Vicken R. Vorperian

Randomized comparison of anatomic and electrogram mapping approaches to ablation of the slow pathway of atrioventricular node reentrant tachycardia.

OBJECTIVES The purpose of this study was to prospectively compare in random fashion an anatomic and an electrogram mapping approach for ablation of the slow pathway of atrioventricular (AV) node reentrant tachycardia. BACKGROUND Ablation of the slow pathway in patients with AV node reentrant tachycardia can be performed by using either an anatomic or an electrogram mapping approach to identify target sites for ablation. These two approaches have never been compared prospectively. METHODS Fifty consecutive patients with typical AV node reentrant tachycardia were randomly assigned to undergo either an anatomic or an electrogram mapping approach for ablation of the slow AV node pathway. In 25 patients randomly assigned to the anatomic approach, sequential radiofrequency energy applications were delivered along the tricuspid annulus from the level of the coronary sinus ostium to the His bundle position. In 25 patients assigned to the electrogram mapping approach, target sites along the posteromedial tricuspid annulus near the coronary sinus ostium were sought where there was a multicomponent atrial electrogram or evidence of a possible slow pathway potential. If the initial approach was ineffective after 12 radiofrequency energy applications, the alternative approach was then used. RESULTS The anatomic approach was effective in 21 (84%) of 25 patients, and the electrogram mapping approach was effective in all 25 patients (100%) randomly assigned to this technique (p = 0.1). The four patients with an ineffective anatomic approach had a successful outcome with the electrogram mapping approach. On the basis of intention to treat analysis, there were no significant differences between the electrogram mapping approach and the anatomic approach with respect to the time required for ablation (28 +/- 21 and 31 +/- 31 min, respectively, mean +/- SD, p = 0.7) duration of fluoroscopic exposure (27 +/- 20 and 27 +/- 18 min, respectively, p = 0.9) or mean number of radiofrequency applications delivered (6.3 +/- 3.9 vs. 7.2 +/- 8.0, p = 0.6). With both the anatomic and electrogram mapping approaches, the atrial electrogram duration and number of peaks in the atrial electrogram were significantly greater at successful target sites than at unsuccessful target sites. CONCLUSIONS The anatomic and electrogram mapping approaches for ablation of the slow AV nodal pathway are comparable in efficacy and duration. If the anatomic approach is initially attempted and fails, the electrogram mapping approach may be successful at sites outside the areas targeted in the anatomic approach. With both the anatomic and electrogram mapping approaches, there are significant differences in the atrial electrogram configuration between successful and unsuccessful target sites.

Recognition and catheter ablation of subepicardial accessory pathways

OBJECTIVES The purpose of this study was to characterize left-sided accessory pathways that traverse the atrioventricular (AV) groove subepicardially and to describe results of radiofrequency catheter ablation within the coronary sinus in the patients studied. BACKGROUND Radiofrequency catheter ablation has proved to be a safe and effective method for treatment of accessory pathways; however, subepicardial accessory pathways may account for some of the failures encountered during endocardial ablation. METHODS The study group comprised 51 consecutive patients with a left-sided accessory pathway who were undergoing radio-frequency catheter ablation. Initially, the ablation catheter was introduced into a femoral artery and positioned on the ventricular aspect of the mitral annulus. If this endocardial approach was unsuccessful, the ablation catheter was introduced into the coronary sinus and energy applied at sites with shorter activation times than those recorded from the endocardium. RESULTS Five (10%) of 51 patients with a left-sided accessory pathway could not have accessory pathway conduction interrupted with a median of 18 endocardial radiofrequency energy applications. Accessory pathway potentials were less frequent during endocardial mapping in these 5 patients than in the 46 patients whose accessory pathway was successfully ablated from the endocardial surface. All five of these patients later had successful ablation using one or two applications of radiofrequency energy from within the coronary sinus. Effective target site electrograms in the coronary sinus were characterized by an accessory pathway potential that was larger than the corresponding atrial or ventricular electrogram. There were no complications or recurrences after ablation within the coronary sinus. CONCLUSIONS Some left-sided accessory pathways may be difficult to ablate from the endocardial surface because they traverse the AV groove subepicardially. The absence of an accessory pathway potential during endocardial mapping in combination with a relatively large accessory pathway potential within the coronary sinus may be a useful marker of a subepicardial pathway. In this select group of patients, radiofrequency catheter ablation from within the coronary sinus appears to enhance efficacy.

Relation between impedance and endocardial contact during radiofrequency catheter ablation

Lesion size during radiofrequency catheter ablation in patients with paroxysmal supraventricular tachycardia (PSVT) is thought to be related to multiple factors, including contact pressure at the catheter-endocardial interface. Therefore a predictor of contact pressure at a potential target site for ablation might be useful. In this study 25 patients underwent duplicate 2 W applications of radiofrequency energy with the catheter in poor and firm contact with the right ventricular endocardium after successful ablation treatment for PSVT. The mean age of the patients was 44 +/- 15 years. Fifteen patients underwent slow pathway ablation for atrioventricular nodal reentrant tachycardia, and 10 patients underwent ablation for an accessory pathway. The mean impedance for low-energy applications in firm contact (139 +/- 24 ohms) was 22% +/- 13% greater (p 0.0001) than in poor contact with the right ventricle (113 +/- 16 ohms). The maximum impedance was 27% greater when the catheter was in firm (147 +/- 28 ohms) rather than poor contact (116 +/- 16 ohms), with the endocardium (p 0.0001). These results suggest that higher impedance measurements may be obtained with low-energy applications of 2 W when the ablation catheter is in firm contact with the endocardium.

A randomized comparison of the right- and left-sided approaches to ablation of the atrioventricular junction

Radiofrequency ablation of the atrioventricular (AV) junction may be performed using either a right- or left-sided approach. This study prospectively compared the left-sided approach with persistent attempts from the right side in patients in whom initial radiofrequency applications on the right side were unsuccessful. Twenty-one of 54 patients did not have complete AV block induced after 3 right-sided radiofrequency applications. These 21 patients were randomly assigned to undergo either the left-sided approach (n = 10) or to undergo additional attempts from the right side (n = 11). The right-sided approach was performed by positioning the ablation catheter to record the largest possible atrial and His bundle electrograms. The left-sided approach was performed by positioning the ablation catheter along the left ventricular septum, where a His bundle potential was recorded. If either approach was not successful after an additional 17 radiofrequency applications, the alternative approach was then used. The AV junction was successfully ablated in all 10 patients randomized to the left-sided approach, but in only 6 of 11 patients randomized to persistent right-sided attempts (p < 0.05). The 5 patients in whom the AV junction was not successfully ablated using the right-sided approach underwent the left-sided approach and had a successful outcome after a mean of 1.2 +/- 0.4 radiofrequency applications. The left-sided approach required significantly fewer radiofrequency applications after randomization than the right-sided approach (3 +/- 3.4 vs 11 +/- 7.6, p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Radiofrequency Catheter Ablation of AtypicalAtrioventricular Nodal Reentrant Tachycardia

Ablation of Atypical Atrioventricular Nodal Reentrant Tachycardia, Introduction: Published reports of radiofrequency ablation of atypical atrioventricular nodal reentranttacbycardia (AVNRT) have been limited. We present our experience in 10 consecutive patientswith atypical AVNRT wbo underwent radiofrequency ablation of the “slow” AV nodal pathway.

Safety and cost of outpatient radiofrequency ablation of the slow pathway in patients with atrioventricular nodal reentrant tachycardia

Abstract Radiofrequency ablation of atrioventricular (AV) nodal reentrant tachycardia has been shown to be an effective and safe treatment and to have a significant cost advantage over other forms of therapy. 1 In studies reported to date, patients were hospitalized for 2 to 10 days after slow pathway ablation to monitor for possible complications or a recurrence of the tachycardia. 2,3 A previous study reported that radiofrequency ablation of accessory pathways can be performed safely on an outpatient basis, 4 but no prior studies evaluated the safety of outpatient radiofrequency ablation of the slow pathway in patients with AV nodal reentrant tachycardia. Therefore, the purpose of this study was to evaluate the safety and cost of performing radiofrequency catheter ablation of the slow AV nodal pathway on an outpatient basis.

Effect of accessory pathway location on the efficiency of heating during radiofrequency catheter ablation

During radiofrequency catheter ablation of accessory pathways there is a poor correlation between applied power and temperature at target sites for catheter ablation. This study was designed to examine the relation between power and temperature during radiofrequency catheter ablation in patients with accessory pathways and to identify the factors that affect the efficiency of heating, defined as the ratio of applied power and temperature. Twenty-nine patients underwent radiofrequency catheter ablation of an accessory pathway. Among 257 energy applications, 108 were applied for ablation of a right-sided accessory pathway, 105 for a left-sided accessory pathway, and 44 for a posteroseptal accessory pathway. During each application of radiofrequency energy, temperature was continually monitored by use of an ablation catheter with a thermistor embedded in the tip of the distal electrode. During some applications of energy, fluctuations in temperature were observed. The average power, impedance, temperature, and efficiency of heating for all applications of radiofrequency energy was 37 +/- 11 W, 100 +/- 9 ohms, 53 +/- 9 degrees C, and 1.7 +/- 0.8 degrees C/W (range 0.9 degrees to 6.6 degrees C/W), respectively. The efficiency of heating varied by location (p < 0.0001), with the greatest efficiency of heating for posteroseptal energy applications (2.3 +/- 1.2 degrees C/W, which were significantly greater than for left-sided (1.8 +/- 0.8 degrees C/W; p < 0.01) or right-sided (1.2 +/- 0.4 degrees C/W; p < 0.0001) applications. Phasic fluctuation in temperature was observed during 127 (49%) energy applications, and the efficiency of heating was 1.5 +/- 0.7 degrees C/W.(ABSTRACT TRUNCATED AT 250 WORDS)

Prospective, randomized comparison of conventional and high dose loading regimens of amiodarone in the treatment of ventricular tachycardia.

OBJECTIVES The purpose of this prospective randomized study was to compare the electrophysiologic effects of conventional and high dose loading regimens of amiodarone in patients with sustained ventricular tachycardia. BACKGROUND Uncontrolled studies in which patients have been treated with an oral loading dose of 2 to 4 g/day of amiodarone have suggested that, compared with a conventional loading dose, this dosing regimen results in more rapid control of spontaneous ventricular tachycardia and ventricular tachycardia induced by programmed stimulation. METHODS Patients in whom sustained monomorphic ventricular tachycardia was inducible by programmed stimulation and who were refractory to class I antiarrhythmic medications were randomly assigned to receive either a conventional (n = 15) or a high (n = 17) loading dose of amiodarone. The conventional dose consisted of 600 mg twice a day for 10 days. The high dose regimen consisted of 50 mg/kg body weight per day on days 1 to 3, 30 mg/kg per day on days 4 and 5 and 600 mg twice a day on days 6 to 10. An electrophysiologic test was performed in the baseline state and after 3 and 10 days of therapy. An adequate response to amiodarone was defined as the inability to induce ventricular tachycardia or the ability to induce only relatively slow (cycle length > or = 350 ms) hemodynamically stable ventricular tachycardia. RESULTS After 3 days of therapy, 2 of 14 patients who received the conventional loading dose and 6 of 15 patients who received the high dose loading regimen had an adequate response to amiodarone (p = 0.08). After 10 days of therapy, four patients in each group had an adequate response to amiodarone (p = NS). Three patients who received the high dose and one patient who received the conventional dose of amiodarone had an adequate response after 3 days of therapy but not after 10 days of therapy. There were significant increases in the sinus cycle length, atrioventricular block cycle length, ventricular effective refractory period and ventricular tachycardia cycle length after 3 and 10 days of therapy compared with baseline values regardless of the dosing regimen. The extent of the effects of amiodarone on these variables after 3 and 10 days of therapy was similar with both dosing regimens. CONCLUSIONS The therapeutic and electrophysiologic effects of conventional and high dose loading regimens of amiodarone do not differ significantly after 3 or 10 days of therapy. High oral loading doses of amiodarone do not offer any significant clinical advantage over a conventional loading dose of amiodarone for controlling ventricular tachycardia induced by programmed stimulation.

Effect of Pacing Site on the Atrial Electrogram at Target Sites for Slow Pathway Ablation in Patients with Atrioventricular Nodal Reentrant Tachycardia

Atrial electrograms recorded from target sites during radiofrequency catheter ablation of the slow atrioventricular (AV) nodal pathway are often fractionated and may be associated with a late, high frequency component (the slow pathway potential). The purpose of the current study was to assess the effects of slow pathway ablation on the morphology of the atrial electrogram and to determine whether target site electrograms display direction dependent changes in morphology during atrial pacing maneuvers. Twenty‐six patients with typical AV nodal reentry had electrograms recorded from target sites before and after successful ablation of the slow A V nodal path way and during pacing from the high right atrium and distal coronary sin us at cycle lengths of 500 and 300 msec. There was no significant change in the duration or degree of fractionation of the atrial electrogram as the result of slow pathway ablation. In contrast, the duration and degree of fractionation were less when pacing from the coronary sinus compared with sinus rhythms or right atrial pacing. Pacing rate did not affect electrogram morphology. These data suggest that the morphology of the slow pathway target site electrogram is dependent on the direction of atrial activation and that the “slow pathway potential” does not represent activation of an anatomically discrete pathway.

Double Retrograde Atrial Response After Radiofrequency Ablation of Typical AV Nodal Reentrant Tachycardia

Double Atrial Response. This case report describes a patient in whom a single ventricular depolarization resulted in a double atrial response and the initiation of atypical A V nodal reentrant tachycardia after successful radiofrequency ablation of typical AV nodal reentrant tachycardia using the slow pathway approach. (J Cardiovasc Electrophysiol, Vol. 4, pp. 695–701, December 1993)