[Hemodynamic examinations concerning the effects of cardiac glycosides in hypertrophic obstructive cardiomyopathy (HOCM)]

Due to fundamental considerations and especially after Braunwald's et al. (1962 (4)) examinations of 5 patients with severe hypertrophic obstructive cardiomyopathy (HOCM) with 0.5-0.75 mg of Ouabain, cardiac glycosides in cases of this disease are to be regarded as contraindicated. Own examinations (right and left-heart catheterizations, monoplane cineangiography of the left ventricle, determination of the cardiac output, and the ejection fraction (EF) were performed in 10 patients with HOCM of different stages. Applying the usual dosage of 0.25-0.375 mg of strophanthin, different hemodynamic effects were observed in discrete forms. In cases with a higher severity, the observations of Braunwald et al. could actually be confirmed. The left ventricular systolic pressure gradients were increased, but cardiac output, left ventricular enddiastolic pressure, pulmonary pressure and resistance, and also arterial pressure and peripheral resistance behaved differently. EF increased slightly. The right infundibular gradients were decreased with one exception, or resp., they were unchanged. Obviously, HOCM reacts especially unfavourably with so-called left-ventricular cavity obliteration. The main importance might belong to the behaviour of the free lumen of the left ventricle. In regard of the principally reserved attitude towards the cardiac glycoside therapy in HOCM, no change has occurred. Only in patients with atrial fibrillation and a rapid heart rate, a therapy trial could be considered, if necessary in combination with beta-blocking agents or calcium antagonists under hemodynamic control. In cases of HOCM with serious obstruction and signs of cardiac failure and inadequate affecting by calcium antagonists, an early surgical intervention should be executed.

[Effect of hyperactivation of the anterior amygdaloid nucleus on heart work in altered reactivity]

It was shown in experiments on random-bred rats that changes in the heart reactivity caused by adrenaline, rausedyl, potassium chloride and strophanthine facilitate the occurrence of cardiac rhythm abnormalities during the creation of the generator of pathologically enhanced excitation (GPEE) in the anterior amygdaline nucleus. The moments of rhythm abnormalities correlate with the occurrence of GPEE epileptic activity. Meanwhile the pattern of cardiac rhythm abnormalities is largely determined by the specificity of action of the pharmacological substances indicated. Analogous effects of cardiac rhythm abnormality facilitation during GPEE creation in the nucleus were obtained in myocardial ischemia caused by the occlusion of the anterior or posterior left coronary artery. At the same time the differences were recorded in the pattern of cardiac rhythm abnormalities depending on the area of ischemia. The data obtained are discussed in the light of concepts of regulation diseases, particularly of the correlation between the role of determinant structures and reactivity disorders in the target organs.

[Participation of trigger membrane mechanisms in the effect of cardiac glycosides on the heart]

Strophanthine (5 X 10(-7) - 1 X 10(-5) g/ml) applied to the epicardium of the right and left auricles of an isolated frog heart produced negative chronotropic and positive inotropic effects. Specific effects of strophanthine developed during complete blockade of alpha-, beta- and M-cholinoreceptors of the heart. Upon isolated blockade or stimulating of the receptors indicated, the effects of strophanthine were shown to be changed. Attempts are made to prove the existence in the auricles and ventricles of the heart of glycoside inhibitory and stimulating receptors that form the constellation system of reciprocal relationships, with the mediator receptors, with this system participating in the triggering mechanism of heart membranes.

[Myocardial accumulation of 99mTc MDP in patients subjected to extended adriblastin treatment. Protective effect of strophanthin and vitamin E]

Myocardioscintigraphy with 99mTc MDP is patients undergoing protracted treatment with adriblastin led to the discovery that accumulation of the isotope was infrequent in subjects protected with strophanthin and vitamin E, contrary to the position in an earlier series for whom no treatment designed to reduce the cardiotoxic effect of the antiblastic drug had been provided.

The prolongation of the action potential in mammalian ventricular muscle at rest. Is it due to intracellular calcium content changes

The conventional microelectrode technique was used to investigate the effect of long periods of rest (greater than 10s) on the action potential duration of mammalian ventricular muscle. The action potential duration increased as the rest period increased. This prolongation of the action potential was the greatest and the slowest in rabbit ventricle, was smaller and more rapid in guinea-pig ventricle, and was practically absent in rat ventricle. The prolongation of the action potential at rest was suppressed with aminazine and strophanthin. Low sodium concentration, lanthanum ions, ruthenium red and acidosis failed to suppress the slow prolongation. It is concluded that the slow prolongation of the action potential at rest is related to changes in the intracellular calcium content induced by a mechanism different from Na/Ca exchange.

[Effect of digoxin, strophanthin and isolanid on oxygen absorption, oxidative phosphorylation and the amount of cytochromes in the myocardial mitochondria and their ATPase activity]

A total of 200 nonlinear rats were used to study the release and utilization of energy in the normal myocardium on administration of clinical concentrations of cardiac glycosides. It was found that cardiac glycosides exert no effect on oxidative phosphorylation under utilization of alpha-ketoglutarate. At the same time digoxin and strophanthin ( to a less degree) intensify the phosphorylating activity of mitochondria, while isolanid has no effect on the oxidative and phosphorylating activity under oxidation of succinate. The content of the enzymes in the terminal portion of the respiratory chain, namely the myocardial mitochondria - cytochromes, did not change under the effect of cardiac glycosides. The test animals were shown to have an increased activity of actomyosin ATPase.

[Effect of strophanthin and celanide on the tonus of the cerebral and peripheral vessels]

Resistography was used in acute experiments on anesthetized cats to demonstrate that cardiac glycosides, particularly celanide, often cause phasic (constrictive-dilative) responses of the perfused vessels and general arterial pressure. The constrictive response of the perfused vessels did not depend on the concentration of calcium ions in the blood and was not prevented by preliminary administration of dihydroergotoxin. However, glycosides prolonged the vasoconstrictive effect of noradrenaline. The vasodilative response to glycosides was reversed by atropine. It is assumed that the constrictive response is myotropic, whereas the dilative one is cholinergic in nature.

Redox state potential influences (+/-) delta [Na+]o activity values during acetylcholine contractures of frog skeletal muscles

1. The slow alterations in the activity of extracellular Na+ concentrations were measured by using ion-selective electrodes. 2. In the first min there is an increase in the changes of the activity of extracellular Na+ following acetylcholine evoked contractures. 3. This increment was significantly inhibited by k-Strophantoside application, suggesting an active transport origin of this first peak. 4. In the second min a strong decrease in the activity of extracellular Na+ concentration followed. 5. Reducing agent (ascorbate) increased, while oxidant (methylene-blue) decreased both the first increment and the sequential decrement in the activity of the extracellular Na+ concentrations. 6. On the basis of these experiments a site of action of the redox regulation of excitatory processes could be the modification of Na+ fluxes.

Influence of acute hemodynamic changes on the negative peak of the first derivative of apex cardiogram during ventricular relaxation in dogs

The effect of various alterations in the preload, the afterload and the inotropic state of the left ventricle on the first derivative of apex cardiogram (dA/dt) was studied in 9 anesthetized dogs to clarify some of the determinants of the negative peak of dA/dt and isovolumic relaxation time. The first derivative of the apex cardiogram was recorded simultaneously with the left (ventricular pressure, conventional left apex cardiogram, first derivative of left ventricular pressure (dP/dt), electrocardiogram and phonocardiogram. Both dA/dt and dP/dt curves were similar in contour and occurred nearly simultaneously. This close relationship was preserved during various acute haemodynamic changes. The maximum negative dA/dt and the isovolumic relaxation period was closely related to the level of afterload. Large rapid augmentation of mean aortic pressure resulted in a significant increase in the negative dA/dt and shortening of the isovolumetric relaxation time, where reduction of afterload had an opposite effect. Isoprenaline acutely augmented minimum dA/dt. It is concluded that measurement of negative peak dA/dt under some conditions is a reliable noninvasive technique for assessing myocardial relaxation.

[Effects of glucosides on a spontaneously active vascular smooth muscle in vitro (author's transl)]

There is no support for the view that cardiac glucosides increase the resting tension in the rat portal vein, although such an effect on vascular smooth muscle might have been expected from the results of investigation on the coronary vessels. Glucosides in a concentration of 10(-4) m inhibit contractility while increasing the frequency of contractions. These changes of spontaneous activity are not accompanied by equivalent changes of the intracellular cation concentrations. There are no significant differences between the effects of g-strophanthine, k-strophanthoside and convallatoxin.

Hemodynamic pattern following K-strophanthin in normal and coronary artery disease patients

Hemodynamic effects of K-strophanthin (0.005 mg/kg i.v.) were evaluated in 7 normal and in 13 non-failing coronary artery disease patients (CAD). Volumetric parameters were obtained by single plane left ventricular angiography. The indexes of "pump" function, the end-systolic pressure-volume relationship and the ratio of peak pressure to systolic volume were also evaluated. Heart rate was maintained constant by atrial pacing. In normal subjects K-strophanthin exerted small effects without peripheral vasoconstriction. CAD patients showed different response to K-strophanthin in vascular tone: an increase (Group 1) or a decrease (Group 2) in total systemic resistance (TSR). No significant differences were found in basal values between the two CAD groups. In Group 2 the indexes of "pump" function increased after K-strophanthin and the end-systolic pressure-volume points shifted upward and to the left, while in Group 1 no improvement in cardiac function was observed and the end-systolic pressure-volume points shifted upward and to the right. Furthermore, we found a direct significant correlation between the percent changes of TSR and end-systolic volume index, and a negative significant correlation between the percent changes of TSR and stroke volume index. Our results show that K-strophanthin in CAD non-failing patients can have either a positive effect or a lack of improvement in ventricular performance. These effects correlate with changes in total systemic resistance.

[Pharmacologic prevention of changes in sensitivity to strophanthin occurring during sensitization by tissue antigens]

Chronic experiments with 110 cats have shown that long-term sensitization with homocardiac antigen (HCA) causes biphasic changes in strophanthine tolerance. The increased susceptibility to strophanthine that occurs during 10 days of sensitization with HCA and depends on dissociation of the mechanisms of specific and nonspecific immunity can be prevented by simultaneous administration of diphenhydramine, methyluracil, hydrocortisone and the beta-adrenoblocker, alpheprol. This increase can be also abolished by premedication with alpheprol and trimecain.

Cardiovascular radiology. Possible factors in intravascular contrast media toxicity

(I.) Toxicity of ionic coronary arteriography contrast media has been shown to depend on their cationic and anionic composition and their osmolality. Using a right coronary injection technique in the dog, the authors have shown a relationship between toxicity as manifested by occurrence of ventricular fibrillation and the presence of calcium binders in the contrast media. Sodium citrate and EDTA have been identified as the specific agents in certain contrast media that significantly increase the incidence of fibrillation in laboratory experiments. (II.) A deleterious synergism between water-soluble angiographic and urographic media and digitalis compounds has now been demonstrated, based on mortality studies (LD50) using bolus intravenous injections in white mice. The testing of a number of other classes of drugs for a similar effect has shown thus far that only the digitalis class exhibits this synergism. Surprisingly, the nonionic contrast medium, metrizamide, has been shown to have a greater synergistic effect with digitalis drugs than diatrizoate ionic media. (III.) In dog experiments under Nembutal anesthesia in which aortic flow, pulmonary artery and vein pressures, systemic arterial pressure, and EKG were monitored, left atrial pressure increases as soon as or before pulmonary artery pressure rises, even at low doses of ionic contrast media administered intravenously. This may indicate 1) flow to the left heart increases dramatically, or 2) there is a very early myocardial depression. The significance of the above findings and application to clinical practice will be discussed.

Nifedipine for digitalis-induced arrhythmias

The calcium antagonist, nifedipine (Adalat; Bayer), has previously been thought by most workers to lack cardiac-anti-arrhythmic properties, thus differing from verapamil. We have found that nifedipine was successful in converting cardiac glycoside (K-strophanthoside)-induced ventricular tachycardia to sinus rhythm in 4 of 5 anaesthetized dogs when given intravenously. In this respect, therefore, nifedipine is similar to verapamil. Further work is advocated before applying these results to the clinical situation in man.

Toxic effect of the glycoalkaloids solanine and tomatine on cultured neonatal rat heart cells

The toxic effects of the glycoalkaloids, alpha-solanine and tomatine, were studied in beating heart cell cultures from 1--2-day-old rats. After addition of alpha-solanine (80 microgram/ml) and tomatine (40 microgram/ml) to the culture medium, the cells ceased beating within a few minutes. At a concentration of 40 microgram/ml alpha-solanine and 20 microgram/ml tomatine, both compounds caused a pronounced increase of the contraction frequency, lasting for at least 2h. K-strophantin, a reference heart glycoside, caused arrhythmic beating at 20 microgram/ml and complete cessation of contractions at 160 microgram/ml.

Intracellular sodium accumulation and transmitter release at crustacean neuromuscular junctions

Since the intracellular concentrations of Na+ and Ca2+ are relatively low and the cell's ability to actively expel or sequester these ions is limited, prolonged, high-frequency impulse activity at many crustacean axon terminals can result in significant increases in [Na+]i and [Ca2+]i. These changes parallel increases in transmitter output and may persist for several seconds (short-term facilitation, or STF) or even for many hours (long-term facilitations, or LTF). These two phenomena appear to be qualitatively distinct processes. The unique properties of LTF include: 1) the need for Na+ (but not Ca2+) in the extracellular media; 2) long decay times (from minutes to hours); 3) acceleration of devolpment and retardation of decay under conditions that inhibit the membrane Na+-K+ pump, e.g., cardiac glycosides, low [K+]o. The subcellular mechanism(s) linking Na+ accumulation to increased transmitter release are unknown but may involve alterations in [Ca2+]i, either through release from intracellular stores or through increased membrane conductance. Sodium-induced modifications in transmitter synthesis, storage, or availability may also be involved. Long-term functional changes in synaptic efficacy like LTF may provide important clues to more general questions of nervous system plasticity.

[Effective concentration and dosage for cardiac glycosides]

The pharmacokinetic fundaments of the glycoside therapy with strophanthin, digoxin and digitoxin are described and compared with the traditional clinically oriented parameters total body stores, decay ratio and so on. Newly introduced is the parameter medium remaining duration in the circulation. A critical analysis of the hitherto cited values of the total body stores and the decay ratio established from the clinical effect shows that on the basis of pharmacokinetic calculations the corresponding values for digoxin and digotoxin need a great correction. The fully active quantity for digoxin lies between 0.5 and 0.8 mg and the subsiding share is 50%. The values for digitoxin lie at 0.9 mg and 9%. Furthermore the causes of the interindividual variability of the maintenance dose are discussed. According to the already existing international experiences an essential improvement of the therapy is possible, when the pharmacokinetically established effective constants are taken into consideration. Examinations of the inter- and intraindividual differences in the kinetics of the glycosides and the development of digoxin preparations with a high (i.e. constant) bioavailability may contribute to a further decrease of the frequency of toxic side-effects in future.

Sodium and potassium fluxes across the dialyzed giant axon of Myxicola

Resting and stimulated fluxes of sodium and potassium across the giant axon of the marine annelid, Myxicola infundibulum, have been characterized using the technique of internal dialysis. In most respects the ion movements were found to be similar to those in squid axons. Sodium efflux and potassium influx were found to be active, cardiac glycoside-sensitive fluxes, with a variable coupling ratio. However, when [ATP]i was lowered to less than 20 microM by treatment with cyanide and continuous dialysis, or to less than 2 microM by dialysis with glucose following injection of hexokinase, Na efflux and K influx were unaltered. The maintained fluxes were not accounted for by an increased passive permeability of the axolemma, although 30-60% of the Na efflux appeared to be due to Na-Na exchange. An altered form of Na pump operation at low [ATP]i is a more likely explanation than an alternate energy source, or an ATP source proximate to the axolemma. The transient response of 22Na efflux to a change in [22Na]i was found to be much slower than in squid, tau = 360 sec. The efflux delay could only be accounted for by an extra-axonal diffusion barrier, which is probably the basement membrane surrounding the ventral nerve cord.

On the cardiac efficacy of helveticosol-3',4'-di-nitrate, a new glycoside

The cardiac and extracardiac effects of a new glycoside, helveticosol-3',4'-di-nitrate (HdN), were compared with those of helveticosol (H) and helveticosol-3',4'-di-propionate (HdP) in isolated guinea-pig heart preparations, in volunteers and dogs. In the atrium and heart, HdN produces positive inotropic effects at the same concentrations as H and at 10 times lower concentrations than HdP. In the heart, the difference between equieffective concentrations of HdN and HdP is smaller, but this is true only for the concentration required to produce the maximum inotropic effect. In the anaesthetized dog equieffective cardiac effects are obtained after oral admiinistration of the glycosides in the ratio 1 : 2 : 0.5 (HdN : HdP : H). After administration of HdN and HdP at equal ratios, no significant differences were observed between the toxic effects in conscious dogs or in the extent of shortening of STI in volunteers. Replacement of the hydrophobic subsituent propionate for the more hydrophilic nitrate residue causes slight changes in cardiac efficiency.

Effect of strophantin on the isolated guinea-pig ileum

The effect of strophantin on isolated guinea-pig ileum was investigated. It was found that strophantin produces a dose-dependent contraction that is not blocked by atropine, ganglionic blockade, but is potentiated by prostigmine. Depolarization of the guinea-pig ileum by a high potassium solution does not change the effect of strophantin. Strophantin response is competitively antagonized by verapamil. The effect is significantly reduced, 5 to 10 min, after the preparation is immersed in zero calcium Tyrode solution. These results support the view that the effect of strophantin is dependent on the influx of calcium through the cell membrane.

[Effect of strophanthin and cytochrome C on myocardial contraction and the incidence of shock and ventricular fibrillation in experimental myocardial infarct]

High ligation of the interventricular artery caused ventricular fibrillation in the first 2--4 minutes in 20% of cats. In the remaining animals myocardial contractility diminished to half its initial value. After that, contractility increased gradually. In cardiosclerosis myocardial contractility reduced by 20--30%. Ligation of the interventricular artery on the background of cardiosclerosis induced cardiogenic shock in half of the animals. Cytochrome C does not reduce the diminution of myocardial contractility after ligation and has a marked antifibrillatory effect. Strophantin does not affect the diminution of contractility of a healthy myocardium but reduces the decrease in contractility of a sclerosed myocardium and also promotes the development of ventricular fibrillation following ligation of the interventricular artery.

[K-strophanthin-beta complexing with calcium, magnesium and dysprosium ions]

Nuclear magnetic resonance, microcalorimetry and the use of the ion-selecting electrode evidenced that k-strophanthine-beta forms complexes with the calcium, magnesium and disprosium ions. Changes in the position of the k-strophanthine-beta carbohydrate parts and aglycones signals bear witness to their participation in the complexing.

Dynamic ventriculography with K-strophantin

Dynamic ventriculography, before and after K-strophantin, was performed in 14 patients with coronary artery disease. Qualitative and quantitative evaluation of hemodynamic and angiographic data has been assessed. Digitalis was found to have different action on asynergic areas--that is improvement in some areas and worsening in others--and little or no action on normokynetic areas. After administration of K-strophantin (0.008 mg/kg), 54% of the examined asynergic zones improved their segmental systolic shortening while 34% worsened or appeared diskynetic. Improvement of asynergic zones could be related to the presence of viable myocardium, while paradoxical systolic motion would suggest the presence of frank fibrosis. Therefore 2 different behaviors of global ventricular function were observed in CAD patients. When ventricular function improves, the values of ejection fraction at midejection show that the improvement is obtained mostly in the first half of ejection. Since heart rate was fixed, enddiastolic volume unchanged and left ventricular systolic pressure increased, it seems likely that the observed changes could be due to a direct inotropic effect of K-strophantin. The author's opinion is that 'strophantin test' could be useful to test whether ventricular function would be enhanced using maintenance digitalis therapy in CAD patients and to determine residual contractile reserve; in addition potential worsening of ejection fraction can be elicited and then a more complete pattern of ventricular function can be provided.

[Rhodopsin regeneration: role of interaction between the photoreceptors and pigment epithelium cells]

Regeneration of rhodopsin has been studied in the eyecup, isolated retina and retinal homogenate of frog Rana temporaia as well as in the eyecup and isolated retina of fish-flounder Limanda aspera (Pallas). Rhodopsin has been found to regenerate only in the eyecup of frog, while isorhodopsin appeared to be the final product in the frog retinal homogenate. Decrease in rhodopsin regeneration level has been resulted from addition of inhibitors--theophyllin (2.10-2 M), papaverine (10-4--10-3 M) and strophantin (2.10-4 M) To the eyecup preparations (60, 20, 23%, consequently). A conclusion is made that structural connection between pigment epithelium cells and photoreceptors is necessary to provide regeneration of native rhodopsin.

[Effect of sodium transport inhibitors on maximal glucose reabsorption and cardiotrast excretion by the kidneys]

Effects of intrarenal infusion of potassium cyanide and strophanthinum were studied in acute experiments on dogs. The decrease fractional of reabsorption of sodium to 80--82 per cent did not affect renal reabsorption of glucose and tubular excretion of cardiotrast. Combined infusion of strophanthinum and cyanide decreased the fractional sodium reabsorption to 65.6 per cent. During this period maximal reabsorption of glucose reduced but not so the tubular excretion of cardiotrast.

Neurogenic coronary vasoconstrictor effects of digitalis during acute global ischemia in dogs

The rapid i.v. administration of digitalis has recently been shown to cause a substantial increase in coronary vascular resistance in the normal heart. This neurogenically mediated decrease in coronary blood flow would be potentially detrimental if it occurred during ischemia. The present study evaluates the effects of i.v. acetylstrophanthidin and digoxin on coronary vascular resistance during acute global ischemia in 29 dogs anesthetized with chloralose and urethane. Under these conditions, 0.5 mg of i.v. acetylstrophanthidin in 15 dogs resulted in erratic increases in coronary vascular resistance. The peak rise was 12+/-5% above control (P less than 0.01). In 7 of the 15 dogs, the initial erratic rise in coronary vascular resistance culminated in a steep rise associated with acute elevation in left ventricular end-diastolic pressure, which in four dogs terminated in ventricular fibrillation. During the nonischemic control periods, the peak rise in coronary vascular resistance with acetylstrophanthidin was 16+/-1% above control (P less than 0.01). In five dogs, prior alpha adrenergic receptor blockade with phenoxybenzamine prevented the rise in coronary vascular resistance with acetylstrophanthidin during ischemia. Similar erratic increases in coronary vascular resistance were observed with i.v. digoxin (1 mg) during ischemia in three dogs. In two of these dogs, there was a progressive rise in coronary vascular resistance associated with elevation of left ventricular end-diastolic pressure and ventricular fibrillation. The increase in coronary vascular resistance with digoxin during ischemia was abolished with phenoxybenzamine in two additional dogs. Thus, i.v. digitalis in the ischemic heart results in potentially detrimental increases in coronary vascular resistance mediated through alpha adrenergic receptor stimulation.

Transient changes in plasma digoxin concentration and the development of cardiotoxicity

1. Eight dogs were given two infusions of digoxin 0.1 mg/kg, one over 9 min and the other one over 90 min in a randomized sequence, allowing at least 12 days between each experiment. 2. Digoxin plasma profiles reflected the rate of digoxin infusion, the peak concentration of drug attained at the end of each infusion being considerably higher but more transient after the 9 min than after the 90 min transfusion. 3. Digoxin reduced the amount of acetylstrophanthidin required to produce electrocardiographic evidence of cardiotoxicity. This increase in cardiac sensitivity at 150 and at 360 min after the start of the digoxin infusion was independent of rate of infusion. 4. These results suggest that the development of cardiotoxicity is dependent upon the quantity of digoxin delivered into the systemic circulation regardless of the plasma concentration. 5. By inference, cardiotoxicity is related solely to the amount and not the rate of absorption from a given dose of digoxin.

Contribution to the biochemical characterization of cardiac glycosides concerning their influence on ATP-ases

1. A comparison of the complex binding constants of different glycosides show no significant differences between these different glycosides at least not in the model containing ATP. 2. There are greater differences regarding the ATP-ase activity of the different glycoside complexes measured by means of the Rb-transport method. 3. The absorption of different proscillaridin and methylproscillaridin preparations was investigated with this method. 4. Using the rat as experimental animal the effect of different glycosides on the Na-K and Ca ATP-ase of the heart muscle was demonstrated showing a remarkable activation of the Ca-activated ATP-ase caused by proscillaridin. In order to find an explanation for the therapeutic and toxic effects these investigations have to be repeated in the pig, which shows more similarities in the ATP-ase distribution to man than the rat.

[Effect of cardiac desympathization, stimulation of the central adrenergic structures and blockade of beta-adrenergic receptors on cardiotonic and cardiotoxic effect of cardiac glycosides]

The object of study were rabbits who had been subjected to ligation of 3 or 4 large branches of the left descending coronary artery 14-20 days before the experiment. In experiments with surgical desympathization of the heart it was established that the inotropic effect of cardiac glycosides did not depend on the concentration of catecholamines in the myocardium. In stimulation of adrenergic structures of the posterior hypothalamus attended with an increase in sympathetic innervation of the cardiovascular system the cardiotoxic threshold of cardiac glycosides was considerably reduced. Propranolol (Inderal) administered in a dose which blocks the beta-adrenergic apparatus of the heart prevents the development of the positive inotropic effect of therapeutic doses of strophanthin K on a hypodynamic left ventricular myocardium.

[Quantitative EEG analysis of the effects of carbocromen, pentetrazole, beta-methyldigoxin, and strophantin-K in normal human volunteers (author's transl)]

With EEG-interval analysis we studied the influence on C.N.S. of some drugs normally used for cardiovascular diseases: carbochromen, pentetrazole, beta-methyldigoxin and Strophantin-K. All investigated drugs induced activation of alpha-waves, especially in frontal areas with primary small alpha-activity. Dominant alpha-frequency was accelerated. These results confirm the direct and stimulating effects of these drugs on C.N.S. in therapeutic doses. Alpha-acceleration may not only indicate psychostimulation but also indicate epileptogenic effects. All these drugs may provoke epileptic seizures in toxic doses.

The extraction of thallium-201 by the myocardium

The concentration of thallium-201 in the myocardium immediately following injection of tracer is the result of both blood flow delivering tracer to the heart and extraction by the myocardium. In these studies, the extraction of thallium-201 by the canine myocardium was determined as a function of heart rate, coronary blood flow, hypoxia, changes in pH, and following administration of propranolol, insulin, and strophanthin. Under basal conditions, extraction fraction measured 88 +/- 2.1%, following pacing to a rate of 195 beats/min extraction fraction remained unchanged at 88.5%. Similar results were found with changes in pH, propranolol, insulin, and strophanthin. Hypoxia caused a significant decrease in extraction fraction to 77.9%. When coronary blood flow was increased in excess of demands by drugs, extraction fraction fell logarithmically.