Biomedical subjects

F Bogun

Publications and source records attributed to F Bogun.

At least 37 records · Page 2Linked to original sources

PubMed1996

Effect of coupling interval and pacing cycle length on morphology of paced ventricular complexes. Implications for pace mapping.

BACKGROUND: Ventricular pace mapping is performed by comparing the QRS morphology of ventricular paced complexes to that of a template arrhythmia, either a premature ventricular depolarization or a QRS complex during ventricular tachycardia. The objective of this study was to evaluate the effect of coupling interval and pacing cycle length on QRS morphology. METHODS AND RESULTS: The study population consisted of 20 patients (mean age, 38 +/- 16 years) undergoing a clinically indicated electrophysiology procedure. In the first 10 patients, the effect of coupling interval on the morphology of single paced ventricular complexes was evaluated visually and by signal processing techniques. Visually apparent differences in QRS morphology occurred in a mean of 4/12 electrocardiographic leads with a change in coupling interval of > or = 100 ms. In the next 10 patients, the QRS complex morphology during ventricular overdrive pacing at cycle lengths of 600 and 300 ms was found to differ significantly in a mean of 4/12 leads. The QRS morphology during overdrive pacing differed significantly from that of a single paced complex whenever the pacing cycle length differed from the coupling interval of the single paced complex by > 80 ms. CONCLUSIONS: The morphology of single paced QRS complexes may vary, depending on coupling interval, and the QRS morphology during overdrive pacing is affected by the pacing cycle length. During ventricular pace mapping, the coupling interval or cycle length of the template arrhythmia should be matched during pacing. If not, rate-dependent changes in QRS morphology that are independent of the pacing site may confound the results of pace mapping.

Adult↗

PubMed1996

Effect of atrial fibrillation on atrial refractoriness in humans.

BACKGROUND: The acute effect of atrial fibrillation (AF) on the atrial effective refractory period (ERP) in humans is unknown. METHODS AND RESULTS: In 20 patients without structural heart disease, the atrial ERP was measured before and after pacing-induced AF at drive cycle lengths of 350 and 500 ms. Immediately after spontaneous AF conversion, the post-AF ERP was measured. The pre-AF ERPs at 350 and 500 ms were 206 +/- 23 and 216 +/- 17 ms, respectively. The time to spontaneous conversion of AF was 7.3 +/- 1.9 minutes. The first post-AF ERPs at drive cycle lengths of 350 and 500 ms were 175 +/- 30 ms (P < .0001 versus pre-AF) and 191 +/- 30 ms (P < .0001 versus pre-AF), respectively. The post-AF ERP returned to the pre-AF ERP value after a mean of 8.4 +/- 0.3 minutes. In 15 patients, during the determination of the post-AF ERP, secondary episodes of AF lasting 1 +/- 1.5 minutes were reinduced 6 +/- 3 times per patient. There was a significant inverse logarithmic relationship between the time to reinduction of AF and the duration of secondary episodes of AF (P < .0001, r = 5). CONCLUSIONS: In humans, several minutes of induced AF is sufficient to shorten the ERP for up to approximately 8 minutes. The temporal recovery of the ERP is reflected in progressively shorter episodes of reinduced AF. These data imply that AF transiently shortens the atrial wavelength and suggest a mechanism by which AF may perpetuate itself.

Adult↗

PubMed1996

Spatial resolution of atrial pace mapping as determined by unipolar atrial pacing at adjacent sites.

BACKGROUND: The purpose of this study was to examine the spatial resolution of unipolar atrial pace mapping by pacing at adjacent sites within the coronary sinus and the right atrium. METHODS AND RESULTS: Unipolar pacing from each pole of a quadripolar catheter was performed in the coronary sinus (n = 29) and in the right atrium (n = 10). Pacing from the distal electrode was used to simulate the site of origin of an atrial tachycardia. These P waves were compared with the P waves generated by unipolar pacing from each of the three proximal electrodes. The P waves were analyzed for changes in amplitude, duration, and configuration. Pacing within the coronary sinus resulted in significant changes in amplitude and duration at distances of 17 and 21 mm from the distal pole, respectively. Similarly, pacing in the right atrium resulted in significant changes in amplitude and duration at distances of 17 and 32 mm from the distal pole, respectively. No significant changes in configuration were noted in the coronary sinus in any lead at packing sites < or = 32 mm from the distal pole. Configurational changes were noted in the right atrium at pacing sites 17 mm from the distal pole. CONCLUSIONS: The spatial resolution of unipolar atrial pace mapping is approximately 17 mm. These findings indicate that mapping techniques that depend on the accurate discrimination of P-wave morphology, such as pace mapping or concealed entertainment, are likely to be imprecise when used in the atria.

Adult↗

PubMed1996

Ventricular rate during atrial fibrillation before and after slow-pathway ablation. Effects of autonomic blockade and beta-adrenergic stimulation.

BACKGROUND: Radiofrequency catheter modification of AV conduction can be used to control the ventricular rate during atrial fibrillation both in the baseline state and during exercise. Slow-pathway ablation has been suggested to be the mechanism for this response. The purpose of this study was to determine the effect of slow-pathway ablation on the ventricular rate in atrial fibrillation during autonomic blockade and sympathetic stimulation in patients with AV nodal reentrant tachycardia (AVNRT). METHODS AND RESULTS: Thirty-five patients undergoing slow-pathway radiofrequency ablation for AVNRT were assigned to autonomic blockade (0.2 mg/kg propranolol and 0.04 mg/kg atropine; n = 14) or isoproterenol (2 micrograms/min; n = 21). Atrial fibrillation was induced before and after slow-pathway radiofrequency ablation. During autonomic blockade, the mean ventricular cycle length (448 +/- 34 versus 525 +/- 103 ms, P < .01) and maximum ventricular cycle length (640 +/- 105 versus 798 +/- 226 ms, P = .04) were prolonged after ablation, whereas the minimum ventricular cycle length did not change significantly (361 +/- 42 versus 403 +/- 83 ms, P = .05). During isoproterenol infusion, the mean ventricular cycle length (375 +/- 52 versus 390 +/- 61 ms, P = .2), maximum ventricular cycle length (520 +/- 88 versus 537 +/- 106 ms, P = .3), and minimum ventricular cycle length (307 +/- 59 versus 298 +/- 33 ms, P = .4) did not change significantly after slow-pathway ablation. CONCLUSION: Slow-pathway ablation slows the ventricular rate during atrial fibrillation under conditions of autonomic blockade but not during sympathetic stimulation. Therefore, slow-pathway ablation alone cannot account for the clinical results obtained with radiofrequency modification of AV conduction in patients with atrial fibrillation.

Adult↗

PubMed1996

Response of type I atrial fibrillation to atrial pacing in humans.

BACKGROUND: High-density mapping studies of atrial fibrillation (AF) have suggested the presence of an excitable gap. The purpose of this study was to assess the local and left atrial response to pacing at the high right atrium during type I AF in humans. METHODS AND RESULTS: Pacing was performed at the high right atrium during type I AF in 24 patients in the electrophysiology laboratory. The response to pacing was assessed at cycle lengths 10, 20, 30, 40, and 50 ms less than the mean baseline atrial cycle length. Digitized tracings of the baseline tachycardia and the response to pacing were recorded from the high right atrium and from the distal coronary sinus. Computer analysis of these signals was used to calculate a left atrial electrogram density before, during, and after pacing. Two hundred eight-eight segments of AF with a duration of 3.9 +/- 0.5 seconds (mean +/- SD) were analyzed. Local capture of the right atrium during AF was demonstrated for at least one pacing cycle length in each patient. The left atrial electrogram density was significantly greater than baseline at each pacing cycle length that resulted in local capture, except when pacing at 50 ms less than the mean AF cycle length. There was no significant change in the baseline left atrial electrogram density compared with baseline when pacing did not result in local capture of AF. CONCLUSIONS: Local right atrial capture is often possible by pacing during type I AF and consistently influences the left atrial electrograms recorded in the coronary sinus. These results confirm the presence of excitable tissue in the right and left atria in type I AF.

Adult↗

PubMed1996

Reasons for prolonged or failed attempts at radiofrequency catheter ablation of accessory pathways.

OBJECTIVES: The purpose of this study was to categorize the reasons for a prolonged or failed procedure in a series of patients undergoing catheter ablation of an accessory pathway. BACKGROUND: Radiofrequency ablation of accessory pathways at times requires a lengthy procedure or a second ablation session, or both, and not prior studies have systematically investigated the reasons for this. METHODS: In a consecutive series of 619 patients undergoing catheter ablation of an accessory pathway, the mean ablation time +/- SD was 68 +/- 64 min. The subjects of this study were 14 patients who had an ablation time >2 SD greater than the mean (>196 min) and 51 patients who required a second ablation session for a successful outcome. The accessory pathway in the 65 patients in this study was located in the right free wall in 19 patients (29%), septum in 14 (22%) and left free wall in 32 (49%). RESULTS: The primary reasons for a lengthy or failed ablation attempt were 1) inability to position the ablation catheter at the effective target site (16 patients, 25%); 2) instability of the ablation catheter or inadequate tissue contact at the target site, or both (15 patients, 23%); 3) mapping error due to an oblique course of the accessory pathway (7 patients, 11%); 4) failure to recognize a posteroseptal accessory pathway as being left-sided instead of right-sided (4 patients, 6%); 5) other errors in accessory pathway localization (6 patients, 9%); 6) epicardial location of the accessory pathway (5 patients, 8%); 7) recurrent atrial fibrillation (2 patients, 3%); 8) occurrence of a complication (2 patients, 3%); 9) unusual right-sided accessory pathway that inserted in the anterior right ventricle, 2 cm away from the lateral tricuspid annulus (1 patient, 1.5%); and 10) unexplained factors (7 patients, 11%). The most common effective strategies employed to achieve a successful outcome in these patients were 1) substitution of a more experienced operator; 2) use of ablation catheters of varying configurations; 3) switching from a retrograde aortic to a trans-septal approach; 4) switching from an inferior to a superior vena caval approach; 5) use of a 60-cm guiding sheath; 6) detailed mapping of the atrial or ventricular insertion of the accessory pathway; and 7) searching within the coronary sinus for a presumed accessory pathway potential. CONCLUSIONS: A lengthy or failed attempt at catheter ablation of an accessory pathway may be due to a variety of reasons, the most common of which are problems related to some aspect of catheter manipulation and errors in accessory pathway localization. Knowledge of the most common reasons for a lengthy or ineffective procedure may facilitate successful outcome of accessory pathway ablation.

Adult↗

PubMed1996

QT dispersion in nonsustained ventricular tachycardia and coronary artery disease.

This study examines the relation between QT dispersion and the inducibility of ventricular tachycardia (VT) in 35 consecutive patients with coronary artery disease who underwent electrophysiologic testing for evaluation of nonsustained VT. The mean age of the patients was 66 +/- 9 years (+/- SD) and the mean left ventricular ejection fraction was 0.36 +/- 0.14. In 6 patients in whom sustained, monomorphic VT was inducible by programmed ventricular stimulation, QT dispersion was significantly greater than in the 29 patients in whom VT was not inducible (126 +/- 35 vs 67 +/- 25 ms, p < 0.001). All patients who had a QT dispersion > 120 ms had inducible sustained monomorphic VT, and no patient who had a QT dispersion < 90 ms had inducible VT. The patients who had inducible VT dis not differ significantly from those who did not with regard to age, gender, ejection fraction, RR interval, or mean QT. In conclusion, in patients with coronary artery disease who have nonsustained VT, inducibility of monomorphic VT is associated with an increase in QT dispersion. QT dispersion may be helpful in predicting which patients with nonsustained VT are and are not likely to have inducible VT by programmed stimulation.

Aged↗

PubMed1996

Prospective randomized comparison of anodal monophasic shocks versus biphasic cathodal shocks on defibrillation energy requirements.

Biphasic shocks are believed to be superior to monophasic shocks. Monophasic anodal shocks, as opposed to cathodal shocks, are associated with improved defibrillation energy requirements (DERs). However, it is unclear how the DER of anodal monophasic shocks compare with conventional biphasic shocks. Therefore the purpose of this study was to prospectively compare the DER of an anodal monophasic shock with that of a cathodal biphasic shock. A transvenous defibrillation lead with distal and proximal shocking electrodes was used. The subjects of this study were 20 consecutive patients with a mean age of 64.2 +/- 10.5 years ( +/- SD) and a mean left ventricular ejection fraction of 0.36 +/- 0.18. Six had had cardiac arrest. The DER, defined as the lowest energy that converted ventricular fibrillation to sinus rhythm, was determined twice with a step-down protocol (25 J, 20 J, 15 J, 10 J, 5 J, 3 J, 1 J). If the DER was > or = 25 J, then a subcutaneous patch was deemed necessary for system implantation. In random order the DER was determined with a monophasic anodal shock (distal electrode positive) and then with a cathodal (first phase, distal electrode negative) biphasic shock. The mean DER with anodal monophasic shocks was 15.1 +/- 8.5 J compared with 13.6 +/- 8.1 J with cathodal biphasic shocks (p = 0.4). A DER > or = 25 J was present in three patients with the monophasic waveform and in three patients with the biphasic waveform (p = NS). In conclusion, the DER and frequency of subcutaneous patch use with an anodal monophasic waveform is comparable to that obtained with cathodal biphasic waveform.

Aged↗

PubMed1996

Atrioventricular node properties in patients with accessory pathways.

A study during the era of surgical ablation suggested that atrioventricular (AV) nodal conduction is faster in patients with accessory pathways than in controls. In the present study, AV nodal characteristics were studied in 30 patients who underwent radiofrequency ablation of an accessory pathway and compared to 23 control patients. Sinus cycle length, AH and HV intervals, AV block cycle length, ventriculoatrial (VA) block cycle length, AV nodal effective refractory period, and VA effective refractory periods were measured in control and postablation accessory pathway patients before and after autonomic blockade with 0.04 mg/kg of atropine and 0.2 mg/kg of propranolol. The mean sinus cycle length in the control and accessory pathway groups did not differ significantly at baseline (798 +/- 211 and 766 +/- 156 msec, respectively) or after autonomic blockade (654 +/- 98 and 649 +/- 108 msec, respectively). The mean AH interval in the accessory pathway group (77 +/- 15 msec) was significantly shorter than in the control group (91 +/- 22 msec; p < 0.05) at baseline; however, there was no difference after autonomic blockade. No other significant differences were observed between the accessory pathway and control groups. These results demonstrate that AV nodal properties of patients with accessory pathways are not significantly different from controls and suggest that previously reported differences may have been due to selection bias.

Adult↗

PubMed1996

Comparison of atrial-His intervals in patients with and without dual atrioventricular nodal physiology and atrioventricular nodal reentrant tachycardia.

The purpose of this study was to compare the atrial-His intervals generated during programmed atrial stimulation in patients with and without dual atrioventricular nodal physiology and with and without inducible atrioventricular nodal reentrant tachycardia. Programmed atrial stimulation at a basic-drive cycle length of 500 to 600 msec was performed in 180 patients. The minimum atrial-His interval was defined as the atrial-His interval of the basic-drive beats. The maximum atrial-His interval was defined as the longest A2H2 interval. The criterion for dual atrioventricular nodal physiology was an increment of 50 msec in the A2H2 interval in association with a 10 msec decrement in the A1A2 interval. The minimum atrial-His interval was significantly shorter (106 +/- 34 msec vs 116 +/- 29 msec; p < 0.05) and the maximum atrial-His interval significantly longer (304 +/- 101 msec vs 222 +/- 56 msec; p < 0.001) in the 87 patients who had atrioventricular nodal reentry than in the 93 patients who did not. Among the 87 patients who had atrioventricular nodal reentry, the maximum atrial-His interval was significantly longer in 53 patients who had dual atrioventricular nodal physiology than in 34 patients who did not (340 +/- 105 msec vs 249 +/- 62 msec; p < 0.001). Among the 66 patients who had dual atrioventricular nodal physiology, the maximum atrial-His interval was significantly longer in 53 patients who had atrioventricular nodal reentry than in 13 patients who did not (340 +/- 105 msec vs 268 +/- 61 msec; p < 0.01). The insensitivity of the conventional dual atrioventricular nodal physiology criterion for the detection of dual atrioventricular nodal pathways is in part attributable to a lesser degree of slowing of conduction in the slow pathway relative to the fast pathway in some patients who have atrioventricular nodal reentry. The inability to demonstrate atrioventricular nodal reentry despite the presence of dual atrioventricular nodal physiology in some persons may be attributable in part to an inadequate degree of conduction delay in the slow pathway.

Atrioventricular Node↗

PubMed1996

Comparison of the ages of tachycardia onset in patients with atrioventricular nodal reentrant tachycardia and accessory pathway-mediated tachycardia.

Atrioventricular nodal reentrant tachycardia and accessory pathway-mediated tachycardia may have different ages of tachycardia onset. Symptom onset data were obtained in 519 patients (atrioventricular nodal reentrant tachycardia, 231, accessory pathway-mediated tachycardia, 288). The mean age of the patients at the time of evaluation was 47 +/- 17 years (atrioventricular nodal reentrant tachycardia) and 37 +/- 15 years (accessory pathway-mediated tachycardia). The mean age of symptom onset was 32 +/- 18 years for atrioventricular nodal reentrant tachycardia and 23 +/- 14 years for accessory pathway-mediated tachycardia. A significantly greater proportion of patients with atrioventricular nodal reentrant tachycardia had the initial onset of symptoms after the age of 20 years (atrioventricular nodal reentrant tachycardia, 67% vs accessory pathway-mediated tachycardia, 41%, p < 0.001). In summary, there is a different mean age of symptom onset for patients with atrioventricular nodal reentrant tachycardia and accessory pathway-mediated tachycardia.

Adult↗

PubMed1996

Evaluation and extraction of the Accufix atrial J lead.

The Accufix (Telectronics Pacing Systems, Englewood, Colo.) atrial active fixation pacemaker lead has a preformed J stiff retention wire that can fracture and erode through the atrium. We screened 85 patients with digital fluoroscopy and detected 18 (21%) lead fractures. Fourteen (16%) leads were successfully extracted by percutaneous techniques. The mean time for extraction and placement of a new atrial lead was 109 +/- 53 min, and a lead > 1 year old but not in the presence of a fracture was associated with a significantly longer extraction time. There were two extraction complications. One patient had a fever following the extraction, and one patient had a focal sensory deficit 1 week after the extraction probably caused by a paradoxical embolus. Standard percutaneous extraction tools can be used for successful and safe removal of a fractured Accufix lead.

Aged↗

PubMed1996

Use of isoproterenol during programmed ventricular stimulation in patients with coronary artery disease and nonsustained ventricular tachycardia.

Twenty-three consecutive patients (20 men and 3 women) with coronary artery disease and nonsustained ventricular tachycardia (VT) in whom sustained VT was not inducible in a baseline electrophysiology test underwent repeated testing during isoproterenol infusion to determine the inducibility of sustained monomorphic VT. After the baseline study, each patient received a 2 to 4 microgram/min infusion of isoproterenol (mean 2.5 +/- 0.8 microgram/min). The sinus cycle length shortened by a mean of 29% +/- 9% and programmed stimulation was repeated. Nineteen patients had no inducible sustained, monomorphic VT, two patients had only inducible nonsustained VT, and two patients had ventricular fibrillation. Patients were followed up for 10 to 20 months (mean 14.4 +/- 2.9 months) and had no syncope, sustained monomorphic VT, or sudden death. Isoproterenol infusion during programmed stimulation in patients with coronary heart disease and nonsustained VT does not facilitate the induction of sustained monomorphic VT.

Aged↗

PubMed1996

Slow pathway ablation in patients with documented but noninducible paroxysmal supraventricular tachycardia.

OBJECTIVES: The purpose of this study was to assess the clinical efficacy of radiofrequency ablation of the slow pathway in patients with documented but noninducible paroxysmal supraventricular tachycardia (PSVT) who have evidence of dual atrioventricular (AV) node pathways. BACKGROUND: Patients with a documented history of PSVT at times do not have inducible PSVT in the electrophysiology laboratory. Because dual AV node pathways serve as the substrate for AV node reentrant tachycardia (AVNRT), ablation of the slow pathway potentially may be useful in these patients. METHODS: The subjects in this prospective study were seven consecutive patients who underwent an electrophysiologic procedure because of documented PSVT and were found to have dual AV node physiology or inducible single AV node echo beats, but no inducible PSVT despite the administration of isoproterenol and atropine. Their mean (+/- SD) age was 33 +/- 13 years, and they had been symptomatic for 12 +/- 12 years. The frequency of the episodes of PSVT ranged from > or = 1/day to 1/month. The rate of the documented episodes ranged from 170 to 260 beats/min, and discrete P waves were not apparent. Slow pathway ablation was performed with 9 +/- 4 applications of radiofrequency energy using a combined anatomic and electrogram mapping approach. RESULTS: All evidence of dual AV node pathways was eliminated in six patients, and dual AV node physiology remained present in one patient. During a mean follow-up period of 15 +/- 10 months (range 8 to 27), no patient had a recurrence of symptomatic tachycardia (success rate 95% confidence interval 65% to 100%). CONCLUSIONS: Slow pathway ablation may be clinically useful in patients with documented but noinducible PSVT who have evidence of dual AV node pathways.

Adult↗

PubMed1996

2:1 atrioventricular block during atrioventricular node reentrant tachycardia.

OBJECTIVES: The purpose of this study was to determine the incidence and to clarify the mechanism of 2:1 atrioventricular (AV) block during AV node reentrant tachycardia induced in the electrophysiology laboratory. BACKGROUND: In patients with 2:1 AV block during AV node reentrant tachycardia, the absence of a His bundle potential in the blocked beats has been considered evidence of intranodal, lower common pathway block. METHODS: In consecutive patients with AV node reentrant tachycardia, the incidence of 2:1 AV block and the response to atropine and a single ventricular extrastimulus was observed. RESULTS: Persistent 2:1 AV block occurred in 13 of 139 patients with AV node reentrant tachycardia. A His bundle deflection was present in the blocked beats in eight patients and absent in five. Patients with 2:1 AV block had a shorter tachycardia cycle length than did patients without such block (mean +/- SD 312 +/- 32 vs. 353 +/- 55 ms, p < 0.01). Atropine did not alter the 2:1 block in any patient. In every patient, a single ventricular extrastimulus introduced during the tachycardia converted the 2:1 block to 1:1 conduction. CONCLUSIONS: The incidence of induced 2:1 AV block during AV node reentrant tachycardia is approximately 10%. The lack of a response to atropine and the consistent conversion of 2:1 block to 1:1 conduction by a ventricular extrastimulus indicate that, regardless of the presence or absence of a His bundle potential in blocked beats, 2:1 block during AV node reentrant tachycardia is due to functional infranodal block.

Adult↗

PubMed1996

Incidence of lead system malfunction detected during implantable defibrillator generator replacement.

Implantable cardioverter-defibrillator (ICD) generator replacement due to a depleted battery is a frequently performed procedure. The frequency with which sensing and defibrillation system failures are identified during device replacement procedures has not been previously described. Therefore, the purpose of this study was to prospectively determine the frequency of lead system malfunction detected at the time of device replacement in 55 consecutive patients undergoing ICD generator replacement. The mean age of the patients was 63 +/- 10 years and 40 of them were men. Forty-nine patients had an epicardial lead system, and six patients had a nonthoracotomy lead system. Four [7%] of these 55 patients were noted to have previously undetected lead system failure, either sensing (n = 3) or defibrillation (n = 1), necessitating system revision. The lead systems that failed were 40 +/- 6 months old (33-49 months). In summary, during ICD generator replacement, previously undetected problems with sensing or defibrillation may be identified in approximately 10% of patients. Therefore, a comprehensive evaluation of the sensing and the defibrillation functions should be an essential component of the ICD generator replacement procedure.

Defibrillators, Implantable↗

PubMed1996

Temperature and impedance monitoring during slow pathway ablation in patients with AV nodal reentrant tachycardia.

INTRODUCTION: Successful radiofrequency ablation of an accessory pathway has been demonstrated to be associated with an electrode-tissue interface temperature of approximately 60 degrees C or an impedance change of -5 to -10 omega. However, the temperature and impedance changes associated with ablation of AV nodal reentrant tachycardia (AVNRT) using the slow pathway approach have not been reported. Therefore, the purpose of this study was to define the temperature and impedance changes achieved during ablation of AVNRT: METHODS AND RESULTS: The study included 35 consecutive patients with AVNRT undergoing radiofrequency ablation of the slow pathway with a fixed power output of 32 W, and using a catheter with a thermistor bead embedded in the distal 4-mm electrode. The procedure was successful in each patient. The steady-state electrode-tissue interface temperature during successful applications of energy was 48.5 +/- 3.3 degrees C (range 42 degrees to 56 degrees C), and the steady-state temperature during ineffective applications was 46.8 degrees +/- 5.5 degrees C (P = 0.03). The mean impedance change during all applications of energy was -1.4 +/- 2.8 omega, and did not differ significantly during effective and ineffective applications. Coagulum formation resulted during five applications (2.7%) in two patients (5.7%). There were no recurrences during 114 +/- 21 days of follow-up. CONCLUSIONS: Successful ablation of AVNRT using fixed power output is achieved at an electrode-tissue interface temperature of approximately 48 degrees C and is associated with a drop in impedance of 1 to 2 omega. These findings suggest that slow pathway ablation requires less heating at the electrode-tissue interface than does accessory pathway or AV junction ablation.

Adult↗

PubMed1996

Randomized comparison of two techniques for titrating power during radiofrequency ablation of accessory pathways.

INTRODUCTION: The purpose of this study was to prospectively compare the value of impedance and temperature monitoring during accessory pathway ablation. Temperature and impedance monitoring can be used during radiofrequency ablation of accessory pathways to titrate power to achieve adequate but not excessive tissue heating. METHODS AND RESULTS: One hundred thirty-two patients with a single accessory pathway were randomly assigned to undergo ablation using either impedance monitoring or temperature monitoring. During impedance monitoring, the endpoint for titration of power was a 5- to 10-omega decrease in the measured impedance while for temperature monitoring the endpoint was to achieve a temperature of 58 degrees to 62 degrees C. Two protocols were used. In protocol 1 (90 patients), impedance monitoring was performed with a nonthermistor catheter and temperature monitoring was performed with a thermistor catheter. In protocol 2 (42 patients), a thermistor catheter was used in all patients. In protocol 1, the success rate (93% vs 93%; P = 1.0), ablation procedure duration (57 +/- 56 vs 41 +/- 41 min), fluoroscopy time (48 +/- 29 vs 41 +/- 23 min; P = 0.3), number of applications (6.2 +/- 4.7 vs 5.7 +/- 4.6; P = 0.8), and the number of applications associated with coagulum formation (0.1 +/- 0.3 vs 0.3 +/- 0.6; P = 0.1) were similar in the two groups. In protocol 2, as in protocol 1, there were no differences in the success rate (91% vs 95%; P = 1.0), ablation procedure duration (49 +/- 37 vs 62 +/- 55 min; P = 0.4), fluoroscopy time (46 +/- 24 vs 49 +/- 36 min; P = 0.8), number of applications (6.8 +/- 7.0 vs 7.8 +/- 12.1; P = 0.7), or number of applications associated with coagulum formation (0.3 +/- 0.6 vs 0.2 +/- 0.7; P = 0.6), between the impedance and temperature monitoring groups. CONCLUSION: Temperature and impedance monitoring are equally effective in optimizing the results of accessory pathway ablation.

Adult↗