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X Copie

Publications and source records attributed to X Copie.

At least 19 recordsLinked to original sources
PubMed2004

[The choice of pacing sites: should we change our practice?].

For the past 45 years the sites used for elective pacing have been the apex of the right ventricle and the right atrium. Although the initial objective of pacing was the "simple" correction of a conduction disorder, a more recent evolution has been to achieve a favourable haemodynamic effect, considering left ventricular filling and synchronisation of ventricular contraction as essential. Demonstration of the benefit in terms of survival brought about by pacing in atrioventricular block has not required large trials. However, it is possible that this improvement in morbidity and mortality is in part offset by the altered haemodynamics due to pacing at the right ventricular apex. At the atrial level, the prevention of AF is the holy grail of atrial pacing, but is far from being attained, perhaps because the physiopathological bases are not clear and have not really been demonstrated, casting doubt on the final objective. The choice of pacing site is essential in this context, as much in the atrium as in the ventricle. The current problem regarding this choice is the same as for all medical treatment, where the risk/benefit ratio is evaluated: if the usual sites are potentially deleterious, is it possible to continue using them or is it necessary to change implantation practices, and what level of proof is needed?

Atrial Fibrillation↗
PubMed2003

[External electrical cardioversion of atrial arrhythmia: predictive criteria of success].

AIM: Supraventricular arrhythmia is a major public health problem because of its prevalence and clinical consequences. The first step of the treatment usually consists in restoring sinusal rhythm. The aim of this study is to evaluate results and predictive factors of success of electrical cardioversion. METHODS: We studied a series of 143 consecutive electric cardioversion preformed in 131 French patients. RESULTS: The rate of successful direct current cardioversion was 91.2%. Negative predictive factors are the height body mass index and the age of arrhythmia. Atrial flutter is a predictive factor of success. These results agree with published results. Our study highlights the interest of some nonantiarrhythmic drugs received by the patient during the period before the direct current cardioversion. Thus, a spironolactone treatment appears to be a new predictive factor of the success of electrical cardioversion (success in patients treated with spironolactone: 100% vs 89% without, P = 0.04). CONCLUSIONS: Our results agree with usual predictive factors of the success of cardioversion. Nevertheless, a new approach is that of the positive effect of spironolactone on cardioversion. A prospective randomized study is necessary to confirm this result.

Adult↗
PubMed2003

[Electrophysiologic remodeling and drug treatment of atrial fibrillation].

Since 1995, a number of studies have established and detailed the mechanisms of electrical and structural atrial remodeling induced by atrial fibrillation. Atrial remodeling involves many cellular components, from ionic channels to connexins. The determination of these mechanisms may help to define a new therapeutic targets of atrial fibrillation, a frequent arrhythmia that remains difficult to treat. Atrial remodeling prevention may lead to limit the evolution of the arrhythmia (early recurrences after reduction, AF secondary to atrial tachycardia, permanent AF, decrease in atrial contractility, sinus dysfunction). Except amiodarone, the usual antiarrhythmic drugs have no effect on atrial remodeling. Calcium channel inhibitors prevent early remodeling but have no effect on prolonged remodeling. Digoxin increases remodeling. Angiotensin II receptor inhibitors have been shown to prevent early AF recurrence after reduction and are very promising in such a direction. Other methods such as the one of antioxidant therapy seem to be promising and could define soon a new antiarrhythmic therapeutic class, the antiremodeling drugs.

Atrial Fibrillation↗
PubMed2003

[Predictive criteria of early recurrence of atrial arrhythmia after reduction by electrical cardioversion].

The management of atrial arrhythmias aims not only to restore sinus rhythm but also to maintain it. Ten to thirty per cent of patients have early recurrence of atrial arrhythmias, the treatment of which remains empiric. The aim of this study was to define factors predictive of early recurrence of atrial arrhythmias and the consequences on the length of hospital stay. A series of 131 patients who underwent reduction of atrial arrhythmias by electrical cardioversion was studied retrospectively. A recurrence within 24 hours was observed in 12.2% of the patients. These recurrences significantly increased the length of hospital stay (6.8+/-6.3 versus 3.6+/-3.8 days, p=0.005). This study confirms two previously reported results with respect to more long-term recurrences. In the "early recurrence" group, the duration of the atrial arrhythmia was longer (p=0.003) and there were fewer treatments with amiodarone (p=0.03). In addition, original results were obtained. In the "early recurrence" group, the patients were more often treated with furosemide (p=0.02), class Ic antiarrhythmics (p=0.007) or anaesthetised with thiopental (p=0.002) than patients without early recurrences. Experimental data explain these results. However, they require confirmation by a prospective randomised trial.

Adult↗
PubMed2001

Heart rate, arterial stiffness, and wave reflections in paced patients.

Elevated heart rate (HR) and pulse pressure (PP) have a cumulative effect on cardiovascular risk, with the exception of HR >/=100 bpm. How an increase in HR may influence the PP level has never been investigated. In 11 patients with pacemaker monitoring, aortic (pulse-wave analysis) and digital (photoplethysmographic device) blood pressure were measured at 3 different levels of HR, together with determinations of carotid dimensions (echo tracking technique), wave reflections (pulse-wave analysis), and aortic pulse-wave velocity. Increased HR is associated with the following: (1) a significant increase of digital systolic, diastolic, and mean blood pressure; (2) a significant reduction of digital and carotid PP, with a more pronounced reduction of the carotid than of the digital PP, resulting in a significant PP amplification; and (3) a reduction in the time required for the backward pressure wave to return toward the heart, without any change of arterial stiffness. Increased HR significantly enhances PP amplification, leading to an increase of peripheral blood pressure without comparable change in central blood pressure. These results are important to consider for a better understanding of cardiovascular risk and the mechanism of white-coat hypertension.

Aged↗
PubMed2001

[Dual chamber rate responsive pacing and chronotropic insufficiency. Comparison of double and respiratory sensors].

Late responsive DDD pacemakers are the most technically advanced devices presently available. These pacemakers are particularly useful in patients with chronotropic insufficiency when the sinus node is incapable of accelerating during exercise. The latest pacemakers have two sensors to reproduce optimal physiological sinus acceleration. The aim of this study was to analyse the performances of a new rate responsive pacemaker with a double activity and respiratory sensor, the interaction of which is automatically controlled by a sophisticated algorithm, in 12 patients (8 men and 4 women) with a mean age of 75 +/- 7 years. Analysis was based on the performance of the sensors used singly or in association: during three exercise stress tests with measurement of the VO2 max; during everyday activities using the data archived by the pacemaker and the answers to a simplified questionnaire on quality of life. The results showed that during exercise stress testing with measurement of VO2 max, the best performances were obtained with the double sensor or the respiratory sensor compared with the activity sensor alone, suggesting that these two sensors are more effective in intense exercise. This tendency was also observed in the analysis of the memory bank of the pacemaker which showed that the total duration of the faster heart rates was greater with the two sensors. On the other hand, the quality of life was not significantly different, whichever sensor was studied. Longer scale trials are necessary to appreciate the real value of these new double sensor pacing devices and to identify the best indications for their usage.

Aged↗
PubMed2000

Temporal and geographical trends in indications for implantation of cardiac defibrillators in Europe 1993-1998. Medtronic ICD System Investigators.

Despite the demonstrated efficacy of implantable cardioverter defibrillators (ICDs) in reducing sudden and total mortality in selected populations, their implantation rates vary greatly between countries. The aim of our study was to analyze temporal and geographical trends in ICD implantations in countries with similar health related expenditure in Western Europe. A total of 2,257 patients from ten European evaluation studies of Medtronic defibrillators and defibrillation electrodes, conducted between 1993 and 1998, representing 12 countries, was included in this analysis. Rates of implantation and clinical characteristics were compared between countries and years of implantation. Rates of implantation differed greatly between Western European countries and did not correlate with indices of health related expenditure (i.e., number of patients per physician and number of patients per hospital bed). However, there was a strong and statistically significant negative correlation between the use of amiodarone and the rates of implantation (r = -0.66, P = 0.02). Temporal trends showed a significant increase in the age of the patients receiving an ICD between 1993 and 1998 (57 +/- 14 vs 61 +/- 12 years, mean +/- SD, P < 0.001). There was also a temporal trend towards an increased incidence of coronary artery disease and a significant decrease in the incidence of cardiomyopathy. There was a temporal increase in implantations in patients with a history of ventricular tachycardia. Despite a general scientific agreement that ICDs are a first line treatment for patients at high risk of sudden cardiac death, their acceptance remains low in several developed countries. This low acceptance may not be entirely related to budget constraint but may also be related to their perceived efficacy by physicians and health authorities.

Amiodarone↗
PubMed2000

[Electrophysiological remodeling induced by atrial fibrillation. An experimental curiosity or major factor in atrial fibrillation in man?].

Atrial fibrillation usually progresses from a paroxysmal to a permanent arrhythmia, even in the absence of underlying cardiac disease. The treatment is more difficult when the arrhythmia is chronic. This progression may be explained by the aggravation of underlying cardiac disease with time. Another explanation is that the arrhythmia induces functional and structural changes of the atrial tissues (remodelling) which promote the perpetuation of the arrhythmia and which make treatment less effective. Although the electrophysiological changes predisposing to atrial fibrillation have been known for over 15 years, it was only in 1995 that experimental studies showed the presence of atrial electrophysiological remodelling induced by the arrhythmia. This process of long term adaptation of the atrial myocytes to the tachycardia comprises marked changes of the parameters which sustain the arrhythmia: changes in refractory period (decreased duration, inadaptation to the heart rate, increased dispersion), reduced conduction speed and sinus dysfunction. Atrial remodelling also affects the contractile function by the structural changes. The calcium currents play a major role in its development. This mechanism has not yet been completely defined in the clinical setting and its importance in sustaining the arrhythmia has not been clearly evaluated. Atrial fibrillation remains one of the most difficult arrhythmias to treat. A better understanding of cellular mechanisms of remodelling could open up new therapeutic approaches to limit the natural history of the arrhythmia with progression to chronicity and structural changes responsible for the degradation of atrial contractility.

Atrial Fibrillation↗
PubMed2000

[Heart rate and mortality: review of the literature].

A great number of studies focussed on a wide variety of subjects have been concerned with the subject of morbi-mortality and the effect of heart rate. These studies show that there is a connection between high heart rate and arterial hypertension, and a significant coronary, cardiovascular, non-cardiovascular and overall mortality risk. Two explanations are possible for this. The increase in heart rate together with associated sympathetic hyperactivity can be considered a cardiovascular risk factor: or it could be viewed as an independent risk factor, associated with an increase in mechanical constraints.

Cardiovascular Diseases↗
PubMed2000

[Chronotropic incompetence: when should a pacemaker be considered? Which pacing system and which settings?].

Chronotropic incompetence is defined as the inability to increase and maintain heart rate appropriately during exercise. Intolerance to exertion is manifested by a number of clinical symptoms, and is almost obligatory if heart rate cannot be increased. Several rate-modulating pacing systems have been developed. The most obvious and reliable way to increase heart rate during exercise is to detect the sinus node. Adding an atrial lead in a patient in complete AV block and VVI pacing is the most satisfactory way to correct chronotropic incompetence in some patients. Rate-adaptive sensors include motion sensors, respiration sensors, QT interval, and right ventricular contractility. Indications for rate-adaptive pacing should be based on clinical symptoms, demonstration of a lack of cardiac acceleration during exercise, and the presence of another indication for pacing.

Heart Diseases↗
PubMed1998

Effects of norepinephrine on the mechanical properties of the human radial artery in vitro.

BACKGROUND: The human radial artery has been proposed as an alternative to coronary grafts in subjects with coronary ischemic disease. Because this muscular artery is known to be prone to spasm, changes in its mechanical properties in response to catecholamines are important to investigate. METHODS: We describe a new echo-tracking technique of high resolution that allows investigation, in vitro, of the diameter and the wall thickness of arterial cylindrical segments. In addition, a classic tissue bath experiment is used to study the vasoreactivity of arterial rings. Mechanical properties of the radial artery are determined over a 0 to 200 mm Hg range of transmural pressure in the presence and absence of norepinephrine in the perfusion medium. RESULTS: With tissue bath experiments, the norepinephrine dose-response curve was characterized by an EC50 value of 1.48+/-1.09 10(-6) mol/L and a maximal developed tension at 10(-5) mol/L. The results obtained with pressurized segments gave similar results with an EC50 value of 8.1+/-2.3 10(-7) mol/L and a maximal change in diameter at 10(-5) mol/L norepinephrine. Under the influence of 10(-5) mol/L norepinephrine, the radial artery constriction reached 22%, significantly affecting the unstressed diameter. Compliance did not show any significant change in the overall transmural pressure range, whereas distensibility significantly increased and elastic modulus significantly decreased. CONCLUSION: The study shows that the capacitive properties of the human muscular radial artery are maintained with norepinephrine not only through decreased stiffness of wall material but also through reduced unstressed diameter. Thus drugs inducing smooth muscle relaxation may be helpful in preventing radial artery spasm after coronary grafts.

Aged↗
PubMed1998

Comparative reactivity and mechanical properties of human isolated internal mammary and radial arteries.

OBJECTIVE: The aim of this study was to analyse the arterial wall mechanics and the vasoreactive properties of the radial artery in comparison with those of the internal mammary artery and to discuss their implications for coronary bypass grafts. METHODS: Measurements of pressure and diameter were obtained from cylindrical segments, whereas measurements of reactivity were obtained from ring segments from the same arteries. We used an echo-tracking technique of high resolution enabling to investigate, in vitro, the diameter and the wall thickness of arterial cylindrical segments. Furthermore, the compliance, distensibility and incremental elastic modulus of the radial and of the mammary arteries were determined for a wide range of transmural pressure (0-200 mmHg) in presence and absence of norepinephrine (NE). RESULTS: Our results show that NE caused vasoconstriction of the two arteries. Strain was found significantly higher for the radial artery than for the internal mammary artery at any given value of stress both in the presence and in the absence of NE. In presence of NE, compliance for radial artery, in the overall transmural pressure range, did not change, whereas, distensibility was significantly increased and the elastic modulus was significantly decreased. Under the same conditions, the distensibility of the mammary artery tended to decrease and its elastic modulus to increase. In parallel, the vasoreactive properties of the two arteries confirmed the previous results showing that radial artery developed a significant higher tension to vasoconstricting agents (KCl, NE and phenylephrine (PHE)) and higher relaxation to isradipine than internal mammary artery. Moreover, radial artery displayed a lesser sensitivity to sodium nitroprusside than internal mammary artery. Furthermore, sensitivity to NE was found to be 7-fold higher for radial artery than for internal mammary artery. CONCLUSION: Taken together, data on the mechanical and reactive properties of radial and internal mammary arteries show why the radial artery displayed a higher potential for spasm than the internal mammary artery and why the use of Ca2+ channel blocker can decrease the incidence of occlusion and spasm.

Biomechanical Phenomena↗
PubMed1998

[Therapeutic strategies in acute myocardial infarction: antiarrhythmic therapy].

Antiarrhythmic therapy is a special case in the therapeutic strategy of acute myocardial infarction. There are very few controlled therapeutic trials and its use is mainly based on clinical experience rather than on scientific evidence. The most common arrhythmias requiring treatment in acute myocardial infarction are atrial fibrillation, ventricular tachycardia and ventricular fibrillation. There is no evidence to support the use Class I antiarrhythmics. Lidocain may be used in some cases. Similarly, contradictory results have been reported with the use of magnesium salts and the general tendency is not to use this ion in acute myocardial infarction. The most commonly used antiarrhythmic agents are the betablockers and amiodarone. The general principles of treatment should be respected: all antiarrhythmic drugs have negative inotropic effects, apart from digitalis. All antiarrhythmics may have a proarrhythmic effect including digitalis, especially in this clinical context. Whenever possible, continuous intravenous infusions are to be preferred to bolus injections. In addition, and when possible, electrotherapy is preferable to antiarrhythmic drug therapy. Finally, a number of cardiac arrhythmias observed in acute myocardial infarction should be "respected" or treated by electrotherapy but never by antiarrhythmic drugs.

Adrenergic beta-Antagonists↗
PubMed1998

[Management of arrhythmias in patients with heart failure].

Cardiac failure is a common cause of arrhythmia. Many factors predispose to the genesis of arrhythmias in these patients. A number of non-invasive methods allow stratification of the risk of arrhythmia in cardiac failure. Approximately half the deaths of these patients are due to arrhythmia. Unfortunately, most of the investigations for risk evaluation have a high negative predictive value but a lower positive predictive value. The treatment of supraventricular arrhythmias, mainly atrial fibrillation, is complex in cardiac failure. Class I antiarrhythmics are contraindicated. The only remaining options are Class II, especially Sotalol, and Class III drugs, especially Amiodarone. In some cases, non-pharmacological methods such as ablation, pacing or an implantable atrial defibrillator must be considered. The treatment of ventricular arrhythmias is also difficult. In this indication, Class I antiarrhythmic agents must also be avoided. Non-sustained ventricular tachycardia may be treated by betablockers or amiodarone. The use of an implantable defibrillator is increasingly recommended after the results of several controlled large scale trials. The indication is obvious in patients resuscitated from sudden death and these devices are also beneficial in sustained ventricular tachycardia in patients with cardiac failure. Many studies are currently under way to determine the value of this therapeutic modality in indications now considered to be "prophylactic".

Adrenergic beta-Antagonists↗
PubMed1997

[Auricular vulnerability: what information can be obtained from the study of auricular vulnerability? How to perform this study?].

The factors involved in atrial vulnerability are the presence of intra-atrial conduction disorders and abnormalities of refractory periods which are short, dispersed and poorly adapted to heart rate. All these factors are arrthythmogenic. The main value of the study of atrial vulnerability consists of investigation of unexplained ischaemic cerebrovascular accidents in young subjects. In practice, atrial vulnerability can be measured in the context of a classical endocavitary electrophysiological investigation. The stimulation and recording parameters must be standardized. Latent atrial vulnerability can be considered to be present when at least one of the following elements are found: significant inducibility, very short and poorly adapted effective refractory periods, decreased latent atrial vulnerability index.

Atrial Fibrillation↗
PubMed1996

[Mechanisms of atrial fibrillation. Recent progress and therapeutic implications].

Atrial fibrillation is usually due to multiple microreentry circuits. However, in some cases, the initial arrhythmia inducing the atrial fibrillation may be an abnormal automatism, or a macroreentry. The initial abnormalities may induce a desynchronization due to multiple macroreentry circuits. The main factors of atrial vulnerability are intraatrial conduction disturbances and changes in refractory periods. Critical mass and effects of autonomic nervous system may also play a role. Shortened refractory periods and decreased conduction velocity imply a short wavelength and an important arrhythmogenic risk. On the other hand, the longer the duration of atrial fibrillation, the more refractory periods will shorten and the more atrium will become vulnerable: atrial fibrillation tends to beget atrial fibrillation because of an electrophysiologic remodelage. In some cases atrial fibrillation, if its duration is long and if its rate is high, may be responsible for the development of a tachycardiomyopathy. The knowledge of atrial fibrillation mechanism may have interesting therapeutic implications such as resynchronization of the atria by stimulation or ablation, for example in the approaches comparable to the maze operation.

Arrhythmias, Cardiac↗
PubMed1996

Short- and long-term assessment of heart rate variability for risk stratification after acute myocardial infarction.

Depressed heart rate variability (HRV) has been shown to be a powerful and independent risk factor in patients following acute myocardial infarction (AMI). A detailed comparison of the predictive values between short- and long-term HRV has not been made. The predictive value of short-term HRV for 1-year total cardiac mortality was studied in 700 consecutive patients after AMI. All patients underwent 24-hour Holter monitoring before discharge from the hospital (5 to 8 days after AMI) and were followed up for 1 year. Short-term HRV was computed as the standard deviation of all normal RR intervals (SDNN) from a 5-minute stationary period selected from 24-hour Holter electrocardiographic recordings. Long-term HRV was computed as an HRV index over the entire 24 hours. There was a significant but relatively poor correlation between SDNN and HRV index (r = 0.51, p <0.001). The positive predictive accuracy of SDNN for 1-year mortality (13% to 18%) was lower than the HRV index (17% to 43%) over a range of sensitivity of 25% to 75%. Assessment of HRV index in > or = 35% of the patients preselected by the lowest SDNN was able to achieve predictive power similar to that of HRV index assessed in all the patients. These data suggest that lower predischarge short-term HRV is associated with increased 1-year total cardiac mortality in patients after AMI. Analysis of long-term HRV for postinfarction risk stratification can safely be limited to patients preselected by depressed short-term HRV measures.

Analysis of Variance↗