Biomedical subjects

M Aldakar

Publications and source records attributed to M Aldakar.

10 recordsLinked to original sources

PubMed1992

[Experimental study of fulguration on a healthy ventricle. I. Acute lesions].

The effect of fulguration shocks applied to the healthy ventricular myocardium in 6 pigs weighing between 63 and 100 kg showed that for shocks with the same energy level as those used in clinical practice, the immediate effects of fulguration result in a hemorrhagic zone with a diameter of up to 15 mm. Histopathological examination revealed tearing of the cardiomyocytes which is probably related to barotraumatic phenomena. Deflagrating shocks of 90 Joules, with a short development time (non-self-inductive circuit) can lead to perforation of the myocardium in both the right and left ventricles. In this animal model, arrhythmia was rare and did not lead to sudden death in any case. No vascular damage was observed.

Acute Disease↗

PubMed1992

[Experimental study of fulguration of healthy ventricle. II. Chronic lesions].

The effect of fulguration shocks was studied using healthy ventricular myocardium of 12 pigs weighing between 63 and 100 kg. With shocks of equal energy to those used clinically, lesions seen 24 hours after the session in two pigs showed the formation of loose fibrosis and of marked cellular infiltration as well as zones of hypercontraction with calcium precipitation. The size of chronic lesions seen during periods ranging from one week to 2 months was studied in 4 pigs. Transmural plaques with a diameter of 1.5 to 2 cm were seen in the right ventricle. For the same energy levels of 240 Joules delivered to left ventricular tissue, lesions were of the same size but were never transmural. Under certain conditions, lesions were disposed in the direction of the neutral electrode.

Acute Disease↗

PubMed1991

[Physical and biophysical aspects of high energy intracardial electrical discharges. 4. Effects of fulguration beads in an isotropic diphasic medium].

Study of the effects of fulgurating electric shocks on an isotropic protein gel more supple than ordinary myocardium provides better understanding of the mechanical effects of fulguration on biological tissues. With a shock and energy level of the type used clinically, a central crater is produced measuring 4 to 6 mm in diameter and a few millimetres deep, surrounded by a crown 30 mm in diameter. Damage due to the mechanical effects of fulgurating shocks is thus 3 to 15 times greater than the size of the electrode. The size of lesions is generally proportional to the energy level and is greater at the anode than cathode. It is also greater with impulses having a short rise time. When the electrode is almost parallel to the wall, the surface area of mechanical lesions is larger and more irregular and it is less deep than when the electrode is perpendicular to the gel.

Biophysical Phenomena↗

PubMed1990

[Physical and biophysical aspects of high energy intracardiac electrical discharges. II. Correlations between the physical and electrical effects of liminal and infraliminal shocks].

The electrical phenomena produced during the fulguration impulses are analyzed using a digital oscilloscope which enables the calculation, with precision, of the energies consumed all along the curve or between chosen times. Moreover, it enables the calculation of the corresponding impedance values and shows that the latter varies during all the discharge. The explanation for these impedance variations is obtained thanks to rapid cinematography, showing the formation of the fulguration bubble. Hence, one can observe an impedance variation which is quite distinctive from the one which would correspond to the simple passage of an electrical current in saline solution. Particularly at the end of the impulse, an important increase in the impedance corresponds to the loss of ionization of the bubble. Therefore, by simply reading these electrical parameters, it is possible to know the main stages of the fulguration phenomenon for impulses situated around the deflagration threshold.

Algorithms↗

PubMed1990

[Repair of post-infarction interventricular communication in a 81-year-old patient].

Post-infarction interventricular fistula (IVF) is a complication with a poor prognosis, particularly when it occurs very early after myocardial necrosis, when it is wide in diameter and even more so if it is at a posterior site, and if there are associated lesions which require surgery. An operation is often considered as contraindicated in cases where the patient is elderly. The authors report on the case of an 81-year-old diabetic patient operated for a wide post-infarctus posterior IVF and aorto-coronary artery bypass surgery. The operation is still a clinical success after 23 months of follow-up, showing that old age is not an absolute contraindication for surgery in cases of post-infarction IVF.

Aged↗

PubMed1990

[Physical and biophysical aspects of high-energy intracardiac electric discharges. III. Correlation between physical and electric effects for the use of supraliminal shocks].

Using the same methods as for the measurement of electrical parameters by means of an oscilloscope with a wave shape calculator to determine at all points the energy and impedance values, as well as high speed cinematography, the analysis of the behavior of these parameters for shocks with energies close to those used in clinical medicine can be carried out. It shows namely an important decrease in the impedance at the current peak due to an important ionization of the fulguration bubble. It underlines the different behavior of the anode and cathode bubbles, in relation with the size of the bubbles obtained thanks to rapid cinematography. Comparative measurements concerning the polarity, the size of the indifferent electrode, the medium used in vitro and in vivo have supplied the elements to enable the precise determination of the adequate electrical parameters for the good use of fulguration.

Animals↗

PubMed1990

[Physical and biophysical aspects of high-energy intracardiac electric discharges. I. The discharge bubble].

Endocavitary discharge produces an electrical spark at the end of the probe. This in turn produces a plume of steam which lasts for about ten milliseconds and which subsequently acts like a cavitation bubble. This phenomenon is well known in the branch of physics dealing with dynamics and fluids, and should be subjected to rapid kinetic recording. It may make it possible to explain various barotraumas which are observed during the discharge. However, the plumes of steam produced by the discharge have some highly specific features which are due to the fact that the discharge is usually produced using a monopole in an electrolyte. In addition, the shape of the electrode also affects the formation of the bubble. This results in a description of the cavitation bubble produced by the discharge as the "discharge bubble".

Biophysical Phenomena↗

PubMed1988

[Invasive and non-invasive methods for the diagnosis of tachycardia].

Surface ECG permits, in most cases, to determine the ventricular or supraventricular origin of a tachycardia with wide complexes, to individualize VTs with aspects of Left Buble Branch and left axis, to visualize epsilon waves in some chronic VTs. The late potentials detected by the sum-mean method seem to be well correlated with the occurrence of ventricular tachycardia, especially after myocardial infarction. The area of origin of a VT may be determined quite precisely by cartography and topographic stimulation. The predictive value of the provocation methods (stress test, transesophageal stimulation, endocardiac stimulation) is discussed. Some arrhythmias may be discovered on ultrasonic cardiography and the exact mechanism of some reciprocal permanent junctional tachycardias is well demonstrated with endocardiac stimulation and fulguration. Nuclear magnetic resonance offers a new possibility of etiological diagnosis in ventricular tachycardias with left delay.

Arrhythmias, Cardiac↗

PubMed1988

[Sinocarotid hypersensitivity].

Hypersensitivity of the carotid sinus corresponds to a ventricular pause equal to or exceeding 3 seconds and/or a blood pressure drop equal to or exceeding 50 mmHg, induced by massage of the carotid sinus (MCS). MCS remains the diagnostic method of these two syndromes: cardio-inhibitor/vasodepressor. It must be performed systematically during the work-up of transient consciousness disorders since it is not unusual that hypersensitivity of the carotid sinus may cause cardiac syncopes. In addition, hypersensitivity of the carotid sinus is often associated with sinus dysfunction and atrioventricular conduction disorders. In the case of hypersensitivity of the carotid sinus with syncope secondary to a pure or dominant cardio-inhibiting response, heart stimulation with a dual-chamber pacemaker is probably the best treatment. In cases of hypersensitivity of the carotid sinus without syncope, therapeutic abstention is commonly accepted.

Arrhythmias, Cardiac↗

PubMedDate not supplied

[Sudden death of a patient with a pacemaker caused by heart rupture in a "cloisonné" pericardium].

Myocardial infarction is sometimes accompanied by bradycardia requiring either temporary or permanent cardiac pacing. In addition an MI reduces the amplitude of endocardial action potentials which produces the conditions for defective detection of spontaneous ventricular complexes by the pacemaker. In this particular condition, the competing cardiac rhythm which arises frequently causes malignant arrhythmias which are potentially fatal. This danger is increased even further by endocardial stimulation of the right ventricle with myocardial infarction of the right ventricle. We have reported in this paper the instructive case of a patient with coronary heart disease, hospitalized for third degree AV block with syncope which developed following a massive postero-diaphragmatic MI, but with few symptoms. After secondary extension of the necrotic area, the artificial pacemaker implanted manifested defective firing which resulted in development of ventricular fibrillation. The latter was controlled by cardioversion, but the patient died from disordered conduction after 30 seconds of complete asystole. For one minute, the pacemaker did not stimulate the ventricle because of "electrical stunt to the myocardium", caused by the shock from the defibrillator. Anatomical examination (at autopsy) confirmed the cardiac rupture.

Aged↗