Characterization of different subsets of atrial fibrillation in general practice in France: the ALFA study. The College of French Cardiologists.

BACKGROUND: The clinical presentation and causes of atrial fibrillation (AF) in the 1990s may differ from AF seen 2 to 3 decades ago. It was the objective of this prospective study to characterize various clinical presentations and underlying conditions of patients with AF observed in general practice in France. METHODS AND RESULTS: The study population comprised 756 patients (19 to 95 years of age) with electrocardiographically documented AF subdivided into paroxysmal (<7 days), chronic (last episode >1 month) and recent onset AF(persistent >7 days and<1 month). Symptoms were present in 670 patients (88.6%). The relative prevalences of paroxysmal, chronic, and recent onset AF were 22.1%, 51.4%, and 26.4%, respectively. Cardiac disorders, present in 534 patients (70.6%), included hypertension (39.4%), coronary artery disease (16.6%), and myocardial diseases (15.3%) as the most common. Rheumatic valvular disease represented a common cause in women (25. 0%) but not in men (8.0%). The paroxysmal group differed by a high percentage of palpitations (79.0%) and a low percentage of underlying heart disease (53.9%). With a mean follow-up of 8.6+/-3.7 months, 28 patients (3.7%) died, including 6 fatal cerebrovascular accidents. Among the 728 patients who survived, congestive heart failure occurred in 30 patients (4.1%), and embolic complications occurred in 13 patients (1.8%). In the paroxysmal AF group, 13 patients (8.0%) developed chronic AF and 51 (31.3%) had AF recurrences. At the time of follow-up, 53 patients (14.3%) from the chronic AF group and 108 patients (55.7%) from the recent onset AF group were in sinus rhythm. CONCLUSIONS: This large-scale study establishes the current demographic profile of out-of-hospital patients with AF and highlights some of the changes that have occurred in the past decades, including a particular shift in cardiac causes toward nonrheumatic AF. This study also demonstrates significant differences between various subsets of AF.

Signal-averaged electrocardiography and detection of heart transplant rejection: comparison of time and frequency domain analyses.

To evaluate the role of the signal-averaged electrocardiogram (ECG) in the detection of heart transplant rejection, findings on 277 ECGs were compared with those in 218 endomyocardial biopsy specimens in 25 patients followed up for a median duration of 5.2 months (range 7 days to 17.5 months). Signal-averaged ECGs obtained at intervals of 16.4 +/- 22.3 days were analyzed in the time domain before and after high pass filtering at 25 and 70 Hz. Frequency domain analysis was performed with use of a fast Fourier transform algorithm. Sixteen severe rejection episodes requiring treatment were observed. These episodes induced significant decreases in peak and root-mean-square voltages of both filtered and unfiltered QRS complexes, as well as in the total spectral area. Conversely, QRS duration and 50- to 250-Hz or 70- to 110-Hz spectral areas were not significantly altered. In 14 cases mild rejection episodes were observed that did not significantly alter any of the variables studied. The root-mean-square voltage of the 70-Hz high pass filtered QRS complex was found to be the most accurate variable in detecting rejection. Moreover, this variable was also the most reproducible in 10 healthy control subjects. The optimal rejection criterion was defined as an 11% decrease in voltage between two consecutive recordings. It provided 87.5% sensitivity with 78.4% specificity. In conclusion, the signal-averaged ECG is helpful in the management of heart transplant rejection. Frequency domain analysis of the QRS complex does not increase the accuracy of the technique compared with the time domain approach.

Comparative study of encainide and disopyramide in chronic ventricular arrhythmias: a double-blind placebo-controlled crossover study.

Ten patients suffering from chronic premature ventricular complexes (greater than 60/h) were treated orally in a double-blind crossover study with encainide (50 mg three times a day) and disopyramide (200 mg three times a day), with five 7 day study periods: survey, placebo, encainide or disopyramide, washout placebo and disopyramide or encainide. At the end of each 7 day period, a 12 lead electrocardiogram, a 48 hour ambulatory electrocardiogram and a treadmill exercise test were performed. Blood levels of encainide and its metabolites and of disopyramide were measured at the end of each treatment (steady state). Drug efficacy was assessed by: 1) more than 80% reduction in the number of premature ventricular complexes per 24 hours, and 2) absence of ventricular tachycardia. Encainide was effective in four patients (complete suppression of premature ventricular complexes) and ineffective in five. One patient who showed a 92% reduction in the number of premature ventricular complexes developed sustained ventricular tachycardia after 24 hours of treatment. Disopyramide was effective in three patients (greater than 80% reduction in the number of premature ventricular complexes) and ineffective in seven patients. With encainide, the percent increase in PR, QRS and QT interval duration was, respectively: 32.7 (p less than 0.001), 30.8 (p less than 0.001) and 10.6% (p less than 0.01). With disopyramide this increase was not significant. Despite the variability of drug blood levels, a relation between blood levels and suppression of premature ventricular complexes on the 48 hour ambulatory electrocardiogram was found with encainide, but not with disopyramide.(ABSTRACT TRUNCATED AT 250 WORDS)

Vasospastic angina without flow-limiting coronary lesions as a cause for aborted sudden death.

Two patients resuscitated from out-of-hospital cardiac arrest were later found to have minor coronary atherosclerosis and no inducible ventricular arrhythmia. Coronary spasm was not elicited during provocative tests but occurred on introduction of the catheter in the right coronary artery and spontaneously recurred after resuscitation, leading to myocardial infarction in one patient. Both patients received an implantable cardioverter defibrillator and subsequent discharges, while receiving calcium antagonists.

Single radiofrequency application to cure atrioventricular nodal reentry: arguments for the slow pathway origin of the high-low frequency slow potentials.

BACKGROUND: High-low frequency slow potentials are thought to be related to the slow AV pathway conduction. Their use was proposed to guide radiofrequency (RF) ablation of atrioventricular nodal reentrant tachycardia (AVNRT). The present study was designed to determine the prospective value of these high-low frequency slow potentials to guide AVNRT ablation using a single RF application. Single RF application could indeed reduce the size of the lesion created in the viciny of the specialized AV conduction system and shorten the radiation exposure and the overall duration of the procedure. RESULTS: Forty-one patients (14 men, 27 women, 45 +/- 16 years old) with AVNRT underwent slow pathway RF ablation guided by high-low frequency slow potentials. High-low frequency slow potentials were found in all patients along the tricuspid annulus and above the coronary sinus. Ablation was always performed in the posterior part of Koch's triangle. The mean A/V amplitude ratio of the successful site was 0.43 +/- 0.59. In 32 patients (78%) AVNRT was no longer inducible after a single RF application. Procedure and radiation times were 35 +/- 31 and 13 +/- 12 min respectively. Five patients required 2, 3 patients 3, and 1 patient 6 RF applications. The mean number of RF applications was 1.4 +/- 0.9 (median = 1). In the 32 patients who required only one RF application, 24 (75%) had an obvious dual AV nodal pathways with a jump before ablation, which completely disappeared in 18 of them (75%) after ablation. In the 6 remaining patients, who still had a jump after 1 RF application, there was no significant change in either conduction times or refractory periods concerning both the anterograde and retrograde AV conduction. No patient had PR interval purlongation. After a mean follow up of 11 +/- 5 months, recurrence was observed in a single patient who received 2 discontinued RF applications. CONCLUSION: Catheter-mediated ablation of AVNRT using high-low frequency slow potentials to localize the slow AV pathway is feasible and safe. Using this technique, a single RF application was successfull in 78% of patients, and slow pathway characteristics were completely eliminated in 75% of patients. The radiation time and the procedure duration were short. This suggest that, in patients with AVNRT, the choice of an appropriate RF target can reduce procedural duration.

Direct recording of sinus node potentials using electrode catheter techniques.

Direct recording of sinus node (SN) potentials using electrode catheter techniques is feasible and may be achieved in 50-86% of patients. It takes 15-30 min using commercially available catheters. However, obtaining stable recordings is often difficult, necessitating direct contact of the distal electrode with the endocardial area underlying the sinus node. There is a wide range in sinoatrial (SA) intervals (30-150 ms) obtained, and an overlap exists between patients with normal and abnormal SN function. Consequently, measurement of the SA interval alone may not be a reliable tool for diagnosing SN dysfunction. However, direct SN recordings have a theoretic value, allowing differentiation of disorders of SA conduction from disorders of the impulse generation.

Comparative cardiac effects of intravenous bolus of ipratropium bromide (itrop) and atropine sulfate in 22 patients.

At the present time, there is no satisfactory pharmacological treatment for arrhythmia or conduction disorders induced by or aggravated by vagal hypertonia. The limited duration of action of the atropine derivatives currently available justifies the development of new compounds with expected longer acting duration. The aim of this study was to compare the effects of a single blind intravenous injection of ipratropium bromide to those of atropine sulfate in 22 patients. These patients were studied with continuous Holter recordings for three days. During the second and the third nights (patient sleeping), boluses of atropine (0.03 mg/kg) and of ipratropium bromide (0.03 mg/kg), respectively, were added to a continuous saline intravenous infusion. Accurate ECG analysis allowed determination of maximal heart rate peak, timing of maximal heart rate, variations in sinus cycle length, atrioventricular conduction, and durations of drug action. A nonsuggestive questionnaire was presented to patients to detect possible occurrence of side effects. The mean maximal heart rate rose significantly (p less than 0.001) for atropine (+46.2%) and for ipratropium bromide (+57.4%). The effects obtained with ipratropium bromide on the heart rate lasted nearly twice as long as those obtained with atropine (respectively, 120 +/- 38.4 min and 70 +/- 30 min- for the pharmacological half-life). Common minor muscarinic side effects (dryness of the mouth) were noted with the two drugs. In conclusion, this comparative intraindividual study confirmed the prolonged vagolytic effects of intravenous ipratropium bromide, which may be valuable in the treatment of patients with vagally mediated automaticity and conduction disturbances.

Propafenone versus disopyramide: a double-blind randomized crossover trial in patients presenting chronic ventricular arrhythmias.

In vitro and in vivo electrophysiological studies have shown that propafenone could be classified as a class I antiarrhythmic agent. The aim of this study was to investigate the short-term antiarrhythmic efficacy and safety of propafenone in 10 patients compared to disopyramide in a double-blind randomized protocol. Included patients suffered from ventricular arrhythmias with at least 60 ventricular premature beats (VPB) per hour refractory to at least two other antiarrhythmic agents. At the end of the control period and of the two treatment periods during which patients received either propafenone (300 mg three times a day) or disopyramide (200 mg three times a day), clinical examination, Holter recordings, electrocardiogram, and clinical laboratory tests were performed. The PR interval and the QRS interval were significantly increased with propafenone, but not with disopyramide. The cQT interval was not significantly changed by either propafenone or disopyramide. Heart rate was decreased with propafenone (p less than 0.05) with no change in the diurnal/nocturnal circadian ratio variation. Heart rate was significantly decreased with disopyramide only during the day. Five of nine patients in the propafenone group and two of nine patients in the disopyramide group showed a reduction in ventricular premature beats greater than 80%. Total resolution of severe arrhythmias (repetitive events) was seen in 5 of 8 patients with propafenone; 2 of 8 with disopyramide. Adverse events, when they occurred, were mild (visual disturbances, epigastric discomfort, changes in taste perception, transient atrioventricular block with propafenone, and photophobia with disopyramide), and did not require reduction or discontinuation of study drug.(ABSTRACT TRUNCATED AT 250 WORDS)

[Thromboembolic complications of arrhythmia due to atrial fibrillation]. / Complications thrombo-emboliques de l'arythmie complète par fibrillation auriculaire.

Fifteen per cent of cerebrovascular accidents have a cardiac origin, two thirds of which are due to atrial fibrillation (AF). The Framingham study showed the risk of an ischaemic cerebral event to be increased by 5.6 in AF unrelated to rheumatic heart disease and by 17.5 when AF is associated with valvular heart disease. The risk of embolism is higher in elderly subjects and in those with underlying cardiac disease. Other high risk conditions include hypertension, diabetes, hyperthyroidism and cases with echocardiographic changes: left atrial dilatation, pre-thrombotic state or intra-atrial thrombus, atheroma of the ascending aorta. This stratification of risk should be taken into account when deciding on treatment. Conscious of the importance of the risk of embolism in AF, several authors have undertaken, over the last few years, randomised studies of the prevention of thromboembolic complications of AF: the AFASAK, BAATAF, SPAF and SPINAF trials. All showed the unquestionable efficacy of warfarin, even at low doses, at the price of a haemorrhagic risk of less than 2% per year for severe haemorrhages. A more recent study (SPAF II) confirmed the value of aspirin at the dosage of 325 mg/day which would seem to be a good alternative to anticoagulant therapy when this is contraindicated, although aspirin is less effective. The indications for anticoagulant therapy have become clearer since the publication of these results. Anticoagulant therapy is essential in permanent AF whether or not associated with rheumatic heart disease.(ABSTRACT TRUNCATED AT 250 WORDS)

[Atrio-ventricular block in rheumatoid polyarthritis. Histological study of the His-Tawara system. Apropos of 2 cases]. / Le bloc auriculo-ventriculaire de la polyarthrite rhumatoïde Etude histologiquie du systéme de His-Tawara. A propos de deux observations

A histological study of the conduction pathways was performed by serial sections in two patients who died with atrio-ventricular block in the course of rhumatoid arthritis. In the first case, the conduction disturbance was preceded by attacks of supra-ventricular paroxysmal tachycardia. The His-Tawara system was wholly infiltrated by a cast of lympho-plamocytes starting from rhumatoid nodules located at the base of both mitral and tricuspid valves and at the root of the aorta. The sinus node was the seat of a common fibrosis. In the second case, the atrio-ventricular block was secondary to amylosis which predominated in the central fibrous node and in the adjacent small coronary vessels. The His-Tawara system was completely destroyed down to its bifurcation. The sinus node was normal.

[Prolongation of the CAST study.Is it justified to consider another trial?]. / Les prolongements de l'étude CAST. Est-il licite d'envisager un autre essai?

A possible prolongation of the CAST would be another trial of the same type, (CAST II), designed for high risk patients (1 year mortality over 20%). The aim of this study would be to confirm the hypothesis that the ratio efficacy/undesirable side effects of antiarrhythmic drugs is beneficial in this type of patient. The most important selection criteria would be an ejection fraction of less than 40%, the presence of repetitive arrhythmias, especially ventricular tachycardia on Holter monitoring and the recording of late ventricular potentials on surface averaging ECG. The patients would be included at about the 20th day after myocardial infarction in order to exclude as much as possible unstable coronary artery disease and ventricular arrhythmias on successive Holter recordings because this would make interpretation of the efficacy of antiarrhythmic drugs impossible. The ideal number of patients would be about 5,000 but this is unrealistic because the trial would only include high risk cases and there would be difficulties in recruiting this number even in a multicenter trial. During follow-up of 2 to 3 years, the surveillance of the therapeutic efficacy of the antiarrhythmics would have to be better than in the CAST. The most delicate methodological problem would be the randomization of patients as the formation of a placebo group is unethical in high risk coronary patients with severe or malignant ventricular arrhythmias. The use of the only proved cardioprotector drugs, the betablockers, in all these high risk patients would be one solution, even if it might introduce a bias in the results.(ABSTRACT TRUNCATED AT 250 WORDS)

[Protein C deficiency and vascular thromboses. Apropos of 2 cases and a review of the literature]. / Déficit en protéine C et thromboses vasculaires. A propos de deux observations associées à une revue de la littérature.

Protein C, a physiological inhibitor of coagulation, acts by inactivating coagulation factors V and VIII. It was identified 20 years ago and purified 10 years later. Its anticoagulant properties have been confirmed by the demonstration of thromboembolic diseases associated with constitutional protein C deficiency. Deficiency is defined as a less than 65 p. 100 level of the protein. There is no correlation between protein C level and clinical severity. Constitutional protein C deficiency is transmitted as an autosomal dominant trait. The protein C level observed in homozygous deficiency is about 50 p. 100, more often quantitative (type I) than qualitative (type II), the other coagulation factors being present at normal levels. Protein C deficiency is responsible for recurrent and familial thromboembolic necrosis and for cutaneous necrosis during treatment with antivitamin K drugs. Protein C assays must now be part of the aetiological evaluation of thromboembolic disease. Physiological variations in protein C levels have been encountered in neonates and pregnant women as well as in some pathological conditions, after surgery or under certain treatments. Familial inquiries are essential to detect asymptomatic protein C deficient subjects. Treatment rests on anticoagulants: antivitamin K drugs after effective heparinization in thromboembolic accidents, prevention of accidents by heparin in protein C deficient subjects and when a risk of thromboembolic disease is present. We report here one case of venous thrombosis and one case of arterial thrombosis, both being characterized by the finding of protein C deficiency during full evaluation of haemostasis factors.

[Gallium-67 scintigraphic evaluation of primary dilated myocardiopathies in adults]. / Le bilan scintigraphique au gallium 67 des myocardiopathies primitives dilatées de l'adulte.

Myocardiopathy (MCP) is diagnosed by exclusion in patients with congestive heart failure in the absence of lesions of the coronary vessels or cardiac valves. Endo-myocardial biopsies and several cases of clinical improvement under immunosuppressive therapy suggest that it may be due due to an immune mechanism. Gallium-67 is taken up by the myocardium and may be regarded as a scintigraphic marker of myocardial inflammation. It may therefore be used to determine which patients would benefit from immunosuppressants. Our study involved 47 patients (mean age 40.1 +/- 10.2 years) with MCP evidenced by angiography and coronary arteriography. Isotopic ejection fraction (EF) and Ga-67 uptake by the myocardium were evaluated in all cases. A significant Ga-67 uptake was observed in 22 patients, 20 of whom could be divided into two groups: group I received an immunosuppressive treatment (azathioprine plus prednisone); group II did not receive such treatment. A new radionuclide cardiac examination was carried out 5 months after the beginning of treatment. No significant Ga-67 uptake could be detected in either group. Significant improvement of EF was observed in 6 patients of group I and in 2 patients of group II. Four patients had died: 1 in group I and 3 in group II. Thus, a decrease in Ga-67 uptake was noted in all patients 5 months after the initial examination, irrespective of the treatment received, which suggests that this decrease belongs to the natural history of the disease. The effect of immunosuppressive therapy on MCP, therefore, ought to be re-evaluated.

[Value of mapping in surgical treatment of ventricular tachycardia]. / Utilité de la cartographie dans la chirurgie des tachycardies ventriculaires.

Surgery may be proposed for patients with a localised aneurysm or akinesia for treatment of monomorphic ventricular tachycardia resistant to antiarrhythmic therapy after myocardial infarction. The multiplicity of tachycardia forms in the same patient, the variability of their mechanism which is not necessarily limited to the subendocardia layers, require mapping to guide the surgeon in the destruction of the anatomical substrates. In a series of 57 ventricular tachycardias recorded in 17 patients with myocardial infarction the authors demonstrated that a system of computerised mapping of the epicardial and endocardial regions optimised the results of this form of surgery. Mapping localised, sometimes at a distance from the scar, classical subendocardial reentry, implicated on occasion the mitral papillary muscle in the mechanism or a tachycardia in cases of inferior or lateral infarction and localised the reentry in the epicardium of the lower layers of the septum. The identification of these "atypical" mechanisms significantly improves the number of patients without inducible arrhythmias after surgery (from 50 to 87% in the authors' experience), without changing the operative mortality. The only really curative approach because of the limitations of catheter ablation, this surgery is a complementary method to implantable defibrillators in the management of post-infarction ventricular tachycardia.

[Automatic implantable defibrillators. Clinical experience apropos of 45 patients]. / Le défibrillateur automatique implantable. Expérience clinique á propos de 45 patients.

The aim of this study was to analyse the efficacy and survival after implantation of an automatic cardioverter-defibrillator.. Forty-five patients including 37 men were followed up for 0 to 51 months. The indications were ventricular fibrillation with no curable cause (n = 27) and sustained resistant or poorly tolerated ventricular tachycardia (n = 17) when programmed ventricular pacing with antiarrhythmic therapy was not applicable or gave poor results. One patient was implanted with this device for torsades de pointes. The underlying cardiac disease was ischaemic in 34 cases, non-ischaemic in 8 cases, and 3 patients had no apparent cardiac disease. Twenty patients were implanted with an epicardial system (group I) and 25 patients with endocardial system (group II). In group II, there was one complete failure of implantation requiring the use of an epicardial system and 2 partial failures requiring an additional epicardial patch electrode. The perioperative mortality was 2/45 (4.4%), both cases being due to permanent arrhythmias. In 5 patients, the minimal effective energy of defibrillation was over 25 Joules at implantation, without any untoward consequences on the clinical outcome. Ten non-fatal complications were observed including two major problems (haemopericardium); there were two cases of late increase of the minimal effective energy of defibrillation requiring the addition of a subcutaneous patch. Twenty-four patient (53%) received at least one appropriate therapy; 14 patients (36%) had at least one inappropriate shock during follow-up. During follow-up, 7 patients died, 6 of a cardiac cause and 3 of an arrhythmic problem.(ABSTRACT TRUNCATED AT 250 WORDS)

[Prognostic factors after sustained ventricular fibrillation or tachycardia. A multivariate study apropos of 160 cases]. / Facteurs pronostiques après fibrillation ou tachycardie ventriculaire soutenue. Etude multivariée à propos de 160 observations.

The authors analysed survival of 160 patients (121 men and 31 women; average age 57.2 +/- 12.5 years; follow-up 29 +/- 20 months) treated for malignant ventricular arrhythmias (sustained ventricular tachycardia, ventricular fibrillation, syncope with inducible ventricular tachycardia). The therapeutic evaluation was frequently invasive (145 patients underwent at least programmed ventricular stimulation, 108 patients underwent full endocavitary electrophysiological studies) and non-pharmacological therapy was widely used (defibrillator n = 44; antiarrhythmic surgery n = 28; ablative procedures n = 19; transplantation n = 7). The following underlying pathologies were observed: ischaemic heart disease n = 120; non-ischaemic left heart disease n = 19; right heart cardiac disease n = 4; and apparently normal hearts n = 17). The average ejection fraction was 40.5 +/- 15.5% and 29 patients were in the NYHA functional classes III or IV. Fifty-five patients had life-threatening arrhythmias whilst receiving amiodarone. At 2 years, the actuarial sudden death rate was 5.9 +/- 2.1% and the actuarial total cardiac mortality rate was 13.1 +/- 2.9%. Univariate analysis showed age, the presence of underlying cardiac disease, the presence of dilated cardiomyopathy, the absence of an invasive approach, the need for basal pacing in electrical cardioversion, the absence of betablocker therapy, a decreased left ventricular ejection fraction and a high NYHA functional class, to be predictive of sudden death. In multivariate analysis, age, the NYHA class for total cardiac mortality and the NYHA class for sudden death, were the only independent predictive factors. The authors conclude that in the era of invasive methods of evaluation and widespread use of non-pharmacological therapeutic methods, the symptomatology of cardiac failure assessed by the NYHA classification remains the most powerful independent prognostic factor after an episode of malignant ventricular arrhythmia.

[Coronary artery spasms]. / Le spasme des artères coronaires.

In a series of 2000 coronary arteriographies, spasm of the coronary artery was found in 52 cases, which were divided into three groups: 41 cases of "iatrogenic" spasm caused by stimulating the ostium of the coronary artery (usually the right) with the tip of the catheter; 8 cases of spasm on top of an organic fixed lesion; 4 cases of coronary spasm on a coronary artery which was reported as "radiologically normal". The study includes a review of the circumstances which favour or impede discovery of coronary spasm, as well as a provocation test using methyl ergometrine. This test seems to be specific in that it only produced coronary spasm in patients with Prinzmetal's syndrome, and excluded the cases of angina with normal coronary arteriography. The patients with spasm on top of a fixed organic lesion underwent a successful aorto-coronary bypass graft together with resection of the pre- and sub-aortic nerve plexus. Patients with a spasm in an artery which was "arteriographically normal" were treated medically by nitrate compounds and vaso-dilators. Three of these patients had an excellent result with medical treatment. Treatment failed in the fourth patient, who then obtained benefit from straight-forward resection of the pre- and sub-aortic nerve plexus with an excellent result which has been maintained for over six months.

[Electrical activity in the region of the sino-atrial node. Experimental study]. / L'activité électrique de la région du noeud sinusal. Etude expérimentale

After finding the landmarks of the sino-atrial node in the dog by means of serial sections, the authors have recorded the electrical activity in the region of the sinus by means of bipolar and monopolar electrodes placed in contact with it. a)A preatrial wave has been recorded, and its origin is discussed. b) Mechanical destruction of the sino-atrial node is followed by the disappearance of this wave and the appearance of a slow junctional rhythm with a retrograde atriogram. c) When lignocain is applied directly to the sino-atrial node, the pre-atrial potential decreases and then disappears and the post-stimulation pause is prolonged. d) Clamping of the peri-sinus region gives rise to an incomplete block, followed by complete block, of the pre-atrial potential and the P wave. The post-stimulation pause remains normal. The disorders of rhythm which have followed these producedures may be regarded as constituting experimental models for sinus lesions and for sino-atrial block.

[Acute hemodynamic effects of betaxolol in uncomplicated arterial hypertension in young persons]. / Effets hémodynamiques aigus du bétaxolol dans l'hypertension artérielle essentielle non compliquée du sujet jeune.

Acute hemodynamic changes induced by Betaxolol (B.) were studied in 10 patients (7 men, 3 women, mean age: 36 years), with uncomplicated essential hypertension. The brachial artery was cannulated with a short Teflon catheter and Swan-Ganz catheter was introduced into the pulmonary artery. Brachial (BAP) and Pulmonary arterial pressures (PAP), cardiac output (dye dilution) were recorded before (To) and after intravenous infusion of B. (0.2 mg/kg) during 5 minutes (T1), followed by the infusion of B. at a rate of 0.4 mg/kg during 15 minutes (T2). Cardiac index (C.I.), Stroke index (S.I.), Systemic Vascular (SVR) and Pulmonary Vascular Resistances (PVR), Left Ventricular Stroke Work Index (LVSWI) were calculated. C.I. declined significantly. This resulted from a significant decrease of heart rate, since S.I. was unsignificantly changed. BAP (systolic and mean) decreased significantly, since unsignificant changes of PAP were noted. SVR and PVR were significantly increased and LVSWI was significantly decreased. Plasmatic Renin Activity was unsignificantly decreased.

[Recording the electrogram of the sinus node. Effects of the injection of tetrodotoxin into the artery of the sinus]. / Enregistrement de l'électrogramme du noeud sinusal. Effets de l'injection de tétrodotoxine dans l'artère du sinus.

The cells of the SA node (SAN) are very resistant to the action of tetrodotoxine (TTX), a drug which. paradoxically, blocks depolarisation of the outer myocardial cells. Injection of TTX into the artery of the SAN brings about asystole; bur regular electrical activity, consisting of a slow wave of 200 to 300 ms duration, can still be picked up by an electrode placed on the SAN. This electrical activity, which can only be picked up over the SAN, and is resistant to TTX but blocked by acetylcholine, is interpretated as being the electrogram of the SAN. After the artery has been washed out by normal saline, the effect of TTX becomes progressively less; under these conditions, all degrees of sino-atrial block can be observed. Arising from a study of the phenomena of capture of the SA and AV nodes, of the effect of artrial stimulation, and of the time relationships between the various electrical events recorded, some hypotheses of the electrophysiology of the SAN and the sino-atrial conduction are put forward.