated that the type of murmur generated is a reflection of the degree of narrowing of the lumen of the ductus produced by active constriction of its muscular wall during life.
Relationships Between the Release and Tissue Depletion of Norepinephrine from the Heart by Guanethidine and Reserpine
Authors: HARRISON DONALD C. , CHIDSEY CHARLES A. , GOLDMAN ROBERT , BRAUNWALD EUGENE 
Published: June 2012

The release of norepinephrine from the heart of anesthetized open-chest dogs has been determined both after the intravenous administration of guanethidine (15 mg/kg) and after reserpine (3 mg/kg) by measuring the plasma norepinephrine concentration with the fluorometric method (THI) in bloods obtained simultaneously from the coronary sinus and femoral artery. In four dogs following the administration of guanethidine, norepinephrine release into the coronary sinus blood occurred and persisted for two to three hours. This release of norepinephrine was accompanied by and adrenergic response of similar duration. The norepinephrine content of atrial appendage was reduced by 24% of control at four hours in these dogs and to extremely low levels in three other dogs 24 hours after guanethidine administration. Thus, the reduction of the tissue content of norepinephrine continued after measurable release of norepinephrine into the coronary sinus blood had ceased.
In four dogs following reserpine administration the adrenergic response was consistently smaller, and detectable release of norepinephrine into the coronary sinus blood was found transiently only in one dog. However, the norepinephrine content of atrial appendage was reduced by an average of 65% of control values at four hours. These findings suggest a difference in the mechanism of norepinephrine depletion in the period immediately after administration of guanethidine and reserpine.
Extracorporeal Circulation: A Device for the Quantitative Study of Thrombus Formation in Flowing Blood
Authors: DOWNIE H. G. , MURPHY E. A. , ROWSELL H. C. , MUSTARD J. F. 
Published: June 2012

A standardized extracorporeal shunt system has been described. It allows examination of the sequence of events in thrombus formation and it provides a means of quantitating it in flowing blood. It further allows assessment to be made of the usefulness of classical in vitro clotting tests in thrombogenesis. The platelet adhesive index and clotting time in silicone showed the best correlation with the amount of thrombus formed.
Pig serum presumably rich in serum thrombotic accelerator (STA) has been shown to enhance thrombus formation from flowing blood.
Within the limits of these experiments, the rate of blood flow has been found to be of little importance.
Vasoactive Peptides and Substrates and Their Relation to Protein Handling by the Kidney
Authors: M.D. RAMON B. 
Published: June 2012

The properties of anephrotensin, a polypeptide liberated by acid incubation of serum, are reviewed. Experiments with antirenin rule out the possibility that renin is the enzyme that liberates anephrotensin.
Serum anephrotensinogen increases after bilateral nephrectomy or after several weeks of treatment with desoxycorticosterone (DCA). There are perallel changes under these conditions in the amounts of anephrotensinogen and angiotensinogen in the serum, suggesting that a common substrate may be involved. The increase in substrate is in accord with the possibility that DCA treatment results in some deficiency in the handling of proteins by the kidney.
There is an increase in urine vasoactive peptides and total proteins in DCA-treated rats. These increases are probably related to deficiency in tubular reabsorption. The increase in the albumin/globulin ratio of the urine proteins under these circumstances supports this idea.
The changes described above are not necessarily related to the onset of hypertension. Whether the changes in protein handling by the kidney are related to the hypertension produced by DCA treatment is an unsettled question.