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PubMed1990

[Electrophysiologic study in 42 cases of unexplained syncope].

Forty two patients with unexplained syncope underwent intracardiac electrophysiologic study to identify the cause of syncope and to select appropriate therapy. Electrophysiologic abnormalities were demonstrated in 26 patients (62%): sustained ventricular tachycardia in 7 patients (27%) of the abnormal group. His-Purkinje system dysfunction in 4 (15.4%), atrioventricular nodal dysfunction in 4 (15.4%), atrioventricular nodal reentrant supraventricular tachycardia in 2 (7.7%), atrial flutter in 1 (3.8%), sinoatrial nodal dysfunction in 2 (7.7%), carotid sinus hypersensitivity in 3 (11.5%) and hypervagotonia in 3 (11.5%). The results of this study suggest that electrophysiologic study should be considered in patients with unexplained syncope. Electrophysiologic study in an effective method for approaching the diagnosis and improving management of unexplained syncope.

Adult↗
PubMed1995

[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.

Arrhythmias, Cardiac↗
PubMed1983

Electroversion after verapamil administration.

Forty-nine consecutive patients (44 with atrial fibrillation and five with atrial flutter) received 10 mg of verapamil five to seven minutes before elective electroversion, to evaluate the feasibility of the latter while verapamil effects were present. Excluded were patients with moderate-to-severe heart failure, acute myocardial infarction, mean ventricular rate lower than 70 beats/minute, those receiving any antiarrhythmic drug other than digoxin, and those in whom sinus node dysfunction was suspected. In six patients, eight complications took place: four instances of hypotension (systolic blood pressure below 80 mm Hg), two instances of junctional escape rhythm (47 and 63 beats/minute) and two instances of junctional tachycardia. In all four instances of hypotension, return to normal values of blood pressure was spontaneous (within five minutes in three patients). Rhythm disturbances were transient, without clinical relevance. This study suggests that electroversion can be safely carried out during clinical action of verapamil in properly selected patients, and that occasional, self-limited hypotension is the only complication of clinical significance to be expected.

Adolescent↗
PubMed2003

Are electrophysiological studies needed prior to defibrillator implantation?

At present, patients with documented sustained VT or resuscitated cardiac arrest (CA) are treated with ICDs. The aim of this study was to retrospectively evaluate if a routine electrophysiological study should be recommended prior to ICD implantation. In 462 patients referred for ICD implantation because of supposedly documented VT (n = 223) or CA (n = 239), electrophysiological study was routinely performed. In 48% of the patients with CA, sustained VT or VF was inducible. Electrophysiological study suggested conduction abnormalities (n = 11) or supraventricular tachyarrhythmias (n = 3) in conjunction with severely impaired left ventricular function to have been the most likely cause of CA in 14 (5.9%) of 239 patients. Likewise, sustained VT was only inducible in 48% of patients with supposedly documented VT. Of these inducible VTs, nine were diagnosed as right ventricular outflow tract tachycardia or as bundle branch reentry tachycardia. Supraventricular tachyarrhythmias judged to represent the clinical event were the only inducible arrhythmia in 35 (16%) patients (AV nodal reentrant tachycardia [n = 7], AV reentry tachycardia [n = 4], atrial flutter [n = 19], and atrial tachycardia [n = 5]). Based on findings from the electrophysiological study, ICD implantation was withheld in 14 (5.9%) of 239 patients with CA and in 44 (19.7%) of 223 patients with supposedly documented VT. During electrophysiological study, VT or VF was only reproducible in about 50% of patients with supposedly documented VT or CA. Electrophysiological study revealed other, potentially curable causes for CA or supposedly documented VT in 12.6% (58/462) of all patients, indicating that ICD implantation can potentially be avoided or at least postponed in some of these patients. Based on these retrospective data, routine electrophysiological study prior to ICD implantation seems to be advisable.

Chi-Square Distribution↗
PubMed1999

[Incidence, clinical characteristics and prognostic significance of supraventricular tachyarrhythmias in acute myocardial infarction].

OBJECTIVES: The study of incidence and prognostic significance of supraventricular tachyarrhythmias in patients with acute myocardial infarction. PATIENTS AND METHODS: Prospective study on 1,239 patients consecutively admitted because of a diagnosis of acute myocardial infarction. Clinical characteristics, indexes of myocardial infarction and complications were analysed. RESULTS: Supraventricular tachyarrhythmias were observed in 116 (9.3%) cases: atrial fibrillation in 96 (7.7%); atrial tachycardia in 15 (1.2%); and atrial flutter in the remaining five cases (0.4%). Patients with supraventricular tachyarrhythmias were older, and presented higher heart rate, lower blood pressure, a higher number of affected leads in ECG, and higher Killip class. A higher creatine kinase peak and a lower left ventricular ejection fraction were associated with the presence of supraventricular tachyarrhythmias. Predictors of supraventricular tachyarrhythmias were: age, systolic blood pressure, number of affected leads in ECG, and congestive heart failure at admission. The following complications were found more frequently in patients with supraventricular tachyarrhythmias: bundle-branch block, complete A-V block, ventricular tachycardia, ventricular fibrillation; heart failure; stroke; and mortality, in-hospital 18.1% vs 11.1% (p < 0.05) and one-year, 38.7% vs 18.4% (p < 0.001). The logistic regression model showed that supraventricular tachyarrhythmias had no independent prognostic value on mortality. CONCLUSIONS: The appearance of supraventricular tachyarrhythmias during the acute phase of myocardial infarction is a relatively frequent finding, often associated with older age and larger infarctions. Supraventricular tachyarrhythmias are accompanied by higher short and long-term mortalities, although there is no independent prognostic significance.

Age Factors↗
PubMed2000

Nonfluoroscopic three-dimensional mapping for arrhythmia ablation: tool or toy?

INTRODUCTION: Conventional mapping and ablation rely on fluoroscopy, which can result in imprecise positioning of the ablation catheter and long fluoroscopic exposure times. We evaluated a nonfluoroscopic three-dimensional mapping system, termed CARTO, and compared the results of ablation using this technique with those of conventional mapping. METHODS AND RESULTS: We compared the results of 88 arrhythmia ablations (79 patients) using CARTO with 100 ablations (94 patients) using the conventional technique. The ablations were separated into four groups: (1) AV nodal reentrant tachycardia (AVNRT); (2) atrial tachycardia/flutter; (3) ventricular tachycardia (VT); and (4) bypass tract tachycardia. We compared the success rate, complications, and fluoroscopy and procedure times. The ablation outcomes were excellent and comparable in all four types of the arrhythmias between the two techniques. Major complications included one cardiac tamponade in each group and one second-degree AV block in the conventional group. Fluoroscopy time was shorter using the CARTO technique: 10+/-7 versus 27+/-15 minutes for AVNRT (P < 0.01), 18+/-17 versus 44+/-23 minutes for atrial tachycardia and flutter (P < 0.01), 15+/-12 versus 34+/-31 minutes for VT (P < 0.05), and 21+/-14 versus 53+/-32 minutes for bypass tract tachycardia (P < 0.01). Procedure times were similar except for the bypass tract patients, which was shorter in the CARTO group, 4+/-1.3 versus 5.5+/-2.5 hours (P < 0.01). CONCLUSION: The electroanatomic three-dimensional mapping technique reduced fluoroscopy time and resulted in excellent outcome without increasing the procedure time.

Atrial Flutter↗
PubMed2000

Atrial flutter in the perinatal age group: diagnosis, management and outcome.

OBJECTIVES: The aim of this retrospective study was to evaluate perinatal atrial flutter (AF) and the efficacy of maternally administered antiarrhythmic agents, postpartum management and outcome. BACKGROUND: Perinatal AF is a potentially lethal arrhythmia, and management of this disorder is difficult and controversial. METHODS: Forty-five patients with documented AF were studied retrospectively. RESULTS: Atrial flutter was diagnosed prenatally in 44 fetuses and immediately postnatally in 1 neonate. Fetal hydrops was seen in 20 patients; 17 received maternal therapy, 2 were delivered and 1 was not treated because it had a severe nontreatable cardiac malformation. In the nonhydropic group of 24 patients, 18 were treated and the remaining 6 were delivered immediately. In the hydropic group, 10 received single-drug therapy (digoxin or sotalol) and 7 received multidrug therapy. In the nonhydropic group, 13 received a single drug (digoxin or sotalol) and 5 received multiple drugs. One patient with rapid 1:1 atrioventricular conduction (heart rate 480 beats/min) died in utero and another died due to a combination of severe hydrops because of the AF, sotalol medication, stenosis of the venous duct and hypoplastic placenta. Of the 43 live-born infants, 12 were in AF at birth. Electrical cardioversion was successful in eight of nine patients. No recurrences in AF have occurred beyond the neonatal period. Four patients with fetal flutter and hydrops showed significant neurological pathology immediately after birth. CONCLUSIONS: Fetal AF is a serious and threatening rhythm disorder, particularly when it causes hydrops, it may be associated with fetal death or neurological damage. Treatment is required and primarily aimed at reaching an adequate ventricular rate and preferably conversion to sinus rhythm. Digoxin failed in prevention of recurrence at time of delivery in a quarter of our patients, whereas with sotalol no recurrence of AF has been reported, suggesting that class III agents may be the future therapy. Once fetuses with AF survive without neurological pathology, their future is good and prophylaxis beyond the neonatal period is unnecessary.

Anti-Arrhythmia Agents↗
PubMed1998

[Radiofrequency catheter ablation of atrial flutter and atrial fibrillation].

Radiofrequency catheter ablation is now considered as a curative approach in patients with typical atrial flutter. Typical atrial flutter is due to a macrore-entrant circuit within the right atrium and it can be eliminated by a linear lesion in the isthmus between the tricuspid annulus and the vena cava inferior. The electrophysiological criterion of a bidirectional isthmus block has been shown to reduce the recurrence rate of atrial flutter after catheter ablation, thus achieving long-term cure of typical atrial flutter. Acute success rates of 85 to 90% and recurrence rates of 10 to 15% have been reported. The risk of paroxysmal atrial fibrillation continues to be clinically relevant in patients who underwent successful ablation of atrial flutter, in particular in patients with previously documented atrial fibrillation. The incidence of a new onset of atrial fibrillation after ablation of atrial flutter seems to be approximately 20%. Isthmus ablation has also been shown to be beneficial for the majority of patients with typical atrial flutter and atrial fibrillation: In addition to an elimination of typical atrial flutter the isthmus ablation apparently reduces the incidence of paroxysmal atrial fibrillation. At present, atrial fibrillation can only be treated by catheter ablation as a curative approach in the rare cases where an accessory pathway, an AV nodal re-entrant tachycardia, typical atrial flutter or an ectopic atrial tachycardia is the induction mechanism of the atrial fibrillation. The majority of patients with atrial fibrillation is apparently not amenable to a curative local ablation. While AV junction ablation and AV node modification can palliate some of the symptoms of atrial fibrillation by a control of ventricular rate, the arrhythmia persists with the loss of AV synchrony and continued risk of thromboembolism. The surgical MAZE procedure implies a compartimentation of the atria by surgical incisions resulting in areas to small to sustain the arrhythmia. Based on this procedure experimental and clinical studies are currently performed in order to develop catheter ablation cure of atrial fibrillation.

Atrial Fibrillation↗
PubMed2004

Early recurrence of arrhythmia in patients taking amiodarone or class 1C agents for treatment of atrial fibrillation or atrial flutter.

Amiodarone use for the prevention of recurrent atrial fibrillation or atrial flutter requires drug loading over a period of several days to weeks, whereas class 1C agents do not. Three hundred thirty-nine patients were evaluated during drug loading with amiodarone or class 1C agents, and it was found that recurrent arrhythmia was common, usually not persistent, and frequently asymptomatic. Recurrent arrhythmia was not more common with amiodarone.

Age Factors↗
PubMed2004

Treatment of atrial fibrillation by catheter-based procedures.

Catheter-based procedures have been developed with a view to reproduce or improve upon the excellent results of the Maze procedure in the treatment of atrial fibrillation (AF). Linear epicardial lesions created using minimally invasive techniques, or endocardial lesions to encircle the pulmonary veins (PV) have been associated with restoration of sinus rhythm in high percentages of carefully selected patients. The tricuspid-caval isthmus interruption procedure for atrial flutter is highly successful and, in patients who have both atrial flutter and fibrillation, prevents the development of AF when combined with antiarrhythmic agents. Modification of atrioventricular (AV) nodal conduction by eliminating the posterior atrial inputs to the AV node is performed to decrease the ventricular rate and alleviate symptoms during AF without the need for permanent pacing, though may be complicated by inadvertent AV block. AV junctional ablation and permanent pacing alleviates cardiac symptoms, improves quality-of-life, and reduces the use of health care resources. Its constraints include the inescapable need for anticoagulation, loss of AV synchrony, and life-long pacemaker-dependency. The variety of methods and results among published studies strongly emphasises the importance of patient selection, and the relative importance of substrate versus trigger. Possible complications of catheter ablation for AF include systemic thromboembolism, PV stenosis, pericardial effusion, cardiac tamponade, and phrenic nerve paralysis. These remain a matter of concern and stimulate research toward the development of less complex procedures.

Atrial Fibrillation↗
PubMed2000

New advances in class III antiarrhythmic drug therapy.

In the past 2 years, significant advances have been made in class III antiarrhythmic drug therapy. In patients with ventricular arrhythmias and implantable cardioverter defibrillators (ICDs), antiarrhythmic agents are increasingly being used as adjunct therapy to decrease the frequency of ICD discharges. Sotalol was recently shown to be effective in reducing tachyarrhythmias in patients with ICDs. Intravenous amiodarone is being used for the acute treatment of unstable ventricular arrhythmia and is being investigated for the treatment of acute out-of-hospital cardiac arrest. Class III agents are increasingly being used for prophylaxis in patients who have atrial fibrillation or atrial flutter, and data point to an important role for these agents in reducing supraventricular tachyarrhythmias after cardiac surgery. Future studies will need to directly compare these agents with pure anti-adrenergic maneuvers in postoperative patients. In addition to terminating atrial fibrillation and atrial flutter, ibutilide significantly reduces human atrial defibrillation thresholds and increases the percentage of patients who can be cardioverted from atrial fibrillation to sinus rhythm. The US Food and Drug Administration is expected to approve dofetilide for clinical use soon, and it is currently reviewing azimilide (which seems to be devoid of frequency-dependent effects on repolarization) for prophylaxis against atrial fibrillation and atrial flutter. Dronedarone, tedisamal, and trecetilide are now under active study intended to determine their usefulness in patients with cardiac arrhythmias. Experimental studies are ongoing to identify pharmacologic agents that will selectively prolong repolarization in the atria without exerting electrophysiologic effects in the ventricles.

Amiodarone↗
PubMed1997

Radiofrequency catheter ablation of atrial flutter that elicits inappropriate implantable cardioverter defibrillator discharge.

The case of a patient with recurrent VT and an ICD is reported. After appropriate device discharges, the patient experienced 40 episodes of inappropriate shock therapy due to atrial arrhythmias confirmed as type I atrial flutter. Since programmed stimulation could reliably initiate atrial flutter, catheter ablation was performed. During delivery of RF current, atrial flutter terminated and was no longer inducible. The patient had no further inappropriate device discharges during 12 months of follow-up. In patients with ICDs suffering from recurrences of atrial flutter leading to inappropriate shock therapy, RF catheter ablation is an effective and curative approach.

Atrial Flutter↗
PubMed1995

Regional differences in transient outward current density and inhomogeneities of repolarization in rabbit right atrium.

BACKGROUND: Recent experimental and clinical studies on atrial flutter have demonstrated that the crista terminalis (CT) plays an important role in the genesis of atrial reentry. To elucidate the underlying mechanism of its role, we characterized the electrophysiological repolarization properties of CT cells by comparing them with those of the pectinate muscles (PM). METHODS AND RESULTS: After action potential properties of both regions were compared by conventional microelectrode technique in multicellular atrial tissues, the whole-cell clamp experiments were applied in atrial cells isolated from both regions. Action potential duration (APD) was more prolonged in CT than in PM in multicellular preparations (APD90 77 +/- 5 ms versus 52 +/- 8 ms at 1 Hz, P < .01), though the other properties did not differ significantly. Similarly, in isolated atrial cells, APD was more prolonged in CT cells than in PM cells (APD90 63 +/- 7 ms versus 41 +/- 6 ms at 0.1 Hz, P < .01). Isolated single cells were larger in CT than in PM. The whole-cell clamp recordings showed no definite distinctions in the density of the voltage-dependent L-type Ca2+ current and the inwardly rectifying K+ current between these cells but revealed a significant reduction of the density of the 4-aminopyridine-sensitive transient outward current (Ito) in CT cells compared with that in PM cells (6.3 +/- 0.7 pA/pF versus 10.3 +/- 0.8 pA/pF at +20 mV, P < .05). However, no differences in the kinetics or the voltage dependence of Ito were observed between the cells. The time course of recovery from inactivation of Ito was also similar in both types of cells. CONCLUSIONS: These results suggest that the preferential reduction in the density of Ito in the CT cells could contribute to prolong their APD, which may be related to the genesis of atrial reentry.

Action Potentials↗
PubMed1998

Clinical pharmacology of antiarrhythmic drugs.

Antiarrhythmic drugs play a major role in the management of the most common types of arrhythmias. The margin between the beneficial and toxic effects of these drugs is often narrow. Thus, a precise knowledge of dosages, drug-target tissue interactions, pharmacodynamics and pharmacokinetics of antiarrhythmic drugs is needed to better predict how effective a particular drug will be in the treatment of a specific arrhythmia in a given patient. Despite the large amount of information that is available on the electrophysiological and pharmacological effects of antiarrhythmic drugs, we still do not know enough about their true mechanism of action in individual patients. The results of the Cardiac Arrhythmia Suppression Trial (CAST) firmly established that the use of class I drugs is potentially dangerous in a specific subset of patients. Additionally, several meta-analyses have reported that quinidine has severe proarrhythmic effects in patients with atrial fibrillation. The management of arrhythmias in elderly patients is difficult because of age-related factors that may influence the pharmacokinetics and pharmacodynamics of antiarrhythmic drugs.

Adrenergic beta-Antagonists↗
PubMed2005

[Safety of new anti-arrhythmic drugs].

The majority of new antiarrhythmic drugs are still undergoing clinical trials and are not yet available on the French market. The studies of efficacy are mainly targeted on the treatment of atrial fibrillation. Intravenous ibutilide prolongs the duration of the action potential by stimulating sodium exchange during phase 2 of the action potential. Used for terminating episodes of atrial flutter and fibrillation, ibutilide has been shown to have a low proarrhythmic effect. Dofetilide is a pure I(Kr) current antagonist and is given orally. The molecule prolongs the duration of the atrial and ventricular action potentials. The amplitude of this effect is inversely related to the heart rate. No effect has been observed on the mortality rate in the post-infarct period. Adjusting the dosage with respect to renal function has reduced the occurrence of torsades de pointe from 4.8 to 2.9%. Azimilide is an I(Kr) and I(Ks) current blocker and its efficacy decreases at rapid heart rates. After oral administration, azimilide does not appear to have a deleterious effect in patients with a history of myocardial infarction and left ventricular dysfunction. The risk of torsades de pointe is less than 1%. Cases of neutropaenia have been reported. Dronedarone is an amiodarone analogue without iodine. The molecule prolongs atrial and ventricular action potentials and its efficacy is maintained at high heart rates. This drug had deleterious effects when given to patients with coronary artery disease and left ventricular dysfunction. Gastrointestinal side effects may be observed at high dosage. The great advantages of dronedarone are the absence of thyroid complications and of pro-arrhythmic effects.

Administration, Oral↗
PubMed1989

[Disorders of heart rhythm in hypertrophic cardiomyopathy].

In 64 patients with hypertrophic cardiomyopathy 24-hour Holter monitoring of the ECG was made in order to detect the incidence of individual disorders of the cardiac rhythm. The examination revealed a large number of potentially malignant ventricular arrhythmias (47% of the patients). Most frequently polytopic ventricular extrasystoles were involved (31.3%), attacks of ventricular tachycardia (20.3%), less frequently bigeminy was recorded (10.9%) and early extrasystoles type R on T (3.1%). As to other disorders of the cardiac rhythm, paroxysmal supraventricular tachycardia was frequent (34.4%), atrial fibrillation or flutter (9.4%) and more numerous supraventricular extrasystoles (7.8%). Sinoatrial (4.7%) and atrioventricular blocks (7.8%) were relatively rare. Examination of patients with hypertrophic cardiomyopathy is an essential prerequisite for the initiation of early and effective treatment which can exert a favourable effect on the subsequent fate of the patients.

Adolescent↗