Extracorporeal shockwave lithotripsy for ureterolithiasis in patients with urinary bilharziasis: efficacy and variables that influence treatment outcome.

OBJECTIVES: Schistosomiasis affecting the ureter is commonly accompanied by ureteric dilatation with or without ureteric stricture and altered ureteric wall motility that can influence extracorporeal shockwave lithotripsy (ESWL) results. This study attempts to identify variables that may influence the outcome of ESWL in the treatment of ureterolithiasis in patients with urinary bilharziasis. PATIENTS AND METHODS: Forty-three patients with urinary schistosomiasis and ureterolithiasis treated with ESWL were reviewed. The study data include characteristics of patients, stones, urinary tract treated and details of ESWL treatment. RESULTS: Thirty-five patients (81.3%) were stone-free at 3 months. Multivariate analysis with logistic regression identified two significant variables that influenced treatment outcome, namely the presence of ureteric stricture (p = 0.004) and the ESWL voltage (p = 0.003). Ten ureteric strictures were encountered in 9 patients (21%), the majority of these were diagnosed post-ESWL when patients failed to pass well-fragmented stones in spite of pre-ESWL evaluation. CONCLUSIONS: In situ ESWL is a safe and effective first line of treatment for urinary stones in bilharzial ureters. The presence of concomitant bilharzial stricture is a significant variable which affects the treatment outcome. Every effort should be made to rule out and deal with possible complicating factors such as ureteric strictures in the pretreatment period.

Extracorporeal shock wave lithotripsy for the rescue of post-endoscopic or surgically retained biliary duct stones: does saline irrigation affect the outcome?

Extracorporeal shock wave lithotripsy (ESWL) has been found valuable in situations where obstructing stones in the common bile or intrahepatic ducts are retained following surgery or attempted endoscopic removal. However, success rates are dependent on the type of ESWL system employed and upon a high frequency rate of repeated treatment sessions. We outline our experience with 23 cases of retained, obstructing bile duct stones, ranging in size from 10 to 40 mm diameter, treated with Dornier HM3 ESWL. In the initial 12 patients in the series, successful stone fragmentation occurred in 83% of cases with a median 1.6 treatment sessions. In the latter 11 cases in the series, patients were treated prone and the stone-bearing biliary duct was irrigated with saline solution during ESWL delivery. With this technique, successful stone break up was achieved in all patients (100%) with a single treatment session. Endoscopic sphincterotomy is, however, a prerequisite for extracorporeal lithotripsy and, despite the high success rates now available with new techniques, we believe the ESWL should continue to be employed in support of primary endoscopic methods of management for obstructing bile duct stones.

Radiofrequency ablation of idiopathic left anterior fascicular tachycardia.

INTRODUCTION: A 45-year-old man with idiopathic ventricular tachycardia (VT) having a right bundle branch block configuration with right-axis deviation underwent an electrophysiologic test. METHODS AND RESULTS: Mapping demonstrated a site on the anterobasal wall of the left ventricle where there was an excellent pace map and an endocardial activation time of -20 msec, but radiofrequency catheter ablation at this site was unsuccessful. At a nearby site, a presumed Purkinje potential preceded the by 30 msec during VT and sinus rhythm, and catheter ablation was effective despite a poor pace map and an endocardial ventricular activation time of zero. CONCLUSION: Idiopathic VT with a right bundle branch configuration and right-axis deviation may originate in the area of the left anterior fascicle. A potential presumed to represent a Purkinje potential may be more helpful than endocardial ventricular activation mapping or pace mapping in guiding ablation of this type of VT.

[Lithiasis of the tonsil. Questions, answers]. / Les lithiases de l'amygdale. Questions, réponses.

Imaging, clinical and frequency of the tonsil's calculi in function of the size of the calculi: inframillimetric calculi much frequent, not visible by imaging; small calculi from 1 to 7 mm frequent, visible by the imaging and much often asymptomatic; big ones superior of 7 mm rare, becoming exceptional and much often symptomatic above 15 mm.

Primary extracorporeal shockwave lithotripsy in management of large bladder calculi.

Large bladder calculi are often outside the range of treatment with conventional endoscopic lithotrites because of either anatomic factors or the mechanical limits of available instruments. Alternative methods of cystolithotripsy: ultrasonic, electrohydraulic, or laser, can prove time-consuming or even hazardous, so that open surgery is often the most expeditious option. We report our experience using Dornier HM3 extracorporeal shockwave lithotripsy (SWL) for initial bladder stone reduction preparatory to transurethral litholapaxy and definitive treatment of any underlying obstructive pathology. Primary cystolitholapaxy was judged impractical in these 24 patients (21 adults and 3 children) presenting 31 large bladder stones (mean size 35.6 mm). In all patients, primary transpelvic SWL was followed immediately by endoscopic evacuation of stone debris or cystolitholapaxy. In addition, 10 of the 24 patients (42%) underwent a definitive endoscopic operation for treatment of an underlying obstructive lesion at either the same or a follow-on session. Morbidity was minimal, and the mean hospital stay after the initial SWL treatment was 3.5 days. In our experience, Dornier SWL has proved invaluable in enabling cystolitholapaxy of very large bladder calculi that would otherwise require protracted and difficult endoscopic manipulation or open surgery.

Incidence of bacteremia and bacteriuria in patients with non-infection-related urinary stones undergoing extracorporeal shock wave lithotripsy.

In a prospective pilot study, 26 patients with non-infection-related renal or ureteric stones and sterile urine were examined for evidence of bacteriuria and bacteremia following extracorporeal shock wave lithotripsy (SWL). Blood samples were obtained for aerobic and anaerobic bacterial culture at the end of, and 1 hour after, the SWL procedure. Urine cultures were performed 24 hours before and after treatment. Bacteremia was recorded in 7.7% of the patients immediately after SWL but in no patient at 1 hour after treatment. None of the patients manifested significant bacteriuria or post-SWL fever. These findings support the contention that, provided the urine is sterile and a negative history of urosepsis is available, antibiotic prophylaxis is unnecessary in patients with non-infected renal stones submitted to SWL treatment.

The economic burden of unrecognized vasodepressor syncope.

BACKGROUND: The objective of this study was to describe the cost of prior diagnostic evaluation in patients referred for evaluation of syncope whose history was typical of vasodepressor syncope. METHODS AND RESULTS: Thirty consecutive patients who were referred for evaluation of syncope of undetermined origin and whose history was highly suggestive of vasodepressor syncope participated in this study. These 30 patients represented 19% of 158 patients referred for evaluation of syncope during the period of enrollment. All patients had positive results of an upright-tilt test, confirming the diagnosis of vasodepressor syncope. At the time of evaluation, the type and results of all diagnostic tests that had been performed prior to referral were recorded for each patient. The cost of diagnostic testing was then determined based on the 1991 cost of these tests at the University of Michigan Medical Center. A mean of 4 +/- 2 major diagnostic tests were performed before referral to the University of Michigan Medical Center. The mean and median costs of diagnostic testing per patient prior to referral were $3,763 +/- 3,820 and $2,678 (range: 0 to $16,606) respectively. Six patients underwent no major diagnostic tests prior to referral and, therefore, the cost of major diagnostic testing was zero in these patients. In the remaining patients, the mean and median costs of diagnostic testing per patient were $4,704 +/- 3,713 and $3,777 (range: $1,025 to $16,606) respectively. CONCLUSIONS: The results of this study demonstrate that a diagnosis of vasodepressor syncope can be established clinically in approximately 20% of patients referred to a university hospital for evaluation of syncope of undetermined origin. Failure to recognize the clinical features of vasodepressor syncope in these patients resulted in up to $16,000 of unnecessary diagnostic testing. A greater awareness of the clinical features of vasodepressor syncope may, therefore, result in significant economic savings.

Inducibility of atrial fibrillation before and after radiofrequency catheter ablation of accessory atrioventricular connections.

INTRODUCTION: The purpose of this study was to evaluate the inducibility of atrial fibrillation in patients with an accessory atrioventricular connection (AAVC) and to determine if the inducibility of atrial fibrillation is altered after successful radiofrequency catheter ablation of the AAVC. METHODS AND RESULTS: Thirty-seven patients with an AAVC and 36 control patients were prospectively evaluated using a standardized atrial pacing protocol. The high right atrium was paced using a 25-beat drive train, 1.5-second intertrain pause, 10-mA pulse amplitude, and 2-msec pulse duration at cycle lengths of 250 to 100 msec, in 10-msec decrements. Pacing was performed twice at each cycle length. Thirty patients with an AAVC underwent repeat atrial overdrive pacing after successful radiofrequency ablation of the AAVC. Atrial fibrillation was induced in 26 (70%) patients with an AAVC and 22 (61%) controls (P = NS). Atrial flutter was induced in 11 (30%) patients with an AAVC and 13 (36%) controls (P = NS). The cumulative percentage of patients with atrial fibrillation/flutter induced at each pacing cycle length was the same in each group. There was no difference in the duration of atrial fibrillation/flutter between control patients and patients with an AAVC. Among the 30 patients who underwent repeat atrial overdrive pacing after radiofrequency ablation of an AAVC, there was no difference in the inducibility or duration of atrial fibrillation/atrial flutter after ablation compared to baseline. CONCLUSION: These findings indicate that the vulnerability of the atrium to fibrillate in response to atrial pacing is independent of the presence of an AAVC.

Association between atrioventricular node reentrant tachycardia and inducible atrial flutter.

OBJECTIVES: The purpose of this study was to evaluate the inducibility of atrial flutter in patients with atrioventricular (AV) node reentrant tachycardia and to determine the effect of radio-frequency ablation of the slow AV node pathway on the inducibility of atrial flutter. BACKGROUND: Studies have shown that both AV node reentrant tachycardia and atrial flutter are reentrant arrhythmias having an area of slow conduction that is located in the low posterior right atrium near the ostium of the coronary sinus. METHODS: Ninety-one patients were prospectively evaluated using a standardized atrial pacing protocol. Three groups of patients were analyzed: 42 patients with inducible AV node reentrant tachycardia, 13 with a history of spontaneous atrial flutter and 36 control patients. A subgroup of 34 patients with AV node reentrant tachycardia who underwent successful radiofrequency ablation of the slow AV node pathway underwent atrial pacing again after ablation. RESULTS: Atrial flutter was more frequently inducible in patients with AV node reentrant tachycardia (88%) and in those with a history of atrial flutter (92%) than in control patients (36%) (p = 0.0001). There were no differences between the patient groups with respect to atrial effective refractory period, P wave duration or PA interval at the His position. Among the 34 patients with AV node reentrant tachycardia who underwent atrial pacing before and after radiofrequency ablation, there were 30 with atrial flutter and 4 with atrial fibrillation before ablation and 29 with atrial flutter and 5 with atrial fibrillation after ablation (p = NS). There was no difference in the duration of the induced atrial flutter before and after ablation. The mean atrial flutter cycle length before ablation (206 +/- 22 ms) was not different from that after ablation (196 +/- 20 ms) (p = NS). CONCLUSIONS: There is a strong association between AV node reentrant tachycardia and inducible atrial flutter, suggesting that there may be a common area of perinodal atrium participating in the two tachycardia circuits. However, radiofrequency ablation of the slow pathway of the AV node reentrant tachycardia circuit does not influence the inducibility of atrial flutter.

A randomized, prospective comparison of anterior and posterior approaches to radiofrequency catheter ablation of atrioventricular nodal reentry tachycardia.

BACKGROUND: Two different techniques have been developed for radiofrequency catheter ablation of typical atrioventricular nodal reentry (AVNRT). Lesions made anteriorly near the apex of the triangle of Koch usually eliminate fast pathway function, whereas lesions made posteriorly near the ostium of the coronary sinus selectively affect slow pathway function. The current study compares the safety, efficacy, and electrophysiological effects of these two techniques in a prospective, randomized fashion. METHODS AND RESULTS: Fifty consecutive patients with typical AVNRT were randomly assigned to receive radiofrequency lesions either anteriorly (n = 22) or posteriorly (n = 28). If the initial approach failed to eliminate inducibility of AVNRT after 1 hour or 10 applications of radiofrequency energy, the alternative ablation technique was used. Patients underwent repeat electrophysiological testing 48 hours and 3 months after ablation. The primary success rates of the anterior and posterior techniques were similar (55% versus 68%, p = NS). All of the patients who failed the initial approach were successfully treated by the alternative technique without developing high-grade atrioventricular block. One patient developed right bundle branch block during an anterior lesion, and another patient developed complete atrioventricular block as the result of a posterior lesion. CONCLUSIONS: The posterior approach to radiofrequency catheter modification of the atrioventricular node is as effective as the anterior approach, and both techniques are associated with a low risk of complications. As long as AVNRT persists, it appears safe to cross over from one technique to the other.

Relation between efficacy of radiofrequency catheter ablation and site of origin of idiopathic ventricular tachycardia.

The results of radiofrequency catheter ablation of ventricular tachycardia (VT) in patients without structural heart disease are reported. Particular attention was focused on the relation between efficacy and the site of origin of the VT. Eighteen consecutive patients (5 women and 13 men; mean age 41 +/- 13 years) with idiopathic VT underwent catheter ablation using radiofrequency energy. Sites for radiofrequency energy delivery were selected on the basis of pace mapping. A follow-up electrophysiologic test was performed 1 to 3 months after the ablation procedure. Twenty VTs were induced. Radiofrequency catheter ablation was successful in eliminating all 10 VTs originating from the right ventricular outflow tract, and 5 of 10 from other sites in the left or right ventricle. There were no complications. The duration of ablation sessions was shorter, the frequency of identifying a site resulting in an identical pace map was higher, and the efficacy of catheter ablation was greater for VTs originating from the right ventricular outflow tract than for those from other locations. The results of this study demonstrate that radiofrequency catheter ablation of idiopathic VT is safe and effective. The efficacy of the procedure is dependent on the site of origin of the VT, with the efficacy being greater for VTs originating from the outflow tract of the right ventricle than for those from other locations.

Safety, feasibility and cost of outpatient radiofrequency catheter ablation of accessory atrioventricular connections.

OBJECTIVES: The purpose of this study was to evaluate prospectively the safety, feasibility and cost of performing radiofrequency catheter ablation of accessory atrioventricular (AV) connections on an outpatient basis in 137 cases. BACKGROUND: The efficacy and low complication rate of radiofrequency ablation as performed in the hospital suggested that it might be feasible to perform it on an outpatient basis. METHODS: In 100 cases (73%) performed between September 1, 1991 and April 20, 1992, patients met criteria for treatment as outpatients. Reasons for exclusion were age < 13 or > 70 years (4), anteroseptal location of the accessory AV connection (5 patients), obesity (> 30% of ideal body weight) (4 patients) or clinical indication for hospitalization (24 patients). Patients with only venous punctures had a recovery period of 3 h and those with arterial punctures had a recovery period of 6 h. There were 63 men and 32 women (5 patients underwent two ablation procedures > 1 month apart), with a mean age +/- SD of 36 +/- 13 years. The pathway was left-sided in 67 cases and right-sided or posteroseptal in 33. RESULTS: The procedure was successful in 97 of 100 cases, with a mean procedure duration of 99 +/- 42 min. In 70 cases the patient was discharged the day of ablation, and in 30 cases the patient required a short (< or = 18-h) overnight stay because the procedure was completed too late in the day for recovery in the outpatient facility. The mean duration of observation was 4.8 +/- 1.5 h for outpatients and 15 +/- 1.4 h for patients who underwent overnight hospitalization. At follow-up study, two patients had a clinically significant complication; both had a femoral artery pseudoaneurysm detected > or = 1 week after the procedure and both required surgical repair. Thirty consecutive patients (22 outpatients and 8 hospitalized overnight) undergoing catheter ablation after January 1, 1992 were chosen for a cost analysis. The mean cost of the procedure was $10,183 +/- $1,082. CONCLUSIONS: The majority of patients undergoing radiofrequency catheter ablation of an accessory AV connection can be treated safely on an outpatient basis.

Titration of power output during radiofrequency catheter ablation of atrioventricular nodal reentrant tachycardia.

Radiofrequency lesions in the anterior, superior aspect of the tricuspid annulus result in selective elimination of fast pathway function in patients with typical atrioventricular (AV) nodal reentry tachycardia. This technique is simple and effective, but has been associated with a significant risk of inadvertent complete AV block. The purpose of this study was to compare the safety and effectiveness of two different techniques for radiofrequency catheter ablation of the fast AV nodal pathway. Initially, a fixed power output was used at each target site. This method was compared retrospectively to a newer technique where power output was gradually incremented at each site. Radiofrequency power was initially applied at 10 watts for 10-15 seconds. If no junctional ectopy or a change in PR interval was seen, power output was incremented by 2 to 4 watts every 10 to 15 seconds up to a maximum of 30 watts. Thirty seven of 38 (96%) patients treated using this incremental power output were cured of their AV nodal reentry tachycardia. None of these patients developed inadvertent complete AV block. In contrast, 92% of historic controls treated with a fixed power output between 20 and 30 watts achieved a primary success and nine of these 89 (10%) historic controls developed inadvertent complete AV block (P = 0.04). There was no difference in the amplitudes of atrial, His, or ventricular electrograms at the effective sites between the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Radiofrequency catheter ablation of ventricular tachycardia in patients with coronary artery disease.

BACKGROUND: Radiofrequency (RF) ablation of idiopathic ventricular tachycardia (VT) has been demonstrated to be highly efficacious, but the efficacy of RF ablation of VT in patients with coronary artery disease has been unknown. Therefore, the purpose of this study was to determine the feasibility of RF ablation of VT in patients with coronary artery disease. METHODS AND RESULTS: Fifteen consecutive patients with coronary artery disease and a history of myocardial infarction underwent an attempt at RF ablation of 16 hemodynamically stable monomorphic VTs that had been documented clinically on a 12-lead ECG and that had not been successfully managed by pharmacological or device therapy. One VT was incessant, five occurred more than 25 times, and the remainder occurred two to 20 times. An additional four VTs that had not been documented clinically also were targeted for ablation. The mean age of the patients was 68 +/- 7 years (+/- SD), and their mean left ventricular ejection fraction was 0.27 +/- 0.08. The mean cycle length of the 20 VTs targeted for ablation was 438 +/- 82 msec. Ablation sites were selected based on endocardial activation mapping, pace mapping, identification of an isolated mid-diastolic potential, or concealed entrainment. Sixteen of the 20 VTs (80%) were successfully ablated in 11 of 15 patients (73%), using a mean of 4.2 +/- 3 applications of RF energy, and no recurrences of the ablated VTs occurred during 9.1 +/- 3.3 months of follow-up. The mean duration of the ablation procedures was 128 +/- 30 minutes. No complications occurred in any of the patients. CONCLUSIONS: The results of this study demonstrate that RF ablation of hemodynamically stable VT is feasible as adjunctive therapy in selected patients with coronary artery disease.

A prospective randomized comparison of direct current and radiofrequency ablation of the atrioventricular junction.

OBJECTIVES: The purpose of this study was to compare direct current and radiofrequency ablation of the atrioventricular (AV) junction in a prospective randomized fashion. BACKGROUND: Catheter ablation of the AV junction can be performed using either direct current shocks or radiofrequency energy. To date, these two techniques have never been compared prospectively or in a randomized study. METHODS: Forty patients with drug-refractory uncontrolled atrial fibrillation-flutter (38 patients) or inappropriate sinus tachycardia (2 patients) were randomly assigned to undergo direct current ablation (20 patients) using up to four shocks of 200 to 300 J or radiofrequency ablation (20 patients) using up to 15 applications of 16 to 25 W for 30 s. If complete AV block was not successfully induced, the ablation procedure was repeated using the alternate type of energy. A rate-responsive ventricular pacemaker was implanted in each patient. The intrinsic escape rhythm was evaluated 15 min, 2 days and 3, 6 and 12 months after ablation. RESULTS: Persistent complete AV block was successfully induced during the first ablation session in 13 (65%) of 20 patients randomly assigned to undergo direct current ablation, compared with 19 (95%) of 20 patients randomly assigned to undergo radiofrequency ablation (p < 0.05). Each patient whose first ablation attempt failed had a successful outcome with the alternate type of energy. The overall efficacy of radiofrequency ablation (26 [96%] of 27 patients) was significantly greater than that of direct current ablation (14 [67%] of 21 patients, p < 0.01). The duration of the direct current and radiofrequency ablation sessions did not differ significantly. The mean peak plasma creatine kinase MB fraction concentration was significantly higher after direct current ablation (58 +/- 29 IU/liter) than after radiofrequency ablation (2 +/- 2 IU/liter) (p < 0.001). An escape rhythm was present 15 min after ablation in an equal proportion of patients undergoing direct current and radiofrequency ablation (78% and 85%, respectively, p = 0.6). An escape rhythm was present in all patients 3, 6 and 12 months after ablation. The mean escape rhythm cycle length 15 min after direct current ablation (2,074 +/- 677 ms) was significantly longer than that 15 min after radiofrequency ablation (1,460 +/- 294 ms) (p < 0.05); however, the mean escape rhythm cycle lengths did not differ significantly at 2 days or 3, 6 or 12 months after ablation. Immediate arrhythmic complications did not occur after either procedure. One patient died suddenly 6.5 months after direct current ablation. CONCLUSIONS: Radiofrequency ablation of the AV junction is more efficacious and safer than direct current ablation and should be the preferred method for inducing complete AV block in patients who are appropriate candidates for ablation of AV conduction.

Differentiation of paroxysmal narrow QRS complex tachycardias using the 12-lead electrocardiogram.

OBJECTIVES: The purpose of this study was to evaluate the utility of the 12-lead electrocardiogram (ECG) for differentiating paroxysmal narrow QRS complex tachycardias. BACKGROUND: Previous studies evaluating the utility of the 12-lead ECG for differentiating paroxysmal supraventricular tachycardia types have shown conflicting results on the usefulness of some ECG criteria, and some criteria that are considered to be useful have never been formally evaluated. METHODS: Two hundred forty-two ECGs demonstrating paroxysmal narrow QRS complex (< 0.11 ms) tachycardia (rate > or = 120 beats/min) were analyzed. All ECGs were analyzed by an observer who had no knowledge of the mechanism of the tachycardia. RESULTS: There were 137 atrioventricular (AV) reciprocating tachycardias, 93 AV node reentrant tachycardias and 12 atrial tachycardias. Six criteria were found to be significantly different between tachycardia types by univariate analysis. A P wave separate from the QRS complex was observed more frequently in AV reciprocating tachycardia (68%) and atrial tachycardias (75%). A pseudo r' deflection in lead V1 and a pseudo S wave in the inferior leads were more common in AV node reentrant tachycardia (58% and 14%, respectively); QRS alternans was present more often during AV reciprocating tachycardia (27%). When a P wave was present, an RP/PR interval ratio > or = 1 was more common in atrial tachycardias (89%). During sinus rhythm, manifest pre-excitation was observed more often in patients with AV reciprocating tachycardia (45%). By multivariate analysis, the presence of a P wave separate from the QRS complex, pseudo r' deflection in lead V1, QRS alternans during tachycardia and the presence of pre-excitation during sinus rhythm were independent predictors of tachycardia type. These criteria correctly identified 86% of AV node reentrant tachycardias, 81% of AV reciprocating tachycardias and incorrectly assigned the tachycardia type in 19% of cases. CONCLUSIONS: Several features on the ECG are useful for differentiating supraventricular tachycardia type. However, approximately 20% of tachycardias may be incorrectly classified on the basis of analysis of the ECG; therefore, the ECG should not serve as the sole means for determining tachycardia mechanism.

Comparison of fixed burst versus decremental burst pacing for termination of ventricular tachycardia.

The objective of this study was to compare prospectively the efficacy of fixed burst pacing with that of decremental burst pacing in terminating VT. Forty-four patients with inducible sustained monomorphic VT were studied. The efficacy of fixed burst and decremental burst pacing for terminating 57 distinct types of VT were compared during 50 electrophysiology tests (mean VT cycle length = 334 +/- 84 msec). Termination of each type of VT was attempted with fixed burst and decremental burst pacing. Both pacing algorithms were delivered in an adaptive fashion with an increasing number of stimuli with each successive attempt at VT termination. Seventy percent of VT episodes were successfully terminated with fixed burst pacing. The mean number of stimuli required for VT termination was 5 +/- 2. Seventy-two percent of VT episodes were successfully terminated with decremental burst pacing. The mean number of stimuli required for VT termination was 5 +/- 2. For fixed burst and decremental burst pacing, the efficacy of VT termination was greater for VTs with a cycle length > 300 msec than for faster VTs (P < 0.05). The efficacy of VT termination and the incidence of VT acceleration were no different for the two pacing algorithms (P > 0.1). The results of this study demonstrate that fixed burst and decremental burst pacing are equally effective in terminating VT and that a single adaptive pacing algorithm is effective in terminating nearly three fourths of VTs.

Temperature monitoring during radiofrequency catheter ablation of accessory pathways.

BACKGROUND: Animal studies have suggested that the temperature of the electrode-tissue interface during radiofrequency catheter ablation accurately predicts lesion size. The purpose of the current study was to evaluate the utility of continuous temperature monitoring during radiofrequency catheter ablation in patients with Wolff-Parkinson-White syndrome. METHODS AND RESULTS: Twenty patients with manifest preexcitation were included in the study. The ablation catheter was positioned on the ventricular side of the mitral annulus for left-sided accessory pathways and on the atrial side of the tricuspid annulus for right-sided and septal accessory pathways. A thermistor imbedded in the distal electrode of the ablation catheter allowed continuous temperature monitoring during each energy application. To define the relation between power and temperature, radiofrequency current was applied several times at each site using outputs of 20, 30, 40, and 50 W. The accessory pathways were successfully ablated in each of the 20 patients. Because of marked variability in the efficiency of heating between sites, power output did not predict temperature. However, at any given site, there was a positive dose-response relation between power and temperature. Radiofrequency energy applications on the atrial side of the tricuspid annulus produced lower temperatures than did applications on the ventricular side of the mitral annulus (49 +/- 7 versus 60 +/- 16 degrees C, p = 0.0001). Transient block in the accessory pathways occurred at a mean of 50 +/- 8 degrees C, whereas permanent block was seen at a mean of 62 +/- 15 degrees C (p = 0.0001). Less than half of the applications at outputs < or = 40 W produced temperatures adequate to interrupt accessory pathway conduction. An abrupt rise in impedance caused by coagulum formation occurred only at temperatures between 95 and 100 degrees C. CONCLUSIONS: Temperature monitoring may facilitate radiofrequency catheter ablation of accessory pathways. By adjusting power output to ensure that adequate but not excessive temperatures have been achieved, a rise in impedance can be avoided and the total number of energy applications and procedure duration may be reduced.