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Biomedical subjects

P Coumel

Publications and source records attributed to P Coumel.

At least 73 records · Page 4Linked to original sources
PubMed1996

Determinants of spontaneous occurrence of sustained monomorphic ventricular tachycardia in right ventricular dysplasia.

OBJECTIVES: We sought to demonstrate the determinants of spontaneous onset of ventricular tachycardia in right ventricular dysplasia. BACKGROUND: Sudden death during athletic activities has been described in patients with right ventricular dysplasia, but few data are available on the clinical circumstances of well tolerated ventricular tachycardias. METHODS: The spontaneous occurrence of 43 episodes of sustained monomorphic ventricular tachycardia was recorded during ambulatory electrocardiographic (Holter) monitoring in 12 patients. RESULTS: The ventricular tachycardia usually occurred without a significant immediate precipitating arrhythmic event: Atrial arrhythmia was never present, and long-short cycle sequences by postextrasystolic pauses or runs of polymorphic extrasystoles were also unusual (four episodes of ventricular tachycardia each). Finally, no arrhythmia was present immediately before the tachycardia in 36 (84%) of the 43 episodes and in 8 of 12 patients. Examination of the sinus rate before the initial episode of tachycardia in each patient showed a continuous increase from 30 min to the few cycles before the tachycardia (mean RR decrease from 876 +/- 778 to 830.5 +/- 189 ms, with a mean slope of approximately 8.4 ms/min; both p = 0.01 by Wilcoxon test). A within-patient comparison showed that the first cycle of the ventricular tachycardia was shorter than that of runs or couplets (389 +/- 88 vs. 453 +/- 121 and 520 +/- 133 ms, p = 0.03 and p < 0.01, respectively, by paired t test) and that the second cycle was shorter than that of runs (383 +/- 96 vs. 435 +/- 120 ms, p = 0.03). Sinus rate measured 15 beats before the event was higher for ventricular tachycardia than for isolated beats (mean RR interval 835 +/- 184 vs. 908 +/- 153 ms, p < 0.01). CONCLUSIONS: Increased heart rate and shortening of the coupling intervals of the first cycles before the tachycardia are due to a change in the vagosympathetic balance with an increased sympathetic tone. This increase appears to be the main determinant of the ventricular tachycardia in this disease in contrast to the multifactorial origin of ventricular tachycardia due to coronary heart disease. It should be considered in patients participating in strenuous athletic activities.

Adult↗
PubMed1996

Are serial Holter QT, late potential, and wavelet measurement clinically useful?

Clinical centers are increasingly using new techniques such as Holter QT, late potential, and wavelet measurements. However, we lack validated databases for the assessment of the performance of the signal-processing methods and their reproducibility. Failure of the QT interval to adapt to changes in the heart rate is considered to be a more meaningful parameter than QT prolongation itself. In this study, different factors that may affect the reproducibility of QT and QTm (onset of the QRS to the maximum of T) measurement are analyzed: the incidence of sympathetic tone and parasympathetic activity on low- and high-frequency QT variability, the very low frequency dependency of the QT interval to changes in the R-R interval, changes in the heart's position, and measurement errors. Typical root-mean-square values of the beat-to-beat measurement errors in upright-position Holter recordings are only 1.5 ms for QT versus 3.4 ms for QTm. Although the dependence of the QT interval on the heart rate is well established, the method for rate correction of the QT interval remains controversial. None of the formulas for heart rate adjustment of the QT previously proposed provide complete correction for all of the rate influences involved due to "memory phenomenon"; that is, there is a time delay, ranging up to 3-4 minutes, between a change in heart rate and the subsequent change in the QT interval. This problem has been solved by developing patient-specific neural networks that are trained to "identify" the dynamic behavior of the QT interval (or QTm) as a function of the R-R interval in order to predict the beat-to-beat changes of the QT interval as a function of the measured beat-to-beat changes of the R-R interval. Computing the differences between the predicted and the measured QT interval will allow for the detection of any significant deviations, both in the steady-state and transient conditions. Recent developments in the analysis of the high-resolution electrocardiogram (HRECG) in the time domain and frequency domain, with emphasis on the assessment of the reproducibility of late potential and wavelet measurements, are also reported in this study. The two main causes of variability in HRECG analysis are physiology and, for time-domain analysis, intermanufacturer variability. Physiologic changes can be overcome by standardizing the clinical protocols and repeating the recordings. The most important technical requirement for the proper use of late potentials is to standardize the algorithm for the detection of QRS offset among different late potential analyzing machines so that clinical data can be exchanged. The recently introduced wavelet transform provides a fruitful alternative to the more classical time-domain methods. Preliminary results show an 8 to 15% performance improvement over conventional time-domain analysis for the stratification of the HRECG after myocardial infarction. Reproducibility is excellent, up to 100%, but needs to be assessed on larger populations matched for age, sex, and pathology.

Artifacts↗
PubMed1996

Progressive ECG changes in arrhythmogenic right ventricular disease. Evidence for an evolving disease.

Electrocardiography results were used to assess diagnosis and evolution of arrhythmogenic right ventricular disease. The initial ECG presentation and long-term changes were analysed in 74 consecutive patients with symptomatic ventricular tachycardia and arrhythmogenic right ventricular disease. On first available tracings, a left axis deviation of the QRS was found in 18 patients. The QRS length in V1 was > or = 110 ms in 39 patients, an epsilon wave was present in 17, and a complete right bundle branch block in four patients. The T wave was negative in V1-V3 in 37 patients (50%). In 36 patients, long-term electrocardiographic follow-up of 9.5 +/- 3.2 years was available. During this period, ECG changes were observed in 20 patients (56%): negative T waves in 11 patients, a new left axis deviation in three, QRS enlargement in 13 (including eight right bundle branch block), right atrial hypertrophy in three, and paroxysmal or established atrial fibrillation in three. On studying all 110 ECG tracings (74 initial recordings +36 follow-up ECGs), we found a strong correlation between QRS or T wave changes and the length of follow-up after the first symptom; mean time interval between first ventricular tachycardia and ECG recording was significantly longer in patients with negative T waves in the right precordial leads, QRS enlargement, or left axis deviation, than in patients without such abnormalities. ECG abnormalities were more frequent at 10 year and 5 year follow-up than on initial tracings. A normal ECG was found in 40% of patients during the first year of follow-up, 8% at 5 years, and never later than the 6th year. In conclusion, electrocardiographic diagnosis of arrhythmogenic right ventricular disease may be difficult in the initial stage of the disease, since a normal ECG is found in up to 40% of patients. During the follow-up, progressive and characteristic ECG changes will occur. Arrhythmogenic right ventricular disease can be excluded if the ECG is found to be normal 6 years or later after a first ventricular tachycardia attack.

Adolescent↗
PubMed1996

Autonomic influences in atrial tachyarrhythmias.

The electrophysiologic characteristics of atrial cells (action potential duration and refractoriness, conduction speed) are modulated differently by vagal and sympathetic influences. The former tend to favor macroreentry phenomena, whereas the latter favor abnormal automaticity and triggered activity. In normal hearts, vagal influences are predominant, thus explaining why the clinical pattern of vagally mediated paroxysmal atrial fibrillation is preferentially observed in the absence of detectable heart disease, in young male adults, with an ECG pattern of common flutter alternating with fibrillation. Sympathetically mediated atrial fibrillation is observed in the presence of any heart disease, the first effect of which is to provoke a vagal withdrawal. The clinical history is a reliable guide for determining which type of physiologic autonomic predominance contributes to destabilization of the arrhythmogenic substrate, but observing the behavior of sinus rate variability just preceding the onset of the arrhythmia only permits documentation of the mechanism. The role of autonomic influences should be taken into consideration every time conventional antiarrhythmic treatment is insufficient. Beta blockers as well as digitalis may be either beneficial or detrimental, depending on the causal mechanism, so the choice of their use as a single or a combined therapy should be appropriate.

Adult↗
PubMed1995

Catecholaminergic polymorphic ventricular tachycardia in children. A 7-year follow-up of 21 patients.

BACKGROUND: Primary ventricular tachyarrhythmias are rarely seen in children. Among them, catecholaminergic polymorphic ventricular tachycardia has a poor spontaneous outcome. Its diagnosis is often delayed after the first symptoms, which is unacceptable because treatment with the appropriate beta-blocker prevents sudden death. METHODS AND RESULTS: We observed 21 children (mean +/- SD age, 9.9 +/- 4 years) at the time of the diagnosis who had no structural heart disease and a normal QT interval on routine ECG. They were referred for stress- or emotion-induced syncope related to ventricular polymorphic tachyarrhythmias. The arrhythmia, consisting of isolated polymorphic ventricular extrasystoles followed by salvoes of bidirectional and polymorphic tachycardia susceptible to degeneration into ventricular fibrillation, was reproducibly induced by any form of increasing adrenergic stimulation. There was a familial history of syncope or sudden death in 30% of our patients. On receiving therapy with the appropriate beta-blocker, the patients' symptoms and polymorphic tachyarrhythmias disappeared. During a mean follow-up period of 7 years, three syncopal events and two sudden deaths occurred, probably due to treatment interruption. CONCLUSIONS: The entity of adrenergic-dependent, potentially lethal tachyarrhythmia with no structural heart disease deserves to be individualized. It may form a variant of the congenital long QT syndrome in which the ECG marker is lacking; this primary ventricular arrhythmia must be looked for in a pediatric patient with stress- or emotion-induced syncope because only beta-blocking therapy can prevent sudden death and therefore must be given for the patient's lifetime.

Adrenergic beta-Antagonists↗
PubMed1995

Spontaneous sequences of onset of torsade de pointes in patients with acquired prolonged repolarization: quantitative analysis of Holter recordings.

OBJECTIVES: This study investigated the cycle length changes preceding the spontaneous onset of torsade de pointes in patients with acquired prolonged ventricular repolarization. BACKGROUND: Torsade de pointes is a polymorphic ventricular tachycardia generally associated with prolonged ventricular repolarization. Because torsade de pointes is not inducible by programmed electrical stimulation, quantitative analysis of Holter recordings of spontaneous episodes may clarify the mechanisms favoring the onset of torsade de pointes in actual clinical conditions. METHODS: The digitized Holter recordings of 12 patients were analyzed by a computerized Holter system (ATREC). All arrhythmias were grouped according to three classes: 1) isolated premature ventricular beats (n = 47,147, mean/patient [+/- SD] 3,929 +/- 11,571); 2) salvos of 2 to 4 consecutive beats (n = 2,003, mean/patient 167 +/- 359); 3) torsade de pointes > or = 5 beats (n = 105, mean/patient 9 +/- 11). For each patient and class of arrhythmias, six variables were computed from the 10 min and the 10 cycles preceding the event onset. RESULTS: A significant heart rate increase in the last minute (p < 0.01) and typical oscillatory short-long-short cycle length sequences preceded the onset of arrhythmias, with greater oscillation preceding torsade de pointes than salvos and premature ventricular beats. The cycle lengths preceding the onset were highly correlated with the class of arrhythmias (r = 0.65, p < 0.005) and allowed the correct classification of 69% of events by discriminant analysis (p < 0.0001). A significant negative correlation was observed between the duration of torsade de pointes and the mean length of the initial cycles (r = -0.62, p < 0.001), indicating that longer torsade de pointes had a faster rate than that at onset. CONCLUSIONS: In patients with acquired prolonged repolarization, the spontaneous onset of ventricular arrhythmias was preceded by an increasing heart rate in the last minute and escalating oscillatory "short-long-short" cycle length patterns, with greater oscillations preceding torsade de pointes than salvos and isolated ventricular beats. These findings suggest that adrenergic- and pause-dependent mechanisms (possibly inducing afterdepolarizations and triggered activity) may have a synergetic role in the genesis of complex ventricular arrhythmias associated with delayed ventricular repolarization.

Aged↗
PubMed1995

Holter functions of the implantable cardioverter defibrillator: what is still missing?

The technology of the implantable cardioverter defibrillator (ICD) offers the opportunity to overcome the present limits of the invasive and noninvasive approaches of clinical electrophysiology. The invasive approach enables us to reproduce severe arrhythmias if they are inducible, but does not give information concerning the way they spontaneously arise. The noninvasive approach (Holter) gives this information, but it usually concerns only trivial arrhythmias with different therapeutic targets. One hopes in the future, by means of an important extension to ICD technology, which is not technically possible for the time being, to have access to pertinent information and to a better understanding of the circumstances leading to severe spontaneous arrhythmias, potentially lethal. For the moment, we only have the diagnostic certainty leading to the therapeutic intervention. It is based on an ECG and on the sequence of cardiac cycles preceding the rhythmic controlled accident. These data allow verification of but not explanation of the events. To have a chance to be understood and explained, these "events" must be replaced in the context of the "nonevents." Ideally, one should have all the gross information concerning the last 24 hours and subsequently analyze them. It is already a big step, thanks to the defibrillators the right to therapeutic error has been gained, a unique and fatal accident has been transformed into a repeatable event, and therefore, access is gained to the evolution of the responsible disease.

Defibrillators, Implantable↗
PubMed1995

Indications of implantable defibrillator.

Implantable cardioverter defibrillators are devices capable of detecting and terminating ventricular tachycardias or fibrillations. They are utilized in the treatment of severe ventricular tachyarrhythmias, and their efficacy in the prevention of sudden death is demonstrated. As a matter of fact, despite the new antiarrhythmics available, and despite nonpharmacological therapies like radiofrequency ablation or surgery, the prognosis of such tachyarrhythmias remains serious.

Defibrillators, Implantable↗
PubMed1995

Readjusting the localization of long QT syndrome gene on chromosome 11p15.

Long QT syndrome (LQT) is an autosomal dominant cardiac disease characterized by ventricular arrhythmia. A first locus for LQT has been identified on chromosome 11p15.5 (LQT1), closely linked to HRAS. To refine the location of LQT1, microsatellites were genotyped in 8 French families and the following order was determined: tel-HRAS-DRD4-D11S922-D11S4046- IGF2-INS-TH-D11S1318-D11S1323-D11S1338-D11S90 9-D11S1346-cen. By haplotype analysis, 12 crossing-over events were identified in affected and unaffected subjects, delineating the LQT1 candidate region to 7 cM. This new delineated localization between D11S1318 and D11S1323 is in a more centromeric region than previously thought and is 5 cM proximal to HRAS.

Chromosome Mapping↗
PubMed1995

[Value of the exercise test in the study of arrhythmia].

Exercise testing may be used to assess symptoms occurring on effort, to search for and evaluate arrhythmias or conduction defects, antiarrhythmic drugs, pacemakers or implantable cardioverter defibrillators. Interpretation of exercise testing is difficult because of the complexity of the factors in play. Exercise itself induces changes in myocardial metabolism and the autonomic nervous system, the nature and importance of which are influenced by the underlying cardiac disease and the presence of cardiac failure or myocardial ischaemia. This is particularly true when studying the behaviour of arrhythmias on effort, which depends on many parameters, in that they may appear or disappear during exercise, irrespective of their relationship to autonomic nervous system activation. The main problem lies in the interpretation of changes in the heart rate before the onset of an arrhythmia. The sinus rhythm is both a passive indicator of the vago-sympathetic equilibrium and one of the determining factor of the arrhythmia (relationship to the rate), but it is, itself, dependent on the presence of myocardial dysfunction, a source of arrhythmias, and its changes then become difficult to interpret. These reasons explain why exercise testing is certainly a valuable tool in assessing arrhythmias but the poor reproducibility, especially in the evaluation of ventricular arrhythmias, advises prudence in the interpretation of results.

Arrhythmias, Cardiac↗
PubMed1995

[Dynamics of ventricular repolarisation].

The clinical value of assessing the QT interval is obvious as it is a marker of ventricular depolarisation and repolarisation and it allows identification of clinical situations carrying a high risk of ventricular fibrillation and sudden death. Until the last few years, analysis of ventricular repolarisation was based on analysis of conventional surface electrocardiography. Technical difficulties explain the limits of our knowledge of the dynamics of ventricular repolarisation. This situation is beginning to change rapidly by computerised analysis of Holter monitoring, opening up a particularly complex and important field of research. The duration of the QT interval depends on different factors, especially changes in electrolyte balance, effects of certain drugs, and changes in heart rate and autonomic nervous system tone. The difficulty resides in selecting the pertinent data in order to study separately the effects of heart rate and those of the autonomic nervous system. The initial results show that this analysis provides important information for diagnosis and probably prognosis, on the status of the myocardium and the action of the autonomous nervous system. They require confirmation and validation on larger series of patients with different pathological conditions.

Action Potentials↗
PubMed1994

Antiarrhythmic drugs: how to evaluate them?

For two decades, the evaluation of antiarrhythmic drugs has essentially been based on the count of premature beats during Holter monitoring and the inducibility of tachyarrhythmias during electrophysiologic studies. These approaches are convenient to provide firmly established short-term evaluations of the effects of type I agents in relatively benign arrhythmias occurring in patients with good cardiac function. However, the situation is much more uncertain for long-term outcome in serious tachyarrhythmias occurring in severely diseased patients with an altered myocardium. In addition, indications for type I agents are not really adapted to beta-blockers and type III drugs, the effects of which are much more difficult to assess and depend at least in part on the target arrhythmia. There is an interest in evaluating drug efficacy in terms of responders and nonresponders and in understanding the reasons for a response rather than reliance on pure quantitative data, the meaning of which may be less relevant in the final analysis. We must also recognize the need to reconcile the multiple obstacles encountered when severely diseased patients must be managed efficaciously and safely in the long term with new drugs, the effects of which need objective assessment.

Adrenergic beta-Antagonists↗
PubMed1994

Clinical relevance of assessing QT dynamicity in Holter recordings.

Ventricular repolarization (VR) duration is an electrophysiologic parameter that is poorly explored in the conventional electrocardiogram. The heart rate (HR) and the autonomic nervous system (ANS) condition its variations. The static QT measurement in the surface electrocardiogram and its correction using the Bazett formula constitute inadequate tools. The three-dimensional Holter recordings and their computerized analysis are better adapted to assess the dynamicity of VR, a relevant image of the myocardial state. QT and RR values are linearly correlated over 24 hours, but this does not allow one to study specifically the respective roles of HR and ANS on repolarization changes. To do so, it is necessary to select appropriately the QRST complexes according to their environment: not only the last RR cycle but the mean HR over the preceding minutes, and the circadian influences must be controlled to differentiate the role of the short- and long-term influences. Combining the ATREC and the CAVIAR softwares now permits control of both time and space dimensions and to measurement of the QT variations with a precision of the order of 1 ms, a performance necessary to assess tiny but meaningful changes. The QT interval is shorter, and the slope of the QT/RR regression line is steeper at daytime compared with night, and many situations modify this normal behavior. Aging lengthens the QT interval and reduces the day-to-night differences of QT duration and dynamicity. In contrast with duration, dynamicity does not depend on gender. Any heart disease, left ventricular hypertrophy, or heart failure alter QT dynamicity.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗