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Biomedical subjects

P Mabo

Publications and source records attributed to P Mabo.

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

Electrophysiological and inotropic characterization of a novel class III antiarrhythmic agent, GLG-V-13, in the mammalian heart.

GLG-V-13, a novel 3,7-diheterabicyclo(3.3.1)nonane, was examined both in vivo and in vitro to characterize its electrophysiological, hemodynamic, and inotropic properties. In anesthetized guinea pigs, GLG-V-13 [0.5-500 micrograms/kg intravenously (i.v.), n = 6] lengthened the epicardial monophasic action potential (MAP) duration, the atrioventricular (AV) conduction time and the RR interval in a dose-dependent manner. At the highest dose, these variables were increased by 30, 13, and 23%, respectively. No significant effects were noted on QRS duration or blood pressure (BP). In rabbit atrial and papillary muscle preparations, GLG-V-13 (0.32-3.2 mg/L) did not exert a negative inotropic action and in isolated rabbit cardiomyocytes the agent blocked the rapidly activating delayed rectifier K+ current (IKr, EC50 = 48 micrograms/L). In 10 intact anesthetized mongrel dogs, the left ventricular (LV) endocardial MAP was measured during atrial pacing before and after administration of GLG-V-13 (3 and 6 mg/kg i.v.). As compared with the drug-free state, the agent induced a significant prolongation of the MAP at all pacing frequencies (2.0-4.5 Hz). In 15 anesthetized dogs studied 1-4 days after two-stage ligation of the left anterior descending coronary artery (LAD), the antiarrhythmic/proarrhythmic potential of GLG-V-13 was compared with that of lidocaine. ECG, His bundle, LV (IZepi), and composite and normal zone composite electrograms were recorded. Programmed electrical stimulation (PES) and burst pacing (4.0-7.0 Hz) were delivered to the right ventricular outflow tract. In the drug-free state, sustained monomorphic ventricular tachycardia (SMVT) was inducible in 6 dogs (6 of 15). After lidocaine, SMVT was induced in 7 other dogs (13 of 15). GLG-V-13 prevented induction of SMVT in 5 of 6 dogs; a proarrhythmic action was noted in 1 dog only. GLG-V-13 slowed the heart rate (HR), increased the AH and the HV intervals, prolonged the paced (2.5 Hz) QT interval, and increased the ventricular effective refractory period (VERP). These effects were associated with 2:1 block of late potentials in the IZepi electrograms, a phenomenon also observed during rapid atrial pacing (2.5-3.5 Hz), suggestive of a marked prolongation of refractoriness in the ischemically damaged myocardium. In light of the recent Cardiac Arrhythmia Suppression Trial (CAST) study, the antiarrhythmic efficacy, together with the low proarrhythmic potential and lack of cardiodepressant properties of GLG-V-13, may merit further investigation of this novel class III antiarrhythmic agent.

Animals↗
PubMed1996

[Value of unipolar and bipolar recordings in radiofrequency ablation of accessory atrioventricular pathways].

The aim of the study was to compare the value of different modes of endocavitary recordings: unipolar alone, bipolar alone and the association of unipolar and bipolar recordings in radiofrequency ablation of accessory atrioventricular pathways. A retrospective analysis by three independent observers of 135 endocavitary recordings obtained immediately before radiofrequency application in 82 subjects who underwent radiofrequency ablation for symptomatic accessory atrioventricular pathways. In each case, the authors selected the "successful" record which corresponded to the final radiofrequency application and 0.1 or 2 records of "failures". Each initial recording being of 3 types (unipolar, bipolar and association of uni- and bipolar), a total of 390 anonymous and randomised recordings were analysed by the observers who determined whether the appearances indicated successful ablation. Univariate analysis of variants showed a correlation between success with the mode of recording (p = 0.03) and a left lateral position of the accessory pathways. In multivariate analysis, three variables remained correlated with successful ablation: the observer variable (p = 0.001), and two interactions observer - mode (p = 0.005) and observer-stability (p = 0.02). The benefits of the association of unipolar and bipolar recordings with respect to bipolar recording alone, seemed to be important in predicting failure. The results of tests of concordance in the group of failures were confirmatory: concordance between observers was only found between the unipolar mode alone and the association of unipolar and bipolar recordings. The results of this study suggest that the association of unipolar and bipolar endocavitary recordings may reduce the number of unnecessary application of radiofrequency energy by improved identification of recording showing failure.

Adult↗
PubMed1996

[Is isolated atrial fibrillation genetically determined? Apropos of a familial history].

The authors report five cases of apparently lone atrial fibrillation in five members of the same family from three generations. The atrial fibrillation occurred at an early age and rapidly became permanent in all cases. With time, in the absence of complications, structural cardiac abnormalities were documented by echocardiography (biatrial dilatation and mitral and tricuspid regurgitation). These observations raise the question of genetic predisposition to lone atrial fibrillation at least in this particular clinical context.

Adult↗
PubMed1996

[Acute relapsing pericarditis induced by screw-in atrial pacing lead. Apropos of 3 cases].

Contrary to the ventricle where pacing leads remain passively implanted, the use of active screw-in atrial pacing leads has rapidly developed during the last few years. This type of fixation in a thin and fragile cardiac wall carries a risk of perforation and thereby of pericardial complications. The authors report three original cases of a period of time. The responsibility of the atrial lead was highly probable given the presence of suggestive symptoms (pericardial pain) or of pericardial complications confirmed at surgery, of the presence of radiological changes in 2 cases (localised bulges of the cardiac silhouette opposite the site of implantation of the pacing lead), the absence of any other detectable cause and, finally, cure after explantation of the causal pacing lead and anti-inflammatory drug therapy. Some simple preventive measures based on the properties of the material (screw length < 2 mm), the technique of implantation, should help avoid these complications or, at least, to reduce their frequency.

Acute Disease↗
PubMed1995

Hemodynamic importance of preserving the normal sequence of ventricular activation in permanent cardiac pacing.

Pacing the right ventricle in the apex profoundly modifies the sequence of activation and thus the sequence of contraction and relaxation of the left ventricle. To evaluate the relative importance of preserving normal ventricular activation sequence and optimal atrioventricular (AV) synchrony in permanent pacing, we compared the effects of three pacing modes: AAI, preserving both normal AV synchrony and normal activation sequence; DDD, with complete ventricular capture that preserves only AV synchrony; and VVI, disrupting both, at rest and during exercise. Hemodynamic and radionuclide studies were performed in 11 patients who had normal intrinsic conduction and who were implanted on a long-term basis with a DDDR pacemaker for isolated sinus node dysfunction. AAI versus DDD and VVI significantly increased cardiac output at rest (6.6 +/- 1.3 L/min vs 6 +/- 0.9 L/min vs 5 +/- 1 L/min; p < 0.01) and during exercise (13.5 +/- 2 L/min vs 12.1 +/- 2.2 L/min vs 14.4 +/- 2.1 L/min; p < 0.01). Pulmonary capillary wedge pressure was lowest with AAI (15.4 +/- 4.5 mm Hg), with an average reduction of 17% compared with DDD (19.6 +/- 5 mm Hg; p < 0.01) and of 30% compared with VVI (25.8 +/- 7 mm Hg; p < 0.01) during exercise. Identical benefits were observed for all other hemodynamic parameters: right atrial pressure, pulmonary artery pressure, left ventricular (LV) stroke work index, and systemic vascular resistances. LV ejection fraction was significantly higher in AAI than in DDD at rest (61% vs 58%, respectively; p < 0.05) and during exercise (65% vs 60%, respectively; p < 0.05). This improvement in LV systolic function resulted principally from the increase in septal ejection fraction. LV filling also was improved in AAI as demonstrated by a significant increase in peak filling rate at rest and during exercise. These data show the importance of preserving, whenever possible, not only normal AV synchrony but also normal ventricular activation sequence in permanent cardiac pacing.

Adult↗
PubMed1995

A technique for stable His-bundle recording and pacing: electrophysiological and hemodynamic correlates.

His-bundle electrograms recorded from intracardiac electrode catheters have been a mainstay of basic and clinical electrophysiology. However, consistent His-bundle pacing has not been as readily achieved. In 13 dogs anesthetized with sodium pentobarbital (30 mg/kg), we recorded leads II and aVR as well as the His-bundle electrogram from the aortic root. A deflectable tip multipolar catheter (4 rings, 5 mm apart) was introduced via the right jugular vein into the right ventricle (RV). In 7 dogs, using fluoroscopy, the tip was placed under the tricuspid septal leaflet. In the other 6, after thoracotomy, the same placement was made by palpation through the right atrial wall. Stable His-bundle and right bundle (Rb) branch recordings were made from distal and proximal electrode pairs, respectively. H-V intervals measured 35 +/- 6 ms from the aortic root and 33 +/- 5 ms from under the tricuspid leaflet (P = NS). Rb-V measured 25 +/- 4 ms. Consistent His-bundle pacing was accomplished from the aortic root with an average stimulus intensity of 6 +/- 10 mA and from the tricuspid leaflet at 16 +/- 8 mA (P < 0.05). In 7 anesthetized dogs we compared the hemodynamic effects of A-V sequential pacing at the same heart rates using the His-bundle recording site under the septal leaflet of the tricuspid valve (A-H pacing) or pacing from the RV apex (A-RV pacing). Under normal conditions there was a significant depression of mean blood pressure when A-RV pacing was compared with atrial pacing (AOO); but no difference was found between AOO and A-H pacing.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

[Importance of atrioventricular synchrony in hypertrophic obstructive cardiomyopathy treated by cardiac pacing].

This study was undertaken to evaluate the effect of permanent dual-chamber cardiac pacing in hypertrophic obstructive cardiomyopathy resistant to medication, paying particular attention to atrioventricular synchrony. Sixteen patients, mean age 59 +/- 13 years (range 36 to 80 years) were divided into two groups after in initial catheter study performed under temporary VDD pacing between March 1990 and April 1993. In group I (n = 11), the gradient was decreased by more than 50% whereas in group II (n = 5), the gradient was unchanged or reduced by less than 50%. The reduction of the gradient was immediately significant in group I, the mean value falling from 104 +/- 33 mmHg (range 60 to 170 mmHg) to 25 +/- 13 mmHg (range 10 to 60 mmHg) (p < 0.0001). In group II, the gradient only decreased initially from 132 +/- 13 mmHg (range 120 to 150 mmHg) to 88 +/- 25 mmHg (range 50 to 130 mmHg) (p < 0.003) but improved atrioventricular synchrony, obtained secondarily either by pharmacological prolongation of the PR interval (association of betablocker and verapamil) or by ablation of the atrioventricular junction, improved the haemodynamic benefits. The residual gradient recorded on the 7th day was only 26 +/- 15 mmHg (range 10 to 50 mmHg) (p < 0.0001). The comparison of the two populations showed that the mean PR interval was shorter in group II (p < 0.016) and the mean value of the optimal AV Delay (the longest AV Delay with complete ventricular capture) was also lower (p = 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗
PubMed1995

[Value of cardiac pacing in hypertrophic obstructive cardiomyopathy refractory to medical treatment].

Recent studies have shown that dual-chamber cardiac pacing could improve patients with hypertrophic obstructive cardiomyopathy resistant to medical treatment. After a brief historical review, the authors report the present status of this original therapeutic option. The results of different studies are in agreement and show that the functional improvement is associated with a large reduction of the intraventricular pressure gradient with permanent DDD pacing. Although the exact mechanism of the improvement remains unknown, all groups underline the importance of complete and permanent ventricular capture. This requires precise regulation of the atrioventricular delay which in most cases must be programmed at a value inferior to 90 ms, which compromises ventricular filling which is already abnormal under basal conditions. The inefficacy of pacing in some cases is explained by the necessity of selecting a very short atrioventricular delay which alters diastolic function and finally masks the benefits of ventricular capture. In this particular situation, the authors propose improving atrioventricular synchrony by pharmacological prolongation of the PR interval, or, when unsuccessful, by ablation of the atrioventricular junction. This attitude was adopted in 5 cases when pacing with an AVD programmed between 20 and 70 ms, provided only a partial haemodynamic result. Improved atrioventricular synchrony allowed selection of an AVD of 100 to 150 ms, so reducing the gradient by more than 70%, compared with 30% under the initial programming parameters. The authors conclude that a positive and sustained benefit of cardiac pacing can only be obtained by an individualised regulation of pacing parameters to optimize atrioventricular synchrony which seems to be the key element of success.

Adrenergic beta-Antagonists↗
PubMed1995

Electrophysiological characterization of a novel class III antiarrhythmic agent, GLG-V-13 in the mammalian heart.

GLG-V-13, a novel 3,7-diheterabicyclo[3.3.1]nonane, was examined both in vivo and in vitro in order to characterize its electrophysiological, haemodynamic and inotropic properties. Left ventricular epicardial monophasic action potential (MAP), surface ECG and mean arterial blood pressure (MBP) were recorded in six pentobarbital-anaesthetized, artificially ventilated and thoracotomized guinea-pigs. When studied in an intravenous dose interval ranging between 0.5 micrograms/kg and 500 micrograms/kg, GLG-V-13 dose-dependently lengthened the MAP duration (p < 0.05 at doses above 5 micrograms/kg), the atrioventricular conduction time (p < 0.05 at doses above 1 microgram/kg) and the RR interval (p < 0.05 at doses above 25 micrograms/kg). At the highest dose (500 micrograms/kg) these variables were increased by 30%, 13% and 23%, respectively. Only minor effects were noted on intraventricular conduction time (QRS interval) and MBP. In rabbit atrial and papillary muscle preparations, GLG-V-13 (0.32 to 3.2 mg/l) did not exert negative inotropic action. In 10 intact anaesthetized mongrel dogs, left ventricular endocardial MAP at 90% repolarization (MAP90) was measured during atrial pacing before and after administration of GLG-V-13, 3 and 6 mg/kg i.v., respectively.

Action Potentials↗
PubMed1995

[Comparative study of the efficacy and tolerability of 2 modalities of intravenous cibenzoline administration in the reduction of recent spontaneous atrial arrhythmia].

This multicentre, single blind, parallel group study compared the efficacy and clinical and electrocardiographic tolerance of a 2 minute intravenous administration of cibenzoline at a dose of 1.2 mg.kg-1 with that of a 10 minute 1.75 mg.kg-1 infusion in patients presenting with spontaneous atrial fibrillation (AF) for less than 6 weeks. Sixty-two patients (40 men and 22 women) with an average age of 62 years and presenting with sustained AF for at least 30 minutes with a ventricular rate greater than or equal to 80 bpm were randomly assigned to groups and received via the intravenous route either one of the two treatments. Efficacy (return to sinus rhythm) was assessed by an ECG recording every 5 minutes and at 45 and 60 minutes thereafter. Sixty-one of the 62 randomised patients were assessed for efficacy. Cibenzoline, administered in the form of a bolus or infusion, proved effective within one hour in 4 patients in each group (13%) and arrhythmia persisted with ventricular rate of less than 80 bpm in 10 (33%) and 5 (16%) of the patients respectively. In patients in whom sinus rhythm was not restored, ventricular rate was significantly reduced by cibenzoline. The patients in whom normal rhythm was restored under one of these treatment regimens were significantly younger. Patients in whom rhythm returned to normal following the administration of the bolus had AF of significantly more recent onset than that of the patients in whom abnormal rhythm persisted, whilst the history of the AF did not differ significantly between these two types of response after the infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Anti-Arrhythmia Agents↗
PubMed1995

[The esophageal approach in rhythmology].

The possibility of detecting the electrical activity of the heart from the oesophageus has been recognised for nearly a century. On the other hand, transesophageal pacing has only been really developped in the last fifteen years, which explains the recent interest for this technique in clinical practice. Easily put into practice, but not always well tolerated, the oesophageal approach has many uses in rhythmology. The principal diagnostic applications are in unlabelled tachycardias whether with narrow or wide QRS complexes, the evaluation of the Wolff-Parkinson-White syndrome, the study of sinus node function or nodal conduction. The therapeutic applications are dominated by the reduction of supraventricular tachycardias especially atrial flutter, with a success rate similar to that of endocavitary stimulation. The facility of realisation, especially at the patient's bedside, without need for fluoroscopie control, makes it a useful tool in emergencies, especially if the endocavitary approach cannot be used. The only reserve is the painful character of pacing in some patients.

Anti-Arrhythmia Agents↗
PubMed1995

[Infections on permanent endocavitary pacemaker leads: value of transesophageal echocardiography].

The prevalence of infection of permanent pacing material ranges from 0.13 to 19.9% of patients according to published series. The seriousness of this condition requires early diagnosis and treatment. Transesophageal echocardiography visualised vegetations on the intracardiac pacing lead in all of 11 patients studied, whereas transthoracic echocardiography and polynuclear leucocyte scintigraphy only provided positive diagnoses in 4 cases for each investigation. Three types of vegetation were visualised; no cases of tricuspid valve endocarditis were observed. Treatment was based on explantation of all implanted material by endovascular traction in 7 cases and by surgery in the other 4 cases according to the results of transesophageal echocardiography. There were no deaths or recurrence of infection. Transesophageal echocardiography is the investigation of choice for imaging a vegetation on an endocavitary pacing lead. Complete explanation is essential for a complete recovery of this infection.

Adult↗
PubMed1994

Facilitation of reentry by lidocaine in canine myocardial infarction.

The authors studied the effects of lidocaine in 18 consecutive dogs with myocardial infarction 1 to 4 days after two-stage left anterior descending coronary artery ligation. Electrophysiologic testing was performed in anesthetized dogs after infarction with single-, double-, or triple-programmed extrastimuli or rapid bursts (3 beats at 240 to 420 beats/min) delivered to the right ventricular outflow tract. Inducibility of sustained monomorphic ventricular tachycardia after an intravenous bolus of lidocaine (3 to 6 mg/kg) was compared in the same animal to the premedicated state. In the control state, sustained monomorphic ventricular tachycardia was inducible in 6 of 18 dogs. After administration of lidocaine, electrically induced sustained monomorphic ventricular tachycardia was initiated in an additional nine dogs (which were previously noninducible; after lidocaine administration vs control p < 0.02). The antiarrhythmic agent induced further rate-dependent slowing of conduction in the periinfarction subepicardium, which at a critical value of rate and amount of conduction delay resulted in sustained reentrant monomorphic tachycardia. These results show that lidocaine has marked proarrhythmic action in this canine model of myocardial infarction, probably because of its depressant effect on injured cardiac tissue.

Animals↗
PubMed1994

Surgery for aortic stenosis in elderly patients. A study of surgical risk and predictive factors.

BACKGROUND: Aortic stenosis is the most common valvular lesion occurring among elderly patients and has become extremely frequent because of changing demographics in industrialized countries. Surgical risk after the age of 70 has increased. The increasing older age of patients having surgery justifies an analysis of mortality predictive factors. METHODS AND RESULTS: Between 1976 and February 1993, we performed 2871 operations for aortic stenosis. This study concerns 675 patients (278 men and 397 women) who were > or = 75 years old. Mean age was 78.5 +/- 3 years. Associated lesions were found in 226 patients. A bioprosthesis was implanted in 632 patients (93.6%). Concomitant surgical procedures were performed in 133 patients. Surgical mortality was 12.4% (84 deaths). A longitudinal analysis has been carried out over four successive time periods to evaluate population evolution during these 17 years. Statistical analysis was performed on 46 variables. Multivariate analysis found age (P < .0001), left ventricular failure (P < .0001), lack of sinus rhythm (P < .01), and emergency status (P < .02) to be presurgical independent predictive factors of mortality. CONCLUSIONS: Risk-reducing strategy should both favor relatively early surgery to avoid cardiac failure and emergency situations and pay careful attention to the use of myocardial protection and cardiopulmonary bypass. Indications for surgery should remain broad since analysis failed to determine specific high-risk groups to be eliminated, and surgery remains the only treatment for aortic stenosis.

Age Factors↗
PubMed1994

Facilitation of reentry by lidocaine in canine myocardial infarction.

Despite continuing controversies regarding its antiarrhythmic and antifibrillatory efficacy lidocaine is frequently used for the treatment of ventricular arrhythmias occurring in the early phase of acute myocardial infarction (MI). The authors studied the effects of lidocaine in 18 consecutive MI dogs 1-4 days (2.8 +/- 0.3 day) after the two-stage left anterior descending coronary artery (LAD) ligation and in 11 dogs, in which the LAD and the distal branches of the left circumflex artery was ligated 12-75 (mean 35) days prior to study. Electrophysiologic testing was performed in anesthetized post-infarction dogs using single, double or triple programmed extrastimuli or rapid bursts (3 beats at 240-420/min) delivered to the right ventricular outflow tract. Inducibility of SMVT (uniform QRS morphology lasting > 30 sec at a rate of > 250 beat/min) after an i.v. bolus of lidocaine (3-6 mg/kg) was compared in the same animal to the pre-drug state. During the control state, SMVT was inducible in 6/18 dogs. After the administration of lidocaine, electrically induced SMVT was initiated in additionally 9 dogs (which were previously non-inducible; post-lidocaine vs control p < 0.02). Sustained reentry was induced by 3 mg/kg lidocaine in 5 dogs (310 +/- 62 beat/min) and by 6 mg/kg in 4 (261 +/- 52 beat/min). In the 8 survivors of the chronic MI group, SMVT was inducible before lidocaine administration in one, but in 7 after lidocaine. The antiarrhythmic agent induced further rate-dependent slowing of conduction in the peri-infarction subepicardium, which at a critical value of rate and amount of conduction delay resulted in sustained reentrant monomorphic tachycardia. These results show that lidocaine has arrhythmogenic/proarrhythmic actions in these canine models of MI probably due to its depressant effect on moderately sick cardiac tissue. The 'modification' of the functional properties of the arrhythmia substrate by lidocaine can promote the formation of new reentrant pathways leading to manifest sustained ventricular reentry under electrophysiologic study.

Acute Disease↗
PubMed1994

[Permanent atrial resynchronization by synchronous bi-atrial pacing in the preventive treatment of atrial flutter associated with high degree interatrial block].

UNLABELLED: Interatrial conduction block results in a very delayed and retrograde activation of the left atrium and is associated with a high incidence of atrial tachyarrhythmias, especially a particular (and specific) form of atypical atrial flutter. Electrophysiologic studies have suggested that these arrhythmias were usually due to reentry and could be directly related to the conduction disturbances in the atrium. If so, we can expect reasonably that permanent atrial resynchronization resulting from simultaneous pacing in different target sites in the atria, may not only correct for interatrial dysynchrony, but also may significantly contribute to prevent arrhythmia recurrences. Twenty-eight patients, mean age 68 years, were included. The mean P wave duration in spontaneous sinus rhythm was 181 +/- 28 ms. In all patients, many recurrences of atrial tachyarrhythmia were documented, especially a specific form of atypical atrial flutter. Medical therapy was constantly ineffective. Three different pacing modes were used: 6 patients, with normal A-V conduction were implanted with a SSI device, programmed in AAT mode and connected, using a Y bifurcated connector, to two atrial leads, one positioned in the right atrium, the second one into the coronary sinus-in 14 patients, with A-V conduction defects, a conventional DDDR unit was implanted and connected to a composite biatrial electrode and a ventricular lead. In that configuration atrial resynchronization was only effective on paced atrial cycles -a specific DDD Chorus ELA Medical device with a special algorithm loaded into the RAM memory was implanted in 14 patients (8 new indications, and 6 patients first implanted with a DDDR unit). RESULTS: during sinus rhythm atrial resynchronization induced a reduction of the P wave duration from 181 +/- 28 ms to 116 +/- 12 ms. During permanent pacing the mean value decreased from 209 +/- 38 ms to 108 +/- 13 ms. During follow-up (34 +/- 15 months) arrhythmia prevention was assessed by history, by monthly surface ECG's and by bimonthly 24 hours Holters recordings and telemetric interrogation of the pacemaker statistics. Twenty-one patients did not experienced any recurrence of arrhythmia. One to three recurrences occurred in the other seven patients, including six patients implanted with a conventional DDDR unit. These preliminary results seem validate the new concept of atrial resynchronization for prevention of atrial arrhythmia associated with interatrial conduction block.

Adult↗