Luis A. Pires

Use of the Saline Infusion Electrode Catheter for Improved Energy Delivery and Increased Lesion Size in Radiofrequency Catheter Ablation

Although radiofrequency catheter ablation has undergone explosive growth as the treatment for a variety of arrhythmias, a limiting factor with the existing catheter delivery system has been the relatively small size of the lesions, which appears to be in part due to coagulum formation around the catheter tip, producing a rise in impedance and limiting energy delivery. In order to test the hypothesis that infusion of saline during radiofrequency current application can increase the lesion size and decrease the incidence of impedance rise, ten dogs were each given two radiofrequency ablation lesions to the left ventricular endocardium. One of these lesions was delivered with a standard 7 French quadripolar catheter with a 2‐mm tip, and the second was done with a 7 French Iuminal electrode catheter (also with a 2‐mm tip) for the infusion of normal saline during the delivery of radiofrequency energy. Energy was delivered for 60 seconds at either 10 or 20 watts at two distinct sites in the left ventricle for each animal. Four to 7 days following ablation, the animals were sacrificed for pathological examination. The lesions created with the saline infusion catheter were significantly bigger than those produced with a standard catheter (7.3 × 7.0 × 5.1 vs 5.2 × 4.9 × 3.5 mm, respectively, P < 0.001). At the lower energy level (10 W), none of the animals with the saline infusion catheter experienced an impedance rise versus 3 of 5 of the animals in whom the standard catheter was used. At the higher level (20 W), only 1 of 5 dogs had an impedance rise with the saline infusion catheter versus 5 of 5 with the standard catheter. We conclude that the use of a saline infusion catheter for radiofrequency energy delivery during catheter ablation produces a significantly larger lesion than that produced with a standard catheter and is effective in preventing impedance rise.

Cardiovascular complications after radiofrequency catheter ablation of supraventricular tachyarrhythmias

Abstract We report the incidence of cardiovascular complications in patients receiving RF catheter ablation for supraventricular tachyarrhythmias. To reduce the incidence of complications, a rigid guideline or policy for the personnel and facilities should be followed. A prospective, multicenter registry program may be needed to further define the complications associated with this procedure.

Prolonged bradyarrhythmias after isolated coronary artery bypass graft surgery

To evaluate clinical and electrocardiographic (ECG) characteristics that may predict the occurrence of bradyarrhythmias after isolated coronary artery bypass graft (CABG) surgery, 1614 consecutive patients who had this procedure performed at our institution from January 1988 to December 1990 were reviewed. Thirteen (0.8%, 7 males and 6 females) patients had prolonged (mean 10.5 +/- 6.5 days) postoperative bradyarrhythmias and required insertion of a permanent pacemaker. Complete heart block occurred in eight patients and sinus node dysfunction in five. These 13 patients (group A) were compared with a group of 490 arbitrarily selected CABG patients (group B) without bradyarrhythmias whose preoperative ECGs were reviewed. Patients in group A were older (mean 69.2 vs 62.8 years; p = 0.0004) and had concomitant left ventricular (LV) aneurysmectomy more frequently (p = 0.02) and internal mammary graft revascularization less frequently (p = 0.022) than group B patients. Review of preoperative ECGs revealed a higher occurrence of complete left bundle branch block (LBBB) (5 of 13 vs 6 of 490; p < 0.0001) and a borderline, more leftward frontal plane QRS axis (-5.3 vs 13.1 degrees, p = 0.068) in group A patients. There were no differences between the groups with respect to gender, number of bypass grafts, location of prior myocardial infarction, and preoperative ECG intervals (PR, QRS, QTc). Multivariate analysis identified the presence of a preoperative LBBB, concomitant LV aneurysmectomy and age > 64 years as independent predictors of severe and prolonged postoperative bradyarrhythmias, mainly complete heart block.(ABSTRACT TRUNCATED AT 250 WORDS)

Radiofrequency Catheter Ablation of the Atrioventricular Junction by a Supravalvular Noncoronary Aortic Cusp Approach

Radiofrequency catheter ablation of the atrioventricular janction is usually achieved from either the right or left atrioventricular junction. We describe a new approach in which the atrioventricular junction was successfully ablated from the supravalvular region of the noncoronary cusp of the aortic valve in an unusual patient in whom conventional approaches were unsuccessful.

Clinical Utility of Routine Transthoracic Echocardiographic Studies After Uncomplicated Radiofrequency Catheter Ablation: A Prospective Multicenter Study

Unsuspected cardiac complications have been occasionally identified on postablation echocardiographic studies; however, the clinical utility of route echocardiographic studies following uncomplicated radiofrequency catheter ablation procedures has not been established. Two‐dimensional/Doppler echocardiographic studies obtained preablation (within 3 months of the procedure) in 355 consecutive patients (180 males and 175 females, mean age 37 ± 21 years) were compared to postablation (within 24 hours of the procedure) studies obtained after a total of 387 uncomplicated RF catheter ablation procedures for AV node slow pathway (n = 120), accessory AV pathways (n = 214), and complete AV junction (n = 39). Postablation studies identified 6 new cases (1.5%) of new wall motion abnormalities, and 3 additional patients had septal wall motion abnormalities during ventricular pacing. LVEF remained unchanged from baseline (62 ± 10 vs 62 ± 11). A small pericardial effusion was detected after 11 procedures (2.8%), and there were 9 (2.3%), 21 (5.4%), and 20 (5.2%) new findings of mild (1 +) aortic, mitral, and tricuspid regurgitation, respectively; and no cases of significant valvular dysfunction in any patient. There were no new cases of cavity thrombus. There was no clear relationship between postablation echocardiographic findings and the type and approach to ablation, and no patient had any clinical sequelae possibly related to any of the new echocardiographic findings during a mean follow‐up of 15 ± 6.0 months (range 1–26 months). Routine transthoracic echocardiographic studies after uncomplicated RF catheter ablation procedures identify occasional minor abnormalities that (1) may or may not be procedure related, (2) are of no apparent clinical consequence, and (3) thus appear to be of limited value.

Temperature-guided radiofrequency catheter ablation of closed-chest ventricular myocardium with a novel thermistor-tipped catheter

Successful lesion formation using radiofrequency energy requires adequate tissue heating. Temperature monitoring during ablation may thus improve the efficiency of radiofrequency catheter ablation. Each of five anesthetized, closed-chest adult mongrel dogs weighing 19 to 24 kg received a single pulsed ablation at four left ventricular and two right ventricular sites using a thermistor-tipped 2 mm electrode catheter. The maximum temperature at the electrode-tissue interface was preset at 90 degrees C and current delivered for 40 seconds (method A) or at 70 degrees C for 40 seconds (method B1) or 80 seconds (method B2). With method C, the temperature was set at 90 degrees C for 20 seconds, after which the temperature setting was turned off and ablation continued until impedance increased or the temperature reached > or = 100 degrees C. The size of the resultant lesion was greater with method A than with methods B1, B2 or C (mean length x width x depth, 5.6 x 4.8 x 6.5 vs 4.1 x 4.0 x 5.1 vs 4.2 x 4.0 x 5.2 vs 5.0 x 4.3 x 5.7 mm, respectively; p < 0.01). There was no significant difference in lesion size between pulse durations of 40 seconds (group B1) and 80 seconds (group B2). Only two ablations, both in the anteroapical right ventricle, resulted in a marked rise in impedance without the temperature reaching > or = 100 degrees C. We conclude that temperature (and thus impedance) monitoring improves control and efficacy of lesion formation during radiofrequency catheter ablation.

Upper-extremity deep-vein thrombosis: Thrombolytic therapy with anistrepalase

A patient with primary axillary vein thrombosis was treated successfully in the emergency department with a single IV bolus of anistrepalase followed by continuous IV heparin. The patients symptoms resolved quickly, and a repeat venogram 16 hours later showed near-complete resolution of the venous obstruction. We discuss briefly the role of thrombolytic therapy in the treatment of upper-extremity deep-vein thrombosis and the potential advantages of using anistrepalase.

Usefulness of follow-up electrophysiologic study and event monitoring after successful radiofrequency catheter ablation of supraventricular tachycardia

We assessed the usefulness of routine follow-up electrophysiologic studies after successful catheter ablation for supraventricular tachycardia and the role of event monitoring as an alternative modality in 310 patients at 11 centers using an investigational catheter ablation system with closed-loop temperature control. A routine follow-up electrophysiologic study between 1 and 3 months after ablation was required as part of the study protocol, and patients developing palpitations after ablation were encouraged to use event monitors. Recurrence of the initially targeted arrhythmia developed in 23 patients (7.4%) at a mean of 1.5 +/- 1.5 months after ablation. However, only 2 of these 23 recurrences were discovered by routine follow-up electrophysiologic study in asymptomatic patients (both with concealed accessory pathways); in the remaining 21 patients a positive follow-up electrophysiologic study was heralded by either recurrent symptoms, documented recurrent supraventricular tachycardia, and/or preexcitation on the electrocardiogram. Eighteen patients complained of palpitations after ablation and received an event monitor, which correctly diagnosed another cause of palpitations and ruled out recurrence of the ablated arrhythmia in 8 patients. Thus, the combination of clinical follow-up and event monitoring appears to be an effective alternative to routine follow-up electrophysiologic studies after catheter ablation of supraventricular tachycardia.

Long-term outcome after radiofrequency catheter ablation of atrioventricular nodal reentrant tachycardia with the anterior-approach method

Previous studies have reported only short-term (6 to 10 months) follow-up after ablation of atrioventricular (AV) nodal reentrant tachycardia by using the anterior approach. The objective of this study was to determine the long-term efficacy and safety of radiofrequency catheter ablation of AV nodal reentrant tachycardia with the anterior-approach method. In 56 patients (16 men and 40 women; mean [+/-SD] age, 44 +/- 19 years) with symptomatic AV nodal reentrant tachycardia. In 53 patients, ablation was performed initially by using a standard 7F, 2 mm-tipped tripolar His bundle catheter when the large-tip electrode was not as available, and in the remaining 3 patients, ablation was performed with a 7F, 4 mm-tipped catheter. Ablation was successful in the short term in 53 (95%) patients after a median of 7 radiofrequency applications. Three (5%) patients developed complete AV block immediately after ablation. Six (11 %) patients had recurrence of tachycardia within 3 months (n = 5) and 13 months (n = 1) after ablation. Repeated ablation resulted in successful outcome in 4 patients and in complete AV block in 1 patient; the other patient refused a repeated ablation attempt. A total of 51 patients was monitored for 36 +/- 12 months (range, 25 to 72 months), and none had tachycardia recurrence or delayed AV block. In conclusion, our results show that the anterior approach to radiofrequency catheter ablation can be used successfully to treat patients with AV nodal reentrant tachycardia with a good long-term efficacy and safety.

Usefulness of the response to intravenous procainamide during electrophysiologic study in predicting the response to oral quinidine in patients with inducible sustained monomorphic ventricular tachycardia associated with coronary artery disease.

The response to intravenous procainamide (15 to 20 mg/kg) and to oral quinidine 324 to 648 mg every 8 hours for 3 to 5 days was prospectively studied in 50 consecutive patients (43 men and 7 women, aged 38 to 83 years old [mean 64 +/- 11]) with coronary artery disease and baseline-inducible sustained monomorphic VT. Mean procainamide and trough quinidine serum levels were 10.5 +/- 2.6 and 2.6 +/- 0.8 micrograms/ml, respectively. Mean left ventricular ejection fraction was 37 +/- 12%. Sustained monomorphic VT was suppressed by intravenous procainamide in 18 patients (36%); 8 of these patients (44%) also had suppression with oral quinidine, but 10 (56%) did not. Of the 32 patients (64%) who continued to have inducibility with intravenous procainamide, 12 (38%) responded to oral quinidine and 22 (62%) did not. The overall concordant response rate to intravenous procainamide and oral quinidine was 56% (28 of 50 patients). It is concluded that the response (i.e., the presence or absence of inducible sustained monomorphic VT) to intravenous procainamide does not adequately predict the response to oral quinidine in patients with coronary artery disease and sustained monomorphic VT.