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Biomedical subjects

T Lavergne

Publications and source records attributed to T Lavergne.

At least 73 records · Page 4Linked to original sources
PubMed1989

Transcatheter radiofrequency ablation of atrial tissue using a suction catheter.

Closed chest ablative technique that avoid barotrauma would be attractive for ablation at thin walled cardiac structures, such as the atrial free wall or coronary sinus. Transcatheter radiofrequency (RF) currents produce tissue necrosis the size of which is dependent on the contact between the tissue and the electrode. In order to assess the effects of transvenous RF ablation of atrial free wall using a suction electrode catheter, we delivered in ten dogs, one single unmodulated RF pulse 1.2 MHz, in a unipolar mode, through the distal electrode of a lumen catheter (USCI 8F) (USCI, Billerica, MA USA) located in the right appendage. During the pulse an 80 KPa vacuum depression was applied to the lumen of the catheter. Each pulse had a 10 seconds duration and the mean delivered power was 4.3 +/- 1.4 W. Aortic pressure and electrocardiogram were monitored during the procedure. A right atrial electrophysiological study was performed at the ablated site, at control, after suction application and after RF pulse delivery. The animals were sacrificed after 14 or 21 days. Atrial pacing threshold values decreased after suction application in comparison to control values after the pulse (0.42 +/- 0.06 vs 0.60 +/- 0.23 mA, P less than O.05) but increased after the pulse delivery (2.60 +/- 1.85 mA, P less than 0.01). In contrast, the atrial effective refractory period did not significantly change after suction, nor after RF pulse delivery. Aortic pressure remained unchanged throughout the procedure. Complex arrhythmias were not observed during or after RF pulse delivery. One dog died suddenly at the first day after ablation, but this death was most probably unrelated to RF ablation. Anatomic lesions had a length of 8.8 +/- 3.3 mm, a width of 4.6 +/- 2.5 mm and a depth of 3.6 +/- 1.1 mm. They were transmural in nine of the ten dogs but without atrial wall perforation in any case. Lesions suggesting tissue volatilization were present in four dogs. These results demonstrate that low energy RF currents delivered with a suction electrode catheter can produce transmural necrosis of free wall, without risk of perforation. Such ablative technique would be of interest for ablation of right sided accessory pathways or atrial ectopic foci. Further experimental data are required in order to define the optimal energy level required to avoid tissue volatilization.

Animals↗
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↗
PubMed1988

Change in human cardiac rhythm induced by a 2-T static magnetic field.

The influence of a 2-T static magnetic field on the cardiac rhythm was studied with 24-hour electrocardiographic monitoring in 12 healthy volunteers for 1 hour before exposure, 1 hour during exposure, and 22 hours after exposure. Four other subjects were exposed to 1 T, and nine control subjects were exposed to 0 T. In the 2-T group, the mean cardiac cycle length (CCL) was 912 msec +/- 83 before exposure. A significant 17% increase in CCL was observed after 10 minutes of exposure. No further significant variation was observed during exposure, and the CCL was back to preexposure values 10 minutes after exposure. No other arrhythmogenic effect was noted during the 24-hour monitoring. No statistically significant change was observed at either 0 or 1 T. The magnetically induced blood-flow potentials superimposed on the T wave were observed. The CCL increase during exposure could reflect a direct or indirect effect of magnetic fields on the sinus node, which is probably harmless in healthy subjects. However, its safety in dysrhythmic patients remains to be determined.

Adult↗
PubMed1988

[Recurrent myocardial abscess during Streptococcus B endocarditis].

The authors report a case of serious streptococcus B endocarditis with a myocardial abscess that recurred after surgery. Streptococcus B endocarditis is a rare disease which is characterized by a pronounced tropism of the organism for cardiac tissues, with severe cardiac valve mutilation and abscess formation in 40% of the cases. A myocardial abscess makes the prognosis worse and must be treated surgically during the acute phase of endocarditis. Modern imaging methods, notably trans-oesophageal two-dimensional echocardiography and computerized tomography should now be used to detect such abscesses.

Abscess↗
PubMed1988

[Effect of the sinusal rate on experimental vagal atrial arrhythmia].

Factors that facilitate the occurrence of cholinergic atrial arrhythmias were studied on 16 rabbit biatrial preparations in spontaneous rhythm. Sinus cycle length and characteristics of the atrial action potential were measured by the microelectrode technique in the basal state, then in the presence of acetylcholine at a concentration of 1.4 x 10(-5) M. Induction of arrhythmia was attempted by programmed stimulation, using an increasing number of extrastimuli. In the presence of acetylcholine the sinus cycle length increased by 106 +/- 63 p. 100 (p less than 0.0001) and the action potential duration, measured at 90 p. 100 repolarization (APD90) decreased from 60 +/- 15 ms to 40 +/- 11 ms (p less than 0.001). Reentrant activities, which had not been found in the basal state, were induced in 5 preparations. Under acetylcholine the sinus cycle of inducible preparations was shorter than that of non inducible preparations (663 +/- 272 ms vs 1218 +/- 531 ms, p less than 0.05). The percentage of sinus cycle lengthening was significantly smaller in inducible preparations (54 +/- 31 p. 100 vs 129 +/- 60 p. 100, p less than 0.05). Although sinus cycle lengthening was different in the two types of preparations, the APD90 was shortened in the same proportions. The vulnerability of the preparations seemed to depend mainly on a frequency effect. Vagal atrial arrhythmias occurred with a relatively small reduction in sinus rhythm. It is probable that an overpotent vagal effect is less arrhythmogenic because of its more homogeneous action on tissues.

Acetylcholine↗
PubMed1987

[Study of sinus function and nodal conduction using transesophageal recordings].

Transoesophageal pacing is mainly used for treatment of supraventricular tachycardias and assessment of refractory periods of accessory pathways. It has been proposed for the study of sinus node function and A-V nodal conduction. The aim of this study was to know if transoesophageal pacing could modify the vago-sympathetic tone, therefore the results of the tests, knowing it can be discomfortable and that endodigestive procedures can induce vagal responses. Furthermore, the stimulation is elicited near the left atrium, and not in the right atrium as during endocavitary tests. We have compared in 20 patients (age 68 +/- 12) the results obtained by both endocavitary and transoesophageal pacing (tension 21.2 +/- 4.5 V, duration 16 msec, interelectrode spacing 30 mm). We measured sino-atrial conduction time (SACT), sinus node recovery time (SNRT), Wenckebach's point and nodal refractory periods. After introduction of the oesophageal lead we observed a significant (p less than 0.01) but slight and transitory tachycardia. The results of A-V nodal conduction parameters were not significantly different and were significantly correlated (r = 0.94 for Wenckebach's point and effective refractory period). For the sinus node function, there was no significant difference between the parameters if the oesophago-atrial delay (mean 104.4 +/- 25.9 msec) is taken into account. The correlation is poor for sino-atrial conduction time (corrected SACT, r = 0.55), tighter for sinus node recovery time (maximal corrected SNRT, r = 0.92).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

[Electrophysiological, hemodynamic and histological effects of fulguration on the ventricular myocardium in the dog].

The myocardial repercussions of endocavitary fulguration depend upon the interaction of different physical phenomena. We studied the influence of energy level on the one hand and of the physical properties of the catheter (Ct) on the other hand on the cardiac effects of right endoventricular fulguration in the dog. A monopolar anodal shock was delivered in 12 dogs. Two levels of energy were applied: 25 J (group A, n = 6) and 100 J (group B, n = 6), and three Ct were used which differed in resistance (R) and active surface (S): Ct 1 (R = 0.3 omega, S = 12 mm2), Ct 2 (R = 0.3 omega, S = 2 mm2) and Ct 3 R = 2 omega, S = 13 mm2). Immediately after fulguration a significant rise of the right ventricular effective refractory periods was observed in group B only (193 +/- 28 vs 174 +/- 19 ms; p less than 0.03). Compared to baseline values, the systolic and diastolic pressures fell by 12% (p less than 0.01) and 18% (p less than 0.01) respectively in group A and by 33% (p less than 0.05) and 34% (p less than 0.002) respectively in group B. In contrast, there was no significant difference between variations of these parameters with the three types of Ct. The incidence of complex ventricular arrhythmia was higher in group B (5/6) than in group A (1/6).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Intracellular and extracellular recordings of sinus node activity: comparison with estimated sinoatrial conduction times during pacemaker shifts in rabbit heart.

Sinoatrial conduction times, estimated by premature atrial stimulation, were compared with direct measurement of the sinoatrial conduction time in 15 isolated rabbit sinus node preparations before and after intrasinusal pacemaker shifts induced by cooling. Transmembrane potentials and surface electrograms were recorded from the sinus node and crista terminalis. Extracellular sinus node activity was recorded in five preparations. Mapping was performed at 38 degrees C and 35 degrees C to determine the site of the dominant pacemaker. The sinus cycle was significantly longer at 35 degrees C (319.4 ms vs 258.1 ms). Intracellular measured conduction time was significantly shorter (63.8 ms vs 70.4 ms) because of caudal shift of the dominant pacemaker. Estimated sinoatrial conduction time was significantly longer (110.3 ms vs 85.4 ms) owing to the depression of automaticity by the extrastimulus. Extracellular measured conduction time did not differ significantly from intracellular measured conduction time. These results suggest that intrasinusal pacemaker shift may explain inaccuracies in indirect estimations of sinoatrial conduction time by atrial pacing techniques. Extracellular recordings appear to be a better method of evaluating sinoatrial conduction times.

Animals↗
PubMed1986

Inhomogeneity of cellular refractoriness in human atrium: factor of arrhythmia?

Spatial inhomogeneity of refractory periods, as measured during clinical electrophysiological studies, is a known predisposing factor of arrhythmia. We studied effective refractory periods (ERP) and action potential duration (ADP90) on isolated human atrium. Twelve samples of right atrium obtained during cardiac surgery from patients with (n = 6) and without (n = 6) atrial fibrillation (AF) were studied by microelectrode technique. For each preparation, ERP were measured at basic cycle lengths (BCL) of 1,600, 1,200, 800, and 400 msec in five different cells located around (0.8 mm) the stimulating electrode. Dispersion of ERP was significantly greater in the AF group (96.7 +/- 9 versus 70.9 +/- 9 msec, p = 0.01). In the non-AF group, we observed a positive linear correlation between ERP and BCL (r = 0.86) ADP90 and BCL (r = 0.93). On the contrary, in the AF group this correlation was absent between ERP and BCL (r = 0.28), poor between ADP90 and BCL (r = 0.62). These results suggest that nonhomogeneous recovery of excitability (dispersion and poor adaptation) may be an important factor of arrhythmia. This inhomogeneity is present at the cellular level as well as in the entire heart.

Action Potentials↗
PubMed1986

Effects of physical parameters of fulguration on electrophysiological and anatomical properties of canine myocardium.

In order to determine the respective roles of catheter (Ct) physical properties and of energy levels in myocardial effects of fulguration, we delivered an electrical shock between the tip electrode of a Ct placed at the apex of the right ventricle and a large cutaneous cathodal electrode in 12 dogs. Two energy levels were used: Group A = 25 J (n = 6) and group B = 100 J (n = 6), and three Cts were studied. These Cts had different resistances (R) and active surface electrodes (S): Ct 1 (R = 0.3 omega, S = 12 mm2), Ct 2 (R = 0.3 omega, S = 2 mm2), Ct 3 (R = 2 omega, S = 13 mm2). Complex ventricular arrhythmias were observed in 5/6 cases at 100 J but only in 1/6 cases at 25 J and were independent of the Ct type. Following the shock, the effective ventricular refractory period (S1 S1 = 300 msec) increased significantly only at 100 J (11%, p = 0.03). Anatomical lesions were wider (10.6 vs. 5.2 mm, p less than 0.05) and deeper (100 vs. 55%, p less than 0.05) in the 100 J group. In contrast, there was no significant difference in the electrophysiological and anatomical changes between the three Cts. In conclusion, arrhythmogenic adverse effects of ventricular Ct fulguration are related to the delivered energy; on the contrary, they seem only slightly dependent on Ct physical properties at these energy levels; a 2 J/kg shock is not only effective but also seems to be safe.

Animals↗
PubMed1986

[Experimental induction of sino-auricular blocks on isolated atria. Microelectrode study of the effects of bepridil].

The effects of bepridil on sinoatrial conduction were studied by perfusing 15 isolate rabbit right atrial preparations. In a preliminary series an increase in cycle length was observed with a dose-dependent effect with concentrations of between 5 X 10(-7) M and 1 X 10(-5) M. At the latter dose, sinoatrial block was observed. Bepridil was therefore used in a series of 10 preparations to induce sinoatrial block (SAB). After 10 minutes perfusion the cycle length increased significantly (14.3%, p less than 0.02). In 4 preparations SAB occurred 18.7 +/- 2.5 minutes after the onset of the perfusion. Sinoatrial block did not occur in 6 cases and in 4 cases an intrasinus shift of the dominant pacemaker was observed. The types of SAB observed were varied and their mechanisms were complex. Different types of SAB occurred in the same preparation. The different types of block recorded were: Blumberger type I SAB, anterograde 2/1 SAB, intrasinus 2/1 block, retrograde 2/1 and advanced block, complete atrio-sinusal dissociation.

Action Potentials↗
PubMed1982

[Lactic acidosis revealing hepatic carcinoma (author's transl)].

The authors report a case of fatal lactic acidosis which occurred in a 77-year old patient with chronic lymphocytic leukemia. Lactic acidosis revealed a hepatic carcinoma. Pathogenesis and therapy are discussed with reference to previously published data.

Acidosis↗
PubMedDate not supplied

Contribution of the high amplitude electrocardiography to the detection of ventricular late potentials in several cardiovascular diseases.

The criteria for detection of ventricular late potentials (VLP) by high amplitude electrocardiography (ECG) in the frequency domain were evaluated in 75 patients with cardiovascular diseases, mostly men (85%), with a mean age of 57 years, distributed by disease type into three subgroups: (1) with a history of myocardial infarction (MI)--53 cases; (2) with syncopes, episodes of prolonged ventricular arrhythmias--18 cases; (3) with unobstructive, primary cardiomyopathies--4 cases. Complete clinical examination, standard ECG, continuous 24 hr Holter ECG, high amplitude ECG (Corazonix system) for detection of VLP by analyses in the time domain (TD) and in the frequency one (FD) were performed in all the cases. The VLP incidence was evidently high in all the cases. By association of the analyses in TD and FD, the accuracy of VLP detection increased by 17.3% in the whole group (from 64% to 81.3%). The incidence of severe ventricular arrhythmias (class 4-5 Lown, i.e., doubled and/or trebled ventricular extrasystoles, salvos of unsustained ventricular tachycardia) was evidently higher in the patients with VLP (88% compared with 77% in the absence of VLP), thus demonstrating the presence, in most of the patients studied, of an arrhythmogenic mechanism by ventricular reentry.

Adolescent↗