[Use of semi-automatic defibrillators outside the hospital]. / Utilisation extrahospitalière du défibrillateur semi-automatique.

With an annual incidence of 1 to 2@1000 and a rate of survival without complication of 2%, sudden death outside hospital constitutes a serious public health problem in France. Ventricular fibrillation (VF) is responsible for more than three quarters of these deaths. The rate of survival is inversely proportional to the duration of VF making early defibrillation a strong link in the chain of survival. The chances of survival are much greater if the cardio-respiratory arrest occurs with a witness, basic first aid is started rapidly, diagnosis of VF is made quickly and the first shock is delivered as soon as possible. These last two criteria are being met more often since the advent of the semi-automatic defibrillator (SAD) and its availability to first line rescuers. The SAD is a light and compact defibrillator capable of automatic analysis of the electrocardiographic trace, charging if it detects ventricular tachycardia (VT) or VF. By analysing the QRS amplitude, its slope, its morphology, its spectral density and the duration of the isoelectric line, the SAD is capable of recognising VF with a sensibility of 98% and a specificity of 93%. The shock, however, is only delivered with a manoeuvre from the operator. The SAD memorizes both the rhythmic event treated and certain parameters relating to its use. During the last decade, the SAD has benefited from the technological evolutions of the implantable automatic defibrillator, with the introduction of a biphasic shock. The use of a biphasic shock allows reduction in the minimal defibrillation charge and thus lightens the apparatus and increases the number of shocks which the SAD can deliver on a charged battery. In authorizing paramedics by statute to use the SAD, it has been possible to reduce the interval from alert to first delivered shock to 8 minutes although it would be 10 minutes if the medical team was awaited, and to obtain a survival rate without complication of 6.3%. The progress achieved by the use of the SAD in the chain of survival cannot be denied. However, to surpass automatic defibrillation and widen the use of defibrillators to an informed and motivated public would certainly bring our results closer to those obtained in America where the survival rate reaches 30% in the best cases; subject to widespread first aid training for the population.

Prospective evaluation of a simplified approach for common atrial flutter radio frequency ablation with only two catheters.

UNLABELLED: Intra-atrial conduction block within the inferior vena cava-tricuspid annulus isthmus (IVCT) has been shown to predict successful common atrial flutter ablation. However, its demonstration requires the use of several electrode catheters and mapping of the line of block. The aim of this study was prospectively to test the feasibility of a simplified ablation procedure using only two catheters. METHODS: Radio frequency (RF) ablation of common atrial flutter was performed in 30 patients with the sole use of a catheter for atrial pacing and a RF catheter. RF ablation lesions were created in the IVCT. Surface ECG criteria were used to monitor the conduction within the IVCT. The end point during low lateral atrial pacing was an increment in the interval between the pacing artefact and the peak of the R wave in surface lead II >50 ms and clockwise rotation of the P wave axis beyond -30 degrees and inferiorly. Then, the line of lesions was mapped during atrial pacing with the RF catheter. Additional RF lesions were applied if mapping disclosed a zone of residual conduction. Otherwise the procedure was stopped if mapping showed parallel double potentials all along the line. Finally, the block was reassessed with a 'Halo' catheter. RESULTS: Surface ECG criteria were met in 26 patients. Mapping the line of lesions showed a complete corridor of parallel double potentials in these 26 cases and in 3 of the 4 patients in whom ECG criteria were not met. Conduction evaluated with the Halo catheter showed bi-directional complete block in these 29 patients. After a follow-up of 16 +/- 4 months there was no recurrence of atrial flutter. CONCLUSION: Surface ECG criteria combined with mapping of the line of block demonstrate evidence of bi-directional IVCT block. This simplified RF ablation of common atrial flutter is feasible with a low recurrence rate.

Long-term evaluation of autonomic tone in patients below 50 years of age with unexplained cerebral infarction: relation to atrial vulnerability.

UNLABELLED: Preliminary studies have described, in young patients with unexplained cerebral infarction, electrophysiological abnormalities similar to those observed in paroxysmal atrial fibrillation. Moreover, in young adults with 'normal' hearts, increased susceptibility to paroxysmal atrial fibrillation with autonomic abnormalities as assessed by heart rate variability analysis have been reported. METHODS: The long-term time and frequency domain measures of heart rate variability were analysed prospectively from 24-h Holter ECG recordings in 25 patients (39 +/- 8 years) with unexplained cerebral infarction, and in 25 age-, sex- and cigarette-smoking-matched healthy control subjects. The day following the Holter ECG recordings, 9 +/- 4 months (mean) after the stroke, stroke patients underwent an electrophysiological study in order to analyse the electrical characteristics of their right atria and also to determine their vulnerability to atrial fibrillation. The correlations between autonomic tone parameters and electrophysiological findings were therefore assessed with linear regression analyses. RESULTS: All the measured components of heart rate variability either in time (SDNN, pNN50, SDANN/5, rMSSD) or frequency domains (total power, low-frequency, high-frequency power, low-frequency/high-frequency power ratio) were similar between stroke patients and controls. During electrophysiological study, atrial fibrillation was induced in 80% of stroke patients. Among these patients, atrial refractory periods were significantly shorter, local electrograms were longer, and latent atrial vulnerability index was markedly decreased when compared with patients having no inducible atrial fibrillation. Concerning heart rate variability analysis, no difference was found between patients with induced atrial fibrillation when compared with a matched subgroup of healthy control subjects. Furthermore, there was no statistically linear correlation between any of the measured autonomic tone parameters and any of the discovered atrial vulnerability markers. CONCLUSIONS: The long-term autonomic tone parameters of young patients presenting with a history of unexplained cerebral infarction are similar to those of healthy control subjects and are not correlated with atrial vulnerability parameters or atrial fibrillation inducibility.

[Determinants of survival after implantation of an automatic defibrillator. Report of 127 patients]. / Déterminants de la survie après implantation d'un défibrillateur automatique implantable. A propos de 127 patients.

The authors present a retrospective and longitudinal study of the predictive factors of mortality in patients having an implanted automatic defibrillator. The population comprised 127 patients implanted between September 1988 and September 1997. There were 107 men with a mean age of 57.7 +/- 13 years. The left ventricular ejection fraction was 39.3%. The proportion of coronary patients was 68%; 20% of patients had atrial fibrillation and 5% were in Class III of the NYHA classification. The indications were: resuscitated cardiac arrest (N = 56) and poorly tolerated ventricular tachycardia (N = 71). The follow-up period was 30 +/- 25 months. There were 23 early and 10 late complications. Seventy-two patients had received an electric shock; 57 had an appropriate shock. There were 23 arrhythmic storms (ventricular arrhythmia requiring at least 2 shocks in less than 24 hours) in 17 patients. The operative mortality was 1.1%; at 1 year, the global survival was 93.9 +/- 2.2%; cardiac survival was 94.7 +/- 2.1%; survival without sudden death was 98.3 +/- 1.2%. Multivariate analysis isolated predictive factors for mortality; atrial fibrillation was predictive for global mortality; an ejection fraction < 30% and the fact of having received an appropriate shock were predictive of cardiac mortality; and an arrhythmic storm was predictive of sudden death.

[Mapping and radiofrequency ablation in different forms of right peri-atriotomy flutter]. / Cartographie et ablation par radiofréquence des différentes formes du flutter péri-atriotomie droite.

Peri-atriotomy flutter is a possible complication of surgical atriotomy. This tachycardia in an indication for radiofrequency ablation. The aim of this study was to determine the mechanism of the flutter, evaluate the possibility of mapping and the role of radiofrequency ablation in its treatment. Eleven patients with a mean age of 45 years (26-70) were referred for ablation of atrial flutter observed on average 15 years after surgical atriotomy. In 7 patients (Group I), the ECG appearances before the procedure were that of a rare flutter. Endocavitary mapping showed a circuit limited to the free wall of the right atrium with a posterior caudo-cranial and an anterior cranio-caudal front. A series of radiofrequency applications joining the atriotomy scar to the inferior vena cava interrupted the flutter in all patients and created a bidirectional block around the atriotomy. In 4 patient (Group II), the ECG appearances were that of a common flutter. A series of radiofrequency ablations in the cavo-tricuspid isthmus led to sudden change in polarity of the F wave in all patients. Repeat mapping then showed a peri-atriotomy circuit identical to that described in Group I. The whole was interpreted as a figure-of-eight circuit. The primary success rate was 100%. There were no complications but the early recurrence rate remained high. This preliminary experience confirms the value of radiofrequency ablation in the treatment of peri-atriotomy flutter and shows ECG polymorphism related to a figure-of-eight reentry circuit.

Single center experience with femoral extraction of permanent endocardial pacing leads.

Between March 1995 and June 1997, 128 leads were extracted from the hearts of 28 women and 50 men, 69 +/- 15 years of age (mean +/- SD, range 22-92 years). The indications for the procedure were: Accufix leads in 18 patients (14%), dysfunction or incompatibility with ICD in 16 (12%), endocarditis on the lead in 41 (32%), pulse generator pocket infection in 28 (22%), and pulse generator and/or lead erosion in 25 patients (19%). The extraction was performed with a snare (lasso), via a femoral vein as a first approach in 116 leads, and as an alternate approach, after extraction from the original site of implantation had failed, in 12 leads. The leads had been implanted for 62 +/- 48 months (range 1-205 months). A Cook sheath was used in 7, and a femoral approach traction in 20 instances. Of the 128 leads, 122 (95%) were completely extracted, and 2 (2%) were partially extracted (the distal electrode remaining attached to the myocardium), and 4 (3%) could not be removed. Four complications occurred: 2 tears of the tricuspid valve without clinical consequences, one separation of the lead's distal electrode which migrated into the hypogastric vein, and one hemorrhage at the femoral puncture site. There was no death or serious complication caused by lead extraction in this series.

Inadequate sympathovagal balance in response to orthostatism in patients with unexplained syncope and a positive head up tilt test.

AIM: To analyse the immediate response of heart rate variability (HRV) in response to orthostatic stress in unexplained syncope. SUBJECTS: 69 subjects, mean (SD) age 42 (18) years, undergoing 60 degrees head up tilt to evaluate unexplained syncope. METHODS: Based on 256 second ECG samples obtained during supine and upright phases, spectral analyses of low (LF) and high frequency (HF) bands were calculated, as well as the LF/HF power ratio, reflecting the sympathovagal balance. All variables were measured just before tilt during the last five minutes of the supine position, during the first five minutes of head up tilt, and just before the end of passive tilt. RESULTS: Symptoms occurred in 42 subjects (vasovagal syncope in 37; psychogenic syncope in five). Resting haemodynamics and HRV indices were similar in subjects with and without syncope. Immediately after assuming the upright posture, adaptation to orthostatism differed between the two groups in that the LF/HF power ratio decreased by 11% from supine (from 2.7 (1.5) to 2.4 (1.2)) in the positive test group, while it increased by 11.5% (from 2.8 (1.5) to 3.1 (1.7)) in the negative test group (p = 0.02). This was because subjects with a positive test did not have the same increment in LF power with tilting as those with a negative test (11% v 28%, p = 0.04), while HF power did not alter. A decreased LF/HF power ratio persisted throughout head up tilt and was the only variable found to discriminate between subjects with positive and negative test results (p = 0.005, multivariate analysis). During the first five minutes of tilt, a decreased LF/HF power ratio occurred in 33 of 37 subjects in the positive group and three of 27 in the negative group. Thus a decreased LF/HF ratio had 89% sensitivity, 89% specificity, a 92% positive predictive value, and an 86% negative predictive value. CONCLUSIONS: Through the LF/HF power ratio, spectral analysis of HRV was highly correlated with head up tilt results. Subjects developing syncope late during continued head up tilt have a decrease in LF/HF ratio immediately after assuming the upright posture, implying that although symptoms have not developed the vasovagal reaction may already have begun. This emphasises the major role of the autonomic nervous system in the genesis of vasovagal (neurally mediated) syncope.