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Biomedical subjects

L Guize

Publications and source records attributed to L Guize.

At least 19 recordsLinked to original sources
PubMed1992

[Treatment of risk factors of coronary atherosclerosis].

The treatment of coronary atherosclerosis risk factors is an essential part of secondary prevention of myocardial infarction. This should be started during the acute phase. Hypercholesterolemia is the principal causal factor and the occurrence of an infarct does not change the relative cardiovascular risk attributable to this factor. The absolute risk, positively correlated to total and LDL cholesterol and negatively to HDL cholesterol, is increased after myocardial infarction because of the higher prevalence of lethal or non-lethal ischemic cardiac events. The benefits of cholesterol reduction on cardiovascular mortality have been clearly established. They are greater with cholesterol-lowering drugs than with diet alone, and all the more significant when the initial cholesterol levels are high, but they are present at every value. A 1% reduction in total cholesterol is associated with a 2.5% reduction in coronary mortality both in secondary and primary prevention. After infarction, the cardiovascular benefits greatly exceed the risk of overmortality from other causes. Therapeutic effects may also be demonstrated by non-progression or regression of stenotic coronary lesions. The benefits of hypertension control are not as evident. Diastolic blood pressures inferior to 85 mmHg are associated with an increased coronary risk. While waiting for the results of specific therapeutic trials, reduction of high blood pressure without excessive lowering of the diastolic pressure is recommended. Stopping smoking is a measure of primary prevention which reduces the number of acute coronary events and of sudden deaths. However, the correlation with atherosclerosis is not remarkable. Treating diabetes, sedentarity and psychological behaviour seems to be useful. An evaluation of a personalized multifactorial approach to individual risk should be performed.

Coronary Artery Disease↗
PubMed1992

[Percutaneous ablation of atrioventricular junction by radiofrequency current in resistant atrial arrhythmia. Results of a series of 24 patients].

Catheter ablation of the atrioventricular junction may be proposed for the treatment of certain atrial arrhythmias resistant to antiarrhythmic therapy. One of the methods currently being evaluated uses radio-frequency energy which has certain advantages compared with direct current ablation because of the progressive and limited lesions it produces. This technique was used in 24 patients with atrial arrhythmias resistant to antiarrhythmic therapy. The radio-frequency energy was delivered without general anaesthesia with HAT 100 and 200 (OSYPKA) generators in the unipolar mode (average 17.4 watts) for an average period of 22.3 +/- 8 seconds. The catheter (8F USCI suction catheter in the first 18 patients and a 7F Polaris Mansfield, deflectable catheter with a large distal electrode in the remainder) was positioned at the nodo-hisian junction at a point where the two distal electrodes recorded a large atrial deflection and the smallest possible hisian potential. The conduction defects induced during the acute phase generally remain stable in cases of complete atrioventricular block and tend to regress in cases of incomplete atrioventricular block despite initial control of atrioventricular conduction. During follow-up (21 +/- 16 months), 14 patients (58%) remained in complete atrioventricular block, 4 patients (17%) had controlled atrioventricular conduction with an acceptable ventricular rate with associated previously ineffective antiarrhythmic therapy. Radio-frequency ablation was a failure in 6 patients (25%). There were no haemodynamic, rhythmic or ischaemic complications during the acute phase or during follow-up. These results suggest radio-frequency energy is a seductive alternative to direct current ablation for percutaneous modification of atrioventricular conduction in patients with refractory atrial arrhythmias. However, simple modulation of atrioventricular conduction gives aleatory results due to the tendency to regression during follow-up. On the other hand, complete atrioventricular blocks created by radio-frequency energy are generally definitive and are associated with a junctional escape rhythm which is usually stable.

Adult↗
PubMed1992

[Quantitative thallium myocardial tomoscintigraphy. Value of intravenous infusion of dipyridamole after negative submaximal exercise test].

Patients with suspected coronary artery disease are sometimes unable to exercise adequately (85% of age calculated maximal heart rate) to validate their ergometric stress test. Some groups suggest performing dipyridamole scintigraphy from the outset but then the information provided by exercise stress testing is lost. The aim of this study was to compare scintigraphies performed after exercise alone and after exercise combined with dipyridamole using a method of quantification. Thirteen patients with ischaemic heart disease without necrosis (coronary lesions greater than 75% luminal narrowing in: 7 right coronary, 10 left anterior descending, 3 left circumflex arteries and 1 left main coronary artery with 50% luminal narrowing) underwent exercise stress testing followed by Thallium imaging. One week later, the same exercise stress test was performed followed by an intravenous injection of dipyridamole and Thallium scintigraphy. The circumference of the radioactivity was traced and the surface of each segment calculated in three different short axis views, subdivided into 4 segments (anterior, lateral, inferior and septal walls). Any segment vascularised by a stenosed coronary artery was considered to be underperfused (105 segments). The ratios of the surfaces of underperfused/normal segments were compared using the two study protocols. Segments of the same wall in the 3 short axis views were grouped in the same myocardial zone. Thirty five myocardial zones were thus obtained: 25 zones were more underperfused after combining exercise and dipyridamole than after simple exercise stress (p = 0.014). The average increase in underperfusion after the combined exercise-dipyridamole was 12.4% compared with 5.5% after exercise alone (p = 0.03). Secondary effects were minimal.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Disease↗
PubMed1991

Wenckebach periods in sinoatrial block: experimental and clinical evidence.

The reality of sinoatrial Wenckebach periods (WP) has been suggested, but not proven, in the literature. We report experimental and clinical data showing WP in sinoatrial blocks. Experimental sinoatrial blocks were induced by superfusion of bepridil (10(-5) M) in 15 preparations of isolated rabbit right atria. Different types of block were observed, including Blumberger I block, i.e., sinoatrial WP. The recordings showed that the typical pattern of Blumberger type IA block and sinoatrial WP may be due to transient acceleration of the sinus rate, without change in the increment. We also observed sinoatrial WP in a 72-year-old patient on direct recordings of the sinus node (SN) electrical activity. In this case, transient acceleration of the sinus rate also seemed to be involved in the genesis of sinoatrial WP. Analysis of these clinical and experimental data showed similarities that may explain the mechanism of the WP. Usually type IA Blumberger block is said to involve a decrease in the sinoatrial increment to explain the atrial sequence (decrease in PP interval followed by a pause shorter than twice the value of the preceding cycle, then a cycle longer than the one preceding the pause). In fact, this pattern can be observed when the acceleration of the higher structure, the SN, induces block within the lower structure, i.e., the atrium.

Action Potentials↗
PubMed1991

Cellular electropharmacology of human atrium: effects of antiarrhythmic drugs.

Human atrial tissue exhibits specific electrophysiological properties such as the presence of plateau shaped action potentials characterized by an initial notch followed by a long lasting plateau. In these cells, the notch and the plateau are due to the activation of transient outward currents Ito and slow inward current Isi. The effects of antiarrhythmic agents on this tissue depend on the morphology of the action potentials. We demonstrated that, in these plateau shaped fibers, action potential duration at 50 and 90% of repolarization was increased by flecainide at the concentration of 5 x 10(-7)M. This increase is due to the effect of the drug on Ito, as shown by experiments with 4 amino-pyridine, a blocker of transient outward currents. We also demonstrated that quinidine at the concentration of 10(-5)M decreased in these cells the action potential duration at 50% of repolarization. This decrease is due to the effects of the drug on Isi, as confirmed by experiments using the patch-clamp technique. These modifications of the repolarization duration were not obtained in triangular action potentials which are observed in young subjects and in patients with chronic atrial fibrillation. In these triangular action potentials both Ito and Isi are inactivated. Since the animal tissues do not exhibit the same electrophysiological inhomogeneity, it is interesting to test the different classes of antiarrhythmic drugs on human atrium. These studies on human tissue, especially on diseased atrium, are closer to clinical situations than those performed on normal animal tissue.

Action Potentials↗
PubMed1990

Factor VII activation and menopausal status.

The incidence of coronary heart disease (CHD) is higher in postmenopausal or oophorectomised women than in premenopausal women of the same age. The difference cannot be explicable in terms of conventional CHD risk factors. Since factor VII may be relevant to the pathogenesis of CHD, we have investigated the menopause-related changes in factor VII activation in 228 healthy women aged 45-54 years. A standard factor VII clotting assay (FVIIc) and a factor VII antigen assay (FVIIag) were carried out on the same plasma samples. Both FVIIc and FVIIag levels were significantly higher in postmenopausal than in premenopausal women. Despite the strong correlation between the two assays (r = 0.80), the FVIIc/FVIIag ratio was positively and significantly associated with the menopause, suggesting that activated factor VII form might in part account for the high FVIIc levels in postmenopausal women. With respect to the type of menopause, the highest levels of both FVIIc and FVIIc/FVIIag ratio were found in women having undergone bilateral oophorectomy. These results suggest that raised factor VII coagulant activity may contribute to an increased risk of CHD in postmenopausal women.

Antigens↗
PubMed1990

Cellular electrophysiological effects of flecainide on human atrial fibres.

STUDY OBJECTIVE: The aim of the study was to examine the electrophysiological characteristics of human atrial specimens collected during heart surgery and to investigate the effects of the class I antiarrhythmic agent flecainide on their electrical activity. DESIGN: Atrial specimens were studied using standard microelectrode techniques, with and without superfused flecainide (5 x 10(-7) M) or the transient outward current inhibitor 4-aminopyridine (0.5 mM). EXPERIMENTAL MATERIAL: Atrial fragments 0.5-1.0 cm2 were obtained at operation from 34 patients, mean age 30 years. There was no history of previous atrial arrhythmia in any patient and drug therapy was stopped 24 h before surgery. MEASUREMENTS AND MAIN RESULTS: Two types of transmembrane action potential were identified: (1) triangular shaped potentials (group A, classically found in animal models); (2) potentials with a large plateau preceded by a notch (group B). The effect of flecainide was compared on the the two types of action potential. In both, flecainide lessened the depolarisation rate. In group B, but not in group A, it increased the action potential duration at 50% and 90% repolarisation (APD50, APD90) and the effective refractory period. The notch in group B action potentials is generated by transient outward currents (Ito). Inhibition of these currents, either by increasing the pacing rate or by adding 4-aminopyridine, limited the increase in APD50, APD90, and effective refractory period generated by the presence of flecainide. CONCLUSIONS: The effects of flecainide on the atrial repolarisation process depend on the shape of the action potential. These effects are more marked in cells with a plateau, where Ito is activated.

4-Aminopyridine↗
PubMed1990

Menopause-related changes in lipoproteins and some other cardiovascular risk factors.

Changes in lipids, lipoproteins and other cardiovascular risk factors associated with the occurrence of menopause have been examined in a cross-sectional study of 435 healthy white women, aged 45-54 years not using sex hormones. Univariate analysis showed that total cholesterol, low density lipoprotein (LDL) cholesterol, apolipoprotein A1, apolipoprotein B, triglycerides, systolic blood pressure and fibrinogen were significantly higher in post menopausal women than in premenopausal women. High density lipoprotein (HDL) cholesterol, diastolic blood pressure and blood glucose did not change with menopausal status. After controlling for the effects of confounding variables (age, body mass index and smoking status), total cholesterol, LDL cholesterol, triglycerides, apolipoprotein B and systolic blood pressure remained significantly increased in postmenopausal women as compared with premenopausal women. Our findings add to epidemiological evidence that menopause adversely affects the lipid and lipoprotein metabolism and thus, may increase the risk of coronary heart disease.

Coronary Disease↗
PubMed1990

Electrophysiologic effects of intravenous nicardipine on sinus node function and conduction in humans.

We conducted an intracardiac study of the electrophysiologic effects and kinetics of intravenous nicardipine (N) in 16 patients with or without impaired cardiac conduction, using a randomized, double-blind, crossover design versus placebo (P). N or P were infused intravenously over 5 min: the dose of N was 9.46 +/- 3.85 mg. Standard electrophysiologic parameters of atrioventricular (AV) conduction and sinus function were measured under basal conditions, between 10 and 25 min, and at 65 min, after beginning the first infusion of N or P, and between 10 and 25 min after beginning the second infusion of N or P. Treatment with N significantly reduced systolic (S) and diastolic (D) blood pressure (BP) at 10 min (35 +/- 19 and 25 +/- 17 mm Hg, respectively). N significantly shortened sinus cycle length (SCL), corrected sinus recovery time (CSNRT), AH interval, AV node (AVN) Wenckebach cycle length, and anterograde and retrograde effective (ERPs) and functional refractory periods (FRPs) of the AVN. Infranodal parameters were unaffected. Mean plasma N concentrations at 10 min were 18.5 +/- 7.7 ng/ml/kg and 5.3 +/- 3 ng/ml/kg at 60 min. Two patients experienced slight adverse effects (anginal pain and nausea); another with sick sinus syndrome developed a sinus pause. We conclude that intravenous N affects nodal, but not His conduction, and that it should be administered with care in the presence of SSS.

Adult↗
PubMed1990

[Ventricular tachycardia during theophylline overdose. Apropos of a case of reduction by magnesium chloride].

The authors report a case of ventricular tachycardia (VT) induced by theophylline toxicity in a patient with ischaemic heart disease complicated by left ventricular failure and chronic asthma. Two episodes of VT were reduced by intravenous injection of magnesium chloride. The aggravating role of a moderate magnesium deficiency is suggested by the synergy of hypomagnesemia and theophylline on intracellular calcium fluxes contributing to an accumulation of intracytoplasmic calcium, a situation which has been shown experimentally to generate delayed after depolarisations. The respective roles of the correction of the metabolic deficiency and of the specific antiarrhythmic action related to the calcium blocking effect of magnesium salts at cellular level are discussed.

Drug Overdose↗
PubMed1990

[Physiopathology of the sinus node and sinoatrial conduction].

New information about the pathophysiology of the sinus node and sino-atrial conduction has been published in the last few years. The sinus node consists of cells separated by a network of collagen fibres. This anatomical disparity explains the different electrophysiological characteristics of the node; the morphology of cellular action potentials depends on the site of recording. The dominant and most automatic pacemaker cells are situated in the cephalic region and the latent pacemaker cells in the caudal region. However, synchronisation of these different cellular activities is possible and results in a coherent signal. This complex synchronisation has been the object of several recent papers. The phenomenon of intrasinusal pacemaker shift and the stimuli which induce it have been studied in depth. In general, positive chronotropic stimuli tend to shift the dominant pacemaker towards the cephalic part and negative chronotropic stimuli towards the caudal part of the node. It is possible to assess pacemaker shift clinically and this phenomenon must be taken into consideration when studying sinus node function. Intercellular conduction and especially electrotonic conduction does not play a role in the genesis of the flux, which represents spontaneous cellular automatism, but in its mode of expression, that is to say the sinus rhythm. The pathophysiology of sinoatrial block is complex because it may be situated within and/or around the sinus node. The extrinsic or intrinsic mechanisms of these blocks may be interrelated. Variations in sinus rhythm must be taken into account in the genesis of sinoatrial block; an acceleration in rhythm may block conduction in the perisinusal region. Finally, our knowledge of the ionic fluxes underlying sinus automatism has also improved with individualization of the pacemaker current (if).(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1989

[Cardiovascular mortality as a function of left electric ventricular hypertrophy. In a male population].

The prevalence of electrocardiographic left ventricular hypertrophy was studied in a population of 19,622 men born and living in France, aged from 40 to 69 years, who volunteered to have a medical check-up at the health centre of preclinical investigations, Paris, between 1972 and 1977. Enquiries were made among local authorities and physicians to determine the number of deaths and their causes. During the follow-up (median 9.5 years), 1,285 deaths were recorded. The overall cardiovascular mortality was 384 deaths: 178 patients died of ischaemic heart disease, 66 of sudden death, 93 of cerebral vascular accident and 47 of various cardiovascular diseases. The presence of an electrocardiographic left ventricular hypertrophy increased the incidence of overall mortality and all causes of cardiovascular mortality in all age-groups. An analysis of survival after adjustment for age, systolic blood pressure, cholesterol level and smoking habits indicated that left ventricular hypertrophy is indeed a predictor of total cardiovascular mortality and of mortality due to ischaemic heart disease.

Adult↗
PubMed1989

Pulsatile versus steady component of blood pressure: a cross-sectional analysis and a prospective analysis on cardiovascular mortality.

Studies on the prognostic significance of blood pressure on cardiovascular disease have essentially investigated the levels of diastolic or systolic blood pressure. However, blood pressure may also be divided into two other components: steady (mean arterial pressure) and pulsatile (pulse arterial pressure). The relations of these two components with cardiovascular risk factors and cardiovascular mortality were investigated in 18,336 men and 9,351 women aged 40-69 years, who were followed up for a mean period of 9.5 years. However, the interpretation of the relations is complicated by the strong correlation existing between these two components. A principal component analysis was performed to obtain two independent parameters: a steady and a pulsatile component index, strongly correlated with mean and pulse arterial pressure, respectively. In the cross-sectional analysis, relations were stronger with the steady component index than with the pulsatile component index; an association was found between left ventricular hypertrophy and the pulsatile component index in both sexes. The survival analysis was not performed in women under 55 as only 11 cardiovascular deaths occurred in this group. The steady component index was a strong prognostic factor of all types of cardiovascular death in both sexes. In women, the pulsatile component index was positively correlated to death from coronary artery disease and inversely correlated to stroke. In conclusion, the steady component of blood pressure is a strong risk factor for cardiovascular death in both sexes; the pulsatile component could be a risk factor independent of the steady component in women older than 55 years.

Adult↗
PubMed1989

[The natural history of 270 cases of Wolff-Parkinson-White syndrome in a survey of the general population].

Among 226,464 ambulatory subjects who underwent medical check-ups over a 15-year period, 270 were found to have Wolff-Parkinson-White syndrome (1.2 case in 1,000). The syndrome was more frequent in men (181 cases, 1.4 p. 1,000) than in women (89 cases, 0.9 p. 1,000). 222 subjects were aged from 20 to 49 years (1.4 p. 1,000) and only 48 were between 50 and 80 years of age (0.7 p. 1,000). 197 subjects were re-evaluated: 119 (60.4 p. 100) complained of palpitations and 78 (39.6 p. 100) were asymptomatic. Palpitations began at all ages, even after 50 years, and usually proceeded in short attacks lasting a few seconds or minutes, with a mean recurrence rate of 5 attacks per annum (76.4 p. 100). This constant pattern sometimes was interrupted for months or years. Conversely, in a minority of cases (23.5 p. 100) an unexpected accentuation occurred which lasted for hours or days. As years went by, palpitations tented to decrease and disappear. The pre-excitation area and its degree of fusion with the normal ventricular activation had no influence on the origin and frequency of palpitations. In contrast, sustained tachycardia seemed to be more frequent in cases with lateral and posterior left pre-excitation. Among 270 subjects with pre-excitation syndrome, 7 died including 4 whose death was not due to a cardiac disease, 2 who died suddenly and 1 who succumbed to ventricular tachycardia after a road accident. None of these patients had an associated heart disease. These last 3 cases might contribute to alter the usually favourable prognosis of Wolff-Parkinson-White syndrome.

Adult↗
PubMed1989

[Electrocoagulation of the His bundle node junction in dogs by a high-frequency current delivered by suction catheter].

High-frequency currents constitute an attractive form of energy for transcutaneous myocardial destruction, but their potential for creating lesions varies with the nature of contact between electrode and skin. The adequacy of a suction catheter for electrocoagulation of the AV node-His bundle junction was assessed in 7 dogs. The high-frequency current (1.2 MHz) was delivered as bursts of 6 watts lasting 30 seconds, between the distal electrode of a bipolar catheter containing a central lumen (USCI 8F) and a wide skin electrode. During firing, an 80 kPa depression was applied to the lumen. Electrophysiological testing was performed before and immediately after firing. Continuous 24-hour Holter recording was carried out before, immediately after, then between the 2nd and 20th days post-firing. Following another electrophysiological study, the animals were killed on the 15th or 21st day for anatomical study. Complete atrioventricular block was obtained in all dogs during the first (n = 4) or second (n = 3) firing and persisted in 6 dogs up to the time of anatomical study. The atrial and right ventricular electrophysiological parameters remained unmodified after firing, and no severe ventricular arrhythmia was recorded during the study. The histological lesions were 4.7 +/- 0.7 mm in mean diameter and 3.1 +/- 0.6 mm in mean depth. It is concluded that electrocoagulation of the AV node-His bundle junction performed with high-frequency currents is a safe and selective technique. Using suction catheters makes this technique well reproducible with moderate amounts of energy. The development of preformed catheters should reduce the duration of the procedure.

Animals↗
PubMed1989

[Electric left ventricular hypertrophy and pulsatile component of arterial pressure in a population study].

High systolic or diastolic blood pressure is a risk factor of left ventricular hypertrophy. However, haemodynamically speaking blood pressure is made of two components: continuous and pulsatile. Few authors have analysed the relationship between these two components and left ventricular hypertrophy. A horizontal study was conducted in 27, 687 subjects who volunteered for a medical check-up in Paris. A principal component analysis led to the estimation of two distinct parameters: a continuous pressure index (CPI) and a pulsed pressure index (PPI). The correlation between CPI and age was linear, whereas PPI was independent of age before 55 years and thereafter increased in a linear manner. This study also confirmed the importance of the relationship between the continuous component of blood pressure and electrocardiographic left ventricular hypertrophy. It is suggested that the pulsatile component might also be a risk factor of left ventricular hypertrophy independently of the continuous component level. Only a prospective study would confirm that an increase in the pulsatile component of blood pressure has a prognostic value as regards ventricular hypertrophy.

Adult↗