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Biomedical subjects

G Lascault

Publications and source records attributed to G Lascault.

At least 55 records · Page 3Linked to original sources
PubMed1990

Endless-loop tachycardias: description and first clinical results of a new fully automatic protection algorithm.

Endless-loop tachycardia (ELT) is one of the most common pacemaker mediated tachycardia. An innovative ELT protection algorithm has proven to be clinically effective. A new improved version that will eliminate the need to program any parameter is now under clinical evaluation. Nine patients entered the study: six men and three women, aged 52 +/- 22 years. This automatic algorithm needs only 10 cycles to detect and confirm an ELT. Three hundred thirty-three ELTs lasting more than 9 cycles have been induced and analyzed. The total results are the following: mean duration: 6.7 sec +/- 3.1; mean ELT rate: 137 +/- 21.9 bpm, mean programmed upper rate limit (URL): 142.5 +/- 26.5 bpm (Only 70% of ELTs presented rates equal to programmed URL). (1) ELTs reduced by postventricular atrial refractory period (PVARP) extension on one cycle: 291 ELTs (87%). ELT rate: 128.5 +/- 18.2 bpm. (2) Retrograde block: algorithm operation may induce a retrograde block due to a short atrioventricular delay (AVD) applied during the confirmation phase to discriminate an ELT from a stable sinus rhythm. Thirty-two ELTs (10%) have been reduced and detected on a retrograde block occurrence. (3) Algorithm failure due to an unstable ventriculoatrial conduction time (VACT) even at fixed rate or to a retrograde Wenckebach behavior on AVD reduction during the confirmation phase. A total of 10 algorithms failed to detect or confirm an ELT have been recorded (3%). Mean duration: 8.2 +/- 4.2 sec, mean ELT rate: 148.9 +/- 14.3 bpm. This new fully automatic algorithm has reduced 97% of ELTs, including high rate episodes (100-175 bpm).(ABSTRACT TRUNCATED AT 250 WORDS)

Algorithms↗
PubMed1990

Assistant programming software: a new tool for an improved programming of pacemakers.

Programming the new DDD pacemakers is becoming increasingly difficult. One must take into account the pacemaker's complexity, the fact that some parameters are linked to others, and the clinical profile of the patient. This difficult problem will lead to the design of software to assist programming, which will help the implanting physicians in choosing adequate programmed settings adapted to the functioning of the device and to the physiology and pathology of the patient. These programming aides should meet certain basic requirements to make them safe, efficient, and easy to use. One such system designed by ELA Médical, "Programming Assistant" is herein described. The preliminary results of an initial study on the acceptance of this programming aide among physicians involved in cardiac pacing are given and discussed.

Adult↗
PubMed1990

Better predictors of successful His-bundle ablation analysis of first shocks.

We have reported here that a longer HV interval in association with a larger His amplitude yields a high rate of success when used to position the ablating catheter for His-bundle ablation. Additionally, we have shown that double discharge shocks are more effective than single discharge shocks, and that negative polarity is more effective than positive polarity. The use of bipolar or tripolar, and not quadripolar catheters, was also associated with a higher success rate. In our institution, using a bipolar catheter, we attempt to record an HV interval greater than 55 msec and a His amplitude greater than 0.35 mV. When both of these criteria are fulfilled, we use 3 to 4 joules per kg, and a single discharge shock. When one or the other of these criteria are not fulfilled, we use the double discharge shock method. Using these techniques, we have achieved successful His-bundle ablation with only one shock in all but one of the most recent 21 consecutive patients.

Bundle of His↗
PubMed1990

Ablation of the slow-conduction area in chronic ventricular tachycardia.

The ablation techniques, which derive from surgical approach in the treatment of ventricular tachycardia, were originally based on the modification of conduction in the so-called site of origin of the arrhythmia. A reentrant tachycardia involves two areas of conduction, one which consists of normal tissue, and the other with slow-conduction properties isolated from the previous structure. We now think that a more appropriate place to deliver the shock should be the area of slow conduction. The purpose of this paper is to review the main electrophysiological characteristics of this tissue, which could be interesting markers to identify the site where the shock should be delivered.

Action Potentials↗
PubMed1990

[Paradoxal cerebral embolism: role of patent oval foramen].

A patent foramen ovale (PFO) is present in 25-35% of people at all ages of life and its size tends to increase with age. It is now possible to detect PFO's by contrast echocardiography and it has been shown that there exists quite frequently a spontaneous transient right-to-left shunt during systole and, moreover, a right-to-left shunt during Valsalva maneuver and coughing. Acute or chronic pulmonary hypertension are also causes of shunt. Besides, a highly statistical correlation has been found between PFO's and strokes of uncertain or absent cause. From 1984 to 1990 the authors have collected 29 cases with 47 embolic cerebral events. Twenty-five cases with 30 embolic cerebral events and a neurological report have been found in the literature from 1930 to 1986. The analysis of these 77 cerebral embolic events is presented. All ages and both sexes are equally affected. Several symptoms and signs can suggest the diagnosis: onset of the neurological disorders during an activity implying a Valsalva maneuver; onset during a recognized phlebitis of the legs of pelvis or, more often, in a clinical setting suggesting the possibility of phlebitis without overt symptoms and signs: post-partum, post-operative conditions with prolonged bed rest; concomitant pulmonary and cerebral embolism. In the authors series of 227 cerebral emboli, such paradoxical emboli account for 12.8% of the cases ant it is likely that the condition is still underdiagnosed.

Adult↗
PubMed1990

[Congenital and acquired right ventricular dysplasia].

Arrhythmogenic right ventricular dysplasia has been described as a developmental malformation occurring during foetal life. This explains a number of familial cases of this condition where dysplasia was the result of a genetic abnormality transmitted in an autosomal dominant mode with incomplete penetrance. Histological data of peroperative or post-mortem specimens of 27 cases showed a large number of grape-like lymphoplasmocytic infiltrations. These appearances suggest an inflammatory origin of the disease, most probably related to an infective etiology. The authors suggest that in addition to the congenital form there may also be a possibility of acquiring arrhythmogenic right ventricular dysplasia after an episode of myocarditis.

Adult↗
PubMed1989

Electrode catheter ablation of resistant ventricular tachycardia in arrhythmogenic right ventricular dysplasia: experience of 13 patients with a mean follow-up of 45 months.

Electrode catheter ablation (fulguration) is a new technique for the treatment of ventricular tachycardia resistant to medical treatment. It proved effective in our hands in a series of 65 cases of ventricular tachycardia of varied origin. This paper reports the early results in a subgroup of 13 patients suffering from arrhythmogenic right ventricular dysplasia in whom shocks ranging from 160 to 280J, single or multiple, in one or up to three sessions were delivered. In the 11 patients surviving the DC ablation procedure single or multiple monomorphic sustained VT was brought under control. However, four patients (36%) required therapeutic antiarrhythmic treatment following the fulguration therapy. During the learning phase one case of death was related to poor catheter selection and the other to poor protocol. The post-mortem study of the effect of shocks depends on the anatomical structure to which the shocks have been delivered.

Adult↗
PubMed1989

Assessment of the optimal atrio-ventricular delay in DDD paced patients by impedance plethysmography.

The beneficial haemodynamic effects of sequential atrioventricular (AV) pacing have been clearly established and are dependent on the AV delay and pacing rate. However, the optimal AV delay is difficult to determine in each particular patient. We used a modified impedance plethysmographic method to assess variations in stroke volume for different AV delay and pacing rate settings. Impedance measurements showed a good correlation with CO2 rebreathing stroke volume measurements in VVI patients. Impedance variations were then used to set the optimal AV delay at different pacing rates in DDD patients. The inverse relationship between the optimal AV delay and the pacing rate has been accurately identified in most of the patients but is not predictable. In all cases, the cardiac output was higher in DDD mode at the optimal AV delay than in VVI mode. In some patients with a damaged myocardium, the stroke volume appeared to be highly sensitive to multiple AV delay settings. Impedance plethysmography can permit such repetitive non-invasive quick measurements, increasing the accuracy of optimal AV delay determination and is well suited for routine examination of patients with cardiac dual chamber pacemakers.

Atrioventricular Node↗
PubMed1989

Non-invasive study of dual chamber pacing by pulsed Doppler. Prediction of the haemodynamic response by echocardiographic measurements.

The increase in stroke volume with DDD compared with VVI pacing was measured at rest using pulsed Doppler echocardiography in 23 patients at a pacing rate of 70 beats min-1. Stroke volume was assessed by measuring the velocity integral of the flow at the aortic annulus using the apical five-chamber window. Pulsed Doppler echocardiography allowed determination of the least and most favourable AV delay haemodynamically. TVI was also measured at each nominal value of AV delay. The percentage increase in stroke volume was determined in every patient changing from VVI to optimum DDD pacing and was used as a measurement of the 'sensitivity' to optimum DDD pacing; the mean increase was 27 +/- 19%. The increase in stroke volume accompanying the change from DDD pacing with the least favourable to the optimum AV delay was also measured, and used as a measurement of 'sensitivity' to changes in AV delay; the mean increase was 23.7 +/- 16.3%. Clinical and standard echocardiographic parameters were studied in order to determine which variable might best identify the patients more likely to benefit from DDD pacing, and to identify those more sensitive to the AV delay setting. With respect to sensitivity to DDD pacing, three echocardiographic variables were selected by linear discriminant analysis from 11 clinical and echocardiographic variables. These were, in order of importance, left ventricular systolic diameter (LVSD), left ventricular wall thickness (LVWT) and left atrial size (LAS) which allowed the prediction of a good or a bad response to optimal DDD pacing with an accuracy of 91.3%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

[Echocardiographic detection of adriamycin cardiotoxicity. Study of the relationship between the shortening fraction-constraint and the systolic shortening fraction-diameter of the left ventricle].

Cardiotoxicity is the main obstacle to the use of high-dosage adriamycin in chemotherapy. It is difficult to decide whether or not treatment should be continued when the cardiac function -- irrespective of the method by which it is evaluated -- is at the lower limit of normality. Some authors consider that chemotherapy can be pursued as long as the shortening fraction of the echocardiographic diameter remains within normal limits in relation to the end-systolic constraint. We have established the limits of normality of this relationship before chemotherapy in 53 patients with normal cardiovascular system. We conclude that the end-systolic constraint essentially depends on the end-systolic diameter, so that the results provided by the study of the shortening fraction end-systolic constraint relationship are qualitatively the same as those of the shortening fraction-end-systolic diameter relationship, which is much easier to obtain. It seems to us that the criteria of cardiotoxicity after administration of adriamycin 300 mg/m2 are: (1) shortening fraction lower than 25 p. 100; (2) ventricular dilatation (end-systolic diameter greater than 40 mm) without associated valve disease; (3) reduction of the shortening fraction (whatever its value) in relation to the end-systolic diameter by more than 2 standard deviations on the regression slope of the correlation; (4) more than 25 p. 100 reduction of the shortening fraction after administration of adriamycin 300 mg/m2, betraying a high sensitivity to the cardiotoxic effects of the drug. Such individual sensitivity, studied in 25 patients, seemed to vary widely from one subject to another and to be independent of the initial status.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

[Prevalence of patent foramen ovale in young patients with ischemic cerebral complications].

We compared the prevalence of patent foramen ovale (PFO), detected by two-dimensional contrast echocardiography, in a group of 60 adults aged under 55 who had experienced a cerebral ischaemic accident and had normal standard examination of the heart, and in a control group of 100 patients. The prevalence of PFO was significantly higher in neurological patients (40 p. 100) than in controls (10 p. 100; p less than 0.001). Within the neurological group, the prevalence of PFO determined blindly, i.e. without any knowledge of the aetiological diagnosis, increased with the uncertainty of diagnosis: 21 p. 100 when a cause could be determined (n = 19), 40 p. 100 when a facilitating factor of cerebral accident, such as mitral valve prolapse, migraine or consumption of oral contraceptives, could be identified (n = 15), and 54 p. 100 when neither cause nor facilitating factor could be found (n = 26; p less than 0.10). In view of the very high prevalence of clinically silent venous thrombosis, these results suggest that paradoxical embolism through a PFO might be responsible for cerebral ischaemic accidents more frequently than is generally believed.

Adult↗
PubMed1989

[Cerebral vascular accidents in young subjects. A study of 133 patients 9 to 45 years of age].

We report 133 cases of strokes in patients aged 9-45 (male: 68, female: 65), mean age: 33.5 years. There were 112 arterial infarcts (84%), 9 venous infarcts (7%), 12 hemorrhages (9%). Among the arterial infarcts, 23 (20.5%) were due to a dissecting aneurysm, 17 (15%) to atherosclerosis, 13 (12%) to cardiac embolism. Echocardiography with contrast was performed in 69 patients showing a patent foramen ovale in 15. Mitral valve prolapse was present in 8, among which 5 had in addition a patent foramen ovale. Among 16 migrainous patients there were 7 dissecting aneurysms and 3 patent foramen ovale. Twenty two of 65 women were taking oral contraceptives at the time of the stroke. Strokes in patients taking oral contraceptives or during the puerperium accounted for 43% of the strokes in women. Ten cases (9%) have had no explanation. Venous infarctions were mainly due to puerperium and oral contraceptives. Hemorrhages were mainly due to arterial hypertension. No cause was found in 4/12 cases. The most useful investigations were angiography and echocardiography with contrast. This study confirms that extensive and early investigations are necessary in strokes in the young and particularly in women taking oral contraceptives, migraine patients and patients with mitral valve prolapse.

Adolescent↗
PubMed1988

Prevalence of patent foramen ovale in patients with stroke.

The cause of ischemic stroke in younger adults is undefined in as many as 35 percent of patients. We studied the prevalence of patent foramen ovale as detected by contrast echocardiography in a population of 60 adults under 55 years old with ischemic stroke and a normal cardiac examination. We compared the results with those in a control group of 100 patients. The prevalence of patent foramen ovale was significantly higher in the patients with stroke (40 percent) than in the control group (10 percent, P less than 0.001). Among the patients with stroke, the prevalence of patent foramen ovale was 21 percent in 19 patients with an identifiable cause of their stroke, 40 percent in 15 patients with no identifiable cause but a risk factor for stroke, such as mitral valve prolapse, migraine, or use of contraceptive agents, and 54 percent in 26 patients with no identifiable cause (P less than 0.10). These results suggest that because of the high prevalence of clinically latent venous thrombosis, paradoxical embolism through a patent foramen ovale may be responsible for stroke more often than is usually suspected.

Adult↗
PubMed1988

Evidence of the inaccuracy of standard echocardiographic and angiographic criteria used for the recognition of true and "false" left ventricular inferior aneurysms.

Diagnosis of so-called false aneurysms of the left ventricle after infarction is judged to be important because the risk of rupture is high and resection of aneurysms with a narrow orifice is usually successful. Aneurysms with larger communication orifices are less likely to rupture. Echocardiographic and angiographic criteria have been devised to classify left ventricular aneurysms into two distinct types. In four cases of inferior aneurysms the echocardiographic and angiographic criteria were typical of a "false aneurysm" but the defects were diagnosed as true aneurysms after intraoperative and histological examination. These aneurysms were characterised by their site in the inferior wall and by late diagnosis and treatment, which may have influenced their occurrence and determined the development of their characteristic shape. These findings suggest that the classic echocardiographic and angiographic diagnostic criteria for "false" aneurysms may have to be abandoned.

Angiography↗
PubMed1988

[Long-term course of conduction disorders in 97 patients with an HV interval superior or equal to 70 milliseconds].

The natural history of disorders of conduction is imperfectly known. The presence of an HV interval of 70 milliseconds or more, which is regarded as pathological, usually results in pacemaker implantation. In this study the course of symptoms and disorders of conduction was investigated in 97 patients with an HV interval of 70 ms or more, and therefore equipped with a pacemaker, followed up for a mean period of 26.5 +/- 19.5 months. Among these 97 patients, 65 had presented with one or several syncopes, 14 had experienced feelings of faintness and 18 were asymptomatic. Among patients with symptoms, these totally disappeared in 63 and became milder in the remaining 12 patients. Complete and permanent AV block was observed in 11 patients. The actuarial incidence of complete permanent AV block was about 5 p. 100 per annum until 4 years. The only predictive parameter for such a course was the occurrence of a second degree type 2 or a third degree paroxysmal block prior to pacemaker implantation (significantly associated with the absence of symptoms).

Adult↗
PubMed1988

[Morphologic study of cardiac cells in sheep before and after electric shock].

A combined electrophysiological and histopathological study was conducted on sheep myocardium fragments rich in easily identifiable conduction cells subjected to electric shocks of varying intensity. Tissue fragments were immersed in a thermostatically-controlled bath at 37 degrees C, perfused with a carbonated standard tyrode solution at the rate of 30 ml/min and stimulated at a constant bipolar 1 C/sec tension twice as high as the threshold of diastolic excitability. After measurement of reference values, electric shocks of 2 to 80 joules were delivered between two electrodes placed on both sides of the tissue fragment. The electrophysiological part of the study showed disorders of conduction which, depending on the energy delivered, were more or less complete and reversible. The histopathological part of the study showed that conduction tissue was extremely fragile, even to low-energy shocks. This fragility was in glaring contrast with the relatively modest damage suffered by myocytes. Liquefaction and/or coagulation of Purkinje's cells was also striking, as it extended over an area much wider than that subjected to the shock. Thus, with medium intensity shocks destroyed conduction bundles were seen to creep between myocytes that often were perfectly normal or showed rare hypercontraction bands. Some myocytes were in the process of degeneration or even eosinophilic necrosis, but except in case of violent shock these were more or less isolated elements in the vicinity of the stimulated area. The fragility of conduction tissue and its selective damage by low-intensity shocks may be explained partly by its low impedance which allows preferential passage of the electric current.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗