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

The field of myocardial perfusion imaging has made many advances but still is in its infancy. The limitations in the technology at this time include limited instrument resolution of 6-9 mm, intrinsic at the energy of the mercury x-ray; significant Rayleigh scatter, which is particularly distrubing because this scatter cannot be removed by pulse-height analysis; and an effective half-life of thallium in the myocardium, which makes repeated imaging over a short period of time very difficult. Although hopes for the development of a technetium-labeled myocardial imaging tracer have burnt brightly, no new agents are presently in sight. Resolution with a technetium-labeled tracer would almost double that of thallium, and the dose that could be administered to the patient would increase by at least a factor of 4. The effective half-life of the tracer in the myocardium would permit multiple images to be obtained at least in the same day. Even with the limitations of the current techniques, however, myocardial perfusion imaging can make a real contribution to the care of the patients with heart disease. Thallium is now produced commercially and reasonably easily obtained. Extraction of thallium by the myocardium is probably somewhat, but not exactly, analogous to potassium. The tracer has major applications in defining shape and size of the heart, thickness of muscle, and especially myocardial ischemia and infarction. This review is aimed at providing a current perspective of these uses.
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PMID:Thallium-201 as a myocardial imaging agent. 31 35

Air quality correlates of chronic disease mortality in 180 census tracts of Harris County, Texas, were studied using 3 years mortality for 1969--1971. This study was designed to test with a different data base the universality of several study results which have reported significant correlations between heart disease and air pollutants. Air quality data (suspended particulates, benzene solubles, sulfur dioxide, and metals associated with particulates: copper, mercury, manganese, lead, nickel, zinc, chromium, and cadmium) were related to both sex and age adjusted crude death rates, and cause-specific death rates for age cohorts for 7 categories of heart disease, and pneumonia, asthma, cancer, tuberculosis, and accident deaths. The results of the study were in agreement with the findings of the other researchers who used national data. Suspended particulates and cadmium concentrations were found to be correlated (r=.38, .36; P less than .001) with ischemic heart disease (IHD). Many other significant correlations are reported but are not cause-specific. Socio-economic indicators were also correlated with IHD, thus confounding the issue. Further work is planned using more sophisticated statistical techniques to disentangle the relative contribution of each of these highly intercorrelated factors. No causality can be assigned at this stage, although this study, with the other cited, points to possible risk factors for IHD which need further evaluation.
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PMID:Air quality correlates of chronic disease mortality: Harris County, Texas 1969--1971. 72 89

The effect of ortho-iodo sodium benzoate (OISB) on the oxyhemoglobin dissociation curve of coronary venous blood was studied in an isolated canine heart preparation perfused at a constant coronary blood flow. Changes in P-50 (millimeters of mercury) [the oxygen tension (pO2) at which hemoglobin is 50% saturated], were used to express hemoglobin-oxygen affinity. Intracoronary infusion of OISB (200, 400 and 800 mg/min) produced a dose-related increase in coronary venous P-50 and a concurrent increase in coronary venous pO2. In addition, OISB produced a significant decrease in heart rate and increase in coronary artery perfusion pressure. During cardiac pacing at 150, 190 and 230 beats/min, OISB (400 mg/min) significantly increased coronary venous P-50, myocardial oxygen exrraction (O2E) and oxygen consumption (MVO2) whereas coronary venous PO2 was not changed. Furthermore, a 5-minute intracoronary infusion of OISB (200 mg/min) during myocardial ischemia produced an increase in O2E, MVO2 and myocardial contractility with little change in coronary venous pO2. These results suggest that acute pharmacological manipulation of the oxyhemoglobin dissociation curve may enhance oxygen release to the myocardium while maintaining the effective driving pressure (as reflected in coronary venous pO2) for diffusion of oxygen to the myocardium.
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PMID:Effect of ortho-iodo sodium benzoate on hemoglobin-oxygen affinity in normal and ischemic myocardium. 90 59

We conducted this study in order to learn whether or nt oxygen inhalation reduces left ventricular size, one of the major determinants of myocardial oxygen demand. In 11 open-chest dogs, a Mercury-in-Silastic gauge was applied to measure left ventricular circumferential length while the dogs were being ventilated with either room air or 100% oxygen. Four characteristic notches were identified on the resulting length curve: L1, length at the beginning of ejection; L2, length at the end of ejection; L3, length in early diastole; and L4, length at end diastole, L1 was shortened from 24.9 +/- 10.5 to 24.4 +/- 9.9 mm (a decrease of 1.4 +/- 2.1%) by oxygen breathing, L2 was also shortened from 26.8 +/- 11.5 to 26.2 +/- 10.7 mm (a decrease of 1.5 +/- 2.9%), L3 from 17.5 +/- 4.4 to 17.4 +/- 4.3 mm (a decrease of 0.7 +/- 2.7%) and L4 from 17.7 +/- 4.8 to 17.5 +/- 4.7 mm (a decrease o 1.3 +/- 2.4%). These changes all disappeared when the inspiratory gas was changed from oxygen back to air. Heart rate and left ventricular end-diastolic pressure showed no significant changes but were accompanied by a slight reduction in aortic pressure and myocardial contractile force. This study demonstrated a small but consistent reduction in left ventricular circumferential length by oxygen breathing. This reduction in left ventricular size will reduce left ventricular tension and thus result in reduction of left ventricular myocardial oxygen demand when oxygen inhalation is applied to patients with ischemic heart disease.
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PMID:Reduction of left ventricular epicardial segment length by 100% oxygen breathing in open-chest dogs. 707 48

Ventricular fibrillation threshold (VFT), the electrical stimulus strength required to fibrillate the heart during the vulnerable period of the cardiac cycle, has been used to evaluate the properties of many arrhythmogenic and antiarrhythmic drugs, and is easily adaptable to determining ventricular vulnerability following coronary arteriography. Using this method, the authors find that there is a large decrease in VFT within seconds following intracoronary arteriography with 1 ml of sodium meglumine diatrizoate. During the first minute, the threshold decreases by an additional 10%, then returns rapidly and completely to control levels. The change in threshold persists much longer than artery-to-sinus transit time, longer than changes in contractility, and somewhat longer than repolarization changes in the surface electrocardiogram. There is a strong dose relation. Injections through impacted catheters or slow injections cause disproportionate decreases in VFT. Ionic solutions of CaCl2 progressively lower VFT, but, when added to sodium meglumine iothalamate solutions, minimize the fibrillatory potential of ionic contrast agents in a complex way. A modified model of myocardial ischemia produced by intracoronary mercury injection is described. With myocardial ischemia, the fibrillation threshold falls, and during coronary arteriography still lower thresholds are seen. The use of VFT measurements is recommended for further evaluation of the fibrillatory potential of contrast media in clinically relevant situations.
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PMID:Cardiovascular radiology. The fibrillatory propensities of contrast agents. 720 25

Regional function parameters under myocardial ischemia are frequently clearly changed when the parameters as the stroke volume, cardiac output, ejection fraction and the like are still unchanged by a compensation mechanism. Length changes can be measured regionally and phasically by means of a mercury wire strain gauge. The active shortening during the ejection time in relation to the total length change in this region is a possibility for the registration of the relative systolic shortening (delta LS%). Changes will be quantified still clearer and earlier if in the x-y display a vector representation of the regional displacements with the pressure in the left ventricle takes place. The plane of this vector decreased already a few seconds after the coronary occlusion. This is therefore a special early change in ischemia. The important for the estimation of therapeutic measures and other indirect measuring methods is accentuated.
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PMID:[Evaluation of regional heart function by means of local changes in pressure and direction in the vector cardiogram]. 721 Jul 62

The study group consisted of 8 men with congestive heart failure. They ranged in age from 33 do 63 years (mean 48). Three patients were in class III NYHA, five in class IV. Idiopathic cardiomyopathy was diagnosed in 6 patients, one individual displayed ischemic heart disease and one patient was after mitral and aortic-valve replacement despite a normally functioning prosthetic valve. L-dopa was given orally beginning with 250 mg every six hours until a total daily dose of 4.0 g was achieved with no side effects (patients additionally received 50 mg of pyridoxine hydrochloride). Afterwards L-dopa was withheld for 24-36 hours. Having completed this washout period, patients underwent right heart catheterization, with placement of a balloon-tipped thermodilution catheter in a pulmonary artery, so that balloon inflation allowed recording of the pulmonary capillary wedge pressure. Right atrial and pulmonary arterial pressures were monitored continuously. Systemic arterial pressure was measured by mercury manometer. Cardiac output was determined by the thermodilution technique. Rest and effort hemodynamic measurements were repeated before and one, three hours after administration of 1-dopa. The base-line hemodynamic values were consistent with the clinical presentation of severe congestive heart failure. The average cardiac index (CI-1/min/m2--rest--1.93; 25 Watt-3.1) and stroke volume index (SVI-m1/m2--rest--22.2; 25 Watt-32.0) were markedly lowered. Left ventricular filling pressure and pulmonary artery pressure were elevated. The systemic vascular resistance was significantly increased (SVR -j.W.--rest--22.7; 25 Watt-14.2). Administration of 1-dopa resulted in the increase in cardiac index and stroke volume index accompanied by a substantial reduction in systemic vascular resistance.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Hemodynamic effects of one administration of l-dopa in patients with left ventricular heart failure (introductory remarks)]. 836 41

Efforts to minimize the deleterious effects of intraoperative myocardial ischemia-reperfusion (I/R) injury have been primarily directed at optimizing cardioplegic solutions and altering reperfusion conditions. Classically, myocardial I/R has been associated with cardiac mechanical dysfunction ("stunning"). Recently, we reported an alpha 1-adrenergic receptor-mediated mechanism of paradoxical myocardial protection against I/R insult induced by a prior episode of transient ischemia, a phenomenon known as "ischemic preconditioning." Myocardial stunning resulting from transient ischemia has previously been associated with ischemic preconditioning, prompting intuitively negative bias against the clinical application of this phenomenon. The purpose of this study was to determine whether transient ischemia of insufficient duration to cause prolonged mechanical dysfunction (stunning) can induce favorable cardiac preconditioning. Isolated-perfused rat hearts were allowed to equilibrate for 8 minutes and were then subjected to either 2 minutes of global, normothermic transient ischemia or 2 minutes of 50 mumol/L phenylephrine infusion. A stabilization period of perfusion lasting 10 minutes after the termination of transient ischemia or phenylephrine infusion was followed by a standard I/R challenge (20 minutes of global, normothermic ischemia; 40 minutes of reperfusion). Ventricular function (measured as developed pressure in millimeters of mercury) recovered rapidly after transient ischemia such that no impairment was present before the subsequent standard I/R challenge. Phenylephrine treatment was associated with no residual inotropy before I/R challenge. Control hearts were subjected only to the standard I/R challenge after an initial 20-minute equilibration period. After reperfusion control hearts exhibited 54.4% recovery of initial left ventricular developed pressure. Transient ischemia- and phenylephrine-preconditioned hearts recovered 84.4% (p < 0.01) and 82.4% (p < 0.01), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Cardiac preconditioning does not require myocardial stunning. 843 Oct 49

Traditional food is culturally, economically and nutritionally important for the Greenlandic Inuit people. In the 1970s the preventive effect of marine fat on cardiovascular disease, thrombosis and atherosclerosis was described. The low incidence of ischemic heart disease among Greenlanders has been related to the high intake of marine food. Since 1990 routine autopsies have taken place in two towns in Greenland, Nuuk and Ilulissat. The autopsies represent 26% of the total number of deaths in these two towns. Samples have been collected from 104 autopsies. International cooperative studies have analysed specimens in relation to ischemic heart disease as a benefit related to diet, as well as the level of heavy metals and organochlorine in organs as a risk related to diet. High amounts of mono-unsaturated and Omega-3 poly-unsaturated fatty acid were found in adipose tissue. Liver analyses of selenium have confirmed the expected high intake among Greenlanders. Reduced atherosclerotic lesions were found in the coronary arteries. Blood pressure levels calculated from renovascholopathia of hypertension indicate prevailing levels similar to those in industrialized countries. Some factors in Greenland may be protecting the coronary arteries, thereby of setting the expected effect of hypertension. The level of methyl mercury in organs is generally high. PCB concentrations found in organs of Greenlanders are higher than among other populations. Health and risk effects of the traditional foods need further investigation.
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PMID:The Inuit diet. Fatty acids and antioxidants, their role in ischemic heart disease, and exposure to organochlorines and heavy metals. An international study. 887 82

Environmental pollution in the Arctic is due to long range transport from lower latitudes or to local industrial activities. Since the latter are not different from point source exposure in the rest of the world the paper focuses on the former aspect which is the main type of environmental pollution in the western Arctic. The environmental pollutants of major significance are heavy metals (mercury, cadmium, lead) and persistent organic pollutants (PCB's, pesticides) and the main exposure is through the traditional diet of sea mammals (mercury, cadmium, persistent organic pollutants) and through smoking (cadmium). There is rather strong evidence that lead is a (weak) risk factor for high blood pressure even at low levels of exposure. Apart from lead there is little evidence that the above mentioned pollutants are significantly related to cardiovascular diseases. Since the pollutants, however, are found in the traditional diet together with n-3 polyunsaturated fatty acids, monounsaturated fatty acids, and selenium which are believed to promote cardiovascular health there is an indirect link between the pollutants and cardiovascular disease. This becomes relevant when dietary guidelines are developed for arctic populations. Epidemiological evidence from Greenland relevant for this discussion is presented, i.e. i) findings from a countrywide interview survey on dietary habits which show that sea mammals are widely consumed and appreciated for health and other reasons and that there is virtually no fear of pollution, and ii) mortality results which do not support the hypothesis that the low rate of ischemic heart disease in Inuit is due to their traditional diet.
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PMID:Cardiovascular disease and environmental pollutants: the Arctic aspect. 887 83


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