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Query: UMLS:C0151744 (myocardial ischemia)
 31,282 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We determined the mechanical and metabolic effects of graded myocardial ischemia in 23 open-chest, anesthetized pigs. By connecting the midportion of the left anterior descending artery (LAD) to the carotid artery via a constant volume, calibrated pump, we reduced the flow in the LAD to 0, 25, 50, and 75% of control rates for periods of 1 h. Flows of 100% and 150% were also examined. Using pairs of ultrasonic crystals to measure segment dimensions, we calculated segment shortening and thickening, and total and systolic stroke work in the ischemic and normally perfused segments. Blood gases, pH, and lactate and inosine balances were determined from the regional coronary venous blood. At coronary blood flows of 0, 25, 50, and 75% of normal resting flow, total segment work was 8 +/- 8, 25 +/- 4, 51 +/- 5, and 80 +/- 6% of control, respectively, while systolic segment work was -2 +/- 5, -10 +/- 5, 40 +/- 5, and 86 +/- 7% of control, respectively (means +/- SE). Thus, the decrease in total segment stroke work is proportional to the decrease in flow over the range 0-100%. However, no useful work (i.e., systolic work) is done until flow exceeds 25%. Segment shortening and thickening are significantly depressed with flows diminished by only 25%. Segmental inosine production correlates with lactate production and parallels decreased mechanical performance.
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PMID:Segment stroke work and metabolism depend on coronary blood flow in the pig. 64 26

Dobutamine was administered by intravenous infusion to 10 patients with ischaemic heart disease who had a low cardiac output syndrome following abdominal surgery. The dosage of dobutamine started from 2.5 mcg kg-1 min-1 and was increased stepwise to 5, 7.5, 10, 12.5 and 15 mcg kg-1 min-1. Cardiac index increased significantly from 2.05 +/- 0.32 to 3.03 +/- 0.61. min-1 min-2 with 15 mcg kg-1 min-1. Heart rate was unchanged with 7.5 mcg kg-1 min-1 but increased significantly from 97.7 +/- 18.5 to 126.1 +/- 21.5 beats. min-1 with 15 mcg kg-1. min-1. Stroke index increased significantly from 21 +/- 4.4 to 25.4 +/- 5.1 ml m-2. beat-1 with 7.5 mcg kg-1 min-1. Pulmonary wedge pressure fell significantly from 14 +/- 2.9 to 9.1 +/- 2.4 mmHg with 2.5 mcg kg-1 min-1. Mean arterial pressure showed no significant change. No side effects were observed in these patients. We conclude that in patients with depressed cardiac function dobutamine at low doses of 2.5 mcg kg-1 min-1 decreases afterload and filling pressures. At the average doses of 5 - 7.5 mcg kg-1 min-1 stroke index and cardiac index are increased. At higher doses of 10 - 15 mcg kg-1 min-1 heart rate and cardiac index increase while stroke index fails to increase further.
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PMID:Dobutamine in the treatment of depressed cardiac function: a study in patients with ischaemic heart disease during the early post-operative period. 64 37

We evaluated the effects of methylprednisolone sodium succinate (MPSS) on 60 minutes of myocardial ischemia during profound (5 degrees C) topical cardiac hypothermia (ice chips) in a canine right heart bypass preparation. The ventricular function curve shifted to the right and downward, but not significantly, after ischemia, and stroke work declined significantly for both control and treated dogs. Contractility (rate of rise of left ventricular pressure and maximum velocity of the contractile element) declined for both groups but not significantly. Total coronary flow, oxygen consumption, and metabolism of lactate and pyruvate were not different for control and treated dogs. Ultrastructure of the outer and inner myocardium did not demonstrate benefit from MPSS. Intracellular and extracellular edema of moderate severity was slightly worse in the subendocardium, and reversible mitochondrial injury of a mild to moderate degreee was symmetrically present. Ice-related injury was not noted. We were unable to deomonstrate that pretreatment with MPSS favorably alters cardiodynamics or ultrastructure after 60 minutes of profound topical cardiac hypothermia.
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PMID:Topical cardiac hypothermia: the effect of methylprednisolone sodium succinate. 65 47

The changes in left ventricular (LV) dynamics induced by brief periods of ischemia (100 seconds) and subsequent reperfusion were analyzed in conscious dogs. Global LV ischemia, induced by partially occluding the left main coronary artery, reduced LV flow homogeneously and impaired LV function as reflected by decreases in LV stroke "work" (89 +/- 4% M +/- SE), systolic shortening (72 +/- 4%), velocity of shortening (56 +/- 6%), LV systolic pressure (34 +/- 5%), and dP/dt (59 +/- 6%). Regional LV ischemia, induced by occluding either the left circumflex or anterior descending coronary artery completely, reduced flow to the ischemic segment (82 +/- 3%) while decreasing segment work (96 +/- 5%), shortening (82 +/- 3%), and velocity of shortening (70 +/- 5%), with minimal depression of overall LV function. In both groups the extent of shortening was reduced more rapidly and greater (P less than 0.01) than shortening velocity. Moreover, with localized ischemia, segment work was reduced more (P less than 0.01) than shortening. With reperfusion, a transient overshoot in function above preischemic control levels was observed in both groups (global work increased by 60 +/- 12% and regional work by 28 +/- 4% above control). This overshoot was not dependent on adrenergic mechanisms, but was prevented by inhibiting reactive hyperemia. Thus myocardial ischemia induces a dissociation between extent and rate of myocardial shortening. A further dissociation between shortening and work is apparent with regional ischemia. After reperfusion there is a transient overshoot in function which appears to be dependent upon the associated reactive hyperemia.
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PMID:Initial myocardial adjustments to brief periods of ischemia and reperfusion in the conscious dog. 65 61

To evaluate the influence of glucose infusate administered with insulin and potassium on left ventricular function during 4 h of ischemia, as well as mechanism of action, four groups of intact anesthetized dogs were studied. Acute regional ischemia was induced with a balloon tip catheter in the left anterior descending artery and infusates were begun after 20 min of ischemia. A threefold increase of plasma glucose concentration was associated with improved left ventricular function during ischemia, compared to animals receiving isovolumic saline. There was a significant decline of left ventricular end-diastolic pressure associated with elevation of stroke volume and ejection fraction to control levels, as determined by indicator dilution. In a separate subgroup studied by cineangiography, shortening of the ischemic anterior wall, after an initial decline, was increased in response to glucose but there was no evidence of extension of injury. Ischemic tissue exhibited a smaller gain of water as well as Na+ per gram dry weight as compared to ischemic controls. On precordial electrocardiogram mapping there was a significant decrease in the sigmaST (sum of ST elevation) as well as NST (number of ST segment elevations), but the reduction of R wave amplitude was not different from controls. To further evaluate long-term effects, eight controls and six treated animals underwent myocardial ischemia and were sacrificed after 4 mo. Calculated area and weight of scar, as well as degree of wall thinning, were similar in both groups. The glucose-treated animals had a significant decrease of plasma FFA in contrast to controls which manifested a significant rise. To examine the postulate that the decrease in FFA was important to therapeutic action, a third group was infused with Intralipid (Cutter Laboratories, Inc., Berkeley, Calif.) and heparin, simultaneously with the glucose infusate, to effect an elevation of plasma FFA during ischemia. Changes in myocardial function and electrolyte composition, as well as precordial electrocardiogram mapping, were similar to that of animals receiving glucose alone. Because serum osmolality was increased approximately 40 mosmol during the glucose infusion, the potential role of hyperosmolality was assessed by infusion of 20% mannitol during acute ischemia in a fourth group. After a transient small increase, there was a moderate decline in function by 4 h, suggesting that the response to glucose is not dependent upon extracellular osmolality. Thus, it is concluded that during the initial hours after the onset of myocardial ischemia the glucose infusate improves ventricular performance without evidence of arrhythmia induction or intensification of ischemic injury. Evolution of irreversible necrosis appears to be delayed rather than prevented under the circumstances of this study.
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PMID:Sustained effect of glucose-insulin-potassium on myocardial performance during regional ischemia. Role of free fatty acid and osmolality. 65 87

The relation between blood pressure before stroke and survival after the event, was examined in the Manitoba study cohort of 3983 men. The last recorded blood pressure before the first stroke and the change in blood pressure from a measurement 5 years earlier were used. Increasing magnitude of systolic blood pressure and its 5-year changes were associated with worsening prognosis. The same association was less apparent for diastolic blood pressure and was not found for 5-year change in diastolic pressure. After adjusting for the effect of age at stroke and previous evidence of ischemic heart disease in multivariate analysis, systolic blood pressure and its 5-year change were each significant predictors of short-term (30 days) mortality. Considering all these factors as well as diastolic blood pressure, systolic blood pressure was the best predictor of short-term mortality. Thus, high blood pressure and large positive 5-year change in systolic blood pressure before stroke occurrence are significant predictors of a poor prognosis.
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PMID:The relation of blood pressure to stroke prognosis. 66 80

Seven patients with severe chronic congestive cardiac failure secondary to ischaemic heart disease performed submaximal supine exercise before and after 5 mg sublingual isosorbide dinitrate at the time of cardiac catheterisation. Exercise before isosorbide dinitrate produced a poor response in left ventricular performance. After isosorbide dinitrate this response was significantly improved. Compared with the control exercise period, cardiac index increased from mean 2.6 to 3.1 1/min per m2 (P less than 0.0025), stroke volume index from mean 22 to 27 ml/m2 (P less than 0.0025), and left ventricular stroke work index from mean 21 to 30 g m/m2 (P less than 0.01). Mean left ventricular filling pressure fell from 37 to 26 mmHg (P less than 0.01). Although isosorbide dinitrate reduced left ventricular filling pressure at rest from mean 26 to 17 mmHg (P less than 0.005), there was no significant change in mean cardiac index or stroke volume index, while left ventricular stroke work index decreased from mean 29 to 22 g m/m2 (P less than 0.05). Isosorbide dinitrate effectively reduces left ventricular filling pressure in the resting patient with congestive cardiac failure but produces a more comprehensive improvement in left ventricular performance during exercise.
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PMID:Improvement in exercise haemodynamics by isosorbide dinitrate in patients with severe congestive cardiac failure secondary to ischaemic heart disease. 68 84

In the presence of regional myocardial ischemia, a 20% decrease in systemic arterial pressure following nitroprusside caused a 25% decrease in coronary perfusion pressure in animals with normal left ventricular end-diastolic pressures. This pressure decrement resulted in a significant decrease in the shortening of the regionally ischemic segment during the ejection phase of systole. A comparable arterial pressure drop of 21% with nitroprusside infusion during ischemia in the animals with elevated diastolic pressures caused a similar 28% decrease in coronary perfusion pressure, but resulted in a simultaneous increase in regional shortening. For the entire group there was no significant change in stroke volume. Even in the 11 animals where stroke volume increased, systolic regional shortening increased in only 4. An increase in stroke volume cannot be used to infer a parallel increase in the performance of a regionally ischemic segment. Nitroprusside appears to improve regional performance only in the presence of severe failure.
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PMID:Effects of sodium nitroprusside on function of regional ischemic myocardium. 75 85

Although hypertension is an acknowledged risk factor in ischaemic heart disease (IHD) the question remains whether antihypertensive therapy is necessarily beneficial. A priori, because coronary atherosclerosis is probably irreversible, the time for effective intervention would seem to be well before the development of clinical manifestations. The Australian National Blood Pressure Study, a long term clinical trial of the treatment of mild hypertension, is in principle better suited than previous trials to answer the question because the trial population selected (4000 subjects aged 30-69) contains substantial proportions of younger age groups (26% below 45) and of females (37%) and none had manifest IHD at entry. Sensitivity to the emergence of IHD in the trial population is increased by including as diagnostic indices angina and ischaemic ECG changes, using suitably objective methods, as well as myocardial infarction and sudden death. Thus morbidity and mortality from IHD which currently accounts for 71% of trial end points (cf 19% for stroke) will effectively determine the outcome of the trial. The occurrence of a substantial proportion of subjects withdrawn from randomised treatment will mean that the question will be answered necessarily in two ways: firstly in respect of those subjects remaining on their assigned treatments and secondly in terms of all subjects initially assigned one treatment or other irrespective of the subsequent need to change treatment on ethical grounds or of the degree of compliance.
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PMID:The Australian National Blood Pressure Study: a test of the effectiveness of antihypertensive therapy on the incidence of ischaemic heart disease. 79 27

Vasodilator therapy has been shown to improve ventricular function in patients with left ventricular failure complicating acute myocardial infarction. Sublingual nitroglycerin also improves ventricular function in these patients but its effects are transient and variable. Infusion of intravenous nitroglycerin in 12 patients with acute infarction resulted in a decrease in left ventricular filling pressure from a mean of 22 plus or minus 2 mm Hg to 12 plus or minus 1 mm Hg (P less than 0.001) associated with a 7 mm Hg decrease in mean arterial pressure (P less than 0.05). Since stroke work index did not change significantly, this represents and improvement in ventricular performance and/or an alteration in ventricular compliance. All six patients in whom serial precordial mapping studies were performed showed a decrease in sigma ST (P less than 0.001). These findings suggest that intravenous nitroglycerin improved left ventricular function and decreased the extent of myocardial ischemia. Longer infusion may act to preserve borderline ischemic myocardium and thus limit infarct size.
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PMID:Intravenous nitroglycerin in acute myocardial infarction. 80 31


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