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Biomedical subjects

E Kabela

Publications and source records attributed to E Kabela.

At least 37 records · Page 2Linked to original sources
PubMedDate not supplied

[The long-term follow-up of 1000 patients with a valve replacement by the prosthesis of the Instituto Nacional de Cardiología Ignacio Chávez].

The long-term follow-up of patients with bioprosthetic valves manufactured at the Instituto Nacional de Cardiología Ignacio Chávez is presented. From February 1983 to May 1990, 1068 patients were operated and 1252 valves were replaced. Eighty two percent had rheumatic heart disease with one or more injured valves. In 17% it was a replacement of a failing valve. Seventy three percent of the patients had a low or medium-low socioeconomical status. There were 176 perioperative deaths in the first month after the operation and 150 patients were lost to follow-up. The rest (740) are the subject of this report. Mortality associated with valve related complications had a probability of 0.74 +/- 0.05, it had a significative increase after month 70th, with a 88% survival at that time. The functional class in the whole group improved 90%, with confidence limits for binomial distribution between 85 and 97%. There was also a significant reduction in heart enlargement. There were 161 prosthesis dysfunctions due to valve calcification or rupture, 50 were replaced. Twenty-three patients had hemolysis, and 19 infective endocarditis. There were 6.5% with systemic embolism in spite that only one half of those in which there was an indication, different of the valve replacement, received anticoagulant medication. The use of this prosthesis is on economical and medical satisfactory solution for the problem of a great number of our population of patients.

Academies and Institutes↗
PubMedDate not supplied

[Mechanisms of conduction disorders in digitalis poisoning].

Ever since the first papers on the mechanism of the arrhythmias of digitalis were first published, during the first two decades of this century, the issue has been a controversial one. Since the automaticity induced by digitalis intoxication has different characteristics when compared to normal automaticity, it has been suggested that probably the mechanisms for these two types of spontaneous activity are different. It has been recently proposed that the automaticity induced by digitalis intoxication could be secondary to the after potential oscillations described in isolated conducting fibers. In order to test this hypothesis we used two experimental models which allow for a careful analysis of the ectopic activity, without the interference of the sinus rhythm. These studies were done in two groups of animals: one, with electrically isolated atria, was used to analyze supraventricular arrhythmias. The other, with chromic atrioventricular block, was used to study ventricular arrhythmias. The results obtained from these experiments show: 1. High therapeutic doses of digitalis enhance the postpacing inhibition of normal pacemakers; 2. When the ectopic rhythms of digitalis intoxication appear, they show postpacing stimulation; 3. Ectopic activity shows a direct relationship with the rate of the conditioning stimulation, and both the coupling period and the number of premature beats depend on this rate. In view of the similarity between the behavior of these arrhythmias and that of the after potential oscillations, we conclude that these oscillations are responsible for the ectopic automaticity of digitalis intoxication.

Animals↗
PubMedDate not supplied

[Policy guidelines and practical considerations for the development of technology at the Instituto Nacional de Cardiología de México].

In order to face the current economical problems of the country, our Institute has intensified its efforts to replace the imports of medical goods by developing its own medical technology. This article summarizes what we have achieved in this field and describes the rules to be followed in the future. We describe the program on the designing and development of heart valve prosthesis together with an hydraulic-electrical system to test them. In the field of computed instruments, we have developed a system of "synchronos color pictures" to be applied in nuclear medicine. In the field of electrocardiography; an EKG paste, a computed program for automatic EKG interpretation and a "filter" of the 60 cycle interference. The Institute is engaged in the designing of a sophisticated EKG machine at low cost, and EKG tracing simulator for teaching purposes. These programs have been shared with others institutions of the country.

Academies and Institutes↗
PubMedDate not supplied

[Effects of several anti-arrhythmia agents on excitability and conduction depressed by digitalis agents].

Digitalis intoxication is characterized by the appearance of most of the types of severe arrhythmias described and also by important disturbances of cardiac excitability and impulse propagation. Most of the antiarrhythmic agents that are used in the treatment of these conditions also depress excitability and impulse propagation. These characteristics are frequently responsible of severe complications. The purpose of this paper is to determine the type of interactions that exist between digitalis and some antiarrhythmic agents, and compare them with the effects of magnesium. The experiments were done in several groups, of dogs anesthetized with pentobarbital and with the chest open. Excitability, conduction time and functional refractory period were determined using the classical methods. The protocol used consisted in the comparison of the actions of toxic doses of digitalis on excitability and conduction times of the atrial and ventricular tissues, under control conditions and in the presence of therapeutic doses of procainamide, lidocaine and magnesium. The results showed that procainamide worsened the depression of excitability and conduction produced by digitalis intoxication, while lidocaine does not add to the digitalis effects and in some cases it produces a partial improvement of these parameters. Magnesium completely reverts the effects on excitability and conduction. These results provide us with rational pharmacological bases for the treatment of digitalis intoxication and suggest that magnesium could be very useful in the management of patients with severe digitalis intoxication.

Animals↗
PubMedDate not supplied

[Automatism: an intrinsic property of cardiac tissues].

Automaticity is an intrinsic property of some types of cardiac tissues, like the nodes and the conducting fibers. Automatic cells are characterized by the appearance, during diastole, of a slow depolarization which is capable of reaching threshold and generate an action potential. This depolarization is the so-called slow diastolic depolarization, or pacemaker potential. Tissues with automaticity do not have the same intrinsic firing frequency, which determines the existence of a true pacemaker; normally this role is assumed by the sinus node and several latent, or subsidiary pacemakers. The latter do not give any manifestation, because, since they have a slower firing frequency than that of the true pacemaker, the impulses generated by the latter will activate them before they can reach threshold. The ionic mechanisms that originate the pacemaker potential are just some of the processes that constitute the electrophysiological properties of the cardiac cell membranes. The mechanism includes the slow inactivation of an outward current combined with a constant inward current. Recently published evidence suggests that the pacemaker potential could be the resultant of an inward current that is slowly activated during the final part of the repolarization, but these data are still controversial and difficult to interpret. The factors that regulate heart rate modify the electrophysiological characteristics of the membrane by means of three major mechanisms: the slope of the pacemaker potential, the voltage of the threshold potential and, the maximum diastolic potential. Some of the most important factors that modulate heart rate include the neurotransmitters of the automatic nervous system, the plasmatic levels of some ions, like potassium and calcium, and changes in the intrinsic properties of the membrane, like the influence of heart rate on the activity of the sodium pump.

Animals↗
PubMedDate not supplied

[Manufacture of valvular prostheses from bovine pericardium, their evaluation and the initial results of the 1st group of implants].

The results obtained with some types of bioprostheses together with the present economical situation of the country pointed out that the manufacture of another type of bioprostheses was necessary. After a careful analysis of the results that had been reported in the literature with the diverse types of bioprostheses had been made, it was concluded that pericardial valves were the best choice for our specific requirements. The first problem that had to be solved was the identification of the adequate fraction of purified glutaraldehyde that would provide for adequate tissue fixation. This was determined using several types of biophysical and biochemical techniques. The next step was to find the adequate manufacturing techniques that would provide us with optimal function valves. This was achieved by testing the functional characteristics of these valves on a cardiac cycle simulator. The first group of 132 patients that received this type of valve includes 9 multiple valve replacements, 24 aortic, 98 mitral and 1 pulmonary valve replacements. All the surviving patients have shown a clear improvement and they all show adequate function of their bioprostheses. The function of the valves has not been involved in any of the patient deaths. Since there has not been any evidence of disfunction, these results show that the manufacturing techniques and the design of these bioprostheses is adequate. Naturally to long-term durability of these valves will have to wait before it can be valorated.

Adolescent↗
PubMedDate not supplied

[Effects of amrinone, a new non-digitalic positive inotropic agent, on the efficiency and coronary circulation of the heart].

It has been reported recently that 5-amino-34,4'-bipyridine-6(1H)-one is a new positive inotropic agent that appears to offer significant advantages over the cardiac glycosides. The effects of this agent were studied in a modified heart-lung preparation which allows the measurement of coronary flow and oxygen consumption in addition to a controlled study of cardiac contractility. In two models of cardiac insufficiency the administration of 5 mg amrinone caused a marked increase in cardiac output and a considerable decrease in left atrial pressure with complete reversal of the failure. In addition, the drug produces a 78% increase in coronary flow. Amrinone produces in these preparations a proportionally larger increase in cardiac output than in oxygen consumption, thus this agent increases cardiac efficiency. These results suggest that this new compound could be very useful in the treatment of cardiac insufficiency in congestive heart failure.

Aminopyridines↗
PubMedDate not supplied

[Mechanism of the antiarrhythmic effect of inorganic phosphates in digitalis poisoning].

THe synergistic effects between calcium and the therapeutic and toxic actions of the cardiac glycosides have suggested that a way of treating digitalis intoxication could be through a decrease in free plasma calcium. In 1966, Burckhardt and La-Due published a study based on the inverse relationship that exists between plasma phosphates and calcium. It was shown then that potassium phosphate had a pronounced antiarrhythmic effect on digitalis induced arrhythmias. The use of potassium phosphate for this study prevented the analysis of the role of the phosphates in these effects, since the actions of potassium in digitalis toxicity precluded any conclusion. The purpose of the present paper is to study the effect of phosphates on digitalis intoxication and its possible mechanism of action. The results obtained demonstrated: 1) Phosphates have a marked antiarrhythmic effect in digitalis induced arrhythmias. 2) This effect is due to a decrease in free plasma calcium. 3) The lowering of this calcium pool occurs in the blood and is not mediated by hormonal or renal mechanisms. 4) The ions that disappear from the free calcium pool do not precipitate. 5) The use of phosphates could be useful in the treatment of some clinical cases of advanced digitalis intoxication.

Animals↗
PubMedDate not supplied

[Mechanism of the decrease in free plasma calcium produced by the administration of inorganic phosphates].

The preceding paper (published in the issue) demonstrated that the administration of sodium phosphates exerted a marked antiarrhythmic effect on several models of digitalis intoxication; this action being due to a decrease in the free calcium fraction. THe purpose of the present paper is to analyze the effects that several concentrations of phosphates have on the different calcium fractions and determine the fate of the ions that are disappearing from the calcium pool. This study was done using two models of digitalis intoxication, one in the intact dog and the other in the heart-lung preparation and two protocols in which the experiments were carried out using blood in vitro. The results show: 1) the administration of phosphates into the intact dog produces a small decrease in the total calcium content of plasma and blood. 2) the increase in phosphate concentration runs parallel to an important decrease in free calcium. 3) In the heart-lung preparation, phosphate administration markedly decreases free calcium but does not lower total calcium in plasma or blood. 4) An increase in phosphate concentration of plasma in in vitro conditions does not alter total calcium and decreases free calcium in a linear relationship with the levels of phosphates. 5) A fraction of the phosphates added to the plasma and the ions that are disappearing from the free calcium pool are binding to a plasmatic macromolecule (most probably a protein) which prevents them from precipitating.

Animals↗