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Query: UMLS:C0038454 (stroke)
 147,016 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In a group of seven patients who had had cardiac operations, intravenous (IV) hydralazine was used to provide afterload reduction in situations of severe left ventricular dysfunction. Despite fluid loading, inotropic support with dopamine, and afterload reduction with sodium nitroprusside, the patients had persistent states of low cardiac output and high systemic vascular resistance. Administration of sodium nitroprusside was limited by its effect on preload and blood pressure, so that it necessitated frequent fluid challenges. The addition of IV hydralazine to this regimen caused a mean increase of 44.7% in the stroke index and a mean reduction of 28.6% in systemic vascular resistance without significant change in pulmonary artery wedge pressure, mean arterial pressure, or heart rate. Rapid weaning of sodium nitroprusside and, on occasion, dopamine was facilitated. Frequent fluid challenges to restore preload were unnecessary. Dose requirements of hydralazine were small: 2.5 to 5.0 mg IV initially, and then a maintenance dose of 2.5 to 7.5 mg IV every 4 to 6 hours. These preliminary clinical observations indicate that in patients with low cardiac output--high resistance states and normal or elevated preload, the important benefit of specific afterload reduction may be provided by parenteral hydrolazine in the early period following cardiac surgery. Prospective, controlled studies with this agent in this situation appear warranted.
J Thorac Cardiovasc Surg 1979 Aug
PMID:Specific afterload reduction with parenteral hydralazine following cardiac surgery. 45 26

Short periods of ischemic arrest may cause myocardial cell damage so that reperfusion does not result in an immediate return to normal metabolic and contractile activity. Studies have been carried out using a rat heart model of cardiopulmonary bypass and ischemic cardiac arrest in order to determine whether the use of inotropic agents (isoprenaline and dobutamine) to augment contractile activity during the early phase of post-ischemic reperfusion extends pre-existing damage and results in ultimate impairment of contractile activity. The results indicated the existance of a substantial metabolic reserve, capable of providing sufficient energy for a marked increase in dP/dt and heart rate, without inducing tissue damage. However, in this isolated rat heart preparation the use of these agents had relatively little effect upon cardiac output and could be shown to induce a dose-dependent reduction in stroke volume.
Thorac Cardiovasc Surg 1979 Jun
PMID:Inotropic agents and functional recovery from ischemic cardiac arrest. 46 63

Maximal changes in haemodynamics and segmental wall motion were seen 2 min after coronary occlusion and were examined in relation to the loading conditions of the left ventricle before occlusion in 20 open chest dogs. There was a significant inverse relationship between the preligation mean aortic pressure and the percentage decrease in stroke volume following ligation. This relationship was observed whether afterload was distributed randomly (mean aortic pressure ranging from 9.7 to 17.6 kPa [73 to 132 mmHg]) between all dogs (r = 0.65; P less than 0.001) or altered by methoxamine (+4 kPa [+30 mmHg]) and nitroprusside (-3.2 kPa [-24 mmHg]) within the same dog (r = 0.82; P less than 0.001; n = 8). Although occlusion of the anterior descending artery caused a small (+5.5%) but significant increase in end-diastolic length of the non-ischaemic epicardial segment, the capacity for compensatory ventricular dilatation was not dependent on preligation afterload. However, the capacity of the ischaemic segment to undergo systolic expansion was significantly greater (+30.2% of end-systolic segment length) in those dogs with the lowest preligation MAP (8 to 12 kPa [60 to 90 mmHg]) compared with systolic lengthening of only 15.8% in the high afterload group (15 to 18 kPa [112 to 135 mmHg]). These data indicate that the loading conditions of the left ventricle predetermine the extent of global and segmental left ventricular dysfunction during the early phase of acute ischaemic injury.
Cardiovasc Res 1979 Mar
PMID:Afterload as a predeterminant of haemodynamics and segmental wall motion following coronary artery occlusion. 47 39

The effects of protamine on left ventricular (LV) function were measured under conditions of controlled heart rate and proximal aortic pressure in eight anaesthetized, heparinised dogs. Protamine 3 mg.kg-1 produced a 21% decrease in LV dP/dt max, a 43% decrease in cardiac output, a 47% decrease in stroke work and decreases in systolic and diastolic pressures (-16%, -19% respectively). Protamine 6 mg.kg-1 resulted in a 17% decrease in LV dP/dt max, a 26% decrease in cardiac output, a 50% decrease in LV stroke work and 25 and 30% decreases in systolic and diastolic pressures. These results show that an impairment of LV function plays an important part in the circulatory depression produced by protamine.
Cardiovasc Res 1979 May
PMID:Effects of heparin and protamine on left ventricular performance in the dog. 47 45

Ventricular function curves relating stroke work and left ventricular end-diastolic pressure were generated in awake dogs during increases in preload produced by infusion of fluid and during increases in afterload produced by administration of phenylephrine. The ventricular function curves produced by preloading were steeply upsloping whereas those produced by afterloading were essentially horizontal. Coronary occlusion produced downward displacement of these horizontal curves, but no change in slope. This increases in afterload did not help to demonstrate the functional impairment produced by coronary occlusion.
Cardiovasc Res 1979 Jul
PMID:Effect of increases in afterload before and after coronary occlusion in awake dogs. 48 80

After severe ischemic injury, it is usually necessary to prolong bypass to enhance recovery. This study tests the hypothesis that the best reversal of ischemic damage is achieved by briefly rearresting the postischemic heart with a continuous infusion of an oxygenated cardioplegic solution (secondary blood cardioplegia) during the period when bypass must be prolonged. Twenty dogs underwent 45 minutes of normothermic ischemic arrest. Fifteen minutes after unclamping, no heart could support the systemic circulation. In all dogs, oxygen demands were lowered by extending bypass for 30 minutes. In 10 of these dogs, demands were further lowered by rearresting the heart for 5 minutes with a continuous infusion of a 37 degrees C blood cardioplegic solution (K+28 mEq/L; pH 7.6; Ca++ 1 mEq/L) at a pressure of 50 mm Hg. Hearts treated with secondary blood cardioplegia showed greater recovery in the rate of contraction (-dP/dt 75% versus 62%, p less than 0.05) and relaxation (-dP/dt 76% versus 58%, p less than 0.05), better recovery of compliance (85% versus 51%, p less than 0.05), a higher stroke work index (0.72 versus 0.50 gm-m/Kg, p less than 0.05), and more ability to augment oxygen uptake (85% versus 45%, p less than 0.05) to meet the demands of the working heart than hearts treated by prolonging bypass alone. We conclude that rearresting the heart with a brief, continuous infusion of a blood cardioplegic solution results in more complete reversal of ischemic damage than possible by prolongation of a bypass alone. We believe that the increased recovery with secondary cardioplegia results from diversion of delivered oxygen toward reparative processes rather than its being expended needlessly on electromechanical work during the time when bypass must be prolonged.
J Thorac Cardiovasc Surg 1979 Nov
PMID:Reversal of ischemic damage with secondary blood cardioplegia. 49 22

Myocardial performance was evaluated intraoperatively in 20 patients undergoing myocardial revascularization when hypothermic potassium cardioplegic arrest was used. High concentrations of potassium (20 mEq/L) were compared to normal concentrations of potassium (5 mEq/L) in hypothermic cardioplegic solutions. The cardioplegic arrest period averaged 53 +/- 3 minutes in the high potassium group and 54 +/- 4 minutes in the low potassium group, Intraoperative calculation of ejection fraction and end-diastolic volume was accomplished by the technique of radiocardiography. All data were grouped according to end-diastolic volume index (EDVI) for both high (HK) and low (LK) potassium comparisons. Comparisons between high and low potassium groups demonstrated no significant differences in ejection fraction (HK = 66%, LK = 61%), cardiac index (HK = 2.74 L/min/m2, LK = 3.0 L/min/m2), stroke work (HK = 36 gm.m/m2, LK = 30 gm.m/m2), oxygen consumption as measured by left heart double product (HK = 9,438; LK = 9,209), and myocardial compliance (HK = 2.8 cc/torr, LK = 4.2 cc/torr at the post-cardioplegic arrest period). The role potassium plays in producing a rapid cardiac arrest is well accepted. Its protective effect on the preservation of high-energy phosphate stores is postulated, but its addition to perfusion hypothermia does not appear to enhance the protective effect observed with perfusion hypothermia alone.
J Thorac Cardiovasc Surg 1979 Nov
PMID:Protection of myocardial function not enhanced by high concentrations of potassium during cardioplegic arrest. 49 23

Noninvasive radionuclide angiocardiography (RNA) provides simple and accurate assessment of parameters of cardiac function during rest and during maximal exercise. Left ventricular function was assessed by RNA in nine patients with isolated mitral stenosis before and approximately 6 months after mitral commissurotomy. Before operation, the mean mitral valve gradient was 14.0 +/- 2.8 mm Hg, and the mean mitral valve area was 1.20 +/- 0.3 cm2. Each patient was evaluated at rest and during maximal exercise on an isokinetic bicycle ergometer before and after commissurotomy. Heart rate, ejection fraction, end-diastolic volume, stroke volume, pulmonary transit time, cardiac output, and diastolic ventricular filling rate were determined by the radionuclide technique. Before operation, patients with mitral stenosis had characteristic changes from rest to exercise which supported restriction to diastolic ventricular filling as the primary limitation in generating a cardiac output during exercise. The stroke volume was unchanged from rest to exercise. Thus the cardiac output during exercise was heart rate dependent. However, after commissurotomy the stroke volume increased from rest to exercise. Therefore, cardiac output during exercise was achieved by heart rate and an augmented stroke volume. Moreover, the pulmonary transit time was reduced during rest and exercise after operation. The maximum ventricular ejection and filling rates were markedly increased during rest and exercise after commissurotomy. These differences in hemodynamic parameters at rest and during exercise document the mechanics of increased exercise tolerance in patients with mitral stenosis after mitral commissurotomy.
J Thorac Cardiovasc Surg 1979 Nov
PMID:Noninvasive assessment of hemodynamic effects of mitral valve commissurotomy during rest and exercise in patients with mitral stenosis. 49 29

Although dopamine is a useful therapeutic agent to augment cardiac function in adults, there is little information about the hemodynamic effects of dopamine in children. To delineate the hemodynamic effects of dopamine in children, we infused two doses of dopamine (2 and 7.75 micrograms/kg/min) into 10 children during diagnostic cardiac catheterization. We measured heart rate, systemic arterial, pulmonary arterial, right atrial, and pulmonary capillary blood pressure, and cardiac output. During infusion of 7.75 micrograms/kg/min of dopamine, cardiac index increased from 3.9 to 5.4 L/min/m2, stroke volume increased from 43 to 57 ml/stroke and systemic vascular resistance declined from 1,697 to 1,165 dynes-cm-5-sec-m2. These indices also were changed significantly from control during infusion of 2 micrograms/kg/min of dopamine. The ratio of mean pulmonary arterial blood pressure to mean systemic arterial blood pressure in one patient with pulmonary vascular obstructive disease increased from 0.73 to 1.15, and ventricular bigeminy occurred during infusion of 7.75 micrograms/kg/min of dopamine. Dopamine is a potentially useful inotropic agent in children, but the use of dopamine may be contraindicated in patients with elevated and fixed vascular resistance.
J Thorac Cardiovasc Surg 1979 Nov
PMID:The hemodynamic effect of dopamine in children. 49 32

Two experimental models were studied to determine the hemodynamic consequences of atrial volume reduction as observed after operative correction of transposition of the great arteries. The volume of the left atrium (LA) was reduced either by inflation of an intracavitary balloon (group A) or by surgical intervention (group B) to 50--60% of the control values as determined by angiography. The angiographic data correlated well with the true volumes obtained by water displacement. This major reduction of LA volume caused small but constant hemodynamic changes. Although the LA stroke volume decreased by 50% and the LA/LV volume relation was reduced by 50% (from 0.42 to 0.21), there was only a slight increase of pulmonary artery pressure (7% in group A and 14% in group B) and a slight decrease in cardiac index (13% in group A and 10% in group B) and in left ventricular end-diastolic pressure (9% in group A and 11% in group B). The reduction of atrial volume results in only minor functional alteration of the intact heart.
Thorac Cardiovasc Surg 1979 Aug
PMID:Hemodynamic changes after experimental reduction of the left atrium. 49 23


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