Intracellular pH regulation in ventral horn neurones cultured from embryonic rat spinal cord.

Intracellular pH was measured with the pH-sensitive fluorescent probe BCECF in spinal cord neurones cultured from rat embryos. At an external pH of 7.3, the average steady-state pHi was 7.18 +/- 0.03 (SEM, n = 97) and 7.02 +/- 0.01 (n = 221) in HEPES-buffered and in bicarbonate-buffered medium, respectively. In both external media, pHi was strongly dependent on external pH (pHe). In HEPES-buffered medium, pHi recovery following an acid load induced by transient application of ammonium required external Na+ and was inhibited by amiloride, indicating the presence of a Na+/H+ exchange. Na(+)- and HCO3(-)-dependent, DIDS-sensitive alkalinizing mechanisms also contributed to pHi regulation in CO2/bicarbonate-buffered medium. The presence of an electrogenic Na(+)-HCO3- cotransporter was confirmed by the alkalinizing effect of KCl application. The fact that pHi is lower in CO2/bicarbonate- than in HEPES-buffered medium and the alkalinization observed upon suppression of external Cl- suggest that the acidifying Cl-/HCO3- transporter plays an important role in defining pHi.

The anatomic basis of connections between the coronary sinus musculature and the left atrium in humans.

BACKGROUND: This study determined the histological features of the atrial myocardium connecting the coronary sinus and the left atrium in humans. METHODS AND RESULTS: Ten necropsied hearts were studied by performing serial longitudinal sections parallel to the long axis of the coronary sinus that extended its full length using a large microtome. In all specimens, the venous wall of the coronary sinus was surrounded by a cuff of striated muscle extending 40+/-8 mm from the ostium. Striated myocardial connections of varying number and morphology left this coronary muscle cuff and connected to the left atrium; they ranged from 1 to 2 fascicles to a widely intermingled continuum (thickness, 2.79+/-2 mm; width, 2.91+/-3.5 mm). These connections originated 8.8+/-5.7 mm from the coronary sinus ostium and inserted 18+/-11 mm distally into the left atrium. The insulating compartment in which the connections traversed between the left atrium and the coronary sinus was mostly formed of adipose tissue. The valve of Vieussens was found in 6 hearts at a mean distance of 3.4+/-3.2 mm from the distal extremity of the coronary sinus muscle cuff. CONCLUSIONS: In the human heart, a consistent but morphologically variable left atrial coronary sinus myocardial connection was found. This emphasizes the need for surgical dissection or catheter ablation in or around the coronary sinus to eliminate these connections.

Chronic inflammatory demyelinating polyneuropathy: immunopathological and ultrastructural study of peripheral nerve biopsy in 42 cases.

The authors recently reexamined the peripheral nerve biopsies from 42 patients with chronic inflammatory demyelinating polyneuropathy (CIDP). There were 27 males and 15 females, aged from 9 to 84 years, and 13 had relapses. No patient had vasculitis, monoclonal gammopathy, tumor, diabetes mellitus, Lyme disease, familial neuropathy, HIV, or any other immune deficiency. In the endoneurium, perivascular inflammatory cell infiltrates were present in only one case, but scattered histiocytes marked by KP1 on paraffin-embedded fragments were present in every case and there were no T-lymphocytes. At ultrastructural examination macrophage-associated demyelination was observed in 17 cases, of which 6 had relapses separated by intervals of several months or years. Axonal lesions without associated primary demyelination were observed in 4 cases and 3 of these had relapses. Thirty-two patients had mixed lesions of demyelination and axonal involvement. This study confirms other recent data indicating that in all cases of CIDP, macrophages are present in the endoneurium. Macrophage-associated demyelination is the characteristic feature of demyelinating forms. On the other hand, isolated primary axonal forms, which have been known since 1989, are relatively frequent and prone to relapses.

[Variability of heart rate after heart surgery under extracorporeal circulation: aortocoronary bypass or aortic valve replacement]. / Evolution de la variabilité de la fréquence cardiaque après chirurgie cardiaque sous circulation extra-corporelle: pontages aorto-coronariens ou remplacements valvulaires aortiques.

The study of heart rate variability allows analysis of modulations of heart rate by the sympathetic vagal system. The authors studied the course of sinus variability by 24-hour Holter monitoring preoperatively, and on the 6th and 42nd postoperative day, in 25 patients undergoing coronary bypass graft (group I) and 10 patients undergoing aortic valve replacement (group II). Surgery was performed under cardiopulmonary bypass with selective antegrade cold crystalloid cardioplegia. The preoperative ejection fraction of these patients was 62% with a mean age of 59.5 years in group I and 61.5 years in group II. All temporal or spectral parameters were significantly decreased in the two groups on the sixth day (p < 0.05). Parameters which remain altered on D42 compared to baseline values were temporal parameters: pNN50 and rMSSD for group I and ASDNN for group II, with a tendency to return to baseline values, but with a higher mean heart rate in group II on D6 and D42 (p < 0.05). In the spectral domain, TP (total power of the spectrum) and LF (Low frequencies) remained decreased in both groups. A reversible alteration of sinus variability parameters was therefore observed in the two groups of patients. Other studies are necessary to define the mechanisms of these alterations, which are most probably related to catecholaminergic flooding related to CPB or partial vagal denervation by ischaemic or surgical damage to nerve structures.

Optimizing the hemodynamic performance of the DDD pacemaker: impact of the atrioventricular delay on the pulmonary venous flow pattern.

UNLABELLED: This study evaluated the impact of the atrioventricular delay (AVD) on the pulmonary venous flow pattern (PVFP). METHODS: Transthoracic Doppler PVFP were obtained during atrial and ventricular pacing at a fixed rate of 70 beats/min in 20 patients equipped with a DDD pacemaker, diastolic dysfunction linked to an impaired relaxation, a mean ejection fraction of 49%, and AV block. Two subgroups were analyzed equally: group I: seven patients with a normal ejection fraction and group II: 13 patients with decreased ejection fraction. Three different AVDs were studied: short (50 ms), intermediate (150 ms), and long (250 ms). RESULTS: As the AVD increased, the diastolic filling time and the peak atrial reverse flow wave decreased (P < 0.001). There was a decreasing D wave and no significant change in the peak velocity of the S wave. The S wave became biphasic in all patients at the longest AVD of 250 ms. The systolic (S) velocity time integral (VTI) of the pulmonary wave and the systolic/total PVF-VTI ratio increased significantly (P < 0.001). A similar response was seen in both group of patients. CONCLUSIONS: These data correlated the AVD with PVFP, supplying critical systolic information completing the diastolic data obtained from mitral Doppler patterns. These systolic measurements were especially useful for patients with heart failure and a DDD pacemaker, in order to obtain the longest diastolic filling time at the lowest atrial pressure.

[Supraventricular arrhythmia after pneumonectomy. Apropos of 100 cases and review of the literature]. / Troubles du rythme supraventriculaire après pneumonectomie. A propos de 100 cas et d'une revue de la littérature.

Supraventricular arrhythmias are frequently observed in pneumonectomy surgery. We retrospectively studied a series of 100 consecutive patients undergoing pneumonectomy for cancer between 1994 and 1996. We found 24% of significant supraventricular arrhythmias, corresponding to atrial fibrillation in 75% of cases, occurring in 80% of cases until the third postoperative day. The only risk factor significantly associated with these arrhythmias was the patient's age. These arrhythmias are easily reduced, spontaneously in 25% of cases, and usually by amiodarone, alone or associated with digitalis alkaloids. While the mortality of the overall group was 12%, 8% of patients with arrythmia died. These deaths concerned patients whose arrythmias occurred after the fourth postoperative day in a context of a pulmonary infection.

Cultured rat sensory neurones express functional tachykinin receptor subtypes 1, 2 and 3.

The neuropeptide substance P (SP) is known to play a key role in peripheral nociceptive processes. We investigated the in vitro pharmacological characteristics of functional tachykinin receptors expressed in dorsal root ganglia (DRG) sensory neurones by analysing intracellular free calcium concentration changes induced after stimulation by SP or specific tachykinin agonists. We observed that about 37% of the tested neurones were responsive to either SP or an NK1-, NK2- or NK3-specific agonist. Tachykinin-responsive neurones had a small soma diameter (<20 microm) and were sensitive to capsaicin. These results suggest the presence of NK1, NK2 and NK3 receptors in noxious sensory neurones.

[Lesions caused by techniques of endocavitary ablation using high frequency currents: anatomo-pathological aspects]. / Les lésions provoquées par les techniques d'ablation endocavitaire utilisant les courants de haute fréquence; aspects anatomo-pathologiques.

Anatomopathological studies have considerably increased our understanding of the ablative technique by radiofrequency current. They have provided information on the nature, extent and time dependency of the lesions induced. Despite variable results according to whether the experiments were performed in vitro or in vivo, a correlation has been observed between the volumes of the lesions and the energies used. One factor is unquestionable: monitoring the temperature allows better control of the lesion size than monitoring current intensity. However, other technical points are essential for this control such as ensuring good contact between the catheter and the endocardium and the definition of the optimal surface area of the electrode. Now that the conditions of efficacy and security of ablation by high frequency currents are known, anatomopathological studies in man have become rare. These studies, which will take a long time to perform due to the very nature of the technique and pathologies treated, should provide interesting anatomo-electrical comparisons to increase our understanding of certain arrhythmias.

[Role of the conditions of recording and analysis of the atrial signal on the results of ECG signal averaged P wave]. / L'influence des conditions de recueil et d'analyse du signal auriculaire sur les résultats de la haute amplification de l'onde P de l'électrocardiogramme.

Several studies have shown that high amplification and averaging of the electrocardiographic P wave may soon enable better identification of people at high risk of paroxysmal atrial fibrillation. The results of this technique are closely dependent on the conditions of recording and analysis of the atrial signal but this factor has not been widely appreciated. The authors, therefore, undertook a study of the reliability of the manual method of measuring P wave duration, the influence of the filters used and the level of background noise on the 3 parameters of analysis: the duration of the P wave (DUR), the root mean square of the amplitude of the terminal 20 milliseconds (RMS20) and the integral under the P curve (IN). The recorder was a Predictor II 5.0 (Corazonix) with a special programme to identify and analyse the P wave in 3 bipolar non-orthogonal leads. DUR was determined manually after amplification and averaging; RMS20 and IN were calculated automatically. In order to assess the reliability of manual determination of the P wave, 48 consecutive patients were studied: two analyses were made with a least a 2 months' interval by entering the data through two filters (unidirectional and FIR). The role of the filters was then studied by passing the preceding 48 recordings to an analysis with three filters: unidirectional, bidirectional and FIR, and comparing the results.(ABSTRACT TRUNCATED AT 250 WORDS)

[Comparative thrombotic risk of two contrast agents in coronary angiography]. / Risque thrombotique comparatif de deux agents de contraste en coronarographie.

The thrombogenic risk of contrast agents in coronary angiography is still a topical issue, particularly in comparisons between ionic and nonionic contrast agents. As a complement to a preliminary study, the repercussions on sensitive markers of haemostasis were investigated in vivo in 38 patients undergoing a standard cardiac catheterisation. After randomization, an ionic low osmolality contrast agent (Ioxaglate 320) was used in 19 patients and a nonionic low osmolality contrast agent (Iopromide 370) was used in another 19 patients, according to an identical protocol. The following parameters were assayed in arterial blood samples obtained before and after the examination in each patient: platelet markers: beta-thromboglobulin (beta TG) and platelet factor IV (PF4); prethrombotic markers: thrombin-antithrombin 3 complex (TAT) and prothrombin fragments 1 and 2 (F1 + 2) as well as partial exploration of fibrinolysis: tissue plasminogen activator inhibitors (PAI). Comparison of the results demonstrated platelet activation and the presence of prethrombotic markers in both groups. No significant difference was detected between the two groups of patients. Consequently, there does not appear to be any difference in activation of coagulation between modern, low osmolality, ionic or nonionic contrast agents. This may suggest an equivalent thrombogenic risk.

[Triple aneurysm of the Valsalva sinus complicated by right coronary occlusion: apropos of a case and review of the literature]. / Triple anévrysme du sinus de Valsalva compliqué d'oblitération coronaire droite: à propos d'une observation et revue de la littérature.

We report a case of aneurysm of all three aortic sinuses. The patient suffered from both cardiac failure and angina pectoris. The diagnosis, suggested by echocardiography, was confirmed by magnetic resonance imaging (MRI) which showed marqued dilatation of all three aortic sinuses. At operation, we observed dilatation of all three aortic sinuses, measuring 2 to 6 cm and partially thrombosed. We performed a Bentall operation with reimplantation of the left coronary artery ostium. The right coronary ostium was thrombosed and was revascularized by a saphenous vein bypass. Despite prolonged circulatory assistance and an intra-aortic balloon counterpulsation, cardiopulmonary bypass could not be stopped and the patient died. This is a new case of multiple aneurysms of the aortic sinuses and also a case of aortic sinus aneurysm (ASA) complicated by coronary insufficiency. This last complication has a poor prognosis, as demonstrated by a review of the 28 cases described in the literature. MRI was found to be important for the diagnosis of the ASA, in combination with echocardiography and angiography which can underestimate the aneurysm because of the frequently associated mural thrombus.

[Antiarrhythmic treatment after reduction of atrial fibrillation by external shock]. / Traitement antiarythmique après réduction d'une fibrillation auriculaire par choc électrique externe.

Among the drugs recommended to prevent recurrences of atrial fibrillation after external electric shock, antiarrhythmic agents of classes Ia (quinidine, disopyramide), Ic (cibenzoline, flecainide, propafenone) and III (sotalol) seem to have the same effectiveness in maintaining the sinus rhythm in about 50 percent of the cases after 6 months and one year. Amiodarone, seldom used as first-line treatment, appears to be the most effective drug. The percentage of side-effects requiring discontinuation of treatment is the same for all drugs (about 10 percent). All these drugs have potential proarrhythmic effects. In case of recurrence electric shocks can be repeated in some special cases. The therapeutic strategy according to the clinical context (atrial fibrillation of vagal nerve or catecholergic origin, normal or altered left ventricular function) is discussed.

[Signal averaged electrocardiogram of the P wave after reduction of permanent atrial fibrillation. A comparison with results obtained in healthy subjects and in patients with atrial fibrillation]. / Electrocardiogramme moyenné de l'onde P après réduction d'une fibrillation auriculaire permanente. Comparaison avec les résultats obtenus chez des sujets sains ou victimes de fibrillation auriculaire paroxystique.

Signal averaging of the ECG P wave is a recent technique used for obtaining predictive and prognostic information in atrial arrhythmias. There have been few publications of its evaluation in this setting. The authors report their results of temporal analysis of the P wave of patients who had undergone electrical cardioversion of atrial fibrillation (group 3, n = 22 patients) and compared them with those of a control group without atrial arrhythmias (group 1, n = 25 patients). After recording signals in three bipolar leads (Predictor 5.0 II Corazonix recorder-analyser), the total duration of the P wave, the root mean square of the P wave amplitude (RMSt) and of the last 20 milliseconds (RMS 20) and the integral under the curve of the P waves (IN) were determined. The comparison was continued with data obtained from a population of patients with paroxysmal atrial fibrillation (group 2, n = 22). All patients had normal left atria on echocardiography, had no valvular heart disease, had no myocardial infarction or signs of cardiac failure. Results showed that the most discriminating parameter was the P wave duration (Group 3: 159.45 +/- 15.1 ms; group 1: 123 +/- 8.5 ms; group 2: 144.6 +/- 12.03 ms; group 1 versus group 2, p < 0.001, group 2 versus group 3, p < 0.01; group 1 versus group 3, p < 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

[Ventricular tachycardia of dilated cardiomyopathies]. / Les tachycardies ventriculaires des cardiomyopathies dilatées.

Patients with dilated cardiomyopathy often have unsustained VT (15 to 60% of cases) but sustained VT is much less common (0 to 10% of cases). The predictive value of sudden death of VT in Holter monitoring is not unanimously accepted. Therefore, it appears that, in patients with non-symptomatic VT, it is the degree of left ventricular dysfunction which is the best predictive factor of mortality because Holter monitoring, signal averaged ECG and programmed stimulation have a low positive predictive value although their cumulated negative predictive value seems to be very good. Programmed ventricular stimulation should be proposed to patients considered to be at high risk of sudden death, presenting with symptomatic unsustained VT or sustained VT. Approximately 3 out of 4 of these arrhythmias will be inducible and benefit from this method for orientating the choice of treatment. In these high risk subjects about 1 in 3 will be satisfactorily protected by antiarrhythmic drug therapy: non-inducible patients from the outset and those remaining inducible despite antiarrhythmic therapy remain at high risk of sudden death. This group of patients probably represents the best indication of implantable cardioverter defibrillators.

[Simultaneous prescription of digoxin and an anti-arrhythmia agent, is it dangerous?]. / La prescription simultanée de digoxine et d'un médicament antiarythmique est-elle dangereuse?

Many anti-arrhythmic drugs modify the pharmacokinetics of digoxin and increase serum levels. This possibility is considered for the majority of main anti-arrhythmics on the basis of a review of the literature. Quinidine, propafenone, flecainide, amiodarone and verapamil increase blood digoxin levels, sometimes to twice their baseline values. Suggested mechanisms involve above all a decrease in clearance of digoxin and changes in its volume of distribution. Reported accidents considered to be a direct consequence of these interactions are nevertheless rare in the literature, and the need for modifying dose and increased cardiological surveillance in the case of such a combination is essentially a question of precaution. Disopyramide, procainamide and mexiletine do not appear to have any reported effects on the pharmacokinetics of digoxin, their combined prescription never having had any effect on blood digoxin levels.

[Drug treatments of atrial fibrillation]. / Les traitements médicamenteux de la fibrillation auriculaire.

Atrial fibrillation is a daily cardiological problem which poses three types of questions, which, though old, are only partially mastered: anticoagulation, reduction and prevention of recurrence. It is a potent source of embolism. The risk is the greatest in patients with rheumatic valvular disease when the fibrillation is recent and when underlying cardiac disease is uncompensated. Long term anticoagulation is mandatory when the cause is rheumatic heart disease. In other pathologies, though anticoagulation has not been shown to reduce mortality, it significantly reduces the number of cerebrovascular accidents, including in the elderly and with low-dose vitamin K antagonist drugs. The efficacy of anticoagulation in preventing arterial embolism has not been established. Reduction of atrial fibrillation is not essential if the arrhythmia is well tolerated, chronic, especially in elderly patients and when several recurrences have occurred despite preventive therapy. In other cases, medical reduction is to be preferred to cardioversion if the fibrillation is recent and well tolerated. Of the oral and injectable preparations, amiodarone seems to be the drug with best benefit/risk ratio. Prevention of recurrence of fibrillation is unnecessary for many after a first episode, especially when idiopathic. In other cases, there are many available drugs but results are uncertain except in those observed in atrial fibrillation related to the autonomic nervous system. Strictly controlled and statistically exploitable studies show comparable efficacy of quinine and other Class I drugs. Beta-blockers are not very useful and the excellent long term results with amiodarone require confirmation.(ABSTRACT TRUNCATED AT 250 WORDS)

Interaction between permanent cardiac pacing and electrocautery: the significance of electrode position.

The danger in utilizing electrocautery during a surgical procedure on a pacemaker patient depends, to a great extent, on the position of the electrodes. We have studied this influence in an experimental model consisting of a plexiglass tank filled with a saline solution. Seven pacemakers were successively attached to an immersed and fixed frame and connected to a lead whose tip remains in the same location throughout the experiments. An ERBOTOM T 400 C generator (450 kHz) was used in an unmodulated unipolar mode at a maximum output (400 W). The high frequency current was delivered between a patch located successively at six preset positions in the tank and another electrode applied to 176 surface locations. For each position, we measured the currents in the lead with a separate measurement circuit connected in parallel on the same lead. Results were displayed on a map. Regardless of the patch position, currents were: (1) at a maximum when high frequency was delivered close to the pacemakers and around the tip of the lead; (2) negligible when applied to the path followed by the lead; and (3) a function of the distance between electrodes. These results may help to formulate recommendations to prevent accidents when using electrocautery in pacemaker patients.

[Effects of electrocautery on the threshold values of permanent pacing. An experimental study]. / Les effets du bistouri électrique sur les valeurs des seuils de stimulation permanente. Etude expérimentale.

One of the hazards of high frequency electrical interference (electrocautery) with cardiac pacing is thought to be related to an increase in the threshold values leading to loss of pacing. This hypothesis was examined in an experimental study performed on 5 dogs. A pacing catheter was introduced via the right jugular vein and positioned at the apex of the right ventricle and connected successively to several stimulators implanted in a latero-cervical subcutaneous pocket. A Bovie 400 CT generator was used to deliver a high frequency 1.75 MHz current between a probe applied near to the pacemaker pocket and an electrode placed under the right leg. One or two 5 second bursts were applied for each make of pacemaker, making a total of 3 to 6 applications per animal. A detecting circuit enabled the measurement of the currents in the catheter during the application. The thresholds of pacing were measured before and after each manipulation for several pacing impulse durations. At the maximal output of the generator, the highest recorded current was 117 mA (modulated) and 141 mA (unmodulated). The thresholds of stimulation did not change significantly and the pacing catheter impedance was also stable. This study suggests that high frequency current does not modify the threshold of stimulation in cardiac pacemaker patients. The loss of pacing sometimes observed after the use of electrocautery is probably related to pacemaker dysfunction.