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Biomedical subjects

G Hellige

Publications and source records attributed to G Hellige.

At least 109 records · Page 6Linked to original sources
PubMed1984

[Comparison of the acute cardiovascular side effects of iopamidol, metrizamide and amidotrizoate after intracoronary and left ventricular injections].

The acute cardiovascular side effects of iopamidol (osmolality: 0.8 osmol/kg), metrizamide (0.6 osmol/kg), and amidotrizoate (2.1 osmol/kg) during coronary arteriography (n = 30) and left ventriculography (n = 9) have been compared in anesthetized closed-chest dogs (n = 5). The influences of these contrast media on hemodynamics, coronary circulation, ECG and physicochemical properties of coronary sinus blood were evaluated. Following intracoronary injection, iopamidol and metrizamide cause positive inotropism while amidotrizoate initially induces cardiodepression. All contrast solutions lead to marked increase of myocardial blood flow. Electrocardiographic changes are greater after amidotrizoate (P less than 0.05). A fall of cationic content in coronary sinus blood is seen after each contrast medium. Amidotrizoate leads to more decrease of potassium (P less than 0.01) and both ionized and total calcium (P less than 0.001). Increase of osmolality and hydrogen ionic content is greater after amidotrizoate than after iopamidol and metrizamide (P less than 0.01). Following left ventricular injection, marked peripheral vasodilation, as seen after amidotrizoate, does not occur after low osmolality compounds. There are no significant differences between iopamidol and metrizamide in spite of the slightly higher osmolality of the former. Thus, both contrast materials should be equivalent with respect to their acute cardiovascular side effects under clinical conditions. Advantages of low osmolality radiological contrast media are discussed.

Animals↗
PubMed1984

[Central venous injection of large amounts of contrast media--advantages of a low osmolar contrast medium in experimentally-induced pulmonary hypertension].

Intravenous administration of contrast material is a prerequisite for the imaging of the cardiovascular system with computed tomography and digital subtraction techniques. Fatal side effects after intravenous contrast injection, particularly in patients with pulmonary hypertension, have been reported repeatedly. The object of this study was to compare hemodynamic side effects of a conventional, ionic contrast medium (amidotrizoate; 2.1 osmol/kg) and a modern, non-ionic compound (iopamidol; 0.8 osmol/kg) after intravenous bolus injection (1.5 ml/kg). Experiments were carried out in 10 open-chest dogs with pulmonary normotension and hypertension induced by embolisation. Under control conditions (PPA = 19.9 mm Hg) both contrast media produced marked pulmonary and peripheral vasodilation. Major effects were seen after amidotrizoate (RPULM 60.3%, RPERI 32.1% vs 72.5% and 70.4% of controls). In pulmonary hypertension (PPA = 44.2 mmHg), iopamidol had similar hemodynamic effects compared to control conditions. In contrast, amidotrizoate initially led to a significant increase in pulmonary pressure and resistance (PPA = 118.6%; RPULM = 141.7%) followed by a delayed depression of right ventricular function (dP/dt = 65.3%; PRVED = 180.9%). Resuscitation was required in 3 dogs with pulmonary hypertension after amidotrizoate injection. Because of these unfavorable hemodynamic side effects of the conventional high osmolality contrast medium in animal experiments, it can be expected that modern compounds with low osmolality pruduce smaller side effects during diognostic interventions in patients with pulmonary hypertension.

Animals↗
PubMed1983

A new model for testing therapeutic interventions during myocardial ischemia.

An open-chest dog heart model is presented which shows highly reproducible hemodynamic, electrophysiologic, and metabolic changes during and after short-term coronary occlusions. We repeatedly performed 3-min coronary ligations of the proximal ramus interventricularis anterior followed by reperfusion periods of 45 min. Thus, hemodynamic, metabolic, and electrophysiologic parameters of myocardial damage were fully reversible. The experimental model presented seems well suited to evaluate interventions which aim at influencing the extent and damage of myocardial ischemia without needing a large number of separate experiments.

Animals↗
PubMed1983

Improvement of the metabolic and energetic situation of ischemically stressed myocardium by verapamil after experimental coronary artery occlusion.

On anaesthetized open-chest mongrel dogs (n = 7) short-time (3 min), repeated ischemia of relatively large parts of the myocardium was produced by proximal, intermittent occlusion of the LAD artery in intervals of 45 min. Usually, 2-3 control occlusions and 2-3 occlusions under therapy were performed. From hemodynamic data, coronary blood flow and AVD-O2 myocardial oxygen consumption (MVO2) and energy demand (Et) were continuously recorded by use of a micro-computer. The occurring difference between MVO2 and Et (dO2) allowed to calculate during the occlusion period the O2-debt (DO2) and during the reperfusion period the O2-repayment (RO2). Furthermore, the releases of the metabolic ischemia parameters lactate, inorganic phosphate and potassium were determined in the first minute of postischemic reperfusion. Compared to control occlusions, premedication with verapamil (Isoptin) 0.12--0.2 mg/kg b.w.) led intra- and interindividually to a significantly reduced O2-debt (p less than 0.001) during the occlusion period combined with a significantly reduced amount of oxygen, additionally taken up in the early reperfusion period (p less than 0.001). Under verapamil the amounts of metabolic parameters released in the first minute of reperfusion decreased significantly: lactate: -36% (p less than 0.001), inorganic phosphate: -32% (p less than 0.001), potassium: -30% (p less than 0.001). The improvement of the metabolic and energetic situation of ischemic myocardium indicates that verapamil may be of importance in reducing the extent and severity of acute myocardial ischemic injury.

Animals↗
PubMed1982

Influence of myocardial substrate utilization on the oxygen consumption of the heart.

The effect of changing myocardial metabolism from predominantly lipid to predominantly carbohydrate utilization on myocardial oxygen consumption (MVO2) was studied in 10 closed-chest dogs. Oxygen saving potency of different metabolic interventions was quantified over a wide hemodynamic range by comparing the directly determined MVO2 with the hemodynamic parameter total left ventricular energy demand (Et), which correlates closely under control conditions with MVO2 (r = 0.98). Stimulation of carbohydrate metabolism by addition of glucose and beta-pyridyl carbinol or by activation of pyruvate dehydrogenase with dichloroacetate (DCA) shifted the cardiac respiratory quotient during beta-stimulation from 0.73 to 1.00 and 0.89, respectively, the nonesterified fatty acid/albumin ratio decreased from 4.0 to 0.5, or remained unchanged with DCA, and MVO2 was reduced by 25 and 16%, respectively. Therapeutic approaches aimed at decreasing MVO2 by changing substrate utilization are discussed.

Animals↗
PubMed1982

[Effects of radiographic contrast media on cellular electrophysiology in the beating heart (author's transl)].

Electrophysiological effects of intracoronarily administered contrast media have been documented in 12 thoracotomized dogs at the cellular level by use of a modified microelectrode technique. Injections (n = 63) of 4 different contrast media uniformly led to a temporary cellular hyperpolarisation of the resting potential and prolongation of the action potential. Additional experiments with intracoronary injections of several electrolyte solutions indicate that the observed effects can be explained by contrast-induced changes in the extracellular electrolyte concentrations, mainly by a local deficiency of potassium ions and an excess of sodium ions. The significance of the findings for mechanisms underlying ECG-changes and ventricular arrhythmia by radiographic contrast media will be discussed.

Animals↗
PubMed1982

[Coronary angiography in chronic and acute coronary artery disease. Advantages of a low osmolality contrast medium].

The advantages of a new low osmolality contrast medium (sodium meglumine ioxaglate) in clinical coronary angiography are demonstrated at two groups of patients in comparison to sodium meglumine diatrizoate. One group included patients undergoing diagnostic angiography in chronic state of CHD, the other during diagnosis and therapy (intracoronary lysis) in state of acute myocardial infarction. Injection of the low osmolality contrast material was followed in both groups by significant reduction of pressure drop and cardiac slowing. In both groups there was also a reduction of changes in ECG compared to side effects of the conventional contrast material.

Aged↗
PubMed1981

Influence of arteriographic contrast media on the Na+/Ca++-ratio in blood.

To investigate the basis of cardiodepressive side effects in coronary arteriography, the isolated effects of different contrast media on electrolyte levels in blood (and blood fractions) were quantified in vitro. Due to their sodium content and calcium chelation, ionic media cause an imbalance in the extracellar Na+/Ca++-ratio that determines myocardial contractility. Ca++-chelation exceeded that due to stabilizing additives indicating a binding by the contrast agents themselves. The amount of calcium bound varied with different media and was greatest with Renografin. It is suggested that the degree of Na+/Ca++-imbalance in blood explains the extent of acute cardiodepression.

Angiography↗
PubMed1981

Basic physiological studies on cardiac pacing with special reference to the optimal mode and rate after cardiac surgery.

Temporary cardiac pacing (CP) is frequently applied postoperatively in the management of low cardiac output (CO) and rhythm instability. However, uncertainty exists about the "optimal" pacing rate, range and mode due to incomplete information on myocardial oxygen consumption (MVO2), related to its hemodynamic determinants, and on myocardial pumping efficiency (eta) at CP. In 10 intact dogs atrial pacing (AP) (90 to 210 beats/min) and ventricular pacing (VP) (70 to 330 beats/min) were investigated in normal and failing hearts. AP and VP were compared at identical rates. MVO2 (4 to 20 ml/min . 100 gr) was measured directly according to the Fick principle. Cardiac efficiency was calculated as the ratio of oxygen equivalent of external cardiac work to MVO2. Rates with maximum CO and a maximal eta occurred only in heart failure. However, maximal CO and eta were obtained at different heart rates (HR). MVO2 was significantly higher (p less than 0.001) under VP as compared to AP at identical rates with a mean increase of 26.5% +/- 6% over AP, although hemodynamics were significantly lower under VP (p less than 0.001). Myocardial pumping efficiency was markedly better under AP with a mean increase of 63% +/- 4.5% over VP even in normal heart. Adjustment of HR at maximal response in CO may become dangerous, particularly under VP, in heart failure. AP, if applicable, may be regarded as the optimal pacing technique due to an optimal relation of improved hemodynamics to MVO2. It may be helpful in correcting an imbalance between oxygen supply and demand in cases of low output syndrome. The pathophysiologic mechanisms and further clinical implications are discussed.

Animals↗
PubMed1981

Effects of AR-L 115 BS on hemodynamics, myocardial oxygen consumption and cardiac pumping efficiency.

The effects of 2-[(2-methoxy-4-methylsulfinyl)phenyl]-1H-imidazo[4,5-b]pyridine (AR-L 115 BS) on hemodynamics, myocardial oxygen consumption and cardiac pumping efficiency were tested on closed-chest dogs in cardiac catheterization technique. Doses in the range of 0.1 up to 4.0 mg/kg b. w. were injected i.v. A therapeutical dose is to be expected in the range of 1.0 mg/kg b. w., showing a distinct positive inotropic effect and reducing endsystolic volume without increase of heart rate and myocardial oxygen consumption.

Animals↗
PubMed1980

[Reduced cardiotoxicity of contrast media in angiocardiography. Comparative clinical study using diatrizoate with added calcium or metrizamide (author's transl)].

Cardiodepressive side effects of angiocardiography can be reduced by using non-ionic metrizamide (Amipaque) or adding calcium to diatrizoate (Urografin 76%). In 15 patients with coronary artery disease undergoing heart catheterization, we compared cardiac side effects of coronary angiography and left ventricular angiography using metrizamide and diatrizoate with and without additional calcium (11.3 mmol/l) as contrast media under randomized conditions. In selective intracoronary injection with diatrizoate alone, peak left ventricular pressure and contractility (dP/dtmax) showed a fall of 30 +/- 11% and 31 +/- 15% (n = 33 injections). Using diatrizoate with added calcium (11.3 mmol/l), the fall was only 23 +/- 12% and 20 +/- 10% respectively (n = 31 injections). With metrizamide (n = 32 injections) cardiac side effects are even less and the decrease in pressure and contractility only 13 +/- 10% and 7 +/- 7% respectively, which its highly significant (p less than 0.0001) compared with the effect of diatrizoate. The heartrate slowing, not essentially altered by calcium addition, was minimal using non-ionic metrizamide. In left ventricular angiography, the pressure fall in the late phase after injection of diatrizoate, caused by decrease peripheral vascular resistance (vasodilation), was lacking when injecting metrizamide (p less than 0.001). Metrizamide has even less cardiodepressive side effects than diatrizoate with additional calcium when used in angiocardiography and seems to be suitable particularly for the evaluation of high risk patients.

Adult↗
PubMed1980

Decrease in cardiotoxicity of contrast media in coronary angiography by addition of calcium ions: a combined experimental and clinical study.

The cardiotoxicity of commonly used contrast media such as sodium methylglucamine diatrizoate is related to nonphysiologic concentrations of ions and high osmolality. Following injection there is an excessive decrease in ambient calcium which disturbs the extracellular Na+/Ca2+ ratio and results in myocardial depression. In animal studies (anesthetized, intact mongrel dogs) this cardiodepressive effect could be fully compensated by adding 22.5 mEq/1 of ionic calcium to the contrast medium. In 16 patients studied for coronary artery disease (CAD) 72 injections of sodium methylglucamine diatrizoate, mainly in the left coronary artery, were thoroughly investigated. There was marked depression of left ventricular pressure (-22%) and (dP/dt)max (-27%), and marked heart rate slowing (-29%). Added calcium in the concentration cited reduced significantly (p < 0.001) the myocardial depression to -15% and -13%, respectively, but did not completely compensate it. The heart rate slowing was not altered significantly. It was concluded that the addition of calcium may be helpful when studying high-risk patients and using high injection volumes.

Angiography↗