Impact of transesophageal electrophysiologic study to elucidate the mechanism of arrhythmia on children with supraventricular tachycardia and no preexcitation.

An electrophysiologic study (EPS) of children and teenagers with paroxysmal supraventricular tachycardia (SVT) and normal electrocardiography (ECG) in sinus rhythm was evaluated. Generally, EPS is performed only before paroxysmal SVT ablation in these patients. In this study, 140 patients (mean age, 15 ± 3 years) with normal ECG in sinus rhythm were studied for SVT by a transesophageal route in baseline state and after isoproterenol. Idiopathic left or right ventricular tachycardia was diagnosed in four patients (3 %). Anterograde conduction over an atrioventricular (AV) left lateral (n = 10) or septal (n = 9) accessory pathway (AP) was noted in 19 patients (13.5 %) at atrial pacing. Orthodromic AV reentrant tachycardia (AVRT) was induced in these children. Five of the patients had a high rate conducted over AP (>240 bpm in baseline state or >290 bpm after isoproterenol). Two of the patients (a 10-year-old girl with well-tolerated SVT and a 17-year-old with syncope-related SVT) had the criteria for a malignant form with the induction of atrial fibrillation conducted over AP at a rate exceeding 290 bpm in baseline state. Of the 140 patients, 74 (53 %) had typical AV node reentrant tachycardia (AVNRT), nine had atypical AVNRT (6 %), 1 had atrial tachycardia (0.7 %), and 33 (23.5 %) had AVRT related to a concealed AP with only retrograde conduction. Electrophysiologic study is recommended for children with paroxysmal SVT and normal ECG in sinus rhythm. The data are helpful for guiding the treatment. Ventricular tachycardia or atrial tachycardia can be misdiagnosed. Masked preexcitation syndrome with anterograde conduction through AP was present in 13.5 % of the patients, and 1.4 % had a malignant preexcitation syndrome.

Design and evaluation of an abbreviated pixelwise dynamic contrast enhancement analysis protocol for early extracellular volume fraction estimation.

INTRODUCTION: T1-based method is considered as the gold standard for extracellular volume fraction (ECV) mapping. This technique requires at least a 10 min delay after injection to acquire the post injection T1 map. Quantitative analysis of Dynamic Contrast Enhancement (DCE) images could lead to an earlier estimation of an ECV like parameter (2 min). The purpose of this study was to design a quantitative pixel-wise DCE analysis workflow to assess the feasibility of an early estimation of ECV. METHODS: Fourteen patients with mitral valve prolapse were included in this study. The MR protocol, performed on a 3 T MR scanner, included MOLLI sequences for T1 maps acquisition and a standard SR-turboFlash sequence for dynamic acquisition. DCE data were acquired for at least 120 s. We implemented a full DCE analysis pipeline with a pre-processing step using an innovative motion correction algorithm (RC-REG algorithm) and a post-processing step using the extended Tofts Model (ECVETM). Estimated ECVETM maps were compared to standard T1-based ECV maps (ECVT1) with both a Pearson correlation analysis and a group-wise analysis. RESULTS: Image and map quality assessment showed systematic improvements using the proposed workflow. Strong correlation was found between ECVETM, and ECVT1 values (r-square = 0.87). CONCLUSION: A DCE analysis workflow based on RC-REG algorithm and ETM analysis can provide good quality parametric maps. Therefore, it is possible to extract ECV values from a 2 min-long DCE acquisition that are strongly correlated with ECV values from the T1 based method.

Long QT syndrome in a patient with allergic rhinoconjunctivitis and auto-immune diabetes: focus on the choice of anti-H1 drugs.

The long QT syndrome is a rare disease. The prevalence is estimated at 1/5 000 to 1/20,000. Numerous drugs are contra-indicated because they can lengthen the QT interval. A case of pollen allergy in an adolescent with LQTS is described. The possibility to prescribe anti-H1 drugs is reviewed since cases of torsades de pointe and even deaths have been reported for terfenadine and astemizole. Diphenhydramine, orphenadrine and hydroxyzine are contra-indicated. No accidents and no effects on the QT interval have been published for ebastine, fexofenadine, desloratadine and levocetirizine. These anti-H1 drugs could be used with great care, without any association with drugs resulting in low serum potassium level. Azelastine eye drops have been authorized and a routine protection by inhaled corticosteroids during the pollinic period has been advised in this adolescent treated by betablockers.

[Prevalence of sudden cardiac death during sports activities]. / Prévalence de la mort subite au cours du sport.

Sudden death during sport is a rare and unexpected event. It essentially affects young males, and a cardiomyopathy that had not been diagnosed during medical examinations is present in the majority of cases. In young subjects, there is generally hypertrophic cardiomyopathy or arhythmogenic right ventricular dysplasia. This is revealed during sporting activity, and sudden death is often the first symptom of the disease. Competitive sport increases the relative risk of sudden death to 2.5 compared to the risk in a non-sporting subject. The prevalence of sudden death during competitive sport is poorly understood. From the rare studies available, it could be estimated at 2.3/100,000 athletes per year. In Europe, it essentially occurs during football matches. However, the prevalence of sudden death during so-called 'recreational' sports is not precisely known. It could be much higher because these activities involve a larger number of people, and take place without supervision and usually without a medical examination beforehand. The participants are older, and coronary pathology is usually implicated.

Factors determining the occurrence of late potentials on the signal-averaged electrocardiogram after a first myocardial infarction: a multivariate analysis.

To determine the natural history of late potentials on the signal-averaged electrocardiogram (ECG), multivariate analysis was performed in 167 patients (138 men, 29 women) with a first anterior or inferior acute myocardial infarction. Seventy-four patients received thrombolytic therapy; the remaining 93 patients were treated conventionally. All patients underwent coronary angiography, left ventricular ejection fraction determination and signal-averaged ECG recording. Eight variables thought to be correlated with the presence of late potentials were studied; that is, age, infarct location, number of diseased coronary vessels, left ventricular ejection fraction, infarct-related coronary artery patency, treatment received, delay between admission and signal-averaged recording and delay between admission and coronary angiography. Statistical analysis showed that two independent factors (coronary artery occlusion and impaired left ventricular ejection fraction) were highly correlated with the incidence of late potentials. The occurrence of late potentials was multiplied by 5 in case of an occluded infarct-related vessel and by 1.75 each time the left ventricular ejection fraction value decreased by 0.10. This study suggests that coronary artery patency is the most important factor that decrease the rate of late potentials after a first acute myocardial infarction and it occurs independently of infarct location and left ventricular function.

Clinical characteristics and electrophysiologic properties of atrioventricular accessory pathways: importance of the accessory pathway location.

OBJECTIVES: This study was designed to assess the influence of accessory atrioventricular (AV) pathway location on the clinical and electrophysiologic characteristics of 384 consecutive symptomatic patients having a single accessory pathway. METHODS: Four locations were studied: left free wall (n = 270), posteroseptal (n = 52), anteroseptal (n = 29) and right free wall (n = 33). Ten clinical variables and 12 electrophysiologic variables were analyzed, including the effective refractory period of the accessory pathway and the different clinically occurring and inducible arrhythmias. RESULTS: Only two clinical findings were associated with accessory pathway location: 1) later age at onset of symptoms in the left free wall versus other accessory pathway locations (24 +/- 12 vs. 20 +/- 11 years, p = 0.02), and 2) later age at the time of electrophysiologic study in the left free wall accessory pathway location (36 +/- 13 vs. 32 +/- 11 years, p = 0.01). Six electrophysiologic variables showed a correlation with the accessory pathway location: 1) retrograde conduction only was found less frequently in right free wall (9%) and anteroseptal (10%) than in left free wall (26%) and posteroseptal (29%) accessory pathway locations (p = 0.05); 2) the retrograde effective refractory period of the accessory pathway was shorter in anteroseptal (253 +/- 52 ms) and left free wall (270 +/- 72 ms) as compared with right free wall (296 +/- 101 ms) and posteroseptal (301 +/- 76 ms) locations (p = 0.05); 3) retrograde decremental conduction over the accessory pathway was present in the posteroseptal (17%) and left free wall (3%) but absent in the other locations (p less than 0.001); 4) anterograde decremental conduction was only seen in the right free wall location (12%) (p less than 0.001); 5) orthodromic reentrant tachycardia was induced less frequently in the right free wall than in other locations (70% vs. 93%, p less than 0.001); and 6) inducibility of atrial fibrillation was greater in anteroseptal (62%) than in right free wall (21%), left free wall (44%) and posteroseptal (36%) locations (p = 0.01). CONCLUSIONS: The location of the accessory AV pathway is associated with specific electrophysiologic characteristics.

Influence of cigarette smoking on rate of reopening of the infarct-related coronary artery after myocardial infarction: a multivariate analysis.

OBJECTIVES: This study sought to determine whether the reopening of the infarct-related vessel is related to clinical characteristics or cardiovascular risk factors, or both. BACKGROUND: In acute myocardial infarction, thrombolytic therapy reduces mortality by restoring the patency of the infarct-related vessel. However, despite the use of thrombolytic agents, the infarct-related vessel remains occluded in up to 40% of patients. METHODS: We studied 295 consecutive patients with an acute myocardial infarction who underwent coronary angiography within 15 days (mean [+/- SD] 6.7 +/- 3.2 days) of the onset of symptoms. Infarct-related artery patency was defined by Thrombolysis in Myocardial Infarction trial flow grade > or = 2. Four cardiovascular risk factors--smoking, hypertension, hypercholesterolemia and diabetes mellitus--and eight different variables-age, gender, in-hospital death, history of previous myocardial infarction, location of current myocardial infarction, use of thrombolytic agents, time interval between onset of symptoms, thrombolytic therapy and coronary angiography--were recorded in all patients. RESULTS: Thrombolysis in current smokers and anterior infard location on admission were the three independent factors highly correlated with the patency of the infarct-related vessel (odds ratios 3.2, 3.0 and 1.9, respectively). In smokers, thrombolytic therapy was associated with a higher reopening rate of the infard vessel, from 35% to 77% (p < 0.001). Nonsmokers did not benefit from thrombolytic therapy, regardless of infarct location. CONCLUSIONS: These observational data, if replicated, suggest that in patients with acute myocardial infarction, thrombolytic therapy may be most effective in current smokers, whereas nonsmokers and ex-smokers may require other management strategies, such as emergency percutaneous transluminal coronary angioplasty.

[Prevalence of Brugada syndrome among 35,309 inhabitants of Lorraine screened at a preventive medicine centre]. / Prevalence du syndrome de Brugada dans une population de médecine préventive en Lorraine a propos de 35,309 cas.

UNLABELLED: Brugada syndrome is a recently identified cause of sudden death. Its primary prevention remains controversial, and epidemiology poorly defined. PATIENT POPULATION AND METHODS: Electrocardiograms (ECG) of 35,309 individuals (mean age = 37.2 years, 47% men) recorded over a 1-year period were reviewed and classified as (1) typical, (2) suspicious, and (3) negative. Subjects whose ECG was suspicious were offered a provocative test with flecainide, 2 mg/kg, i.v., and individuals whose ECG was typical were advised to undergo programmed ventricular stimulation (PVS). RESULTS: In 14 men and 6 women between the ages of 24 and 77 years (mean =47.5), ECGs were typical (n=6) or suspicious (n=14). Among 6 subjects with typical ECGs, 3 underwent PVS, which was positive in 1, who received an implantable cardioverter defibrillator (ICD). Among 14 subjects whose ECGs were suspicious, 5 declined further investigations and 5 developed typical ECG characteristics of Brugada syndrome after flecainide administration. PVS was negative in 4 subjects who consented to the procedure. Overall, among 35,309 individuals screened, 11 had ECG findings consistent with Brugada syndrome and, over a follow-up of 30 months, all had remained free of adverse cardiac event. CONCLUSIONS: we estimated a prevalence of Brugada syndrome of 0.3% in Lorraine. A single patient received an ICD for inducible ventricular tachyarrhythmia during PVS, representing a potential 30 per million asymptomatic adult rate of ICD implantation for this indication.

The 12-lead electrocardiogram in midseptal, anteroseptal, posteroseptal and right free wall accessory pathways.

The 12-lead electrocardiograms of 50 patients with 1 anterogradely conducting accessory pathway were analyzed to obtain characteristics of electrocardiographic findings in the midseptal, anteroseptal, true posteroseptal and right free wall accessory pathway locations. Locations were confirmed by surgery (33 patients) or radiofrequency catheter ablation (17 patients). This study analyzed (1) QRS in the frontal plane, (2) delta wave axis in the frontal plane, (3) the angle between QRS and delta wave axes, (4) the R/S ratio in lead III, (5) negativity of delta wave in inferior leads, and (6) the R/S ratio in precordial leads.(ABSTRACT TRUNCATED AT 250 WORDS)

Improvement in left ventricular function by ablation of atrioventricular nodal conduction in selected patients with lone atrial fibrillation.

Left ventricular (LV) function was studied in 30 patients with lone atrial fibrillation (AF) (paroxysmal [n = 27] and persistent [n = 3]) before and after ablation of atrioventricular conduction. In all patients, drug treatment did not control ventricular rate during AF or prevent recurrences of the arrhythmia, or both. LV ejection fraction, and LV end-systolic and end-diastolic, and left atrial dimensions were measured by echocardiography before (mean 7 +/- 10 months, range < 1 to 37) and after (14 +/- 20 months, < 1 to 77) ablation. Before ablation, LV ejection fraction was < or = 50% in 12 patients (group I) and > 50% in 18 (group II). After ablation, LV ejection fraction increased significantly in group I from 43 +/- 8% to 54 +/- 7% (p < 0.0001). There were also significant decreases in LV-end systolic and end-diastolic, and left atrial dimensions. No changes in these parameters were observed in group II. Groups I and II had a significant difference in the duration of AF (group I: mean 11 years, range 8 to 28; and group II: 5 years, 2 to 14) (p < 0.05). No difference was present in age, sex, New York Heart Association functional class for dyspnea, or type of ablation procedure. Thus, some patients with lone AF may show deterioration of LV function, which appears to be related to the duration of the arrhythmia; in these cases, LV function may improve significantly after ventricular rate control is accomplished by ablation of atrioventricular conduction.

Value of the 12-lead electrocardiogram in arrhythmogenic right ventricular dysplasia, and absence of correlation with echocardiographic findings.

The 12-lead electrocardiogram during sinus rhythm was studied in 20 patients with arrhythmogenic right ventricular (RV) dysplasia with symptomatic ventricular tachycardia. Findings were analyzed, together with echocardiographic evaluation of site, extent and progression of RV wall abnormalities. Electrocardiographic abnormalities were found in 90% of patients. No correlation was found between abnormalities on the initial 12-lead electrocardiogram, and the echocardiographic extent and location of RV involvement. Over time, echocardiographic progression of the disease was observed; RV size increased in 6 of 7 patients from 34 +/- 3 to 39 +/- 3 mm (p = 0.01), and there was progression in the extent of RV wall motion abnormalities in 4 of 7 patients. Analysis of serial electrocardiographic recordings did not reveal changes indicative of progression of the disease during follow-up of 71 +/- 48 months. It is concluded that electrocardiographic abnormalities suggesting arrhythmogenic RV dysplasia are present in 90% of symptomatic patients on the first electrocardiogram recorded during sinus rhythm. However, serial electrocardiographic recordings in these patients do not provide information regarding anatomic progression of the disease.

Prognostic value of thrombolysis, coronary artery patency, signal-averaged electrocardiography, left ventricular ejection fraction, and Holter electrocardiographic monitoring for life-threatening ventricular arrhythmias after a first acute myocardial infarction.

Prognostic studies after acute myocardial infarction (AMI) have mainly been performed in the prethrombolytic era. Despite the fact that modern management of AMI has reduced mortality rates, the occurrence of malignant ventricular arrhythmias in the late phase of AMI remains an important issue. We prospectively studied 244 consecutive patients (97 treated with thrombolytics) who survived a first AMI. All patients underwent time domain signal-averaged electrocardiography (vector magnitude: measurements of total QRS duration, terminal low [<40 microV] amplitude signal duration, and root-mean-square voltage of the last 40 ms of the QRS complex), Holter electrocardiographic monitoring, and cardiac catheterization. Late life-threatening ventricular arrhythmias were recorded. Eighteen arrhythmic events occurred during a mean follow-up period of 57 +/- 18 months. Three independent factors were associated with a higher risk of arrhythmic events: (1) left ventricular ejection fraction (odds ratio 1.9/0.10 decrease), (2) terminal low-amplitude signal duration (odds ratio 1.5/5 ms increase), and (3) absence of thrombolytic therapy (odds ratio 3.9). Low-amplitude signal duration sensitivity for sudden cardiac death was low (30%). Left ventricular ejection fraction had the highest positive predictive value for sudden cardiac death (10%). Thus, thrombolysis decreases both the incidence of ventricular tachycardia and sudden cardiac death with a higher reopening rate of the infarct-related vessel. Signal averaging predicts the occurrence of ventricular tachycardia and an impaired left ventricular ejection fraction predicts the occurrence of sudden cardiac death.

Effects on the signal-averaged electrocardiogram of opening the coronary artery by thrombolytic therapy or percutaneous transluminal coronary angioplasty during acute myocardial infarction.

One hundred twenty-nine patients were retrospectively analyzed and divided into 3 groups according to (1) the presence of a patent artery obtained either spontaneously or after thrombolytic therapy but without percutaneous transluminal coronary angioplasty (PTCA) (group I, n = 83), (2) the presence of a patent artery after opening by PTCA (group II, n = 29), or (3) absence of reperfusion despite thrombolytic therapy or PTCA (group III, n = 17). Thrombolytic therapy was given within 4 hours after onset of symptoms (mean 2.5 +/- 1.0 hours) and PTCA was performed within 24 hours after the onset of symptoms (mean 6 +/- 6 hours). Signal averaging was performed within 24 hours after cardiac catheterization. An abnormal signal-averaged electrocardiogram was present in 10 of 83 (12%) group I, 9 of 29 (31%) group II and 7 of 17 (41%) group III patients (p < 0.05 group I vs II, p < 0.01 group I vs III, no statistical difference group II vs III). Therefore, in contrast to reperfusion by thrombolytic therapy the incidence of abnormalities on the signal-averaged electrocardiogram early after myocardial infarction is not reduced by an early opening of the culprit vessel by PTCA.

Beneficial effects of L-canavanine, a selective inhibitor of inducible nitric oxide synthase, on lactate metabolism and muscle high energy phosphates during endotoxic shock in rats.

Overproduction of NO by an inducible NO synthase (iNOS) plays a role in the pathophysiology of septic shock. In such situations, NOS inhibition might be of therapeutic value, although detrimental side effects possibly related to inhibition of constitutive NOS have been reported. The use of L-canavanine, a selective inhibitor of iNOS, might be more suitable. The aim of the study was to compare in a rodent endotoxic shock the effects of saline (2 mL/h), N(G)-methyl-L-arginine(L-NMMA) (10 mg/kg/h) and L-canavanine (100 mg/kg/h) on muscle intracellular pH (pHi) and intracellular bioenergetic patterns (ATP, phosphocreatine/inorganic phosphate ratio) using in vivo 31P magnetic resonance spectroscopy (31P MRS). Three groups of anesthetized, mechanically ventilated and paralyzed rats received an intravenous infusion of 15 mg/kg of endotoxin. A fourth time-matched control group (n = 8) received 2 mL/h of saline. Mean arterial pressure, femoral blood flow, arterial blood gases, lactate, nitrate level, and 31P nuclear magnetic resonance (31P MRS) measurements were acquired at onset (T = 0), 90 min (T = 90), and 180 min (T180) after the endotoxin challenge. Femoral oxygen delivery was calculated as the product of femoral blood flow (mL/min) and arterial oxygen content. Endotoxin induced a marked decrease in arterial pressure and femoral oxygen delivery and an increase in lactate level. Intracellular pH and phosphocreatine/inorganic phosphate ratio decreased. ATP level did not change. Both L-NMMA and L-canavanine reversed the endotoxin-induced decrease in arterial pressure. L-NMMA attenuated the decrease in femoral oxygen delivery and the increase in lactate level while these were corrected by L-canavanine. Considering 31P MRS derived bioenergetic indices, the endotoxin-induced decrease in pHi and Pcr/Pi was attenuated by L-NMMA and corrected by L-canavanine. In conclusion, in a rodent model of endotoxinic shock, the continuous infusion of L-canavanine, a selective iNOS inhibitor, improved the systemic hemodynamic parameters and the intracellular bio-energetic patterns estimated by in vivo 31P MRS. To the contrary, the continuous infusion of both constitutive and inducible NOS inhibitor L-NMMA was not followed by the same achievement.

Adult presentation of MCAD deficiency revealed by coma and severe arrythmias.

We report the case of a 33-year-old man who presented with headaches and vomiting. Soon after admission he became drowsy and agitated, developed ventricular tachycardia and his neurological state worsened (Glasgow coma score 6). Blood analysis showed respiratory alkalosis, hyperlactacidemia (8 mmol/l), hyperammonemia (390 micro mol/l) and hypoglycaemia (2.4 mmol/l). Subsequently, he developed supraventricular tachycardia, ventricular tachycardia and ultimately ventricular fibrillation resulting in cardiac arrest, which was successfully treated. A CT scan of the head revealed cerebral oedema. Whilst in the intensive care unit, he developed renal failure and rhabdomyolysis. The metabolic abnormalities seen at the time of admission normalised within 48 h with IV glucose infusion. Biological investigations, including urinary organic acids and plasma acylcarnitines, showed results compatible with MCAD deficiency. Mutation analysis revealed the patient was homozygous for the classical mutation A985G. This is one of only a few reports of severe cardiac arrhythmia in an adult due to MCAD deficiency. This condition is probably under-diagnosed in adult patients with acute neurological and/or cardiac presentations.

Reproducibility of bipolar endocavitary electrogram measurements at sites of radiofrequency energy delivery in patients with the Wolff-Parkinson-White syndrome.

BACKGROUND: Radiofrequency ablation of atrioventricular accessory pathway is widely used to cure patients with the Wolff-Parkinson-White syndrome. The site of successful ablation is determined using electrophysiological parameters, endocavitary bipolar electrogram measurements being the most commonly used. Interobserver reproducibility of these measurements may limit the reliability of ablation criteria based upon bipolar measurements only but, to our knowledge, this reproducibility has not been evaluated so far. Such was the aim of this study. METHODS: Three independent observers reviewed the bipolar electrograms recorded at sites were radiofrequency energy was delivered (successfully or not) in 28 consecutive patients with the Wolff-Parkinson-White syndrome. In each tracing, 4 intervals were measured: (1) A0V0 (onset of the atrial electrogram to onset of the ventricular electrogram), (2) AaVa (activation time of the atrial electrogram to activation time of the ventricular electrogram), (3) V0-QRS (onset of the ventricular electrogram to onset of delta wave on the surface ECG) and (4) Va-QRS (activation time of the ventricular electrogram to onset of delta wave on the surface ECG). RESULTS: The interobserver reproducibility was low since only 50% of A0V0 intervals were measured with an interobserver difference lower than 10 ms and up to 43% of Va-QRS intervals were measured with an interobserver difference greater than 30 ms. The reproducibility of interval measurement was graded from the highest to the lowest as follows: A0V0, AaVa, V0-QRS and Va-QRS (Chi-square statistic, chi 2 = 71.72, p < 0.0001). Kappa values were lower than 0.40, indicating a poor interobserver reproducibility. CONCLUSIONS: Our study suggests that interobserver reproducibility of only bipolar electrograms interval measurements at sites of radiofrequency ablation of atrioventricular accessory pathway is poor, which limits the reliability of bipolar criteria to predict a successful ablation site.

Effects of radiofrequency catheter ablation on patients with permanent pacemakers.

The objective of this study was to assess the effects of radiofrequency energy application on implanted pacemaker functions. Radiofrequency (RF) catheter ablation may cause pacemaker dysfunction due to electromagnetic interferences. The effects of RF on pacemaker behavior were studied in a series of 38 pacemakers, implanted 18 +/- 26 months prior to a RF procedure using either a right ventricular approach (AV node ablation, n = 35) or a left ventricular approach (left concealed accessory pathway ablation, n = 1; VT ablation, n = 2). The 38 patients (mean age 65 +/- 9 years) included 20 men and 18 women. Before energy applications, the 23 different pacemaker models were programmed to the VVI mode at the lowest available rate. The continuous surface ECG was recorded throughout the procedure. Thorough testing of the devices was performed before and after each RF delivery. Unusual pacemaker responses occurred in 20 of the 38 cases studied (53%). The impact of RF delivery was unpredictable, and variable dysfunctions were observed at different times for a given patient or could vary for a given model. Unusual pacemaker responses included pacemaker inhibition (n = 8), untoggled backup mode (n = 3), electromagnetic interference noise mode (n = 3), temporary RF-induced pacemaker tachycardia (n = 2), erratic behavior (n = 1), oversensing of RF onset and offset (n = 8), and transient loss of ventricular capture, (n = 1). Postablation, most devices automatically toggled back to full functionality. The three devices in the untoggled backup mode had to be reprogrammed to obtain normal operations. At the end of the procedure, pacing thresholds remained unchanged in all but one patient, in whom the increase in ventricular threshold was due to a nicked lead. In conclusion, implanted pacemakers frequently exhibit transient, unpredictable responses to RF energy application. Although all pacemaker functions were restored postablation, some devices had to be reset manually. The anomalies observed during the RF application argue for the simultaneous use of an external pacemaker in pacing-dependent patients.

[Primary ventricular fibrillation]. / Les fibrillations ventriculaires primitives.

In the absence of autopsy studies, the etiological diagnosis of this form of ventricular fibrillation (VF) depends on the exclusion of cardiac disease by all available invasive and non-invasive diagnostic methods. Primary VF is rare and affects young adults. There are few clinical markers and published electrophysiological data indicates that sustained ventricular tachycardia or VF is unlikely to be induced by programmed ventricular stimulation. The underlying mechanism of the arrhythmia is poorly understood. However, a possible arrhythmogenic substrate has been suggested in small zones of fibrosis within normal Purkinje tissues, as encountered in some minor forms of arrhythmogenic right ventricular dysplasia. Also, the role played by the autonomic nervous system in triggering VF seems to be particularly important. Some described cases resemble curiously "torsades de pointes" with a short coupling interval. The "cardiac" prognosis of resuscitated patients is usually good. However, arrhythmic recurrences are common, and, classically, antiarrhythmic drugs are usually ineffective. The indication for implantation of an automatic defibrillator is therefore justified in patients surviving primary VF. The lack of understanding of this condition is an argument in favour of setting up a French register of patients with primary VF in order to establish its clinical features.

[Radiofrequency ablation of Kent's pathways. Apropos of 30 cases]. / Ablation par radiofréquence des faisceaux de Kent. A propos de 30 observations.

Radiofrequency catheter ablation is a modern radical treatment of the Wolff-Parkinson-White (WPW) syndrome. The authors report their experience of this method in 30 consecutive patients (12 women, 18 men, mean age 34.2 +/- 13 years, range 14 and 63 years) with the WPW syndrome poorly controlled by antiarrhythmic therapy in 27 out of 30 cases. An average of 10.1 applications (1-33) was necessary to suppress anterograde and retrograde conduction in 26 of the 30 patients during the first session (87% success rate). At the time of effective ablation, the average atrioventricular interval was 41 ms (35-55) and in the two patients with a retrograde Kent bundle, the average ventriculoatrial interval was 72 ms (70 and 75 ms). The average duration of the procedure was 3.5 hours (45 mins to 7 hours) with an average fluoroscopy time of 61.6 minutes (9-182 minutes). There were four complications: one pneumothorax, one subacute femoral arterial obstruction and in two patients with a left Kent bundle, one TIA which regressed within 1 hour and one hemiplegia which regressed in 24 hours. After an average follow-up period of 8.3 months (2-16 months) the 26 patients are asymptomatic without any treatment. Radiofrequency catheter ablation therefore seems to be an effective method with a low morbidity for the radical treatment of symptomatic or high risk WPW syndromes.

[Correlation between parameters measured by high amplification ECG and results of programmed ventricular stimulation after myocardial infarct]. / Corrélation entre les paramètres mesurés par l'ECG haute amplification et les résultats de la stimulation ventriculaire programmée après infarctus myocardique.

The presence of late ventricular potentials and the induction of sustained ventricular tachycardia (SVT) by programmed ventricular stimulation (PVS) after myocardial infarction are markers of the risk of serious ventricular arrhythmias. The authors studied the value of signal averaged electrocardiography (SAECG) compared with induction of SVT by PVS in 118 consecutive patients 4 to 8 weeks after myocardial infarction. In addition to this study population, a control group of 22 patients with spontaneous SVT after myocardial infarction was also considered. Three parameters were measured after averaging 200 QRS complexes: the duration of the filtered QRS complex (QRSd), the duration of signals not exceeding 40 microV (LAS) and the root mean square of the voltage of the last 40 milliseconds (RMS). Abnormal values were defined as: QRSd > or = 120 ms, LAS > or = 39 ms, RMS < or = 20 microV. Patients in the study population were subdivided into 3 groups: Group I (n = 17) inducible SVT; Group II (n = 72) no inducible arrhythmias; Group III (n = 29) induction of sustained ventricular flutter or primary ventricular fibrillation requiring immediate cardioversion. The results showed a good correlation between SAECG and induction of SVT. The sensitivity (Se), specificity (Sp), positive predictive value (PPV) and negative predictive value (NPV) were as follows: 1) QRSd > 120 ms: Se = 82%, Sp = 80%, PPV = 41%, NPV = 96%; 2) LAS > 39 ms: Se = 59%, Sp = 85%, PPV = 38%, NPV = 92%; 3) RMS < 20 V: Se = 59%, Sp = 88%, PPV = 43%, NPV = 93%.(ABSTRACT TRUNCATED AT 250 WORDS)