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Biomedical subjects

G A Medrano

Publications and source records attributed to G A Medrano.

At least 73 records · Page 4Linked to original sources
PubMedDate not supplied

[Vectorcardiographic manifestations of left intraventricular conduction disorders].

Both, the vectorcardiographic changes produced by the various degrees of left bundle branch block and these observed with the different types of left distal block, are described. When a "wave jumping" phenomenon exists, the vectorcardiographic changes are more characteristic in the horizontal plane than in the frontal plane and can be interpreted satisfactorily in basis of the ventricular activation sequence. The normal counterclockwise rotation of the horizontal vectorcardiogram persists in the presence of left bundle branch block of slight and moderate degrees, since the electromotive forces of the free left ventricular wall are still predominant. In the majority of intermediate degree blocks, the middle portion of the RH loop develops with a clockwise rotation and general aspect with a clockwise rotation and the general aspect of the ventricular loop resembles an eight figure. This is due to the electromotive forces originated by the delayed depolarization of the left septal mass that starts to predominate. With advanced degrees of block, the largest portion of the RH loop shows a clockwise rotation, as well as marked notchings and slurrings. The initial anterior portion of the horizontal vectorcardiogram does not disappear, but is situated to the left of the anterior-posterior axis with a counterclockwise rotation (first right septal vector). Otherwise, the direct electrical sign of left distal block emphasized: evidence of delayed activation in a limited zone of the homolateral ventricle. This local delay gives rise to an asynchronism of the activation phenomenon between the upper and lower regions of the ventricle. The diagnosis of left bifascicular block is based essentially on the evidence of unequal delay of the activation sequence in the basal regions and in the inferior ones of the homolateral ventricle and also on the frequent persistence of the first left septal vector.

Adult↗
PubMedDate not supplied

[Vectorcardiographic diagnosis of the myocardial inactivatable zone].

Clinical importance of the vectorcardiographic exploration (distant and spatial) of the myocardial electrical phenomenon is emphasized. This technique constitutes a useful integration of electrocardiographic exploration (near and analytical). The more characteristic morphological and chronological changes due to an inactivatable area are discussed in the light of ventricular myocardial depolarization. Some typical vectorcardiographic features corresponding to the presence of a myocardial inactivatable zone are presented. The utility of the complementary elements which vectorcardiography can bring to electrocardiography is emphasized. Both of these procedures integrate a rational exploration of electrical activity of the myocardium, the solid base of prognostic and therapeutic decisions in cases of myocardial infarction.

Aged↗
PubMedDate not supplied

[Vectorcardiographic manifestations of the W-P-W syndrome with associated cardiopathy].

Electro-vectorcardiographic curves corresponding to Wolff-Parkinson-White syndrome associated with cardiopathy are analyzed on the basis of the sequence of the ventricular depolarization phenomenon as well as of the heart's position and rotation. A more than 30 msc interval between the end of the initial slurring and the vertex of the R loop, or of that of the R wave in the left leads, permits us to infer the coexistence of left ventricular hypertrophy. Segmental irregularities or distortions of the vectorcardiographic ventricular curves suggest the presence of a limited inactivable+ zone. Extensive deformations are more suggestive of diffuse myocardial damage. Sometimes primary disturbances of ventricular repolarization, probably due to antiarrhythmic medication, are observed.

Adolescent↗
PubMedDate not supplied

[Electrovectorcardiographic manifestations of supraventricular ectopic rhythms (an interpretive hypothesis)].

When a low right atrial rhythm is present, P waves are negative in the low leads, they are variable in a VR and positive in a VL and LI. The figure eighth PF loop is located in the first quadrant, the PH loop has a counterclockwise rotation, and the PS can rotate in either direction. In the presence of upper left atrial rhythms, P waves are positive in the low leads and negative in a VL and a VR. The PF and PH loops can be found in the third quadrant of both planes with a clockwise rotation. If the rhythm originates in low left atrial regions, negative P waves are recorded in left precordial leads and positive ones in a VR and a VL. The PF loop has counterclockwise rotation or its branches superimposed and is situated in the second quadrant; PH with clockwise rotation is registered in the third quadrant; PS with either counterclockwise or clockwise rotation develops above and slightly ahead of the E point. When a nodal rhythm exists, P waves are negative in the low leads. The P loops show a counterclockwise rotation or a figure eight morphology. In the absence of atrial enlargements, the PF loop can be recorded in the first quadrant and the PH in the first or the fourth quadrant.

Arrhythmias, Cardiac↗
PubMedDate not supplied

[Experimental subendocardial anterolateral infarctions].

Epicardial and thoracic unipolar tracings were recorded in 44 dog hearts after chemical necrosis had been produced on the anterior face of the free left ventricular wall by intramural injection of 96 percent alcohol. The damaged area was transmural (22 cases), intramural (10 cases) or localized in the interior half of the left ventricular wall. The last is commonly described as subendocardial necrosis (12 cases). Generally, direct leads recorded QrS complexes, with the R wave delayed according to the degree of damage to the myocardial muscle. These complexes were registered in at least one of the direct or semi-direct leads when myocardial necrosis was transmural or subendocardial in the interior half of the wall. Nevertheless, a small subendocardial (3 mm or less) or intramural necrosis created tiny Q waves, somewhat slurred but of normal duration, followed by R waves of low voltage. These signs alone are not diagnostic of myocardial necrosis. However, the presence of these Q waves in V2 and V3 only, or from V2 to V4 with greater voltage than in V5 and V6, implies the existence of non-transmural necrosis. The same applies when polyphasic ventricular morphologies are recorded in two intermediate precordial leads in absence of intraventricular conduction disturbances. These can mask the manifestation of transmural myocardial necrosis. Electrophysiologic data are sufficient to establish diagnosis if the infarcted area involves a substantial part of the thickness of the ventricular wall. However, in cases of small subendocardial or intramural necrosis, there are not always signs of dead tissue. At the same time, if the extension of transmural necrosis is more longitudinal than transverse, there is less probability of recording QS complexes in the precordial leads.

Animals↗
PubMedDate not supplied

[Pseudonormalization of repolarization during physical exercise and the hemodynamic findings].

The meaning of normalization of abnormal T waves during exercise is still unclear, twenty patients with this electrocardiographic pattern during treadmill stress test were studied with coronary arteriography. They were classified in two groups: Group I: In which 3 patients had isolated "pseudonormalization" of the T wave, and Group II with "pseudonormalization" of the T wave plus a positive stress test or an old myocardial infarction. Results allowed us to conclude that this phenomenon per se is not a diagnostic clue of coronary injury; however when we observe it associated with a positive stress test or an old myocardial infarction it may be indicative of severe and multiple coronary vessel injury.

Adult↗
PubMedDate not supplied

[Experimental left atrial infarct].

Electrical changes produced by an experimental left atrial infarction were studied in 15 mongrel dogs, anesthetized by sodium pentobarbital intravenously and submitted to intratracheal intubation, medical sternotomy and heart exposition without open the pericardial sac. 5 to 8 ml of alcohol 96 degrees were infiltrated into left atrial myocardium by means of a thin needle introduced superficially and parallel to the visceral pericardium. Left atrial damage reduces the electromotive, forces corresponding to the anterolateral portions of the left atrium giving rise to QS or QR slurred P waves with very delayed activation when left portion of interatrial band was damaged. Surface ECG records bimodal wide P waves with or without a qp wave in V2-V4 leads, associated to STa elevation in lead a VL and higher leads in the fourth and third left intercostal spaces at the vertical line of V4. QTac interval is more prolonged in right than in left registries as it was observed in right atrial damage, which implies a more earlier repolarization of left atrium. These data are useful for diagnosis of infarction or myocarditis.

Animals↗
PubMedDate not supplied

[History and perspectives of electro-vectorcardiography].

A panoramic view of the development of electrovectorcardiography from its beginnings until the present is reported. The functional essence of this exploratory method is emphasized and the basic steps of its evolution are described: the bipolar or differential leads in the beginning, the distal unipolar leads and the initial vectorcardiography in the 30s, the proximal unipolar leads in the 40s, the His electrograms and intracavitary and thoracic mapping in the 60s and later, the continuous records on a magnetic band. The evolution from Einthoven's original electrocardiograph to the modern apparatus of direct inscription and cathode-ray oscillographs is also described. Finally, the contribution of the Mexican School to a rational approach to electrovectorcardiography and clarification of some aspects of myocardial electrophysiopathology is presented.

Electrocardiography↗
PubMedDate not supplied

[The P-wave in systemic arterial hypertension].

An abnormal electrocardiographic P wave (AEPW) has been interpreted as indicative of heart failure, hypertrophy or dilatation of left atrium, or diminished left ventricular compliance. In order to determine the significance of this electrocardiographic sign we studied 47 cases of systemic arterial hypertension (SAH) without heart failure or coronary obstruction. Patients were assigned at 2 groups: group A (22 cases with P wave duration greater than 0.11 seg. (LEAD D2); and group B 25 cases with P wave duration less than this. The following data were studied in all cases: left ventricular ejection fraction (LVEF), left ventricular presystolic filling fraction (LVPFF), Sokoloff electrocardiographic index (SEI), final diastolic pressure of LV (FDPLV), and systolic arterial pressure (SAP). Results were: (Table: see text). There were not statistical differences in these values between groups A and B (including the FDPLV value not shown in the table). Correlation coefficient between duration of P wave and the other parameters studied were also no significant. AEPW in SAH is not related to an specifically degree of left ventricular hypertrophy or disfunction; therefore, hypertensive heart disease should not be classified taking in account this electrocardiographic sign.

Blood Pressure↗
PubMedDate not supplied

[Regarding so-called ischemia, injury and necrosis].

The authors emphasize that "necrosis", "injury" and "ischemia" are terms employed with different meanings by electrocardiographists, hemodynamists and pathologists. In the electrocardiographic field, they correspond respectively to complete diastolic depolarization, partial diastolic depolarization and slow repolarization: the three key concepts of the electrophysiopathology. The terms as used in electropathology reflect functional changes based on metabolic and electrolytic conditions which must be explored by means of such functional methods as electrocardiography. Therefore the electrical meanings of the terms "ischemia", "injury" and "necrosis" do not correspond to those understood by hemodynamists and pathologists. The electrophysiopathologic terminology should always be used to indicate functional phenomenon which originates at the cellular level in order to avoid diagnostic pitfalls and mistakes.

Coronary Disease↗
PubMedDate not supplied

[Electro-echocardiographic correlation in mitral valve prolapse].

The study was performed in 33 patients with echocardiographic diagnosis of mitral valve prolapse (PVM), without any other associated heart disease. A 19 derivations electrocardiogram (ECG) was performed a direct inscription 4 channel Samborns 150 machine at 25 and 50 mm/sec. The purpose of the study was determine the alterations in ventricular depolarization and repolarization, and to correlate them with valve prolapse, as well as with cavitary and parietal dimensions, as measured by M mode and/or two-dimensional echocardiography. Left ventricular hypertrophy detected by ECG agreed with the ECO test in 77%; the sensitivity was of 86% and specificity of 67.5%. Left ventricular hypertrophy detected by ECG was not related with the type of prolapse. Ventricular repolarization alteration was very frequent (84.8%). Association of this parameter with initial notch of R in a VF becomes important for diagnosis suspicion (p less than 0.01). When the abnormal repolarization affected the anterolateral wall, posterior valve prolapse was frequent; when the posteroinferior region was the affected one, the prolapse occurred more frequently in both valves. An important correlation (p less than 0.01) was found between left ventricular dilatation detected by ECO and the abnormal ventricular repolarization.

Adolescent↗
PubMedDate not supplied

[An experimental model of helicoid ventricular tachycardia (torsades de pointes). Preliminary report].

Studies on twenty dogs were performed. With open thorax, aconitine was injected into the thickness of the interventricular septum. D2 and direct derivations were registered in the epicardium of the right atrium, on right and left septal surfaces and in the His bundle. As the experiment ended, the heart was taken out to determine the placement of the electrodes and the site of application of aconitine. "Torsades de pointes" were obtained in 15 dogs, with a rotation of 180 degrees during the episode. The rotation of A QRS occurred with a beat of intermediate direction which corresponded to a ventricular capture of a sinus beat or a ventricular echo after that beat, and a sequence of activation of AHV established in various beats, the first of which had a prolonged AH (p less than 0.01). The consecutive change of direction of QRS happened when that sequence of activation disappeared, and there was an A-V dissociation as in the beginning of the episode. In conclusion, in this experimental model, the Torsades de pointes were produced by double mechanism, an increased focus of automatism and a macro-re-entry that involves the two branches of the His bundle, the A-V node and the atrium.

Animals↗
PubMedDate not supplied

[Electro-vectorcardiographic examination in cardiopathy of pulmonary origin].

We describe the electrical signs due to the positional changes of the heart and those related to hypertrophy and dilatation of the right heart chambers in subjects with chronic cor pulmonale. The positional changes mainly reflect the vertical position of the heart, which is almost constantly associated with some degree of clockwise rotation, because of the descent of the diaphragm and increase of lung volume owing to chronic emphysema. The electrovectorcardiographic alterations observed in right ventricular hypertrophy owing to permanent pulmonary arterial hypertension differ depending on the type of hypertrophy: global or segmentary. The first is generally observed in the chronic hypertensive pulmonary cardiopathy of vascular origin and produces an increase in the magnitude and manifestation of all the principal vectors of right ventricular activation. The second is frequently present in the chronic hypertensive pulmonary cardiopathy of bronchial origin and increases only the magnitude and manifestation of the right basal vector. The progressive dilatation of the right heart chambers evident during the evolution of the chronic hypertensive pulmonary cardiopathy toward the congestive heart failure produces SAQRS rotation to the right, downward and forward or backward. During acute intercurrent bronchopulmonary infection or embolia, transient electrical signs of right cardiac chambers dilatation are present.

Arrhythmias, Cardiac↗
PubMedDate not supplied

[Value of the DI and AVL leads in the diagnosis of infarction of the right ventricle].

The present study attempts to analyze the sensitivity and specificity of the S-T segment depression in I and a VL leads in the diagnosis of postero-inferior myocardial infarction with right ventricular extension. Thirty four specimens from autopsies performed in the Instituto Nacional de Cardiología Ignacio Chávez with histopathological evidence of postero-inferior myocardial infarction, with an adequate clinical, enzymatic and electrocardiographic documentation were studied. In 23 the postero-inferior myocardial infarction had extended to the right ventricle (group I) and in ll only left ventricle was involved (group II). There were not significative differences in severity and extension of coronary obstructions between the two groups studied. Sensitivity of S-T segment depression in DI lead ad diagnosis of right ventricular extension had 82.6%, specificity 90.9%, positive predictive value 95%, negative predictive value 71.4% and diagnostic efficiency 85.2%. Sensitivity of S-T segment depression in a VL lead as diagnostic of right ventricular extension was 91.3%, specificity 81.8%, positive predictive value 91.3%, negative predictive value 81.8% and diagnostic efficiency 88.2%.

Electrocardiography↗
PubMedDate not supplied

[Disorders of intraventricular conduction].

An electrophysiologic approach to intraventricular conduction disturbances, preeminently functional phenomena, is presented. They are divided into two groups: the proximal type corresponding to obstruction of excitation impulses in the main trunk of one intraventricular specific system; distal or peripheral type, due to an obstruction in the distal subdivisions of the system (fascicular) or to regional myocardial alterations (parietal). Trunkal blocks produce global delay of the activation sequence of the ipsilateral ventricular myocardium. Consequently they are recognized by slurred R waves and delayed time of onset of intrinsicoid deflection in all ipsilateral leads. Distal or peripheral blocks cause a segmentary delay of the activation phenomenon of ipsilateral ventricular myocardium. This is revealed by slurred R waves and delayed time of onset of intrinsicoid deflection only in those leads which explore the affected region. Peripheral blocks can be classified from a topographic point of view when they appear in the area of distal subdivisions of the intraventricular conduction system.

Electrocardiography↗
PubMedDate not supplied

[Biventricular infarctions].

Posterior biventricular myocardial infarctions are more frequent than anterior ones. Unipolar right and high abdominal leads are necessary for the diagnosis. These supplementary leads are dependable, can be repeated as many times as necessary and show the evolution from signs of injury to those of inactivable tissue (Q waves of 0.04 sec or more). This information on evolution increases the diagnostic value of the electrocardiogram since signs of an injury current can be observed in other conditions as well. The diagnosis of right ventricular infarction can be established even in the presence of RBBB, but the differential diagnosis with acute cor pulmonale must be established on clinical as well on laboratory basis. The signs of an inactivable zone of the free right ventricular wall are more frequently observed in posterior biventricular infarctions than in the anterior ones. In the latter, signs of subepicardial injury are more accentuated in right thoracic leads than in V2 and V3, which indicate anterior right ventricular involvement. The same signs are also observed in experimental studies. A review of medical literature concerning the prognosis and evolution of biventricular myocardial infarctions is presented.

Electrocardiography↗
PubMedDate not supplied

[Electrovectocardiographic manifestations of left ventricular and biventricular growth].

The basic criteria for the electrical diagnosis of left ventricular and biventricular enlargements are discussed on the basis of the myocardial depolarization and repolarization sequence. Left ventricular dilatation secondary to isolated diastolic overloading increases the manifestation of the main vectors resulting from the activation of this ventricle. These changes reflect the proximity of the left ventricular walls to the exploring electrodes. The above mentioned vectors appear as tall R waves and wide ventricular curves with counterclockwise rotation on the three planes. If the diastolic overload is a isolated phenomenon, T waves are positive and asymmetric on the left leads while the T loop, of secondary type, is concordant in its orientation with the R loop. This fact is due to a prolonged duration of the repolarization phase of the left ventricle. Global left ventricular hypertrophy produced by a sustained systolic overloading increases the magnitude and manifestation of all the vectors resulting from the depolarization of this ventricle (I, II l, III l) owing to the prolonged duration of the corresponding activation fronts. When LBBB is also present, the first septal vector is not evident. In extreme degrees of the systolic overload, the T wave is inverted and shows morphologic secondary characteristics in left leads, and the T loop opposes the R loop on frontal and horizontal planes. The directional changes of the repolarization fronts of free left ventricular walls can satisfactorily explain these features. Left ventricular hypertrophy of a segmentary type, such as that observed in idiopathic myocardiopathy, generally increases the magnitude and manifestation of septal vector I and II left. When both ventricles are hypertrophied, the electromotive forces originating in the more severely affected heart chamber predominate in electrical records.

Cardiomegaly↗