[Complete atrioventricular block, a possible complication of radiofrequency ablation of reciprocating nodal tachycardia]

Radiofrequency ablation of the slow pathway of the reentry circuit is the usual radical treatment of nodal tachycardia. It is, however, possible to create atrioventricular conduction defects, the significance of which is not known. The aim on this study was to report the history of these conduction defects created during ablation of the slow pathway of the intranodal reentry circuit. Four cases were observed in a series of 27 patients. In one female patient, complete atrioventricular block was observed for 5 minutes before conduction returned to normal followed by recurrence of the tachycardias. Three other women developed complete atrioventricular block one to four days after the ablation. The block regressed after a maximum delay of 7 days. Six months to one year after the procedure, these three patients remain free of tachycardia and have only first degree atrioventricular block on the surface ECG. These patients were not implanted with a pacemaker. The authors conclude that complete atrioventricular block after ablation of the slow pathway may be treated conservatively, providing it is well tolerated. It normally regresses within few days.

[Syncopes associated with mitral valve prolapse. Mechanisms]

Prolapsed mitral valve prolapse (PMV) is classically associated with disorders of ventricular excitability whose significance is unclear. However, syncope can suggest the possibility of a serious ventricular arrhythmia. The objective of this study was to try to identify the mechanisms of dizziness and syncope associated with PMV. We report the results of programmed atrial and ventricular stimulation performed under baseline conditions and after administration of Isuprel in 56 patients with PMV: 27 patients had a history of presyncope or syncope (group I), 14 had spontaneous atrial or supraventricular tachycardias without dizziness or syncope (group II) and 15 were asymptomatic and investigated for VEBs or conduction disorders (group III). The following results were obtained: In group I, 6 patients experienced sustained inducible ventricular tachycardia (VT); an atrial tachycardia (atrial tachycardia and/or atrial fibrillation) (AT) was also induced in 5 of them. In another 19 patients, a supraventricular tachycardia (SVT) and/or AT was induced. A total of 24 atrial or junctional tachycardias were triggered in this group. In group II, AT and/or SVT were reproduced in 13 out of 14 cases (93%). In group III, AT was triggered in 3 patients (20%). SVT were induced by Isuprel while AT were triggered prior to administration of Isuprel, under baseline conditions, and 3 of them were reproduced during vagal manoeuvres. A ventricular arrhythmogenic effect was observed in two cases in group II while taking class I antiarrhythmics. In conclusion, spontaneous AT and SVT of PMV are easily inducible with a sensitivity of 93%, but are difficult to induce in asymptomatic subjects. The high incidence of TA and SVT in the case of unexplained presyncope in subjects without documented tachycardia therefore appears to be suggestive of a relationship between these presyncopes and AT or SVT. However, the search for VT should take precedence. SVT appear to be catecholaminergic while AT tend to be vagal.

[Effects of age on the response to Tilt test in patients with malaise or syncopes]

The diagnosis of vasovagal malaise or syncope, suspected from the clinical history, may be confirmed by the tilt test. The aim of this study was to assess the effects of age on the results of this test in 346 patients who had unexplained malaise or syncope. Thirty-one patients were 7 to 19 years of age (group I), 59 were 20 to 40 (group II), 72 were 41 to 60 (group III) and 184 were 61 to 85 years old (group IV). The patients were maintained in the dorsal decubitus position for 20 minutes and then raised to 70 degrees until a malaise was observed or for a maximum of 40 minutes. The malaise or syncope was reproduced by the tilt test in 135 cases (39%). The number of positive responses was comparable in group I, II, III and IV (45, 42, 32 and 40%, respectively). The time before the malaise occurred was also similar in the four groups (17, 19, 15 and 20 minutes, respectively). Two responses to the tilt test characterised the different age groups: the greater number of malaises occurring independently of a drop in blood pressure or change in heart rate ("psychiatric" syncope) in group II compared with groups I, III and IV (40% versus 7, 9 and 9.5%); the higher frequency of pure vasodepressive forms in group IV compared with groups I, II and III (66% versus 28.5, 32 and 39%). In conclusion, the probability of a positive tilt test does not change with age. The mechanisms of the symptoms produced is the only difference observed with age.

[Can signal-averaged electrocardiograms be interpreted in cases of complete bundle branch block?]

The aim of this study was to evaluate the results of signal-averaged (SA) ECG in cases of complete right (RBBB) or left bundle branch block (LBBB). One hundred and seven patients had RBBB; 42 without cardiac disease (0), 56 with chronic myocardial infarction (MI) and 9 with primary cardiomyopathy (CMP). Seventy-four patients had LBBB: 20 without cardiac disease, 26 with chronic myocardial infarction and 28 with primary cardiomyopathy. A SA ECG (Cardionics, Fidelity) was performed with a 40 Hz band pass and compared with the recordings of 72 healthy controls without bundle branch block. The duration of the averaged QRS (QRS dur), the voltage of the last 40 milliseconds (RMS40) and duration of terminal activity < 40 microV (LAS) were measured. The analysis of results showed that QRS dur was significantly longer in subjects with ventricular tachycardia (VT) (p < 0.05) and in those with advanced cardiac disease (p < 0.05), whatever the type of bundle branch block, and that only the RMS40 distinguished patients with VT from those without VT, irrespective of the underlying cardiac disease and the type of bundle branch block. However, the study of the diagnostic value of each parameter showed very mediocre results: RMS 40 < 20 microV in myocardial infarction and < 17 microV in cardiomyopathy had sensitivities and specificities in RBBB of 73% and 50% respectively, incalculable in CMP, in LBBB 70% and 33%, 77% and 60% respectively; the LAS was unusable. The authors conclude that it is hazardous to interprete SA ECG in bundle branch block, especially in advanced cardiac disease where the specificity of the criteria becomes very low (< 50%).

[Heart rate response to ventricular stimulation]

Analysis of heart rate variability (HRV) by Holter monitoring is the method of choice for assessing the cardiac autonomic regulation. Rapid ventricular stimulation also provokes changes in the autonomic nervous system tone. The aim of this study was to compare time and frequency domain analysis of HRV (Elatec version 3.02) with variations of HR observed after incremental ventricular stimulation to 200/min in 130 patients. In 80 patients, ventricular stimulation provoked an initial acceleration in HR followed by a slowing with a variation of over 10%. In the other 50 patients, these variations were not observed. Holter analysis of HRV showed concordance between the two methods. In time domain analysis, the standard deviation of normal R-R intervals, the coefficient of variability [(CV = SD/mean RR) and percentage of adjacent RR intervals with a difference of more than 50 msec (pNN 50) were significantly reduced in the abnormal group, the respective values in the normal and abnormal groups being: SD 122 vs 72 msec; CV 15 versus 9% and pNN50 9 versus 5%)]. In frequency domain analysis, there was a reduction of low and high frequency spectra and of the ratio of low/high frequencies in abnormal subjects. The authors conclude that the disappearance of HR changes after ventricular stimulation is correlated to the absence of HRV on Holter recording. This simple test may be performed systematically during electrophysiological investigations. The measurements are reproductible and the results are not affected by arrhythmias or technical problems of quality recording by the Holter method which may affect analysis of HRV.

Significance and prevalence of inducible atrial tachyarrhythmias in patients undergoing electrophysiologic study for presyncope or syncope

The purpose of the study was to report the prevalence of inducible supraventricular tachyarrhythmias (SVTA) in 827 consecutive patients aged 17 to 90 years who did not have spontaneous documented SVTA and who had unexplained presyncope and/or syncope. The electrophysiologic study (EPS) included programmed atrial and ventricular stimulation up to two extrastimuli at three cycle lengths, and the study of sino-atrial and AV conduction. The results were as follows. EPS was normal in 386 patients. Inducible junctional tachycardia or atrial flutter and fibrillation was the only finding in 187 patients (23%). In the remaining patients we found ventricular tachycardia in 103 (12%), heart block in 67 (8%), sick sinus syndrome in 56 (7%) and increased vagal tone in 28 (3%). The presence of an underlying heart disease (47%) and salvos of atrial premature beats on Holter monitoring (39%) were significantly correlated with the induction of SVTA. However, the comparison with similar groups without syncope indicates that only the induction of SVTA in patients with hypertrophic cardiomyopathy and mitral valve prolapse was significantly correlated with the history of syncope. In patients without heart disease or with prior myocardial infarction or decreased left ventricular function, the induction of SVTA, which is not associated with hypotension in the supine position, could require an induction after head-up tilting, because of the lack of specificity of programmed stimulation in these patients. Programmed atrial stimulation should be systematically performed in patients with unexplained syncope, in particular in those with hypertropic cardiomyopathy and mitral valve prolapse, who require a specific treatment, if a SVTA is induced. In other patients the results of programmed atrial stimulation should be interpreted cautiously.

[Comparative effects of cibenzoline and hydroquinidine in the prevention of auricular fibrillation. A randomized double-blind study]

The objective of this study was to compare the efficacy and safety of cibenzoline (130 mg twice a day) and sustained-release hydroquinidine (300 mg twice a day) in the prevention of recurrent atrial fibrillation (AF). This randomized double-blind study was conducted in 87 patients, with a mean age of 62 years, presenting with a history of AF for 72 hours to a maximum of 3 years. After restoration of sinus rhythm, in order for the subjects to be included in the study, echocardiography had to reveal a left ventricular shortening fraction of more than 20%. Patients were followed for one year by clinical examination, ECG and 24-hour Holter monitoring performed 7 days after inclusion, then after 3, 6, 9 and 12 months. The two groups, treated with either cibenzoline (n = 40) or hydroquinidine (n = 44), were comparable. The AF recurrence rates with cibenzoline or hydroquinidine were 34.9% had 36.4% at 6 months, and 41.9% and 43.2% at 12 months, respectively (NS). Most recurrences occurred during the first month. Adverse effects were reported in 10 patients (23.3%) with cibenzoline and 12 patients (27.3%) with hydroquinidine. They led to discontinuation of treatment in 6 patients (14%) treated with cibenzoline and 5 patients (11.4%) treated with hydroquinidine. Serious adverse events included one death from hypoglycaemic coma and one case of persistent ventricular tachycardia with hydroquinidine. In conclusion, oral cibenzoline demonstrated the same antiarrhythmic activity as hydroquinidine in the long-term prevention of recurrent atrial fibrillation, with a similar degree of safety. This drug can therefore constitute an alternative to conventional antiarrhythmics in this context.

[Influence of the duration of myocardial infarction on QRS duration measured by signal averaged electrocardiography]

The aim of this study was to determine the influence of the chronicity of myocardial infarction on QRS duration. The signal-averaged electrocardiogram (SA ECG) was recorded with a 40 Hz filter in 239 patients with a history of myocardial infarction. The infarction was recent (up to 6 weeks) in 105 patients (group A) and chronic (> 1 year) in the other 134 cases (group B). In group A, 35 patients had inductible sustained ventricular tachycardia (VT) at less than 270/mn; 40 had negative electrophysiological investigations and 30 had inducible ventricular flutter or fibrillation (VF). In group B, 58 had inducible VT, 54 had negative investigations and 22 had inducible VF. The three SA ECG parameters (QRS duration, amplitude of RMS 40 and duration of LAS) differed significantly in subjects with VT with respect to those with negative investigations and inducible VF, irrespective of the chronicity of infarction. On the other hand, only QRS duration differentiated patients with recent infarction from those with chronic infarction, irrespective of the results of programmed pacing, QRS duration being longer in group B. The best diagnostic value of QRS duration for identifying subjects with VT < 270/mn and negative investigations was 110 ms in group A and 120 ms in group B (sensitivity 46% and 77.5% respectively). In chronic infarction, the increase in QRS duration was significantly correlated to the decrease in left ventricular ejection fraction. The authors conclude that the criteria of abnormality of QRS duration are dependent on the chronicity of myocardial infarction. Although a duration of 110 ms is abnormal in the early post-infarction period, after a period of one year, a value of 120 ms should be considered to be pathological, especially when the sequellae of infarction are important.

[Ablation of the bundle of His through a patent foramen ovale, by approach from the left side]

The authors report the case of a 60-year-old male patient in whom resection of the bundle of His via a right-sided approach to treat permanent very rapid atrial fibrillation was attempted, but failed. The bundle of His tissue was resected very easily on the left side due to the presence of a patent foramen ovale, which also avoided the risks of the left catheterism in this patient.

[Should a signal-averaged electrocardiogram be requested in the evaluation of malaise and syncope?]

In order to determine whether signal-averaged electrocardiography was useful in the diagnosis of syncopal ventricular tachycardia, 244 subjects with malaise or unexplained syncope without documented ventricular tachycardia underwent endocavitary electrophysiological study and signal-averaged electrocardiography with a 25 Hz bandpass filter. Ninety-three patients had no apparent cardiac disease whereas 151 patients had cardiac problems. ventricular tachycardia was induced in 91 patients. Fifty-two of them (57%) had ventricular late potentials. Twenty-two patients without inducible ventricular tachycardia also had late potentials (14%). The diagnostic value of signal-averaged electrocardiography depended on the cardiac disease: in the absence of cardiac disease, its sensitivity was poor (31%) but the specificity was excellent (96%). In the presence of cardiac disease, the sensitivity improved (63%) but the specificity was not as good (67%). The lack of sensitivity in the group with cardiac disease generally concerned subjects with inducible rapid ventricular tachycardia. The authors conclude that signal-averaged electrocardiography should not be requested in the investigation of unexplained syncope in subjects without cardiac disease to demonstrate abnormal ventricular excitability which is very rate in these subjects. On the other hand it is more valuable in those with underlying cardiac disease although inducible rapid ventricular tachycardia may still escape detection.

Programmed ventricular stimulation in survivors of acute myocardial infarction: long-term follow-up

The prognostic significance of ventricular tachyarrhythmias induced by programmed ventricular stimulation was evaluated in 492 consecutive survivors of acute myocardial infarction (AMI). Holter monitoring, signal-averaged electrocardiogram (ECG) and measurement of left ventricular ejection fraction (EF) were also performed. The protocol used up to 3 extrastimuli. Sustained monomorphic ventricular tachycardia (VT) < 270 beats/min, > 270 beats/min (ventricular flutter) (VFI), and ventricular fibrillation (VF) were induced in 99, 66 and 52 patients, respectively. Long term follow-up (mean 3.7 +/- 2.2 years) showed that most episodes of VT occurred during the first months following AMI (n = 14), but some patients (n = 6) could develop VT as late as 4 years after AMI. Sudden death (SD) (n = 22) always occurred during the first year following AMI. Multivariate analysis demonstrated that EF < 30% and induction of a VT < 270 beats/min were the only predictors for total cardiac death (P < 0.001). EF < 30%, induction of a VT < 270 beats/min and also of VFI (P < 0.05) were predictors for VT and SD: the risk was 4% in patients without inducible VT, 12% in those with inducible VF1, and 21% in those with inducible VT < 270 beats/min. In conclusion, induction of a sustained monomorphic VT < 270 beats/min or > 270 beats/min is a predictor of arrhythmic events during the first year as well as 4 years after myocardial infarction. However the risk of arrhythmic sudden death decreases after the first year, while the risk of VT persists. Because of the low positive predictive value of programmed stimulation (respectively 21% and 12% for the induction of a sustained VT and VFI), we recommended the indication of programmed stimulation in only the patients with one abnormal non-invasive investigation.

[Is the transesophageal approach preferable to endocavitary approach in the evaluation of Wolff-Parkinson-White syndrome?]

Now that the radical treatment of the Wolff-Parkinson-White syndrome is established, it is essential to evaluate the prognosis of this condition accurately. Initiation of atrial fibrillation is one of the factors which influence the prognosis. The aim of this study was to compare the results of electrophysiological studies performed by the endocavitary and transoesophageal approaches in the measurement of the initiation of atrial fibrillation. Twenty-six patients with a patent Wolff-Parkinson-White syndrome were studied by the two methods with a similar protocol: incremental atrial pacing to the Wenckebach point, programmed atrial stimulation using up to two extrastimuli, repeated with an infusion of 20 to 30 ug of isoproterenol. Sixteen patients had reciprocating nodal tachycardia or were asymptomatic (group I) and the other 10 had spontaneous atrial fibrillation (group II). In group I, atrial fibrillation was induced in 9 cases (56%) by the endocavitary and in two cases (12.5%) by the transoesophageal method. In group II, spontaneous atrial fibrillation was reproduced in all cases by the endocavitary and transoesophageal protocols. None of the patients in group I developed atrial fibrillation during follow-up (average 2 years +/- 9 months). The authors observe that all spontaneous atrial fibrillation of the Wolff-Parkinson-White syndrome can be triggered by oesophageal stimulation. The prevalence of atrial fibrillation was overestimated by endocavitary studies in asymptomatic or paucisymptomatic patients. The assessment of atrial vulnerability of a Wolff-Parkinson-White syndrome may therefore be performed by transoesophageal electro-physiological studies.

Changes in spontaneous sinus node rate after ventricular pacing as an estimate of autonomic tone: clinical applications

Rapid ventricular pacing (VP) reproduces neurohumoral variations associated with ventricular tachycardia. This study was set up to analyse the mechanisms that cause changes in sinus heart rate after rapid VP and to find the clinical factors that adapt sinus heart rate to VP, and the clinical value of the method. Rapid VP was performed in 356 patients aged 15 to 86 years, in increments of 10 beats, at progressively faster rates every 10 s up to 200 beats.min-1. Group I comprised 122 patients with no underlying heart disease; group II comprised 234 patients with an underlying heart disease. The sinus heart rate (HR) was initially accelerated (SR1), in comparison with the basal sinus HR, for 2 to 5 s (90.5 beats.min +/- 21 vs 71 +/- 19 in group I, 89.5 +/- 26 vs 76 +/- 16 in group II). Five seconds later, there was a decrease in HR (SR2) which was slower than the basal HR (62 beats.min +/- 22 in group I, 75 +/- 15 in group II). The variations in HR, defined as SR1-SR2/SR1, were significantly higher in group I than group II: 31 +/- 18% vs 19 +/- 15%, (P < 0.001). With the injection of 2 mg atropine in 14 group I patients the variations in HR were suppressed after ventricular pacing. When oral beta-blockers were administered to 21 group I patients, there were still significant changes in HR. The changes in HR were reproducible during electrophysiological study.(ABSTRACT TRUNCATED AT 250 WORDS)

[Hidden electric phenomena]

Concealed electrical phenomena are activations which penetrate the specialised tissue incompletely, which do not have a direct electrical effect but which usually affect the conduction of the following normal impulse. The phenomena are extremely common. They arise physiologically in the node of Aschoff Tawara and express the relationship between flutter waves and their propagation to the ventricle. Any extrasystole or ectopic rhythm may give rise to these phenomena and modify conduction in the anterograde or retrograde direction if the ectopic rhythm is ventricular, by slowing the rate but also, in some cases, by paradoxically improving it. In addition, some reciprocating nodal tachycardias are due to a concealed bundle of Kent invisible in sinus rhythm, the presence of which may be suspected by the ECG appearances of the reciprocating tachycardia (negative P wave in lead 1, phenomenon of delaying bundle branch block or simply the auriculogram after the ventriculogram.

[Changes in heart rate after ventricular stimulation; correlations with vagal tone]

The authors report a new method of studying the autonomic nervous system, especially vagal tone, during endocavitary electrophysiological studies. After termination of fixed ventricular pacing at incremental rates to 200/min, an initial acceleration of the heart rate is observed followed about 5 seconds later by a sudden slowing. This phenomenon was studied in 278 patients. Ninety seven patients had no cardiac disease: the variation in heart rate was 33 +/- 18%. In the 181 other patients with cardiac disease (ejection fraction 35 +/- 16%) the variation was only 21 +/- 16% (p < 0.01). When the ejection fraction was less than 30%, the variation was only 13 +/- 4%. When the heart rate variation was less than 10%, the prognosis was poor because, of the 48 patients with this sign, 13 died, whereas there were only 2 deaths in the 133 other patients with cardiac disease and preserved adaptation. In 14 patients without cardiac disease the injection of 2 mg of atropine suppressed all adaptation of the heart rate, whilst in 18 other patients, oral betablockers reduced the variation but it persisted to a significant degree. The authors conclude that the adaptation of the heart rate after rapid ventricular stimulation is probably a reflection of vagal tone and may be used to assess the prognosis of subjects undergoing electrophysiological investigations.

Value of oesophageal pacing in evaluation of atrial arrhythmias

The study of 'atrial vulnerability' is often clinically indicated but it requires the use of invasive intracardiac stimulation. The purpose of the study was to assess the use of oesophageal pacing in the evaluation of atrial tachyarrhythmias (ATA). Fifty-five patients with documented ATA (group I) and 60 without (group II) were studied. The protocol of oesophageal pacing consisted of atrial pacing up to the second-degree AV block and programmed stimulation in the control state and after isoproterenol infusion. ATA was induced in 47 group I patients (85%) either in the control state (n = 27) or during isoproterenol infusion (n = 20) and in three group II patients (5%). There was no other electrophysiological abnormality. The presence of underlying heart disease did not precipitate ATA in group II. In conclusion, because of its good sensitivity (85%) and specificity (95%) transoesophageal pacing could be used to evaluate atrial arrhythmias.

Criteria of QRS duration in relationship to the age of myocardial infarction

QRS duration is one of the most important factors analysed by signal-averaged electrocardiography. The purpose of the study was to compare three methods of QRS duration measurement (conventional 12 lead ECG, Frank vectorcardiogram [VCG] and signal-averaged electrocardiography [SA ECG]) and to look for the factors associated with changes in QRS duration. The recordings were made at the same time in 113 consecutive patients with a PC-based system ECG and VCG (Cardionics) and high resolution ECG (Cardionics) based on methods described by Simson. Patients with bundle branch block were excluded. All patients had presented a myocardial infarction and were studied either for spontaneous ventricular arrhythmias or systematically, early after infarction (3 to 6 weeks) in 45 patients (group I) or late after infarction (> 9 months) in 68 patients (group II). 21 patients of group I had inducible sustained monomorphic ventricular tachycardia (VT) (group I) and 24 did not (group Ib). 36 patients of group II had inducible VT (group IIa) and 32 did not (group IIb). The comparison of the 3 methods for the evaluation of QRS duration shows that the QRS duration was related to 2 factors, the inducibility of VT, and the age of the infarction: 1. QRS duration was prolonged in patients with inducible sustained VT in groups I and II. 2. QRS duration was longer in patients of group I than in group II. A value > 110 ms in group I was pathological, while a value > 120 ms was required ingroup II to be considered as pathological.(ABSTRACT TRUNCATED AT 250 WORDS)

Initiation of ventricular fibrillation by atrial fibrillation

We report the case of a patient who developed spontaneously a ventricular fibrillation during atrial fibrillation, 8 min after a perfusion of isoproterenol was stopped. Two mechanisms could explain the ventricular arrhythmia: silent ischaemia and a long-short cycle sequence just before ventricular fibrillation.

Correlation between inducibility of sustained ventricular tachycardia and QRS duration

Some studies provide a link between the width of QRS complexes and late potentials occurring at the end of the QRS complex in signal-averaged recordings. The purpose of this study was to compare three methods of QRS duration measurement: the conventional 12 lead ECG, the Frank vectorcardiogram (VCG) and the signal-averaged electrocardiogram. The recordings were made at a similar time in 121 consecutive patients with the Cardionics PC-based system (ECG and VCG) and the Cardionics high resolution ECG, based on methods described by Simson. Patients with bundle branch block were excluded. All patients had presented a myocardial infarction and were studied either for spontaneous ventricular arrhythmias or systematically 3 to 6 weeks after an acute myocardial infarction. The signal-averaged ECG and VCG QRS durations were similar in 41 patients without inducible ventricular arrhythmias and with normal signal-averaged ECG but were longer (P < 0.001) than the conventional ECG QRS duration. In 36 patients with spontaneous and inducible ventricular tachyarrhythmias, the QRS duration was significantly longer on signal-averaged ECG than on VCG (P < 0.05) and longer on VCG than on conventional ECG (P < 0.05). The QRS duration was also significantly (P < 0.001) longer with the three techniques in patients with spontaneous ventricular tachycardia (VT) than in patients without spontaneous and inducible VT. A QRS duration on VCG > or = 110 ms and on conventional ECG > or = 100 ms had a sensitivity of 93% and 77% and a specificity of 83% and 85% respectively for predicting an abnormal signal-averaged ECG. In conclusion, the measurement of QRS duration with the conventional ECG, VCG or the signal-averaged ECG could be a simple method to detect the patients with myocardial infarction prone to VT.

[Paroxysmal atrial fibrillation: main cause of syncope in hypertrophic cardiomyopathy]

The aim of this retrospective study was to determine the mechanism of syncope in idiopathic hypertrophic cardiomyopathy (HCM). An electrocardiographic study was undertaken in 43 patients with HCM: 27 (Group I) had a history of syncope and 16 (Group II) had no history of syncope but were investigated for conduction defects (n = 7) or unsustained ventricular tachycardia (VT) (n = 9). The stimulation protocol used programmed atrial pacing with 1 and 2 extrastimuli and ventricular pacing using up to 3 extrastimuli delivered at 2 sites. The following results were obtained: sustained atrial fibrillation (AF) (> 1 min) was induced in 21 patients in Group I (78%), 4 in Group II (25%); VT was induced in 3 patients in Group I (11%), and 3 in Group II (19%); infra-Hisian block was detected in 1 patient in Group I. The mechanism of syncope was elucidated in 23 patients in Group I (85%): one atrioventricular block 1 sinus node dysfunction, 18 atrial fibrillations, 2 associations of AF-VT and 1 VT. The authors conclude that the prevalence of inducible AF was higher in patients with HCA and syncope than in controls and HCM without syncope: this was the only detectable difference in 67% of patients with unexplained syncope. Paroxysmal AF could therefore explain malaise or syncope in up to 2/3 of cases of HCM.

[Outcome of Doppler parameters of left ventricular systolic function during atrial stimulation as a function of coronary disease]

The authors studied the effects of transoesophageal atrial pacing on Doppler parameters derived from flow in the left ventricular out flow tract (maximal velocity (V max), velocity-time integral (VTI), mean acceleration of aortic flow (Acc), acceleration force (AF) of the left ventricle). These parameters were recorded in patients with normal left ventricular wall motion at rest, with and without coronary disease. Eight patients had angiographically normal coronary arteries (Group 1) and 21 had coronary disease (Group 2) including 10 with an isolated stenosis of the left anterior descending artery (Group 2a) and 11 with multivessel disease (Group 2b). The heart rate was increased by increments of 20 beats per minute from 90 to 130 each minute. In coronary patients, atrial pacing resulted in a fall in V max from 0.99 +/- 0.15 to 0.90 +/- 0.12 m/s, p < 0.0005 and in AF from 23.1 +/- 6.3 to 19.6 +/- 4.8 Kdynes, p < 0.0005, whereas the Acc remained stable (13.51 +/- 3.27 and 13.53 +/- 2.47 m/s/s, NS). Conversely, V max (1.04 +/- 0.11 and 1.04 +/- 0.11, NS) and AF (25.2 +/- 5.7 and 26.3 +/- 6.7, NS) were unchanged in normal controls and the Acc improved from 13.87 +/- 3.61 to 17.04 +/- 3.49, (p < 0.05). The VTI fell significantly in both groups. The percentage variations of V max, Acc and AF were significantly different in coronary patients compared with normal controls. There were no differences between the two coronary subgroups.(ABSTRACT TRUNCATED AT 250 WORDS)

[Results of systematic programmed ventricular stimulation after myocardial infarction. Which protocol should be recommended?]

The authors report the prognostic value of ventricular arrhythmias induced by routine programmed ventricular stimulation after the acute phase of myocardial infarction. The protocol consisted of two extrastimuli in the first 185 patients and 3 extrastimuli in 308 patients. The use of 3 extrastimuli increased the incidence of inducible sustained monomorphic ventricular tachycardia (VT) < 270/mn, from 17 to 22% and, more importantly, that of ventricular fibrillation from 4 to 17%. Induction of ventricular flutter (monomorphic VT > 270/mn) was not increased. A long follow-up period (average 4 +/- 2 years) showed that the risk of VT was increased during the first months after infarction (n = 14), and that, 4 years later, other patients develop VT (n = 6). The risk of serious arrhythmias (VT and sudden death) was significantly higher in patients with inducible VT < 270/mn (20%) than in patients without inducible VT, but it was also higher in patients with inducible ventricular flutter (12.5%). The use of a third extrastimulus has a low positive predictive value for arrhythmic events (10%). This study confirms that the induction of sustained monomorphic VT after myocardial infarction is associated with an increased risk of arrhythmic events but the positive predictive value is relatively low (17%). In view of the risk of inducing non-specific ventricular fibrillation, the authors recommended using a stimulation protocol with only 2 ventricular extrastimuli.

[Cardiac arrest reversed: causes and treatments]

The aim of this study was to report the probable mechanism of resuscitated cardiac arrest without acute myocardial infarction. Fifty-seven cases were recensed but the arrest was only documented in 44 subjects. Systematic non-invasive investigations and programmed stimulation showed that the diagnosis of cardiac arrest was probably false in 5 patients and, in the others, that a ventricular arrhythmia was probably the cause (63%). The occurrence of cardiac arrest under antiarrhythmic therapy may reveal an underlying abnormality requiring specific therapy (3/8). The absence of cardiac disease did not exclude the risk of VF (3 cases). When reproducible, ventricular arrhythmias were present during programmed stimulation, the prognosis was good if the arrhythmia could not be induced under antiarrhythmic therapy. It was easier to find an effective treatment for inducible ventricular fibrillation-flutter (13/17) than for inducible ventricular tachycardia (7/17). The prognosis was poor if the arrhythmia was unchanged during programmed stimulation under antiarrhythmic therapy and non-pharmacological treatment was required.

Effect of isoproterenol on serum potassium and magnesium

Some ventricular arrhythmias can be related to a decrease in the level of potassium (K) and/or magnesium (Mg). Because adrenergic stimulation decreases serum K+ and Mg++, we decided to investigate the effects of a beta-receptor agonist, isoproterenol, on serum K+ and Mg++, and their consequences on the induction of tachycardia. Programmed atrial and ventricular stimulation was performed in 95 patients before and during infusion of 1.6 micrograms.ml-1 of isoproterenol. During isoproterenol infusion, 61 patients had no inducible tachycardias (group I) and 34 had inducible sustained tachycardias (group II): 16 of them (group IIA) had inducible sustained supraventricular tachyarrhythmias and 18 (group IIB) had inducible sustained ventricular tachycardia. Serum K+ and Mg++ were measured at the end of stimulation in the control state and during isoproterenol infusion. The basal values in groups I and II did not differ (3.8 +/- 0.38 vs 3.86 +/- 0.39 mEq.l-1 for K+, and 20.18 +/- 2.68 vs 19.83 +/- 1.63 mg.l-1 for Mg++). Isoproterenol infusion induced a significant (P < 0.001) hypokalaemia in all groups and a decrease in serum Mg in group II: there was a significant decrease in serum Mg++ (P < 0.05) in group IIA (19.55 +/- 1.7 vs 20.4 +/- 4.6). The decrease in serum Mg++ in group IIB (18.9 +/- 1.55 vs 19.32 +/- 1.63) was not significant. However the serum Mg++ level during isoproterenol infusion was significantly lower in group IIB than in group I. In conclusion, the infusion of isoproterenol was responsible for a significant hypokalaemia, which did not explain the induction of tachycardia.(ABSTRACT TRUNCATED AT 250 WORDS)

[Non invasive exploration of ventricular tachycardia]

Complementary investigation of ventricular tachycardia requires the use of non-invasive techniques before treatment, before considering other methods. Non-invasive investigations are usually complementary. Signal averaged electrocardiography allows detection of after potentials, a sign of a reentry circuit. Twenty-four hour Holter monitoring and exercise testing may reveal ventricular arrhythmias which could induce tachycardia. They may also show a "trigger" of tachycardia such as the catecholamine factor which is particularly sensitive to exercise testing and Holter monitoring. The latter investigation also informs on the variability of the heart rate, the disappearance of which is an argument in favour of the risk of sudden death. Holter recording and exercise testing should also be repeated after starting antiarrhythmic treatment to control the efficiency and detect possible proarrhythmogenic effects. The problem with these investigations is that they lack sensitivity as they are sometimes normal in patients with documented VT or lack specificity, ventricular arrhythmias being common and often without clinical significance.