Biomedical subjects

M Hocini

Publications and source records attributed to M Hocini.

64 records · Page 4Linked to original sources

PubMed1998

Specific electrocardiographic features of manifest coronary vein posteroseptal accessory pathways.

INTRODUCTION: Some posteroseptal accessory pathways (APs) can be successfully ablated by radiofrequency current only from inside the coronary sinus (CS) or its branches, because of an absolute or relatively epicardial location. The aim of this study was to identify ECG features of manifest posteroseptal APs requiring ablation in the CS or the middle cardiac veins (MCVs). METHODS AND RESULTS: One hundred seventeen consecutive patients with manifest posteroseptal APs successfully ablated: (1) > or = 1 cm deep inside the MCV (group MCV: n = 13); (2) inside the CS, including the area adjacent to the MCV ostium (group CS: n = 10); (3) at the right (group R: n = 60); or (4) the left posteroseptal endocardial region (group L: n = 34) were included. We reviewed delta wave polarity (initial 40 msec) and QRS morphology during sinus rhythm and atrial pacing as well as electrogram characteristics in these patients. The local target site electrogram in groups MCV and CS was characterized by a longer atrial to ventricular electrogram interval, suggesting a longer course of the pathway and more frequent recording of a presumptive AP potential compared to the group ablated at the right or left endocardium. The most sensitive ECG feature for group CS or group MCV was a negative delta wave in lead II in sinus rhythm (87%), but specificity (79%) and positive predictive value (50%) were relatively low. A steep positive delta wave in aVR during maximal preexcitation possessed the highest specificity and positive predictive value (98% and 88%, sensitivity 61%) which increased to 99% and 91%, respectively, when combined with a deep S wave in V6 (R wave < or = S wave). CONCLUSION: These data suggest that posteroseptal APs ablated inside the coronary venous system have highly specific features, including the combination of a steep positive delta wave in lead aVR and a deep S wave in lead V6 (R wave < or = S wave) during maximal preexcitation. The highest sensitivity is provided by a negative delta wave in lead II. These findings may be helpful for anticipating and planning an epicardial ablation strategy.

Adolescent↗

PubMed1998

Origin of heat-induced accelerated junctional rhythm.

INTRODUCTION: The application of high-frequency current to the AV junctional area results in a temperature rise in the myocardium and may cause accelerated junctional rhythm (AJR). The aim of the study was to characterize heat-induced AJR in an in vitro animal model. METHODS AND RESULTS: Studies were performed in isolated perfused pig and rabbit hearts. Using a small heating probe, we could induce AJR from a discrete area located in the middle of the triangle of Koch, which was smaller than the area from which RF energy application could elicit AJR. Histology showed that the heat-sensitive area was located over, or close to, the compact AV node. It did not correspond with the areas where double potentials were found or with the site(s) of earliest atrial activation during VA conduction. Microelectrode recordings revealed that AJR arose in nodal-type cells. Heat increased the slope of the phase 4 depolarization and shortened the action potential duration. Two types of AJR were observed: the first one was regular and the second one showed irregularity in the intervals. Interaction of multiple foci and the presence of conduction block between the foci and the His bundle caused the irregularity of the His-His intervals during the second type of AJR. CONCLUSION: AJR observed during heat and RF application in the AV nodal area results from the effect of heat on AV nodal cells with underlying pacemaker activity. The heat-sensitive area is located over, or very close to, the compact AV node.

Action Potentials↗

PubMed1997

Three-dimensional mapping of the common atrial flutter circuit in the right atrium.

BACKGROUND: The full circuit of common atrial flutter using conventional methods of sequential or multielectrode activation mapping is not completely understood. METHODS AND RESULTS: We performed three-dimensional right atrial endocardial activation mapping during common counterclockwise atrial flutter in 17 patients (16 men, 1 woman; mean age, 53+/-11 years) by using the Cordis-Biosense EP Navigation system and assessed the distribution of estimated conduction velocities and double and fractionated potentials. ECG flutter wave morphologies were compared with activation patterns. Points (91+/-29) were sequentially acquired covering 88+/-11% of the flutter cycle length of 239+/-22 ms. A wide and variable posterior zone of double and fractionated potentials coincided with blocking and colliding wave fronts and formed the posterior limit of the circuit. A progressively widening septal (sep) wave front ascending from just beyond the coronary sinus ostium, passed cranially as a broad front anterior to the superior vena cava (SVC) in 14 patients, whereas fusion around the SVC formed the superior (sup) limb of the circuit in 3. Bounded anteriorly by the tricuspid valve, the wave front descended down the lateral (lat) aspect of the right atrium before completing the circuit in all cases through the inferior vena cava-tricuspid annulus isthmus. The estimated conduction velocity in the medial isthmus (0.6+/-0.3 m/s) was lower than in the other limbs of the circuit (sup=1+/-0.5 m/s, lat=1+/-0.5 m/s, sep=0.9+/-0.4 m/s, P=.05). Double and fractionated potentials were constant and more prevalent in the posterior right atrium. ECG flutter wave morphology did not correlate with three-dimensional activation maps. CONCLUSIONS: Interindividual variations occur in the right atrial circuit of common atrial flutter, with constant activation through the cavotricuspid isthmus. A variable zone of block forms the posterior limit. Fusion around the SVC can occur, and ascending medial septal activation does not follow a consistent pattern.

Adult↗

PubMed1997

Simplified electrophysiologically directed catheter ablation of recurrent common atrial flutter.

BACKGROUND: Despite verification of bidirectional conduction block after radiofrequency (RF) catheter ablation in the inferior vena cava (IVC)-tricuspid annulus (TA) isthmus, recurrence of common atrial flutter is relatively common. Although complete linear reablation is usually performed, we evaluated a simplified electrophysiological strategy selectively targeting recovered conducting isthmus tissue. METHODS AND RESULTS: Twenty-one patients (18 men and 3 women, age, 54+/-10 years) with a recurrence of typical atrial flutter 6+/-7 months after an apparently successful catheter ablation in the IVC-TA isthmus prospectively underwent electrophysiologically targeted reablation during flutter. Sites with narrow electrograms or fractionated electrograms interposed between adjacent sites with double potentials considered to represent gaps were ablated without movement of the catheter. Mapping showed that 18 of 21 patients had a single gap. Successful ablation required a single application in 14 patients and, in the group as a whole, a median of one application (mean, 2+/-2; range, 1 to 11) with resultant bidirectional block in 13 of 16. A single narrow electrogram (duration, 48+/-6 ms; amplitude, 0.1+/-0.05 mV) was noted at the successful site in 11, whereas a fractionated electrogram (97+/-32 ms, 0.05+/-0.04 mV, P<.05) was noted in 9. There were four additional recurrences during a follow-up at 7+/-5 months; three were similarly ablated with a median of one pulse. CONCLUSIONS: Transmural ablation lesions in the isthmus can be recognized during flutter by double potentials separated by an isoelectric interval. Postablation recurrent flutter is usually due to a single discrete recovered gap; this is represented by a single or a fractionated potential spanning the isoelectric interval of adjacent double potentials, which can be selectively targeted to minimize repeat ablation.

Adult↗

PubMed1997

A focal source of atrial fibrillation treated by discrete radiofrequency ablation.

BACKGROUND: Atrial fibrillation is usually thought to be due to multiple circulating reentrant wavelets. From previous studies, a focal mechanism is considered to be very unlikely. In this report, focal atrial fibrillation is defined on an ECG pattern of atrial fibrillation and later demonstrated to be due to a focal source. METHODS AND RESULTS: Nine patients (five men and four women, age, 38 +/- 7 years) with paroxysmal focal atrial fibrillation are reported here. All were free of structural heart disease and had frequent episodes of atrial fibrillation despite the use of a mean of 4 +/- 2 antiarrhythmic drugs. Atrial fibrillation was associated with runs of irregular atrial tachycardia or monomorphic extrasystoles. The electrophysiological study demonstrated that all the atrial arrhythmias were due to the same focus firing irregularly and exhibiting a consistent and centrifugal pattern of activation. Three foci were found to be located in the right atrium, two near the sinus node and one in the ostium of the coronary sinus. Six others were located in the left atrium at the ostium of the right pulmonary veins (n = 5) and at the ostium of the left superior pulmonary vein (n = 1). All atrial arrhythmias were successfully treated by use of a mean of 4 +/- 4 radiofrequency pulses. CONCLUSIONS: In some patients, the surface ECG pattern of atrial fibrillation is due to a focal rapidly firing source of activity that can be eliminated by discrete radiofrequency energy applications.

Adult↗

PubMed1997

Analysis of electrophysiological activity in Koch's triangle relevant to ablation of the slow AV nodal pathway.

Atrioventricular junctional reentrant tachycardia (AVJRT) is the most common form of paroxysmal regular supraventricular tachycardia. In patients with disabling, drug refractory AVJRT, catheter ablation has evolved rapidly from a last-resort treatment in the form of interruption of atrioventricular (AV) conduction to selective modification of AV nodal function as an ideal treatment. This article will focus on the frequently unappreciated electrophysiological activities recordable in man in Koch's triangle during ablation of the so-called slow pathway.

Atrioventricular Node↗

PubMed1997

Electrical activity in Koch's triangle.

The authors have conducted several experimental studies of the cellular electrophysiology of the atrioventricular (AV) node employing the Langendorff-blood perfused heart of both dogs and pigs. Two types of experiments are described: experiments showing that cells with electrophysiological characteristics of typical nodal cells can be found outside Koch's triangle; and mapping experiments during the induction of ventricular echo beats in an attempt to delineate the reentrant circuit thought to underlie AV nodal reentry.

Animals↗

PubMed1996

Right and left atrial radiofrequency catheter therapy of paroxysmal atrial fibrillation.

INTRODUCTION: Atrial fibrillation (AF), the most common arrhythmia, is due to multiple simultaneous wavelets of reentry in the atria. The only available curative treatment is surgical, using atriotomies to compartmentalize the atria. Therefore, we investigated a staged anatomical approach using radiofrequency catheter ablation lines to prevent paroxysmal AF. METHODS AND RESULTS: Forty-five patients with frequent symptomatic drug-refractory episodes of paroxysmal AF were studied. Progressively complex linear lesions were created by sequential applications of radiofrequency current in the right atrium and then in the left atrium if required. The outcome of the procedure was considered a success when the episodes of AF were either eliminated or recurred at a rate of no more than one episode (lasting < 6 hours) in 3 months. Patients who had no more than one episode per month were considered "improved." Right atrial ablation organized local electrical activity and led to stable sinus rhythm during the procedure in 18 (40%) of the 45 patients. However, sustained AF remained inducible in 40 of 45 patients, and the lesions failed to produce evidence of a significant linear conduction block/delay in all but four patients. There were no significant complications except for two transient sinus node dysfunctions. The procedure duration and fluoroscopic time were 248 +/- 79 and 53 +/- 22 min, respectively. Additional sessions were required in 19 patients to treat sustained right atrial flutter or arrhythmias linked to ectopic right or left atrial foci. During a mean follow-up of 11 +/- 4 months, right atrial ablation was successful in 15 (33%) patients, 6 without medication and 9 with a previously ineffective drug. Nine (20%) additional patients were improved. Ten patients with an unsuccessful outcome then underwent linear ablation in the left atrium. The procedure duration and fluoroscopy time were 292 +/- 94 and 66 +/- 24 min. A hemopericardium occurred in one patient. Two patients required reablation to treat ectopic atrial foci. Left atrial ablation terminated AF during the procedure in 8 patients, and sustained AF could not be induced in 5. Subsequent success was achieved in 6 (60%) patients, including 4 without medication, and 1 additional patient was improved. CONCLUSIONS: Successful radiofrequency catheter ablation of drug-refractory daily paroxysmal AF is feasible using linear atrial lesions complemented by focal ablation targeted at arrhythmogenic foci. Ablation only in the right atrium is a safe technique providing limited success, whereas linear lesions in the left atrium significantly increase the incidence of stable restoration of sinus rhythm, the inability to induce sustained AF, and the final success rate. The described technique is promising but must be considered preliminary because significant improvements are required to optimize lesion characteristics and shorten total procedure duration.

Adult↗

PubMed1996

Electrophysiology of the A-V node in relation to A-V nodal reentry.

During A-V nodal reentry the impulse is supposed to travel through two distinct pathways in the A-V nodal junction, called slow and fast pathways. Clinically, catheter ablation of these pathways has been very successful in abolishing A-V nodal reentrant tachycardias. So-called double potentials have been used as a marker for the slow pathway, and the occurrence of accelerated junctional rhythms (AJR) following ablation is an indicator of successful destruction of the slow pathway. In Langendorff, blood-perfused porcine and canine hearts, extensive mapping of extracellular potentials, combined with microelectrode recordings, was carried out to answer the following questions: 1) what is the origin of double extracellular potentials? 2) what causes post-ablation AJR? 3) what is the activation pattern of the AV junction during ventricular echoes? 1) Two types of double potentials were found: a low-frequency component followed by a high-frequency deflection, the LH potential was caused by asynchronous activation of the sinus septum above the coronary sinus and the region between the coronary sinus orifice and tricuspid annulus, where the L component is a far field potential. HL potentials (high-frequency deflection followed by a low frequency component) were caused by asynchronous activation of atrial cells and cells with AV nodal characteristics at the same location. These cells were present around the entire tricuspid annulus, and were not part of the compact node. The proximity of LH potentials to the slow pathway is probably serendipity, HL potentials could represent the slow pathway. 2) Two types of AJR could be initiated both by application of radiofrequency energy and by heat: a regular rhythm that progressively accelerated and an irregular rhythm. The discrete sites where heat application induced AJR did not correlate with areas showing double potentials, nor with exit regions during ventricular pacing. They were close to the compact node and the underlying mechanism was accelerated phase 4 depolarization in single or multiple foci, the latter accounting for irregular AJR. The association between presence of AJR and successful slow pathway ablation is probably also serendipity. 3) During ventricular pacing, two separate areas of earliest atrial activity were found. When ventricular echoes were induced by premature stimulation, the retrograde impulse activated both atrial exit sites and still returned in the ventricles as an echo. Thus, no evidence was found that atrial tissue forms part of the reentrant circuit.

Animals↗

PubMedDate not supplied

Radiofrequency catheter ablation for AV nodal reentrant tachycardias (AVNRT).

Radiofrequency (RF) catheter ablation is the curative treatment of choice for atrioventricular (AV) nodal reentrant tachycardia (AVNRT). Analogous to the development of surgical techniques, catheter ablation has evolved from AV nodal ablation to selective "fast" and "slow" pathway ablation. "Slow" ablation is now the method of choice because of the lower incidence of associated AV block. Though slow pathway ablation can be achieved with equal success using either the anatomic or the electrogram-guided approach, fewer applications of RF energy are required for the potential-guided technique.

Catheter Ablation↗