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Biomedical subjects

I Préda

Publications and source records attributed to I Préda.

At least 55 records · Page 3Linked to original sources
PubMed1994

Connection between right ventricular pressure and the ECG.

According to the literature, electrocardiographic signs of right ventricular hypertrophy have low sensitivity. The cause of this low sensitivity may be attributed to the original studies that were performed mostly in children with hypoplastic left ventricles or congenital heart abnormalities. In adulthood cases of normal or hypertrophic left ventricles, electrocardiographic right ventricular hypertrophy can only be detected during the late phase of ventricular depolarization. Two hundred four adult cardiac patients with complete noninvasive and invasive records were systematically studied by conventional and vectocardiographic methods. The terminal QRS (S wave) of the standard lead I has proved to be informative for detecting electrocardiographic signs in the presence of elevated right ventricular pressure. In cases of chronic right ventricular pressure overload (right ventricular hypertrophy) the terminal depolarization QRS vectors pointed posteriorly and to the right; therefore, a characteristic terminal S wave was represented in the standard lead I. If right and left ventricular hypertrophy were simultaneously present, the same resultant vectors pointed posteriorly and slightly to the left. In these cases, notching of the declining phase of the R wave was frequent, and a flatness of the terminal R wave portion was characteristic. The latter electrocardiographic sign has been called "simultaneous overloading of both ventricles" by the authors. The clinical utility of the new signs have also been proved by statistical methods.

Adult↗
PubMed1994

QRS alterations in body surface potential distributions during percutaneous transluminal coronary angioplasty in single-vessel disease.

Body surface QRS potentials were recorded with 63 chest leads in 20 patients with proximal single-vessel disease located on either the left anterior descending coronary artery (n = 10), the right coronary artery (n = 6), or the left circumflex coronary artery (n = 4) before, during, and after percutaneous transluminal coronary angioplasty. In each case, three consecutive inflations of relatively short duration (37 +/- 14 seconds) were carried out. Electrical activity was displayed as unipolar electrograms and body surface potential maps. The total QRS complex duration decreased in 14 of the 20 patients. Focal conduction disturbances were observed in six cases; all six had left anterior descending coronary artery occlusion and two were also accompanied by a clear shortening of the right epicardial breakthrough time. In these two cases, an initial activation loss seemed to be characteristic, whereas in the other four cases, a rather diffuse slowing of intraventricular conduction, especially during the terminal portion of the QRS, could be observed. Individual and group mean isointegral difference body surface potential maps (during-minus-before dilation) were considered valuable for the interpretation of localized changes in intraventricular conduction during percutaneous transluminal coronary angioplasty, and their individual variations could, at least partly, be explained by the presence or absence of collateral circulation. Two different hypotheses are suggested to account for the QRS complex shortening observed during short-term myocardial ischemic injury: (1) coronary artery occlusion delayed activation of the portion of the septal region that is normally activated early during the QRS, and/or (2) coronary artery occlusion increased the speed of propagation within the ventricles. Both of these hypotheses are discussed in light of earlier clinical and experimental results.

Angioplasty, Balloon, Coronary↗
PubMed1993

[The role of two-dimensional echocardiography in the detection of pacemaker-induced endocarditis].

UNLABELLED: The authors analysed the data of eight patients who had to undergo open heart surgery because of pacemaker endocarditis in the last four years. Repeated surgical interventions on the pacemaker system was the most predisposing factor. The most common causative organisms were Staphylococcus aureus and Staphylococcus epidermidis. Two-dimensional echocardiography (2DE) had a decision making role in the diagnosis beside the clinical picture and blood culture. CONCLUSIONS: 1. Each pacemaker patient with fever must be considered to have a pacemaker endocarditis; 2. All these patients must be examined by two-dimensional echocardiography.

Adult↗
PubMed1993

[Dual-chamber rate responsive cardiac pacing].

The authors describe in this report their first experience with the implantation of a rate responsive, dual chamber pacemaker. They emphasize the advantages of this type of pacemakers: the maintenance of AV-synchrony and the rate increase in response to exercise. Meanwhile they call attention on the complexity of the ECG interpretation.

Adult↗
PubMed1993

A computer heart model incorporating anisotropic propagation. II. Simulations of conduction block.

This study describes the simulation of the more common types of conduction blocks with a computer model of the heart incorporating anisotropic propagation. The rationale was to test the model as to its ability to simulate these blocks by physiologically justifiable adjustments of the conduction system alone. The complete blocks were generated by simply blocking conduction totally at selected sites in the proximal conduction system, and the incomplete blocks by slowing down the conduction velocity in the proximal system. Also simulated were the left fascicular blocks and the bilateral blocks. All simulated electrocardiograms, vectorcardiograms, body surface potential maps, and epicardial isochrones for these blocks were similar to clinically observed data, with the exception of the left posterior hemiblock, which was slightly atypical. This could be because such blocks are usually accompanied by other cardiac pathologies not included in our simulations. The model also supports van Dam's observation that during left bundle branch block the passage of activation from right to left occurs via slow myocardial activation with no evidence of a local delay due to a septal barrier. Finally, the model suggests that a left bundle branch block with a normal frontal plane QRS axis may simply represent a case of an incomplete left bundle block, whereas one that exhibits a left axis QRS deviation in the frontal plane represents a more severe complete left bundle branch block.

Anisotropy↗
PubMed1991

[Clinical value of body surface mapping in the diagnosis of ischemic heart disease].

A series of 137 patients suffered in clinically documented angina pectoris were analyzed by 12-lead exercise ECG, exercise body surface potential mapping and exercise thallium scintigraphic methods and the results were compared to that of selective coronary angiography and left ventriculography. If coronary artery stenosis were considered to be significant in the presence of more than 70% vessel narrowing, the sensitivity figures were 76, 93 and 88% for exercise 12-lead ECG, exercise body surface potential mapping and exercise thallium scintigraphy, respectively. In considering 50% coronary artery narrowing to be significant, the same figures were 78, 94 and 89%. Specificity figures at the same order were 59, 65 and 80% for more than 70%, and 64, 70 and 88% for more than 50% coronary obstructions. Exercise body surface potential mapping and exercise thallium scintigraphy applied parallelly gave a sensitivity of 100% and specificity of 53%. False-negative and false-positive exercise body surface potential mapping and thallium scintigraphic tests were analysed taking into consideration left ventricular function indices and respective patients. The authors suggest that the outstanding high sensitivity of the above mentioned two tests applied parallelly reveals that they highlights partially different aspects of coronary artery disease, and that is why the overlapping between the methods is relatively small. The majority of false-positive tests characterize a pathological state, and in these cases the exact diagnosis should be cleared up by other noninvasive/invasive methods.

Angina Pectoris↗
PubMed1990

Comparative evaluation of the effect of balloon dilatation by exercise precordial mapping and exercise 201-thallium scintigraphy.

Precordial exercise electrocardiographic mapping and exercise 201-thallium scintigraphy were simultaneously used on sixteen patients before, shortly after and three months after percutaneous transluminal coronary angioplasty (PTCA) to evaluate the immediate and late results of the intervention. In spite of the limited number of observations, positive exercise precordial mapping and or a reversible 201-thallium perfusion defect after PTCA seem to be indicative of failure of balloon dilatation or of development of restenosis in a given coronary artery. "Reverse minimum", that is the minimum in the resting precordial map which disappears on exercise, may be a sign of segmental coronary artery occlusion and well functioning collateral supply.

Adult↗
PubMed1986

Detection and localization of ventricular preexcitation in Wolff-Parkinson-White syndrome (comparative study with body surface mapping).

21 patients with Wolff-Parkinson-White (WPW) syndrome were investigated through radionuclide imaging and body surface mapping. Ventricular preexcitation was localized by display of identical phase ventricular regions (phase display). In 79% of the cases radioisotope and body surface mapping methods have identical results for the site of preexcitation. In two patients of the control group (10 patients with Lown-Ganong-Levine (LGL) syndrome), false positive outside-of septum ventricular preexcitation was detected, i.e. an 80% specificity. It is concluded that phase display might be a suitable method in the diagnosis of WPW syndrome. The sensitivity of this method can be improved using several views.

Adult↗
PubMed1983

The effect of experimentally induced myocardial ischemia on the norepinephrine metabolism of the dog heart.

Myocardial ischemia is known to provoke an excess in circulating norepinephrine and thus be related to an increased irritability of the heart. In the present experiments, we studied the norepinephrine and potassium content, oxygen tension, and pH values of the effluent of coronary sinus after thoracotomy and catheter placement into the coronary sinus. Once a steady state was reached, the measurements were repeated in the fifth, tenth, 20th, and 60th minutes of experimental myocardial ischemia provoked by coronary ligation of the left anterior descending coronary artery. The parameters obtained were compared to the corresponding values measured in the peripheral vessels. The results indicate an increased release and probably an increased turnover of norepinephrine in the ischemic myocardium. The role of metabolism acidosis in the changes in norepinephrine metabolism was suggested. It is assumed that intracellular acidosis is involved in the enhanced accumulation and release of norepinephrine in the damaged myocardium and that an increase of norepinephrine concentration in the myocardium may be considered a risk factor in supporting heart function.

Animals↗
PubMed1982

The effect of potassium canrenoate (Aldactone) on the norepinephrine metabolism and potassium ionic currents of the heart.

Under experimental conditions, potassium canrenoate causes a significant increase in [3H]norepinephrine (NE) uptake by the heart, although the NE content remains unchanged. The increased NE uptake and unchanged NE content indicate an augmented NE turnover caused by the drug. In saluretic-pretreated animals, the intracellular hypopotassemia can be restored by Aldactone. This effect can be explained by the inhibition of the outward potassium current. When we simulated the pathophysiological conditions of the acute phase of myocardial infarction by using a K+-rich superfusate to partially depolarize the myocardial cells, slow action potentials were elicited by NE in isolated papillary muscles. Our microelectrode experiments revealed that Aldactone, by its blocking effect on the potassium conductance, increases the duration of the slow action potentials and decreases the threshold NE concentration required to elicit the slow responses. However, in clinical conditions with a higher level of circulating catecholamine and/or hyperpotassemia, the administration of the drug has a considerable risk of provoking arrhythmias.

Animals↗
PubMed1981

Polarcardiographic (triaxicardiometric) study on the effect of isosorbide dinitrate on exercise-induced myocardial ischemia.

30 patients suffering from stable angina pectoris were studied by triaxicardiometric (polarcardiographic) method. Triaxicardiometry including the X, Y, Z Frank leads, azimuth (H degrees), elevation (V degrees) angle derivations and spatial magnitude (M) tracings were taken at rest and after submaximal bicycle ergometer exercise. After receiving 30 mg/day isosorbide dinitrate for a minimum of 5 days the whole procedure was repeated, stored by an analogue tape recorder and evaluated by a TPA/i computer. It has been stated that the method of triaxicardiometry has an excess sensitivity on the demonstration of ischemic alteration of anterior and posterobasal left ventricular wall compared to the traditional X, Y, Z leads. According to the pre- and post-exercise bicycle ergometer testing estimated by triaxicardiometry, isosorbide dinitrate caused a significant reduction of subendocardial myocardial ischemia.

Angina Pectoris↗
PubMed1980

The role of potassium-canrenoate in the 3H-noradrenaline uptake and metabolism of the rat heart.

The influence of potassium-canrenoate (Aldactone) on the noradrenaline (NA) uptake and metabolism of the heart was studied in normal and hypopotassemic rats. The administration to normal rats resulted in a marked increase of 3H-NA uptake both in the atrial and ventricular tissues, but the NA content was unchanged. An increased NA uptake of myocardium in the presence of an unchanged content suggested an increased rate of NA turnover under the influence of the drug. In saluretic pretreated animals the substance normalized both the previously decreased NA uptake and the low intracellular potassium level of the heart tissue. The augmentation of catecholamine metabolism due to the drug may be involved in an enhanced activity of adenyl cyclase and form the basis of the positive inotropic effect of the compound.

Animals↗
PubMed1979

Surface potential distribution on the human thoracic surface in left bundle branch block.

The sequences of myocardial excitation in the cases of human LBBB have been studied by the surface mapping technique. Analysis of the surface map patterns of 12 subjects has enabled 4 different types to be described. It is suggested that Type I represents a complete LBBB in the presence of an intact right bundle branch, while Types II and III show different degrees of conduction defect in the right bundle branch, too. The left ventricular activation of these 3 types has a similar pathway in phases II and III which is determined by orientation of the main subepicardial muscle layer coursing through the apex and terminating in the anterobasal region. The terminal anterobasal activation in the cases of LBBB has not only theoretical, but clinical significance, since in the presence of anteroseptal myocardial infarction the signs of necrosis must be hidden not in the early, but in the terminal parts of the QRS complex of conventional ECG. The lack of terminal anterior positivity of surface maps in the case of LBBB may be indicative of chronic anterior myocardial infarction.

Bundle-Branch Block↗