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Biomedical subjects

J Clementy

Publications and source records attributed to J Clementy.

At least 55 records · Page 3Linked to original sources
PubMed1996

Electrophysiological effects of catheter ablation of inferior vena cava-tricuspid annulus isthmus in common atrial flutter.

BACKGROUND: The electrophysiological mechanisms for successful catheter ablation of atrial flutter (AFI) targeting the inferior vena cava-tricuspid annulus (IVC-TA) isthmus have not been determined. METHODS AND RESULTS: Twenty patients with common AFI were studied. All had inducible common AFI, and 8 of them had both common and reverse AFI. Right atrial (RA) activation sequences were investigated during pacing from sites proximal (low lateral RA) and distal (proximal coronary sinus) to the IVC-TA isthmus both during entrainment of common or reverse AFI and during pacing in sinus rhythm. This was repeated after ablation. During pacing in sinus rhythm from the low lateral RA, the septum was activated by caudocranial and craniocaudal wave fronts. Similarly, during pacing from the proximal coronary sinus, the lateral RA was activated by two wave fronts. Catheter ablation of the IVC-TA isthmus induced dramatic changes in mapping due to the loss of caudocranial wave front in all but 1 patient. The septum and the lateral RA were activated by a single craniocaudal front as during entrainment of reverse or common AFI, respectively. After a follow-up of 8 +/- 2 months, common or reverse AFI occurred in 4 patients. Two had no or only unidirectional changes in the isthmus conduction induced by ablation. The other 2 had a late recovery of conduction. CONCLUSIONS: The present study provides evidence that the mechanism of successful AFI ablation targeting the IVC-TA isthmus is local bidirectional conduction block. This change can be used as a new and complementary electrophysiological end point for the procedure. AFI recurrences are associated with failure to achieve a permanent block.

Aged↗
PubMed1996

Daytime and nighttime ambulatory blood pressures should be calculated over the true sleep/waking cycle and not over arbitrary periods.

The present study was done to compare the values of mean daytime and nighttime blood pressure (BP) calculated over arbitrary periods to those calculated over the true retiring and rising times of the individual patients. A total of 88 individuals, including 55 untreated hypertensives (office BP > 140/90 mm Hg) and 33 normotensives, were recruited. Ambulatory BP was monitored over 24 h during the normal routine of the patient. The patient was requested to trigger a recording on going to bed and on rising in the morning to clearly identify these periods. The mean daytime and nighttime values were calculated over arbitrarily defined periods (6 AM to 10PM daytime and 10 PM to 6 AM nighttime) and as a function of the true retiring and rising times of the individual patients. The true daytime BP was significantly higher than the value calculated over the arbitrary period and the true nighttime BP was significantly lower than the value calculated between 10 PM and 6 AM (paired t test, P < .05). Employing a cutoff value of 135/85 mm Hg for daytime BP, a significant proportion of patients classified as normotensive when daytime BP was calculated over arbitrary periods were in fact classified as hypertensive from the values calculated over true retiring and rising times.

Adult↗
PubMed1996

Radiofrequency catheter ablation of atrial tachycardias.

Atrial tachycardias are frequently unresponsive to medical therapy. His bundle ablation has been proposed as a palliative treatment to treat symptoms and prevent development of tachycardia-mediated cardiomyopathy. Experience with catheter ablation directed at the atrial origin of the tachycardia remains limited. We reviewed the initial success rate and long-term follow-up of radiofrequency ablation of atrial tachycardias. Thirty-six patients underwent electrophysiologic study and radiofrequency ablation of atrial tachycardias, excluding atrial flutter. The suspected mechanism of the clinical arrhythmia was automatic in 16 patients, intraatrial reentrant in 15, sinoatrial reentrant in 3, and unknown in 2. One or two ablation catheters with a 4 mm distal electrode were used to find (1) the earliest local atrial activation time compared to P-wave onset in the bipolar recording mode and (2) a QS pattern in the unipolar mode. When two ablation catheters were used, an encircling approach was taken. Pace-mapping during sinus rhythm and entrainment techniques were occasionally used for mapping. Tachycardia rose from the right atrium in 33 of 36 patients and from the left atrium in the remaining three. Three patients showed multiple foci during the procedure. Successful ablation was obtained in 31 (86%) of 36 patients, with a median of two radiofrequency applications (range 1 to 32) at 10 to 50 W for 10 to 60 seconds. Failure occurred in 5 patients (including the 3 patients with multiple atrial foci). Late follow-up (18 +/- 15 months) showed recurrence of atrial tachycardia in 2 patients, each of whom underwent a successful second ablation. Emergence of another atrial tachycardia was noted in 2 other patients, and an uncommon atrial flutter was noted in 1 patient with repaired atrial septal defect. No late sinus or atrioventricular nodal dysfunction were observed. In conclusion, radiofrequency catheter ablation is a safe and reasonable alternative for atrial tachycardias that do not respond to drugs. However, as previously suggested by the surgical experience, the success rate of ablation appears less satisfactory in patients with multiple sites of origin of ectopic atrial tachycardia.

Adult↗
PubMed1996

Ventricular protection against atrial arrhythmias in DDD pacing based on a statistical approach: clinical results.

Atrial arrhythmias (AA) are commonly encountered in DDD paced patients. Newer dual chamber pacemakers (PM) possess mode switching functions that convert pacing to an asynchronous mode when AAs are detected. The lack of a reliable mode switch leading to rapid, irregular ventricular responses may result from AA undersensing. To avoid this the DDDR PM Chorum 7234 Ela Medical AA diagnosis is based on a statistical approach: the PM constantly compares arrhythmic and sinus cycles and, based on "strong" and "weak" criteria, provides for rapid or slower mode switch. The aim of the study was to evaluate the efficiency and reliability of these two criteria. Thirty-one patients with a Chorum 7234 implanted for AV block (11), sinus dysfunction (10), both (5), or hypertrophic obstructive cardiomyopathy (5) were evaluated at 24 hours and 1 month using the internal memory (IM) of the PM, surface 24-hour Holter recordings, and exercise testing. Interrogation of the IM on the first day of study showed that 8 patients had mode switching episodes, based only on the strong criterion confirmed by the surface Holter recording. At 1 month, the IM revealed mode switching episodes in 12 patients, 6 of whom had used the weak criterion. No inappropriate mode switching episodes was recorded during exercise testing at the 1-month follow-up. These results confirm the reliability and efficiency of this algorithm as well as the requirement for a specific algorithm to compensate for transient loss of sensing during AA.

Algorithms↗
PubMed1996

Beyond blood pressure measurements: monitoring of the appearance time of Korotkoff sounds.

We have recently proposed a new method to evaluate the physical properties of arteries based on measurement of the QKD interval together with blood pressure and heart rate with an ambulatory blood pressure monitoring device. This interval is the time between the onset of the depolarization (QRS) on the electrocardiogram (Q) and detection of the last Korotkoff (K) sound at the level of brachial artery during cuff deflation, corresponding to diastolic blood pressure (D). The QKD interval is the sum of the pre-ejection period and of the pulse transmission time from the aortic valves and the microphone. Thus, it is linked to the pulse wave velocity on an arterial segment which includes the ascending aorta and a portion of the subclavian and brachial arteries. From each 24 h monitoring, the average 24 h QKD, the slope of variation of QKD against blood pressure and a normalized QKD (QKD100-60) for systolic blood pressure of 100 mmHg and heart rate of 60 beats/min are calculated. Stiffer arteries as observed with ageing or hypertension are characterized by the reduction of these three parameters. The reproducibility of this method is good. In a pilot study of elderly hypertensive patients we have shown that QKD 100-60 has a strong and independent predictive value for future cardiovascular events. Therefore, this method may add significant information to ambulatory blood pressure monitoring.

Journal Article↗
PubMed1996

[Assessment of arterial distensibility by ambulatory monitoring of QKD interval. Reproducibility of the method].

We have proposed the use of the ambulatory monitoring of the timing of Korotkoff sounds (QKD interval) to assess arterial distensibility. This interval is inversely linked to pulse wave velocity. The study of its variations according to spontaneous blood pressure changes during 24 h allows to calculate indices of arterial distensibility independent of actual blood pressure. A normalized QKD100-60 is calculated as the value for a 60 batt/min heart rate and a 100 mmHg systolic blood pressure from the individual multivariate linear relationship between these 3 variables. This interval decrease with arterial distensibility. We tested the reproducibility of this method in 28 normal subjects (14 males, 14 females, aged 43 +/- 16 years) who underwent two 24 h recordings during daily routine separated by one week. Standard deviation of differences for QKD100-60 was 12 ms, the coefficient of variation 6% and the coefficient of repeatibility 24 ms. So QKD100-60 shows a good reproducibility in the same range that 24 h blood pressure means.

Adult↗
PubMed1995

Radiofrequency catheter ablation of common atrial flutter in 80 patients.

OBJECTIVES: The purpose of this study was to evaluate the efficacy and safety of radiofrequency catheter ablation of common atrial flutter and to determine the optimal target sites in a large series of patients. BACKGROUND: Recent studies report the efficacy of radiofrequency current application in the low right atrial region to interrupt and prevent recurrences of common atrial flutter. However, larger groups of patients are required to confirm the efficacy of this technique and to specify the target sites. METHODS: Two different approaches were used to target the ablation site in 80 consecutive patients. In the first 50 patients, target sites were localized using both anatomic landmarks and electrophysiologic variables. Three anatomic landmarks were used: area 1 = between the tricuspid valve and inferior vena cava orifice; area 2 = between the tricuspid valve and coronary sinus ostium; area 3 = between the inferior vena cava and coronary sinus. The electrophysiologic criterion was to ablate when there was a stable atrial electrogram during the plateau phase. In the next 30 patients we assessed the effect of application of radiofrequency energy in a single line in area 1, 2 or 3 in groups of 10 patients. RESULTS: Overall atrial flutter was interrupted and rendered noninducible after a single session in 72 patients (90%) and could not be interrupted in 8 (10%). The mean (+/- SD) number of radiofrequency applications was 12 +/- 8. After a mean (+/- SD) follow-up of 20 +/- 8 months, recurrences occurred in 14 patients (17%). The location of the final successful site in the first group of 50 patients was in area 1 in 39%, area 2 in 36% and area 3 in 25%. In the next 30 patients, when lines of radiofrequency lesions were placed at several sites, they produced success rates of 70%, 40% and 10% at areas 1, 2 and 3, respectively. CONCLUSIONS: Radiofrequency catheter ablation of atrial flutter can be performed with a high success rate and is safe. The highest success rate is achieved with radiofrequency energy applied in the isthmus between the inferior vena cava orifice and tricuspid valve.

Actuarial Analysis↗
PubMed1995

Coronary reserve in experimental myocardial hypertrophy.

Three types of dysfunction of the coronary circulation have been described in experimental models of hypertension associated with left ventricular hypertrophy: (1) reduced coronary reserve, (2) a relative decrease in perfusion of subendocardial layers, (3) a shift to the right, i.e. to higher pressures, of the circulation pressure autoregulation range. These abnormalities are also observed in hypertensive patients, although it is significant that they do not appear to be related to the extent of left ventricular hypertrophy. The exact causes of these abnormalities have yet to be elucidated. Left ventricular hypertrophy does not seem to be an essential factor, although in certain experimental models of hypertension, there does appear to be a mismatch between the development of the coronary vasculature and hypertrophy of the myocytes. The stresses in vessels due to the increase in systolic, and especially intraventricular diastolic pressure can be viewed as additional aggravating factors. The essential abnormalities are structural and/or functional alterations in arterial walls. The structural alterations are reflected by a narrowed lumen due to parietal thickening. This may result from growth of muscle fibres (hypertrophy or hyperplasia) or collagen tissue and/or remodelling of tissues with no overall change in mass. Functionally, the reduced ability of the arteries to stretch, resulting from endothelial alterations may also play a role in the abnormalities observed in hypertensive patients. In our studies, we examined the effect of the antihypertensive drug perindopril on the coronary circulation in renovascular hypertensive rat (two kidneys--1 clip). We found that this inhibitor of angiotensin converting enzyme (ACE) led to a regression of left ventricular hypertrophy with a return to normal of the coronary reserve. Other studies using either this model or the spontaneously hypertensive rate has also pointed to a beneficial action of ACE inhibitors and other antihypertensive agents on the coronary circulation with reversal of the structural alterations in arterioles. Coronary disease is the main cause of mortality in hypertensive patients. Ironically, antihypertensive therapy has yet to live up to its promise of reducing significantly either the incidence or severity of coronary disease in such patients. Specific alterations of the coronary circulation may account for the relative failure of antihypertensive drugs, despite their proven efficacy in other systems (e.g., stroke prevention). The coronary circulation is unique in certain important respects. It is tightly regulated, maintaining an almost constant flow rate over a wide range of aortic arterial pressures (40-160 mmHg). Extraction of oxygen by the myocardium is almost maximal under resting conditions, and so the circulatory reserve depends almost entirely on the capacity to increase blood flow. This reserve is quite large since there may be a 4 to 5-fold increase in coronary flow rate in response to effort. Another significant detail is that myocardial contraction may lead to an interruption of coronary flow, especially in the deep subendocardial layers, which thus tend to be perfused solely during diastole. This last factor can be seen as the Achilles heel of the coronary circulation, which may be severely limited by myocardial hypertrophy, especially in patients with hypertension.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1994

Assessment of arterial distensibility by monitoring the timing of Korotkoff sounds.

The timing of Korotkoff sounds, blood pressure, and heart rate can now be monitored in the ambulatory patient: the QKD interval is the time between the onset of the depolarization on the electrocardiogram (Q) and detection of the last Korotkoff sound (K) at the level of brachial artery during cuff deflation, corresponding to diastolic blood pressure (D). Because this interval is inversely related to pulse wave velocity, this recently developed device enables evaluation of the influence of blood pressure on arterial rigidity, providing valuable information on the properties of the arteries. In this study, we examined the influence of hypertension and age on the above parameters and their correlations to left ventricular mass. QKD interval, blood pressure, and heart rate were monitored over a period of 24 h (four measurements/hour) in 33 normotensive and 70 untreated essential hypertensive patients. The slopes of the plots of QKD interval versus systolic and pulse pressure during the 24 h were calculated for each patient. The influence of age and hypertension on these slopes was tested by comparison of matched groups and multivariate analysis. Moreover the relationships between these parameters and echocardiographically assessed left ventricular mass were studied in 37 patients. We found a reduction in mean QKD interval with age and hypertension, reflecting the recognized higher pulse wave velocity in these patients. The slopes of the plots of QKD interval versus blood pressure were also lower in these patients, indicating the smaller influence of a change in blood pressure on pulse wave velocity in patients with stiffer arteries.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Catheter ablation of accessory pathways in children.

The efficacy and safety of catheter ablation of accessory pathways (AP) was studied in 79 children (age, 4-16 years), using DC shocks (n = 25) or radiofrequency energy (n = 54). All patients had documented arrhythmias including ventricular fibrillation in four. Organic heart disease was present in four patients. AP locations were left lateral (n = 36), posteroseptal (n = 36), right lateral (n = 8), Mahaim fibres (n = 2) and right anteroseptal (n = 6). Seven patients had multiple AP. One patient had a preexcitation which appeared secondary to an atrio-infundibular connection (Fontan procedure). The ablation site of concealed or overt AP was identified by retrograde or anterograde conduction mapping, respectively. A mean of 2.6 +/- 1 cathodal shocks (80-160 J) was delivered to 25 patients over 29 sessions, resulting in initial AP ablation in all. Fulguration was uncomplicated in all except in one patient (4%) who developed a secondary complete AV block post-ablation. During a follow-up period of 30-69 months, intermittent preexcitation recurred in two asymptomatic patients, but no significant tachycardia was inducible at late electrophysiological study, including under isoproterenol infusion. Radiofrequency energy was applied to 54 patients during 62 sessions, using 20-40 watts for 30-60 s. AP ablation was initially achieved in all patients using a median of three impulses, without significant immediate side-effects. Two patients (4%) developed a short episode of blurred vision possibly due to a microembolism. After discharge, the follow-up period was 10 +/- 5 months (range 1 to 24). All patients but one (98%) were asymptomatic without any drug therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Correlation of signal-averaged P wave with electrophysiological testing for atrial vulnerability in strokes of unexplained etiology.

UNLABELLED: Atrial fibrillation is considered the main cause of cardioembolic strokes. After detailed investigations, about 30% of ischemic strokes remain unexplained. A percentage of these ischemic attacks may result from asymptomatic episodes of paroxysmal atrial fibrillation (PAF). Previous studies have demonstrated that electrophysiological testing and signal-averaged P wave (SAPW) ECG are useful to detect patients with PAF. METHODS AND RESULTS: Twenty patients with unexplained ischemic strokes had electrophysiological studies (EPS) to determine atrial vulnerability and SAPW recordings. At EPS, patients were classified in group I (10 patients) if they had a latent atrial vulnerability index < 2 and/or more than 1 minute of sustained atrial arrhythmia. Otherwise they were classified in group II (10 patients). In group I, the filtered P wave duration was greater: 142 versus 120 msec (P = 0.03) and RMS 30 tended to be lower: 2.54 versus 4.13 microV (P = 0.11) than in group II. A filtered P wave duration > 125 msec associated with a RMS 30 < 3 microV had a positive predictive value of 78% and a negative predictive value of 88% for the detection of patients with abnormal atrial vulnerability at EPS. CONCLUSIONS: SAPW may be useful to identify patients at risk of PAF who may be candidates for EPS.

Atrial Fibrillation↗
PubMed1994

Clinical significance of white-coat hypertension.

DEFINITION AND PREVALENCE OF WHITE-COAT HYPERTENSION: White-coat hypertension describes the phenomenon of an abnormal blood pressure reading when taken by a physician and a normal reading with ambulatory or home monitoring. The results of studies suggest that the true prevalence of white-coat hypertension may be 20%. The magnitude of the effect using either the oscillometric or the auscultatory method of measurement appears to be comparable. PROGNOSTIC SIGNIFICANCE: The prognostic significance of the white-coat effect is not established, and prospective trials are needed to assess the risk. At present, because of the unpredictability and unreliability of this effect, we recommend that patients with white-coat hypertension should not be included in trials on the efficacy of antihypertensive drugs.

Blood Pressure Determination↗
PubMed1993

'White coat' hypertension. No harm for the heart.

The superiority of ambulatory blood pressure monitoring over casual blood pressure measurement for the prediction of target-organ damage is now well established, although the significance of "white coat" hypertension is still controversial. Is an office blood pressure measurement that is higher than the mean ambulatory value an added risk? Because left ventricular hypertrophy is a potent risk factor, the effect of hypertension on left ventricular mass merits attention. Left ventricular mass indexed for height was measured by M-mode echocardiography in 204 essential hypertensive patients (140 males, 64 females; mean age [SD], 50 [11] years). Blood pressure over 24 hours was monitored routinely with a noninvasive auscultatory device. Office blood pressure after 10 minutes of the subject in the supine position was measured by the same physician under the same conditions. The white coat effect was defined as the difference between the office and average daytime values of systolic and diastolic blood pressures. Patients were divided into four quartiles according to their office and daytime blood pressures. Two-way analysis of variance was used to assess the influence of the white coat effect at a given level of daytime blood pressure on left ventricular mass. Left ventricular mass increased significantly (P < .001) with daytime systolic blood pressure but was independent of white coat effect for both the whole population and the 143 untreated patients. We conclude that the white coat effect has no influence on left ventricular mass, favoring the view that white coat hypertension is a benign condition.

Adolescent↗
PubMed1992

Flecainide acetate in the prevention of paroxysmal atrial fibrillation: a nine-month follow-up of more than 500 patients.

In order to assess efficacy, safety, and long-term tolerance of flecainide for the prevention of paroxysmal atrial fibrillation (PAF), 944 patients (555 male) were enrolled in an open multicenter study. All patients had had greater than or equal to 1 episodes of atrial fibrillation and were in sinus rhythm at the time of entry. The mean age was 65.3 +/- 11 years, and 43% of patients had no detectable heart disease. The mean daily dose of flecainide was 190 +/- 34 mg. Clinical examination, electrocardiogram (ECG) and 24-hour Holter monitoring were performed at entry into the study and on months 3, 6, and 9. Of the patients, 189 were lost to follow-up. Of the remaining 755 patients, 562 (74%) continued the treatment during the 9-month period and 193 (26%) dropped out. A total of 84 adverse effects were reported in 7.6% enrolled patients and in 9% of patients during follow-up, with treatment interruption in 50% of the cases. There were only 3 minor cardiovascular side effects, all leading to treatment discontinuation. No deaths in patients with recurrent PAF and no proarrhythmic events were reported. Flecainide appears to be effective in preventing PAF, with 65% of patients being arrhythmia-free after 9 months of treatment at a mean daily dose of 200 mg. Side effects were common, but clinically significant adverse events were infrequent.

Atrial Fibrillation↗
PubMed1992

Evaluation of bepridil efficacy by electrophysiologic testing in patients with recurrent ventricular tachycardia: comparison of two regimens.

The purpose of the study was to evaluate this effect of different doses of intravenous and oral bepridil on the induction of ventricular tachycardia. Thirty-eight patients underwent electrophysiologic evaluation for recurrent ventricular tachycardia (VT). Sustained monomorphic VT was induced by programmed ventricular stimulation, using up to three extrastimuli in all patients. The effects of intravenous bepridil (2 mg/kg) were evaluated during the initial study. Intravenous bepridil prevented the induction of sustained VT in eight patients (21%). Electrophysiologic study was repeated after oral bepridil. In six patients the study was stopped because of adverse effects or VT recurrence. Thirty-two patients underwent repeat study 7 days later, taking oral bepridil, 500 mg/day (n = 16) or 900/day (n = 16). A dose of 500 mg/day of bepridil prevented the induction of sustained VT in only one patient. A dose of 900 mg/day of bepridil prevented the induction of sustained VT in eight patients. There were no significant clinical adverse effects, except in one patient receiving intravenous bepridil. The response to intravenous bepridil did not predict the response to oral bepridil. The response to intravenous or oral bepridil was not related to the plasma level of bepridil but was related to a higher left ventricular ejection fraction. Eight patients (21%) in whom VTs were noninducible on oral bepridil were discharged on 300 mg/day of bepridil if their initial loading dose was 500 mg/day or on 600 mg/day if their initial loading dose was 900 mg/day. They remained free of VT during a follow-up of at least 6 months.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1991

[Low calcium channel inhibitors: modalities for use].

The recent discovery of numerous new "calcium inhibiting" molecules and the multiplicity of their indications in cardiology and in other specialties have made it necessary to clarify their position in the armory of medical treatments in cardiology and their associations with other treatments. Before describing the various protocols for the use of calcium channel inhibitors, the article describes the basic factors involved in the choice of the most appropriate calcium channel inhibitor on the basis of their mechanisms of action, the tissue selectivity, the pharmacokinetic profile and the formulations available.

Calcium↗