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Biomedical subjects

Alfredo de Micheli

Publications and source records attributed to Alfredo de Micheli.

At least 19 recordsLinked to original sources
PubMed2005

[Early and late effects of adenosine in experimental ventricular tachycardia].

INTRODUCTION AND OBJECTIVE: To study the action of adenosine in experimental ventricular tachycardia. MATERIAL AND METHOD: We studied 173 mongrel dogs weighing 13-17 kg anesthetized with 30 mg/kg sodium pentobarbital given intravenously. Myocardial lesions were provoked with the injection of 1-1.5 mL phenol in the free wall of the left ventricle. Ventricular arrhythmia was induced 30 min later with aconitine crystals inserted into the periphery of the damaged area. The potential early and delayed antiarrhythmic action of adenosine was systematically investigated in 85 animals. Leads DII, aVR and aVL, unipolar right and left intraventricular leads, and one unipolar lead on the wall of the superior vena cava were used to record control tracings and tracings in the presence of myocardial damage during ventricular tachycardia and after injection of the drug. RESULTS: Sinus rhythm did not reappear in 72 control animals that did not receive adenosine. In the 63 animals with aconitine-induced ventricular tachycardia associated to myocardial damage, the optimal response to 6 mg adenosine-early and fleeting sinus rhythm-was seen in 45% of the dogs; delayed sinus rhythm was seen in 5%. In 67% of the 18 animals with ventricular tachycardia due only to myocardial damage, early and late sinus rhythm appeared with doses of 6 and 12 mg, and late sinus rhythm was seen with a dose of 12 mg. CONCLUSIONS: The antiarrhythmic action of adenosine was seen not only in ventricular tachycardia due to aconitine (triggered activity), but also in tachycardia induced by the myocardial damage (microreentries).

Adenosine↗
PubMedDate not supplied

[Disclosure of "Brugada's syndrome" with intravenous propafenone].

We present the case of a woman with familial antecedents of a brother who died suddenly at the age of 39 years, and an other with Brugada syndrome. The ECG had not shown the typical pattern of the Brugada syndrome. Based on these antecedents, we decided to perform a pharmacological test with endovenous propafenone, which revealed the electrocardiographic alterations at 10 min after the administration. This is the first case in our knowledge in which endovenous propafenone manifested a concealed Brugada syndrome.

Adult↗
PubMedDate not supplied

[Epistemological focus on sphygmomanometry].

In the XVIII century, the English naturalist Stephen Hales started to apply blood sphygmomanometry in animals. Direct recording of the blood pressure was first applied, in the XIX century, by AE Chauveau and JLM Poiseuille. However, it was not until 1856 that it was possible to perform a direct determination of blood pressure in humans by means of a device designed by Faivre. The first sphygmomanometer appeared at the end of the XIX century. The physician Samuel K. von Basch, native of Prague and who lived a few years in Mexico, fabricated successively three models of sphygmomanometers. The first (1881), with a mercury column, proved to be the most practical and useful. This instrument inspired the sphygmomanometer of the Italian physician Scipione Riva-Rocci who presented it in 1896. His sphygmomanometer, supported on the Vierordt principle, could measure manometrically the force needed to stop the pulse wave. Thanks to the research of Russian physician N. Korotkoff, the auscultatory method was added to sphygmomanometry. During the XX century other instruments to measure blood pressure were fabricated: the Pachon's and Plesch's oscillometers, as well as the aneroid manometer. On the other side, the use of direct tensional recordings has subsisted which has allowed to document the wide oscillations of arterial pressure levels during the day. Anyway, the sphygmomanometer with a mercury column has persisted until the present and will still be used for a long time. A new evolving methodology is the continuous ambulatory sphygmomanometry.

Animals↗
PubMedDate not supplied

[ECG in ventricular hypertrophy].

The electrophysiological criteria for the diagnosis of ventricular hypertrophies, in the light of the sequence of ventricular depolarization and repolarization, are described. Hypertrophy of the right ventricle due to sustained systolic overloading can be global or segmental. In the first case, the magnitude and manifestation of the main vectors resulting from depolarization of this ventricle, i.e., IIs, IIr and IIIr, are increased. In the second case, the magnitude and manifestation of only some vectors resulting from its depolarization are increased; for example, vector IIr (right parietal) in the most frequent type of Fallot's tetralogy and vector IIIr (right basal) in chronic corpulmonale of obstructive origin. Left ventricular hypertrophy, which is generally of global type (aortic stenosis, systemic arterial hypertension), induces an increase in magnitude and manifestation of all the main vectors resulting from depolarization of this ventricle: I (first septal), II (left parietal) and III (left basal). But the left ventricular hypertrophy can also be of segmental type; for example, in idiopathic hypertrophic cardiomyopathy, in which the manifestation of an anteroseptal vector usually predominates. Biventricular hypertrophies produce different electrocardiographic patterns, depending on the preponderance of right or left electromotive ventricular forces. An example of electrocardiographic findings in biventricular hypertrophy is presented. It corresponds to an 18 year-old woman with a large patent ductus arteriosus compressing the left inferior laryngeal nerve, which produced a cardio-vocal syndrome. The patient had pulmonary and systemic hypertension and arterial hyposaturation. The surgical treatment of the patent ductus arteriosus normalized the pulmonary pressure as well as the arterial saturation.

Adolescent↗
PubMedDate not supplied

[Erasmian influences among renaissance physicians].

The fundamental aspects of Erasmus's ethic humanism consisted of ideals of universal peace and tolerance. These ideals are exposed in the great works of his maturity Colloquia and Adagia read and meditated on by renaissance physicians in England, Spain, Germany, Italy, and also in the New Spain. Erasmus's readers were learned and numerous. Among his pupils and supporters in Spain were humanist physicians of Madrid such as Doctors Suárez and Juan de Jarava. Other supporters were in the group of the Sevillian physicians and naturalists. Among the Erasmist physicians, residing in other regions was doctor Andrés Laguna, who translated into Spanish the Dioscorides treatise on medical botany. Many physicians living in New Spain owned copies of Erasmian works, such as Doctors Pedro López (the second) and Juan de la Fuente, who was in charge of the first medical chair at the University of Mexico. The protophysician Francisco Hernández, in response to a petition of Archbishop Pedro Moya de Contreras, wrote a Christian catechism of Erasmian influence, destined for humanists in NewSpain. As asserted by Johan Huizinga, Erasmus was the sole humanist who really wrote for everyone, i.e. for all cultured people.

Europe↗
PubMedDate not supplied

[Usefulness of adenosine to detect advanced paroxysmal atrioventricular block as a cause of syncope].

We present the case of a 66 years old man with recurrent episodes of syncope, up to three times during the last two months without previous symptoms. An ECG after the syncope showed a bilateral block (left anterior fascicle block and right bundle branch block) and first grade atrioventricular block. The exercise test did not demonstrate either AV conduction disorders or tachyarrhythmia episodes. Holter monitoring showed premature ventricular complexes; tilt testing and carotid sinus massage were normal. The electrophysiologic study revealed no alteration in the conduction system. Throughout atrial and ventricular stimulation documented no tachyarrhythmias. However, intravenous administration of 12 mg of adenosine induced complete AV infra-His block with ventricular asystolia of 7.2 sec duration. Adenosine testing can identify patients with syncope due to paroxysmal AV block even when the electrophysiological findings and other conventional tests are not conclusive.

Adenosine↗
PubMedDate not supplied

[Non-complicated and complicated polyfascicular blocks].

Septal necrosis + Peripheral blocks. Because of an extensive septal necrosis, the manifestation of the initial ventricular activation forces decreases in the precordial leads. With left bifascicular block, first ventricular activation forces become evident, and the electrical signs of a sepatal necrosis are concealed. In the presence of a trifascicular block, the manifestation of the first ventricular electromotive forces diminishes again and the electrical signs of septal necrosis become evident once more. Small Q waves are present in leads V1 to V4. Extensive anterior necrosis + Peripheral blocks. Such a necrosis is manifested by QS complexes from V2 to V6. An associated left bifascicular block reduces the electrical manifestation of dead tissue: QS complexes persist only in V3 and V4. A trifascicular block determines the presence of QS complexes from V2 to V5. Posteroinferior necrosis + Peripheral blocks. Electromotive forces of the ventricular activation shift upward, due to a posteroinferior necrosis. QS or QR complexes are recorded in leads a VF, II, and III. A left bifascicular block displaces the main electromotive forces downward, posteriorly and to the left, due to a delay of the posteroinferior activation. QRS complexes become positive and wider in all leads, the reflect the potential variations of the inferior portions of the left ventricle: aVF, II, and III, sometimes V5 and V6. The electrical signs of necrosis are reduced or abolished. With a trifascicular block, wide and slurred QS complexes appear in aVF, II, III, and sometimes in V5 and V6 too.

Bundle-Branch Block↗
PubMedDate not supplied

An experimental contribution to the concept of "jumping wave" phenomenon in the interventricular septum.

OBJECTIVE: The purpose of this study was to evaluate the existence of a histologically bipartite interventricular septum and the electrical independence of both septal masses, as well as to understand the changes of septal activation fronts in the presence of bundle branch blocks. METHODOLOGY: We examined the histological characteristics of both septal masses in 12 canine hearts. Furthermore, in another 11 anesthetized dog hearts, we analyzed morphological and chronological data of intraseptal records with normal activation and in the presence of proximal blocks. RESULTS: A histological discontinuity between the two septal masses in canine hearts seems to exist. Analysis of intraseptal and intracavitary electrical records confirmed slow transmission of the activation fronts from one septal mass to the other when proximal blocks were present. Morphological and chronological changes of the intracavitary complexes agree with the "jumping wave" phenomenon theory. CONCLUSIONS: These results support the validity of this approach to the activation of both septal masses and explain the chronological and morphological changes of the intracavitary records in the presence of ventricular blocks. In addition, this approach is a useful tool to detect the possible coexistence of dead septal tissue.

Animals↗
PubMedDate not supplied

[History of blood transfusion].

The idea of transfusing blood of an animal to another or from an animal to a man or from one to another man, is very ancient. When the doctrine of blood circulation was diffused, in the first third of the XVII century, this idea was give fresh impetus. On began also to inject some substance into the blood, wich will permit to introduce medicaments intravenously. It is worthy to be remembered that in the same year when the Harveyan monography De motu cordis et sanguinis in animalibus was published (1628), the Paduan professor Giovanni Colle suggested a procedure for blood transfusions. Later (1645) the Tuscan physician Francesco Folli showed another procedure, in the presence of the great duke of Toscana, Ferdinando II de Medici. On his side, the surgeon Giovanni Guglielmo Riva realized blood transfusions from animals to men in 1668. Transfusions were already carried out by Richard Lower in London and by Jean-Baptiste Denis in Paris. During the XVIII century, blood transfusions were not effectuated because of some failure occurred in the formed century and of the proscription by civil and religious authorities. Nevertheless these were renewed during the first third of the XIX century in England as well as in the continental Europe. In Mexico the first blood transfusion was effectuated in 1845 by the physician Matias D. Beistegui. At the time persisted the problem of blood coagulation, which could be resolved during the XX century in North America (Crile, 1906) as well as in Latin America (Luis Agote, 1914). Moreover the blood groups were described in 1900 by the Austrian physician Karl Landsteiner, who identified later the Rh factor. It seems completely justified the inscription shining on the façade of the National Archive in Washington: "The past is only prologue".

Blood Transfusion↗
PubMedDate not supplied

[On the clinical value of electrocardiogram].

Emphasis is given to the clinical value of the electrocardiogram, a simple, quick and unexpensive method for heart exploration. It provides functional information and reliably reflects the metabolic and electrolytic characteristics of myocardial fibers. Such an information cannot generally be obtained by other more sophisticated and expensive methods. The localization and extension of myocardial infarction, the positional and structural changes observed during the evolution of chronic cor pulmonale of obstructive origin, some characteristics of atrial and ventricular arrhythmias, the site of preexcitation in WPW syndrome and troubles due to a dysfunction of the ionic channels because of metabolic or genic alterations, are particularly examined. 1. A good correlation exists between the anatomical site and electrocardiographic indication of the infarcted area. 2. In the obstructive chronic cor pulmonale, positional and structural changes of the heart are observed. The first ones correspond to a vertical heart, due to a descent of the diaphragm and an increase of lung volume. The structural changes are due to an enlargement of the right heart: dilatation and hypertrophy. 3. Ventricular arrhythmias habitually present the "jumping wave" phenomenon between both septal masses and the consecutive aberrance of the ventricular complexes. 4. In the WPW syndrome, the thoracic circle permits to infer the site of preexcitation by the orientation of the first fronts of anomalous ventricular activation. 5. Modifications in the Q-Tc interval reflect the variations of ionic intracellular concentrations in a more reliable way than the changes of plasmatic concentrations. The aforementioned evidences the great usefulness of the electrocardiogram in the clinical setting.

Animals↗
PubMedDate not supplied

[Electrical features of hypertrophied left heart].

Chronological and spatial characteristics of the main resultant vectors of the left atrial and ventricular depolarization in normal conditions and in presence of hypertrophy, due to a sustained overload, are described. The coexistence of interatrial, intraatrial, and intraventricular conduction disorders can modify the orientation of these vectors. The main electrocardiographic sign of left atrial hypertrophy is a P wave duration > 0.10 sec in adults. In case of left ventricle hypertrophy, the time of onset of the intrinsicoid deflection (TOID) is prolonged in the near left unipolar leads, and the S wave voltage is increased in opposite regions, i.e. in the right precordial or transitional leads. It is necessary to bear in mind other useful electrocardiographic signs. Hence, absence of the right basal vector (IIId) manifestation in a clockwise rotating heart is probably due to an increase in the basal electromotive forces of the left ventricle (vector IIIi) due to hypertrophy or ipsilateral ventricular conduction disorders. For a correct evaluation of these signs, it is mandatory to perform a rational analysis of the traings, not just a stereotyped electrical exploration. Besides it is very important to determine the Q-Tc interval in the left unipolar leads to establish whether, in these leads, the inverted T wave is of secondary type (normal Q-Tc) or of primary type (prolonged Q-Tc) due to a coexisting subepicardial or transmural ischemia. From these considerations, the usefulness of the thoracic circle and high abdominal unipolar leads is inferred.

Heart Atria↗
PubMedDate not supplied

[Infrequent electrocardiographic changes during exercise stress test in a patient with Brugada's syndrome].

38 year old patient with a syncope history and family background of sudden death had an electrocardiogram compatible with the "Brugada Syndrome". When an exercise stress testing with Bruce protocol was done, we found that during the effort phase and at maximum effort, contrary to a ST segment normalization, a discreet increase of the ST segment elevation of 2 mm in V1 and V2 occurred. During recovery phase a decrease in the ST segment elevation was observed, at a normal level as before the test.

Adult↗
PubMedDate not supplied

[Ischemia-reperfusion myocardial injury].

In this article, we present some considerations on the myocardial damage due to a deficit of oxygen supply. In fact, this damage properly constitutes a partial diastolic depolarization or injury, i.e., a moderate reduction of the rest transmembrane potential. This phenomenon is characteristic of the acute phase of the myocardial infarction syndrome and is responsible for the main electrical manifestations appearing in this phase: disorders of rhythm and conduction, as well as a reduced contractility of the involved myocardial fibers. All the mentioned phenomena are due to a defect of the myocardial energetic mechanisms, owing to the mitochondrial alterations in myocytes: early reduction of the nicotinamide adenine nucleotides, accumulation of calcium ("calcium overload") into mitochondria, and a drop in oxidative phosphorylation. These changes can present again, more exaggerated, in a following phase of evolution of the myocardial infarction due to myocardial reperfusion. Its severity is related to the duration of the initial ischemia period. Moreover, consequences of the oxidative stress can add producing cellular damage by liberation of reactive oxygen species. Oxidant stress causes also alterations in the mitochondrial DNA, i.e., mutations due to oxidation of nitrogenous bases. During the initial ischemia phase, as well as during reperfusion, metabolic therapy can be very useful as, for example, glucose-insulin-potassium solutions (G-I-K). These could act as scavengers of the free radicals derived from oxygen and avoid or reduce the myocardial damage due to reperfused myocytes. Metabolic drugs, as for example trimetazidine, antioxidants, etc, can also be used in the myocardial reperfusion phase.

Electrophysiology↗
PubMedDate not supplied

[On metabolic therapeutics G-I-K in surgery of cardiac patients].

The basic principles of the metabolic therapeutics with glucose-insulin-potassium solutions, already proposed by Dr. Demetrio Sodi Pallares, are exposed. Chronologic succession of this treatment during the preoperative, transoperative and postoperative phases of heart surgery, as well as some personal observations of one of the authors, are described. The glucose-insulin-potassium solution is a powerful system, providing very useful energy to protect the injured myocardium during cardiovascular surgery. Many publications support this assertion. The most recent ones indicate a reduction of low output syndromes due to interventions on coronary arteries, as well as a significant diminution of circulating fatty acids after primary angioplasty. The mentioned solution, in higher concentrations than the initial one, could become routine therapeutics in medicine and surgery centers, in general.

Cardiac Surgical Procedures↗