[Results of high amplification electrocardiogram in primary dilated cardiomyopathy]

Idiopathic dilated cardiomyopathy carries a high risk of sudden death. It is also associated with sustained ventricular tachycardia. A complex ventricular arrhythmia is recorded in 3/4 of cases on Holter monitoring which has a low specificity. The aim of the study was to determine whether signal-averaged electrocardiography could provide a better evaluation of the prognosis of this condition. The results of signal-averaged electrocardiography were compared with those of 24 hour Holter monitoring and of systematic programmed ventricular stimulation in 58 patients with idiopathic dilated cardiomyopathy. Late ventricular potentials were recorded in 13 of the 14 subjects with inducible and usually spontaneous sustained ventricular tachycardia. The sensitivity of the technique for evaluating the risk of sustained VT was therefore good (93%). Late potentials were also recorded in 9 patients with induced ventricular flutter or fibrillation, these patients being symptomatic (dizzy spells). Late potentials were also demonstrated in 14 of the 35 asymptomatic patients without inducible VT, indicating that this non-invasive investigation had a limited specificity (60%). In addition, during follow-up of the patients, the risk of sudden death was difficult to demonstrate. Late potentials were only found in subjects with inducible sustained VT but no in the other cases. In conclusion, signal-averaged electrocardiography seems to be valuable for evaluating the risk of sustained VT in subjects with idiopathic dilated cardiomyopathy and complex ventricular arrhythmias. The detection of the risk of sudden death is probably impossible by this technique.

Electrophysiological characteristics of asymptomatic Wolff-Parkinson-White syndrome

Although most asymptomatic patients with the Wolff-Parkinson-White syndrome have a good prognosis, some die suddenly. Electrophysiological testing may identify patients at possible risk of sudden death. The mechanism of sudden death in these patients is believed to result from ventricular fibrillation due to atrial fibrillation with rapid anterograde conduction over the accessory pathway. Consequently, we performed electrophysiological studies in 40 asymptomatic patients with the Wolff-Parkinson-White syndrome. Certain electrophysiological properties clearly identified these patients: (1) in most patients sustained reciprocating tachycardia could not be induced and this explains the absence of symptoms of regular fast palpitations; (2) the incidence of inducible sustained atrial tachyarrhythmias (30%), of short RR intervals between pre-excited beats (20%) and of risk of sudden death (12.5%) was similar to the incidence in symptomatic patients with the Wolff-Parkinson-White syndrome and reciprocating tachycardia. Because of the ease with which transoesophageal study can be performed we think that the asymptomatic Wolff-Parkinson-White syndrome should be systematically evaluated so as to reassure patients with the benign form that they can lead a normal life and take part in sport and secondly to define the real prognosis of the patients whose characteristics suggests a risk of sudden death.

[Incidence of inducible supraventricular tachycardia in dysplasia of the right ventricle]

Arrhythmogenic right ventricular dysplasia (ARVD) is classically associated with ventricular tachycardia and the prevalence of supraventricular tachycardia in this condition is not well known. The aim of this study was to observe the response of 20 patients with ARVD to programmed atrial stimulation and compare it with 150 subjects without cardiac disease or spontaneous supraventricular tachycardia. The protocol used 2 atrial extra-stimuli delivered on 3 paced cycles. Programmed atrial stimulation with 1 extrastimulus was repeated after infusion of 20 to 30 micrograms of Isoproterenol. Sustained supraventricular tachycardia could be induced in 13 patients with ARVD (65%) and 17 control subjects (11%) (p < 0.001). It was not possible to distinguish patients with inducible supraventricular tachycardia from those without inducible arrhythmias by electrophysiologic parameters. Isoproterenol facilitated the induction of VT but not supraventricular tachycardia. Three patients with inducible supraventricular tachycardia developed spontaneous atrial fibrillation. In conclusion, there is a relatively high incidence of inducible supraventricular tachycardia in ARVD: Isoproterenol does not facilitate this tachycardia, contrary to ventricular tachycardia.

Clinical significance of rapid ventricular tachycardia (> 270 beats per minute) provoked at programmed stimulation in patients without confirmed rapid ventricular arrhythmias

Rapid uniform ventricular tachycardia (VT) (> 270 beats/min) or ventricular flutter induced during electrophysiological studies is thought not to be clinically significant in patients without cardiac arrest or documented rapid VT. The purpose of the study was to follow up 73 patients with inducible ventricular flutter but without confirmed rapid spontaneous VT. A long follow up (mean 3.5 years) identified two groups of patients. The first group had an excellent outcome and was characterised by a normal 24 hour Holter monitoring. In the second group, however, the risk of cardiac mortality was high (35%) and spontaneous VT was < 270 beats/min (26%) and was characterised by couplets or salvos of extrasystoles on Holter monitoring. In this group the history of syncope and decreased left ejection fraction increased the risk of mortality and VT. The presence of late potentials increased the risk of spontaneous VT. Electrophysiologically guided antiarrhythmic therapy reduced the risk of VT. Ventricular flutter was a non-specific finding in patients with normal Holter monitoring. In contrast, in patients with salvos of extrasystoles, ventricular flutter was associated with a high risk of cardiac mortality and VT.

[Characteristics and prognosis of ventricular tachycardia induced by atrial fibrillation]

The aim of this study was to evaluate the clinical significance of ventricular tachycardia (VT) induced by atrial pacing. A group of 145 patients with spontaneous and induced VT was studied. Twenty-four VTs were induced by atrial stimulation (Group I) and 121 by ventricular stimulation (Group II). The underlying cardiac disease was comparable in the two groups (ejection fraction 32 +/- 14% versus 34 +/- 17%). Spontaneous bi-tachycardias, syncope and VT induced by exercise testing were more common in Group I. The prognosis was worse with 7 cardiac deaths in Group I versus 23 in Group II; recurrences of VT were commoner in group I. In this group, an electrophysiological (branch to branch or fascicular reentry) or clinical mechanism (ischaemia or poor haemodynamic status) could usually be demonstrated. Some cases of idiopathic VT were also observed in young patients. These results suggest that atrial stimulation should be performed routinely during electrophysiological studies of VT because the induction of VT by this method is not uncommon (16%). In addition, these cases of VT usually have a precise mechanism and a poor prognosis and, therefore, an appropriate treatment should be given.

Lack of prognostic implications of spontaneously occurring or stimulation induced atrial tachyarrhythmias in patients with dilated cardiomyopathy

A prospective study was undertaken in 102 patients with idiopathic dilated cardiomyopathy to assess the significance of spontaneous and inducible atrial tachyarrhythmias (ATA). Twenty-six patients were in chronic atrial fibrillation (group I) and 76 patients were in sinus rhythm (group II); 14 patients in group II had a clinical history of ATA or episodes of ATA during Holter monitoring. An electrophysiological study was systematically performed. Programmed atrial stimulation was carried out in group II, and used up to two atrial premature stimuli from the right atrium at 2 cycle lengths (sinus cycle length--10%, 600 ms) and then one atrial extrastimulus under infusion of 1 to 4 micrograms. min-1 of isoproterenol. Programmed ventricular stimulation was performed in groups I and II. Sustained atrial tachyarrhythmia (ATA) was induced in 33 patients in group II (42%); isoproterenol infusion facilitated the induction of ATA in only one other patient, who had exercise-related ATA. Eleven patients in group II with spontaneous ATA had inducible sustained ATA. The sensitivity of programmed atrial stimulation to reproduce an ATA was 78.5% and its specificity 64.5%. Inducible ATA was related to a shorter atrial effective refractory period (209 +/- 25 ms vs 228 +/- 32, P less than 0.02). Inducible and spontaneous ATAs were related to older age but not to the existence of spontaneous or inducible ventricular tachycardia; they did not have prognostic significance: the left ventricular ejection fraction and the prognosis were similar in patients with spontaneous or inducible ATA and those without ATA.(ABSTRACT TRUNCATED AT 250 WORDS)

[Significance of tachycardia induced by atrial stimulation in Wolff-Parkinson-White syndrome]

Increased atrial vulnerability is one of the criteria of malignant Wolff-Parkinson-White syndrome. The aim of this study was to try to define the methods of induction of atrial tachycardias (tachycardia, flutter, fibrillation) by endocavitary and oesophageal stimulation characterising an increased vulnerability. The incidence of induced sustained tachycardia by fixed atrial stimulation at incremental rates until the Wenckebach point is attained and programmed atrial stimulation using 1 and 2 extrastimuli under basal conditions and then with isoproterenol was compared in subjects without cardiac disease, Wolff-Parkinson-White or spontaneous tachycardia (Group I) and patients with Wolff-Parkinson-White and spontaneous tachycardias (Group II). Atrial stimulation only induced tachycardia in 2.5% of normal subjects under basal conditions or with isoproterenol, by the endocavitary or oesophageal approaches. Programmed stimulation induced tachycardia in 15% of normal subjects under basal conditions or with isoproterenol by the endocavitary approach alone. In Group II, tachycardia was reproduced under basal conditions or with isoproterenol by atrial stimulation or programmed stimulation in all patients. In conclusion, the induction of a tachyarrhythmia by incremental atrial stimulation up to the Wenckebach point is always pathological even with isoproterenol. Programmed atrial stimulation is less specific except by the oesophageal approach. The use of bursts of very rapid stimuli in the Wolff-Parkinson-White syndrome is of no value as tachycardia can be induced by classical methods in all subjects at risk.

Evaluation of bepridil efficacy by electrophysiologic testing in patients with recurrent ventricular tachycardia: comparison of two regimens

The purpose of the study was to evaluate this effect of different doses of intravenous and oral bepridil on the induction of ventricular tachycardia. Thirty-eight patients underwent electrophysiologic evaluation for recurrent ventricular tachycardia (VT). Sustained monomorphic VT was induced by programmed ventricular stimulation, using up to three extrastimuli in all patients. The effects of intravenous bepridil (2 mg/kg) were evaluated during the initial study. Intravenous bepridil prevented the induction of sustained VT in eight patients (21%). Electrophysiologic study was repeated after oral bepridil. In six patients the study was stopped because of adverse effects or VT recurrence. Thirty-two patients underwent repeat study 7 days later, taking oral bepridil, 500 mg/day (n = 16) or 900/day (n = 16). A dose of 500 mg/day of bepridil prevented the induction of sustained VT in only one patient. A dose of 900 mg/day of bepridil prevented the induction of sustained VT in eight patients. There were no significant clinical adverse effects, except in one patient receiving intravenous bepridil. The response to intravenous bepridil did not predict the response to oral bepridil. The response to intravenous or oral bepridil was not related to the plasma level of bepridil but was related to a higher left ventricular ejection fraction. Eight patients (21%) in whom VTs were noninducible on oral bepridil were discharged on 300 mg/day of bepridil if their initial loading dose was 500 mg/day or on 600 mg/day if their initial loading dose was 900 mg/day. They remained free of VT during a follow-up of at least 6 months.(ABSTRACT TRUNCATED AT 250 WORDS)

Heart rate variations during isoproterenol infusion in congestive heart failure: relationships to cardiac mortality

A marked derangement of heart rate modulation in patients with severe cardiac heart failure (CHF) has been reported. The purpose of the study was to correlate the variations of sinus cycle length (SCL) during infusion of 4 micrograms/min of isoproterenol with the prognosis of 83 patients with CHF (mean left ventricular ejection fraction 28 +/- 9%). During a mean follow-up of 28 +/- 9 months, nine patients died from CHF (group I), nine died suddenly (group II), and 65 are alive (group III). Compared with groups II and III, a significantly weaker ejection fraction (20 +/- 8% versus 29.5 +/- 11% and 28 +/- 9%), a smaller control state SCL (571 +/- 65 versus 722 +/- 200 and 747 +/- 195), and a smaller percentage of SCL shortening during isoproterenol infusion (11.5 +/- 7% versus 36 +/- 16% and 33 +/- 13%) were noted in group I. The sensitivity and specificity of a percentage of SCL shortening during isoproterenol infusion less than or equal to 15% for predicting death from CHF were 89% and 93%, respectively. Therefore the injection of small doses of isoproterenol (4 micrograms/min) may be proposed to evaluate the prognosis of patients with CHF; a weak increase in heart rate during this infusion is a sign of bad prognosis with a high risk of cardiac death as a result of CHF.

Provocation of supraventricular tachycardias by an intravenous class I antiarrhythmic drug

Antiarrhythmic drugs may aggravate or induce ventricular arrhythmia. The induction of a supraventricular tachycardia or its facilitation has rarely been reported. The purpose of the study was to know whether the potential for supraventricular proarrhythmic effect of a class Ia intravenous antiarrhythmic drug can be exposed during electrophysiologic study. Ajmaline was chosen because of its short duration of action. The protocol of the study consisted of an electrophysiological study and programmed atrial stimulation using 1 and 2 extrastimuli on driven rhythm and atrial pacing up to second-degree atrioventricular block. Then 1 mg/kg of ajmaline was injected and atrial pacing was performed 3 minutes after its injection. Supraventricular proarrhythmic effect of ajmaline was defined as the spontaneous occurrence of a supraventricular tachycardia or the facilitation of its induction. Seventy patients among 1955 presented a proarrhythmic effect: 63 developed a supraventricular tachyarrhythmia (atrial flutter, fibrillation, tachycardia) and 7 an atrioventricular reentrant tachycardia, either spontaneously (n = 23) or during atrial pacing (n = 47). Risk factors were identified in most patients: old age, underlying heart disease, history of spontaneous supraventricular tachycardia and/or induction of a supraventricular tachycardia by 2 extrastimuli on driven rhythm in the control state (34 patients), sinus node dysfunction (22 patients). Compared with patients without proarrhythmic supraventricular effect only the history of spontaneous supraventricular tachycardia and the existence of a sinus node dysfunction were significantly more frequent (P less than 0.05) in patients with proarrhythmic effect of ajmaline. In conclusion, the supraventricular proarrhythmic effect of intravenous ajmaline exists and is related both to the electrophysiologic characteristics of the drug and to the arrhythmia substrate. The results indicate that a supraventricular tachyarrhythmia may be induced by a class I antiarrhythmic drug.

[Changes in high amplification ECG during the 2 years following the acute phase of myocardial infarction]

Late potentials have been reported 1 to 15 days after the onset of myocardial infarction but the evolution during long-term follow-up is not so well known. In order to determine if the signal averaged electrocardiogram remained stable or if it was necessary to repeat the investigation during a period of 2 years, 90 patients underwent 2 recordings on average 3 weeks after the onset of the infarct and then 2 years later. After the first recording, 16 patients (18%) had late potentials. The second recording was performed under the same conditions by the same operator. Globally, the signal averaged electrocardiogram recorded by Simson's method remained remarkably stable (83/90). It was rare to observe late potentials occurring for the first time after the initial recording (4 cases, 5%) in this study. It was more common to observe their disappearance (3 cases, 19%). No explanation could be found except in one case. These possible long-term changes in the signal averaged electrocardiogram suggest that the investigation should only be repeated in patients with abnormalities on the initial recording. Some authors have reported a better prognosis in patients in whom late potentials disappeared but this was not verified in this study.

[Changes in high amplitude ECG during hospitalization for myocardial infarction]

The aim of this study was to determine the optimal time for recording the signal averaged electrocardiogram in order not to miss cardiac events after acute myocardial infarction. Three signal averaged electrocardiograms were recorded by Simson's method in the early post infarction period at Day 1 (24 to 48 hours after the onset of symptoms) at Day 8 (8 days after the onset) and Day 15 (2 weeks after the onset) in 66 patients. The results showed late potentials in only 18% of patients at Day 1 and that this was not related to a greater risk of ventricular arrhythmia in the acute phase. Late potentials were recorded in 34.8% of patients on Day 8 and 28.7% at Day 15. We suggest that signal averaged electrocardiography be performed one to two weeks after the onset of myocardial infarction; 13 of 66 patients had abnormalities at Day 8 but not on Day 1.

[Electrophysiological characteristics of asymptomatic Wolff-Parkinson-White syndromes]

The management of the Wolff-Parkinson-White syndrome (WPW) is controversial especially when the patient is asymptomatic. The aim of this study was to evaluate the electrophysiological characteristics of such patients. Thirty two asymptomatic subjects with overt WPW on the surface ECG aged 14 to 68 years (average 36 +/- 15 years) underwent endocavitary or oesophageal electrophysiological study with the following protocol: programmed atrial stimulation using 1 or 2 extrastimuli over 3 cycles to evaluate the induction of paroxysmal junctional tachycardia and atrial fibrillation; atrial pacing at increasing frequencies to assess the shortest cycle conducted by the bundle of Kent. This protocol was repeated during intravenous infusion of 20 to 30 mg of Isoproterenol. Four electrophysiological characteristics were identified: the incidence of induction of junctional tachycardia was very low (2 cases, 6%); the incidence of induction of atrial fibrillation or tachycardia was similar to that of symptomatic WPW (9 cases 30%); the incidence of rapid conduction via the bundle of Kent (cycle conducted by the Kent less than 250 ms under basal conditions less than 200 ms with Isoproterenol) was 19% (6 cases); the incidence of potentially serious forms of WPW with rapid conduction in the bundle of Kent and atrial vulnerability (induction of atrial fibrillation at a frequency less than the Wenckebach point by programmed atrial stimulation) was similar to that in symptomatic WPW, 3 cases (10%). In conclusion, the asymptomatic character of the WPW is very probably due to the absence of junctional tachycardias. Nevertheless, these patients are at risk of atrial fibrillation with an incidence of potentially serious forms of 10%.(ABSTRACT TRUNCATED AT 250 WORDS)

[Programmed ventricular stimulation in unexplained syncope: risk factors for induction of ventricular tachycardia]

The aim of this study was to identify the factors associated with the induction of ventricular tachycardia (TV) by programmed ventricular stimulation in patients with unexplained syncope. Sustained VT was induced in 71 out of 619 patients (11.5%) with syncope. A comparison of subjects with inducible VT and those without inducible VT showed underlying cardiac disease to be more common (89% versus 16%), more Holter abnormalities (Grade IVa ventricular extrasystoles) (60.5% versus 10%) in the first group but that signal-averaged ECG, recorded in 51 cases, was not sufficiently specific to differentiate the two groups (delayed potentials in 57% versus 43%). When syncope occurred in a subject without apparent cardiac disease with a normal Holter recording, inducible VT was rare (1%). On the other hand, when syncope was associated with cardiac disease and/or an abnormal Holter recording, VT could be induced in 45 to 64% of cases. In addition, as inducible VT was associated with severe infrahisian conduction defects in 3 cases, the following strategy is suggested in patients with unexplained syncope: programmed ventricular stimulation should be performed systematically during endocavitary electrophysiological investigation of AV conduction in patients with cardiac disease and if the non-invasive investigations, Holter monitoring or echocardiography, are abnormal.

[Results of programmed ventricular stimulation in induced non-sustained polymorphic ventricular tachycardia and maintenance of stimulation]

Programmed ventricular stimulation risks inducing non-pathological ventricular fibrillo-flutter. The aim of this study was to determine if the induction of a non-sustained polymorphic ventricular tachycardia (over 5 intraventricular reentries) could prevent this incident. One hundred and thirty-three non-sustained polymorphic tachycardias were induced by 2 or 3 extrastimuli during 1450 programmed ventricular stimulation studies. Ventricular stimulation was continued and led to ventricular fibrillo-flutter in 46 cases (Group I); to induction of sustained ventricular tachycardia in 26 cases (Group II) or to no other arrhythmias excepting the non-sustained tachycardia in 61 cases (Group III). The duration of the salvo was similar in all 3 groups. The rate of the induced arrhythmia was significantly lower in Group II (234 vs 290/min). The essential difference between the three groups was the clinical context. Only patients in Group II had previously documented sustained ventricular tachycardia and only patients in Group III had no apparent underlying cardiac disease. These results suggest that the decision to stop programmed ventricular stimulation should be based on the clinical indications of the study. In patients with previously documented or probable sustained ventricular tachycardia, it would seem to be necessary to continue ventricular stimulation irrespective to the rate and duration of the induced non-sustained ventricular tachycardia.

Study of P wave morphology in lead V1 during supraventricular tachycardia for localizing the reentrant circuit

Paroxysmal supraventricular tachycardia (SVT) is a benign form of tachycardia that generally does not require costly evaluation. The purpose of this study was to describe a new sign permitting delineation of the mechanism of SVT by analysis of the P wave in lead V1 and the left atrial electrogram, which may be registered by the esophageal electrode. Among 146 patients with SVT, 72 had a ventriculoatrial interval greater than 70 msec. The P wave in lead V1 during SVT was discernible in 69 of them. The precession of the left atrial electrogram on the P wave in lead V1 was always associated with reentry through a left lateral (n = 37) or posteroseptal (n = 4) accessory atrioventricular (AV) connection. When the P wave in lead V1 preceded or occurred simultaneously with the left atrial electrogram, reentry was through either the AV node or a right-sided accessory AV connection. On the other hand, although the P wave in lead V1 was more frequently negative in reentry through a right-sided connection and positive in reentry through a left-sided connection, the polarity was not specific enough to identify the reentry. The precession of the left atrial electrogram recorded by the esophageal electrode on the P wave in lead V1 during SVT was a specific criterion of reentry through a left accessory AV connection, and this technique could be useful for preliminary localization of the accessory connection before electrophysiologic study.

Diagnostic value of ventricular stimulation in patients with idiopathic dilated cardiomyopathy

To assess the response to programmed ventricular stimulation and the clinical outcome, we performed a prospective study in 103 patients with idiopathic dilated cardiomyopathy. The protocol used up to three extrastimuli delivered at two right ventricular sites during sinus rhythm and ventricular pacing at 100 and 150 beats/min and was repeated during infusion of 1 to 4 micrograms/min of isoproterenol. Sustained monomorphic ventricular tachycardia (VT) was induced in 8 of 11 patients with spontaneous sustained VT, in none of 35 patients without significant ventricular arrhythmias during Holter monitoring, and in 9 of 56 patients with salvos of ventricular premature beats. Isoproterenol infusion facilitated the induction of two episodes of sustained VT in patients with spontaneous sustained VT; however, in all but one of the remaining patients, induction of ventricular tachyarrhythmias was not impaired. During the follow-up period there were eight sudden deaths among patients who initially had syncope, inducible sustained VT, or both and three episodes of sustained VT in patients who initially had nonsustained VT but inducible sustained VT. Isoproterenol infusion can be used to safely facilitate induction of ventricular tachyarrhythmias in patients with dilated cardiomyopathy. The induction of sustained VT was associated with a poor prognosis.

Incidence and significance of inducible supraventricular tachyarrhythmias in patients with chronic myocardial infarction

In order to evaluate the incidence and significance of inducible supra-ventricular (SVTA) in patients with chronic myocardial infarction (MI), the results of systematic programmed atrial stimulation were compared in two groups of patients: 150 patients (group I) without MI or underlying heart disease, studied for syncope or conduction disturbances, 296 patients (group II) studied after an acute Mi (greater than 1 month). None of them had spontaneous SVTA, and 24-h Holter monitoring showed no SVTA. The atrial stimulation programme used one and two extra stimuli delivered during sinus rhythm and atrial pacing (600 ms and 10% less than the sinus cycle length). A sustained (S) (greater than 30 s) supraventricular tachycardia (SVT) (atrial flutter, fibrillation, tachycardia) was induced in 17 patients in group I (11%) and in 120 patients in group II (40.5%). In group II inducible SVTA could not be correlated with the occurrence of a SVT during acute MI, the location of MI, the value of LV ejection fraction (EF), the incidence of inducible sustained ventricular tachycardia (VT), or fibrillation (VF). However, inducible SVTA could be correlated with a significantly shorter effective atrial refractory period (197 +/- 23 ms vs 220 +/- 35 ms, P less than 0.001) and a shorter retrograde block cycle length (518 +/- 215 vs 585 +/- 215 ms, P less than 0.03). The patients in group II were followed-up for at least 6 months; 12 of them developed sustained episodes of supraventricular tachycardia; 11 of them had inducible SVTA (P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

[Signal averaged ECG and mechanisms of sudden death]

The aim of signal averaged electrocardiography is to detect late potentials (LP) which are markers of ventricular tachycardia. As sudden death is often due to ventricular fibrillation which can complicate ventricular tachycardia, some workers have suggested that the presence of LP may increase the risk of sudden death. We analysed the results of signal averaged ECG in 17 subjects who died suddenly and compared them with 8 patients who died from ventricular tachycardia. These two groups of patients were part of a general population of 450 subjects who underwent programmed ventricular stimulation and signal averaged ECG by Simson's method (25 Hz filter). Three parameters of this ECG were analysed: total QRS duration (Dur QRS), amplitude of the signal 40 ms before its termination (V 40), and the duration of the terminal activity less than 40 microV (Dur LP). The criteria of diagnosis of Lp were: Dur QRS greater than or equal to 120 ms, V 40 less than or equal to 20 microV, Dur LP greater than or equal to 40 ms. The results of signal averaged ECG of patients who died suddenly were different to those of patients who died from VT: Dur QRS 116 +/- 40 vs 140 +/- 25 ms, V 40 27 +/- 24 vs 7 +/- 8 microV, Dur LP 39 +/- 27 vs 59 +/- 14 ms. Only 8 patients who died suddenly had LP (47%) whereas all patients who died of VT had LP. A correlation was observed between the presence of LP and 2 factors: the LV ejection fraction which was significantly lower in patients with LP (28 +/- 8 vs 46 +/- 19%) and the results of programmed ventricular stimulation: patients with induced sustained VT less than 270/mn usually had LP (15/16). LP were usually absent (4/6) in cases of ventricular flutter (VT greater than or equal to 270/mn) or induced VF. The presence of LP in 2 patients could signify a risk of developing VT later on. In conclusion, 9/17 patients who died suddenly did not have LP. The risk of sudden death due to primary VF or V flutter cannot be predicted. Other causes of VF are even harder to identify.

[Induction of supraventricular tachycardia (paroxysmal junctional tachycardia and atrial tachycardia) by esophageal stimulation]

Transesophageal stimulation is tending to replace endocavitary electrophysiological studies in the investigation and treatment of supraventricular tachyarrhythmias. The aim of this study was to determine the sensitivity of this technique in the evaluation of paroxysmal junctional tachycardia (PJT) and atrial tachycardia (AT). Fifty-eight patients with these arrhythmias (PJT, n = 23; AT, n = 35) were investigated under basal conditions and then during Isoproterenol infusions with a protocol using incremental atrial stimulation and programmed atrial stimulation delivering one and two extra-stimuli on two paced rhythms (400-600 ms). It was possible to induce the arrhythmia in the 23 patients with PJT either under basal conditions (n = 16) or during Isoproterenol (n = 7). A reentrant mechanism was suggested in 22 patients by the following findings: position of the auriculogramme with respect to the ventriculogramme, presence or absence of a delaying branch block, situation and morphology of the P wave in lead V1 compared with atrial activation recorded by the esophageal catheter. Atrial tachycardia was induced in 26 patients (74 per cent), 19 under basal conditions, 6 with Isoproterenol and once after carotid sinus massage. As a conclusion, we can say that the sensitivity of transesophageal stimulation is the same as for endocavitary stimulation.

[Electrophysiologic effects of enoximone]

Most inotropic agents risk aggravating atrial and ventricular hyperexcitability associated with cardiac failure by their catecholergic-like effects. The aim of this study was to evaluate the electrophysiological effects of a powerful inotropic agent, enoximone, and to determine whether it had any arrhythmogenic effects. Endocavitary electrophysiological studies of conduction, induction of supraventricular tachycardia (SVT) by programmed atrial stimulation up to two extrastimuli and induction of ventricular tachycardia by programmed ventricular stimulation using up to 3 extrastimuli were undertaken before and 15 minutes after an injection of 1 mg/kg of enoximone in 10 minutes followed by an infusion of 0.75 mg/kg over 20 minutes. The studies were undertaken in 14 patients with severe cardiac disease (average ejection fraction: 26%): all had complex ventricular arrhythmias on Holter monitoring but only 7 had inducible sustained VT less than 270/mn under basal conditions. The following effects were observed with enoximone: significant shortening of all parameters of conduction; no aggravation of supraventricular excitability; no significant inducible ventricular arrhythmias in subjects without inducible sustained VT under basal conditions; facilitation of induction and acceleration of VT induced in 6 of the 7 patients with inducible sustained VT under basal conditions (VT cycle shortening from 307 +/- 13 to 240 +/- 34 ms). In conclusion, enoximone has no supraventricular arrhythmogenic effects and does not facilitate the induction of ventricular arrhythmias in subjects without inducible sustained VT under basal conditions. However, it can accelerate the VT rhythm in patients who have inducible sustained VT under basal conditions.

[Effect of complete bundle-branch block on the averaged signal of high amplification electrocardiogram]

Intraventricular conduction defects delay ventricular activation and change the appearances of the signal averaged electrocardiogram. The aim of this study was to determine criteria capable of identifying patients with bundle branch block at high risk of ventricular tachycardia (VT). Two hundred and twenty four patients were studied by Simson's method. One hundred and twenty eight patients (Group I control) had narrow QRS complexes and sequellae of previous myocardial infarction. Eighty four patients had no clinical or inducible VT; 44 had clinical and/or inducible VT with programmed stimulation. Forty six patients (Group II) had complete right bundle branch block (RBBB); 30 had no VT and 16 had VT. Twenty seven patients (Group III) had complete left bundle branch block of whom 18 had no VT and 9 had VT. Twenty three patients (Group IV) had RBBB with operated tetralogy of Fallot; 16 had no VT and 7 had VT. In the control group, the results of signal averaged ECG were the same as those reported in the literature: prolongation of the duration of the averaged QRS (136 +/- 35 ms vs 104 +/- 14 ms), decrease in amplitude of the last 40 ms (11 +/- 15 microV vs 43 +/- 28 microV) and an increase in the duration of less than 40 microV terminal activity (53 +/- 30 ms vs 28 +/- 11 ms) in those subjects with VT compared to those without VT. In Groups II, III and IV no significant difference was found in the amplitude of the last 40 ms or duration of less than 40 microV activity between patients with and without VT.(ABSTRACT TRUNCATED AT 250 WORDS)

[Correlation of the results of high-amplification ECG and the cycle of induced ventricular tachycardia. Prognostic value]

Analysis of high amplification ECG results as a function of the results of programmed ventricular stimulation on the fate of 240 patients provides the following data: when programmed ventricular stimulation is negative, there are no late potentials since sudden cardiac death is probably due not to a disturbance in primary rhythm but to a disturbance in ischaemic rhythm; in the case of sustained ventricular tachycardia, cardiac mortality is highest (16 per cent) when due to sudden cardiac death or ventricular tachycardia and late potentials are usually present (14 times out of 15); ventricular fibrillation or flutter are accompanied by appreciable cardiac mortality (between 10 and 13 per cent), basically due to sudden cardiac death and, in this case, there are no late potentials. It is possible to observe late potentials which induce ventricular flutter in subjects during programmed stimulation and this might be a risk factor in the subsequent development of ventricular tachycardia.