Search PubMed⌕ Search

Biomedical subjects

J Brugada

Publications and source records attributed to J Brugada.

At least 91 records · Page 5Linked to original sources
PubMed1996

What to do in patients with no structural heart disease and sudden arrhythmic death?

The term "idiopathic" ventricular fibrillation is used to describe those episodes of unexpected sudden arrhythmic death due to ventricular fibrillation in patients with no demonstrable structural heart disease. Idiopathic ventricular fibrillation has been reported to account for 5-100% of all sudden arrhythmic deaths. Post mortem analysis have shown that about 80% of patients might have some kind of structural anomalies, mainly atherosclerosis, myocarditis, or right ventricular dysplasia. Follow-up of patients with idiopathic ventricular fibrillation has shown a high incidence of recurrent episodes of malignant ventricular arrhythmias. The absence of structural heart disease generally implies an excellent long-term prognosis if ventricular fibrillation can be avoided. Patients with an implantable defibrillator should have a mortality rate similar to the general population. New subsets of patients are being recognized as belonging with those previously classified as idiopathic ventricular fibrillation. More than 60 patients have been identified in different centers around the world with the so-called "right bundle branch block, ST segment elevation, and sudden death syndrome." Recurrence rate of malignant ventricular arrhythmias is very high in these patients, despite antiarrhythmic therapy. An implantable cardioverter-defibrillator seems the treatment of choice. Asymptomatic forms of the syndrome have been described. Follow-up in these asymptomatic patients has shown that some of them might become symptomatic during follow-up. Also, intermittent forms of the syndrome have been described, with transient normalization of the electrocardiogram. Administration of class I drugs in these patients unmasks the typical electrocardiographic pattern. In some of the patients previously classified as having idiopathic ventricular fibrillation, ajmaline or procainamide administration unmasks the electrocardiographic pattern of the syndrome, suggesting that its incidence may be higher than previously suspected.

Bundle-Branch Block↗
PubMed1996

[Electrophysiologic mechanisms of atrial fibrillation].

Atrial fibrillation is the most common arrhythmia in clinical practice. Atrial fibrillation is characterized by a complete disorganization in atrial electrical activity and sinus node pacemaker activity is lost. The physiopathological mechanisms of atrial fibrillation is based on the simultaneous presence of multiple wavelets in the atria. These multiple wavelets are continuously changing in localization, direction and duration resulting in a chaotic electrical activity. This theory has been confirmed by several studies using detailed mapping of the atria during atrial fibrillation. Also, the functional nature of the reentrant circuits during atrial fibrillation has also been demonstrated. For an episode of atrial fibrillation to perpetuate, the wavelength of the cardiac impulse has to be adapted to the length of the atria. Modifications of the wavelength by drugs may result in perpetuation or in termination of the atrial fibrillation episode.

Atrial Fibrillation↗
PubMed1996

Electrophysiologic and proarrhythmogenic effects of therapeutic and toxic doses of imipramine: a study with high resolution ventricular epicardial mapping in rabbit hearts.

Electrophysiologic and proarrhythmogenic effects of imipramine were studied by use of 21 Langendorff-perfused rabbit hearts and high-resolution mapping to analyze epicardial activation of the left ventricle. In 16 hearts, a thin layer of epicardium was obtained by an endocardial cryotechnique (frozen hearts). Five hearts were kept intact (nonfrozen imipramine-treated group). Preparation stability was verified in six frozen hearts. In 10 frozen and in 5 nonfrozen hearts, 0.01, 0.1, 1.0, 2.0 and 5.0 micrograms/ml imipramine were administered. In nonfrozen imipramine-treated hearts, imipramine induced bradycardia at 5.0 micrograms/ml (291.8 +/- 40.5 vs. 495.2 +/- 54.4 msec, P = .02), one A-V block at 5.0 micrograms/ml and two monomorphic ventricular tachycardias (MVT) at 2.0 and 5.0 micrograms/ml. In 4/10 frozen hearts, three MVT were induced at 1.0 microgram/ml imipramine and one MVT at 2.0 micrograms/ml imipramine. All MVT were based on reentry around a line of functional conduction blocks. Imipramine (2.0 micrograms/ml) slowed longitudinal and transversal ventricular conduction velocities at a pacing cycle length of 1000 msec from 71.7 +/- 6.1 to 63.0 +/- 7.7 cm/sec (P = .008) and from 32.9 +/- 2.6 to 27.7 +/- 2.8 cm/sec (P = .009), respectively, and prolonged ventricular effective refractory period from 141.9 +/- 9.3 to 279.1 +/- 112.6 msec (P = .03). Imipramine induced dose- and use-dependent slowing of ventricular conduction velocity facilitating functional conduction blocks and reentrant MVT.

Animals↗
PubMed1996

[One thousand consecutive radiofrequency ablation procedures. Indications, results, and complications].

INTRODUCTION: Radiofrequency ablation has become the treatment of choice in the majority of patients suffering from cardiac arrhythmias. In this study we present our experience in a large group of patients treated using this procedure. METHODS: Between January 1992 and February 1996, we performed 1000 consecutive ablation procedures in 938 patients with different cardiac arrhythmias. The indication for ablation were: tachycardias due to the presence of an accessory pathway (n = 487), atrio-ventricular nodal reentrant tachycardia (n = 284), atrio-ventricular nodal ablation (n = 104), atrial tachycardia (n = 42), atrial flutter (n = 41) and ventricular tachycardia (n = 42). RESULTS: Radiofrequency ablation was initially effective in 908 out of the 938 patients (97%). Effectiveness ranged from 100% in atrio-ventricular nodal ablation to 83% in atrial tachycardia. During follow-up, a total of 45 recurrences of the arrhythmia were documented (5%) ranging from 2% in atrial tachycardia to 28% in atrial flutter. In 40 out of the 45 patients a second procedure was performed, being effective in 34 of them. Finally, radiofrequency ablation was effective in 896 out of the 938 patients (96%). A total of 13 significative complications were observed (1.3%). Of them, 10 occurred during the 250 initial procedures (4%) and 3 in the remaining 750 procedures (0.4%). CONCLUSIONS: In centers performing a large number of procedures, radiofrequency ablation is a safe and effective method for the treatment of the majority of cardiac arrhythmias.

Adolescent↗
PubMed1995

Radiofrequency catheter ablation of atriofascicular accessory pathways guided by discrete electrical potentials recorded at the tricuspid annulus.

BACKGROUND: The purpose of this study was to test the feasibility of using the recording of discrete electrical potentials to guide radiofrequency catheter ablation of atriofascicular accessory pathways with Mahaim-like properties. METHODS AND RESULTS: Four patients (3 females, 1 male) who fulfilled criteria for having atriofascicular accessory pathways with Mahaim-like properties and preexcited reciprocating tachycardia underwent radiofrequency catheter ablation. The mean age was 35 years (range 27-47). Symptoms were present for a mean of 10.5 years (range 6-18). Recording of discrete electrical potentials of the atriofascicular pathway was attempted by mapping the tricuspid annulus in sinus rhythm, during atrial pacing, and during reciprocating tachycardia. During atrial pacing, a mean of seven radiofrequency pulses (range 1-14), delivered to the tricuspid annulus at the area where electrical potentials were recorded, eliminated conduction through the atriofascicular accessory pathway in all patients. No complications occurred. Tachycardia did not reoccur during a mean follow-up of 5 months (range 3-9). CONCLUSIONS: Recording of discrete electrical potentials at the tricuspid annulus identifies an optimal ablation site where radiofrequency current can safely eliminate conduction through atriofascicular accessory pathways with Mahaim-like properties.

Adult↗
PubMed1995

A fast and reliable algorithm to localize accessory pathways based on the polarity of the QRS complex on the surface ECG during sinus rhythm.

BACKGROUND: Many criteria have been published to localize accessory pathways from the 12-lead ECG during sinus rhythm. This study analyzed whether the localization of an accessory pathway could be predicted by using the polarity of the QRS complex during sinus rhythm on the surface ECG, instead of the delta wave polarity as used in many reports. METHODS: The ECGs of 140 patients with an overt and single accessory pathway were evaluated. Eight localizations were taken into account. The precise location was previously known from successful radiofrequency ablation sites. RESULTS: In 128 patients (92%), the new algorithm allowed an accurate diagnosis of the site of implantation of the accessory pathway. CONCLUSION: Analysis of the polarity of the QRS complex on five electrocardiographic leads provides an easy, fast and reliable way to localize accessory pathways during sinus rhythm.

Algorithms↗
PubMed1994

Mapping of reset of anatomic and functional reentry in anisotropic rabbit ventricular myocardium.

BACKGROUND: Premature stimulation is used to characterize the reentrant circuit during ventricular tachycardia (VT) in patients. The goal of this study was to compare the effects of premature stimulation on functional and anatomic reentrant VT. METHODS AND RESULTS: In 18 Langendorff-perfused rabbit hearts, thin layers of anisotropic left ventricular subepicardium were created by a cryoprocedure. In 8 hearts, rapid pacing induced reentry around a line of functional conduction block; in 10 hearts, reentry occurred around a fixed epicardial obstacle created by a cryoprobe. The cycle lengths (CL) of functional and anatomic VT were 110 +/- 10 and 167 +/- 17 milliseconds, respectively. During anatomic VT, the excitable gap measured 43% of the CL and premature stimuli could always reset VT (44 +/- 12 milliseconds). During early premature beats, conduction of the orthodromic wave was slightly depressed, but anatomic VT was never terminated. Reset curves at different sites in the ventricle revealed three different response types, both determined by and characterizing the spatial and temporal relation between pacing and recording sites. Premature stimulation during functional VT revealed a local excitable gap at the pacing site measuring 27% of the cycle length of VT. However, in only 3 of 8 hearts, premature stimuli could reset functional VT by 8%. In 5 VTs, advancement of the paced activation was fully compensated by prolongation of the return cycle, and VT was not reset. Due to slow conduction both toward and inside the circuit, the paced orthodromic wave lost its prematurity already within a distance of 6 to 10 mm from the pacing site. CONCLUSIONS: Both during anatomic and functional reentry, an excitable gap is present in the reentrant circuit. Three different response curves reveal the localization of the pacing and recording sites in the circuit. Anatomic VT can always be reset by premature stimuli, whereas in 5 of 8 hearts, functional VT could not be reset. In the other 3 hearts, VT could only be reset for less than 7% to 11% of the VT interval. Therefore, it seems very unlikely that clinical VT based on functional reentry can be reset.

Animals↗
PubMed1994

Effects of heptanol, class Ic, and class III drugs on reentrant ventricular tachycardia. Importance of the excitable gap for the inducibility of double-wave reentry.

BACKGROUND: Double-wave reentry (DWR) can be a mechanism for acceleration of ventricular tachycardia (VT) with a large excitable gap (EG). The purpose of this study was to determine the effects of heptanol, class Ic, and class III drugs on the inducibility of DWR. METHODS AND RESULTS: In 11 Langendorff-perfused rabbit hearts, a thin ring of anisotropic left ventricular epicardium was created by a cryoprocedure. VT with a revolution time of 180 +/- 26 milliseconds and an EG of 106 +/- 8 milliseconds was induced by incremental pacing. During control, entrainment with 10 stimuli at a 99 +/- 15-millisecond interval terminated VT in seven hearts. In four hearts VT was accelerated from 205 +/- 24 to 115 +/- 14 milliseconds by introduction of a second circulating wave in the ring. In the seven VTs that could not be accelerated, 0.5 mumol/L Org7797 (class Ic) and 1.0 mmol/L heptanol (uncoupling agent) prolonged the cycle length of VT by 32% and 37%, respectively. Because the refractory period (RP) only increased by 11%, the EG prolonged by 71% and the ratio between EG and RP was increased from 0.66 to 1.00. Under these conditions, DWR could be induced in all seven hearts. In the four VTs that could be accelerated during control, administration of the class III drug D-sotalol (35 mumol/L) only slightly slowed VT by 6%. Because the RP was prolonged by 15%, the ratio between the EG and the RP decreased from 0.76 to 0.63. Entrainment now failed to accelerate VT in two of four hearts, whereas in the two other hearts, double-wave reentry self-terminated within eight cycles. CONCLUSIONS: Drugs that increase the ratio of EG and RP enhance the susceptibility to acceleration of VT, whereas drugs that decrease this ratio prevent induction of sustained double-wave reentry.

Alcohols↗
PubMed1994

Atrioventricular nodal reentrant tachycardia: a review.

BACKGROUND: Atrioventricular nodal reentrant tachycardia (AVNRT) is the most common form of regular narrow complex tachycardia. It is due to dual atrioventricular nodal conduction over two pathways with different electrophysiological properties. The first pathway ('fast' pathway) conducts faster but has longer refractory period than the second pathway ('slow' pathway). OBJECTIVES: To review AVNRT. Clinically, AVNRT patients usually have palpitations in their neck during attacks. On the surface electrocardiogram, the diagnosis is suggested by the absence of P waves during tachycardia or very discrete P waves immediately after the QRS or an rSr' pattern in lead VI. Electrophysiologically, it can be reproducibly initiated or terminated by cardiac pacing. The reentrant circuit is limited to the atrioventricular node and a small amount of perinodal atrial tissue. Acute termination of tachycardia can be achieved by vagal manoeuvres or drugs. Adenosine compounds are excellent drugs, as are calcium channel blockers, for acute termination of the arrhythmia. If chronic therapy is indicated, digitalis, calcium blockers and beta-blockers are effective and simple initial options. Catheter ablation, especially using radiofrequency energy, antitachycardia pacing and surgery are therapeutic alternatives for the resistant patient. CONCLUSION: Because of its high success rate and low incidence of complications, radiofrequency ablation is becoming the therapy of first choice for the treatment of AVNRT.

Adenosine↗
PubMed1994

[Radiofrequency ablation of the slow nodal pathway in cases of paroxysmal nodal reentry tachycardia].

INTRODUCTION: We describe our experience in the treatment of supraventricular tachycardia due to atrioventricular nodal reentry by radiofrequency catheter ablation of the slow pathway. PATIENTS AND METHODS: Thirty-four patients (mean age 52 +/- 13 years) with recurrent drug refractory atrioventricular nodal reentrant tachycardia underwent radiofrequency catheter ablation of slow-pathway as the first procedure. Maximal energy used was 28 +/- 8 W, mean time was 4.4 +/- 2.8 min, and a mean number of 13 +/- 9 discharges per patient. RESULTS: Of the 34 patients 14 were successfully treated (no slow-pathway conduction, no AV nodal reentrant echo complexes, no inducible tachycardia), 11 were considered as partially successful (no inducible tachycardia, with slow-pathway conduction or echoes) and 9 patients were unsuccessfully treated (all of them underwent fast-pathway ablation with a successful outcome). Eight recurrences were observed during a mean follow-up period of 7 +/- 4 months: One in a patient with previously successful ablation (remained asymptomatic while taking beta-blockers), 6 in patients with first procedure partially successful (all of them underwent effective second slow-pathway ablation) and 1 in a patient with an unsuccessful procedure that underwent fast pathway ablation. A repeated procedure was successful in ablating the slow pathway. None of our patients developed complete atrio-ventricular block. One patient developed cardiac tamponade that needed surgical drainage. At last follow-up all patients are free from tachycardias. CONCLUSION: Slow pathway ablation is an effective method of treatment in patients with atrio-ventricular nodal reentrant tachycardia. Long term success is related to complete abolition of slow pathway conduction.

Adolescent↗
PubMed1993

Investigation of palpitations.

The uncomfortable awareness of a beating heart--palpitations--is a common complaint that can occur under normal or abnormal circumstances. For example, normal palpitations occur with exercise, emotions, and stress, or after taking substances that increase adrenergic tone or diminish vagal activity (coffee, nicotine, and adrenergic or anticholinergic drugs). Normal palpitations are recognised as such because individuals who experience them realise or are told that something happened to accelerate the normal rhythm of the heart. However, some people find sinus tachycardia troublesome enough to seek medical attention. In other situations palpitations are clearly abnormal. The heart beat which is felt for no apparent reason, may be fast, or strong and slow, or feel like a missed or extra beat. Although these abnormal palpitations usually point to a cardiac arrhythmia, this is not always the case. Moreover, many patients with arrhythmias do not have palpitations but manifestations such as syncope, shock, and chest pain (sudden death is also possible). We will discuss the approach to the patient who seeks medical attention because of a history of palpitations, with special emphasis on the history, physical examination, and 12-lead electrocardiogram (ECG) because they are simple and inexpensive diagnostic tools that are available to most physicians.

Arrhythmias, Cardiac↗
PubMed1993

Epicardial and subselective transcoronary chemical ablation of incessant ventricular tachycardia.

Incessant ventricular tachycardia in patients with severely depressed ventricular function remains a major therapeutic challenge. Although alcohol ablation via the tachycardia related vessel has been shown to be an effective alternative, it might not be applicable in some cases due to anatomic limitations. In three patients with ischemic cardiomyopathy and incessant ventricular tachycardia no effective antiarrhythmic therapy could be found. Alcohol ablation was then attempted but the tachycardia related vessel could not be intubated. A subselective injection of alcohol into a more proximal segment of the coronary artery was then performed in two cases. In one patient as subselective injection was also not possible, the injection was performed epicardially after thoracotomy. Ablation was successful in all cases. In very selected cases of incessant ventricular tachycardia that have failed all other therapeutic interventions, alcohol ablation of the tachycardia can be performed using an epicardial or subselective transcoronary injection of alcohol.

Aged↗
PubMed1993

Cibenzoline transforms random re-entry into ordered re-entry in the atria.

The goal of this study was to test the hypothesis that class I drugs modify the electrophysiological substrate of atrial fibrillation. The effects of a single intravenous dose (1.4 +/- 0.3 mg.kg-1) of the new class I drug, cibenzoline, were studied in 20 patients with spontaneous (n = 11) or induced (n = 9) atrial fibrillation, during an electrophysiological study. In one additional patient with chronic atrial fibrillation, the effects of a single intravenous dose of 2 mg.kg-1 of cibenzoline were studied intra-operatively before undergoing a 'corridor' operation. High resolution epicardial mapping (248 channels) was used to reconstruct the atrial activation patterns before and after administration of the drug. In 18 out of 20 patients administration of cibenzoline resulted in conversion of atrial fibrillation into regular monomorphic atrial tachycardia. In these 18 patients, the mean atrial cycle length was prolonged from 147 +/- 34 ms during atrial fibrillation to 302 +/- 34 ms after cibenzoline (P < 0.001). In eight out of the 18 patients, spontaneous (n = 3) or pacing induced (n = 5) conversion into sinus rhythm was observed after administration of the drug. In the patient undergoing the 'corridor' operation, epicardial mapping of both atria showed that the multiple wavelets present during atrial fibrillation fused into a single broad wavefront circulating counterclockwise around the caval veins after cibenzoline. In conclusion, cibenzoline transforms random re-entry into ordered re-entry in the atria. This effect seems related to the depression of conduction produced by the drug.

Adult↗
PubMed1993

Class III actions in an experimental model of ventricular tachycardia.

Simplified models of re-entry may help in our understanding of the electrophysiologic effects of class III drugs. In a model of re-entrant ventricular tachycardia around a ring of epicardium in Langendorff-perfused rabbit hearts, the electrophysiologic effects of class III antiarrhythmic drugs were studied and compared to those of class I drugs. Class III drugs were effective in terminating fast re-entrant ventricular tachycardias. Prolongation of the refractory period without affecting conduction velocity resulted in a closure of the excitable gap and collision of the head of the propagating impulse against its own tail of refractoriness. In slow ventricular tachycardias, despite a similar increase in refractory period, the excitable gap remained large enough to allow perpetuation of the tachycardia.

Animals↗