Thrombogenicity of radiofrequency lesions: results with serial D-dimer determinations

Measurements of immature platelet fraction and inflammatory markers in atrial fibrillation patients - Does persistency or ablation affect results?

PURPOSE

Atrial fibrillation (AF) is associated with platelet hyperactivity and a higher proportion of immature platelets. We aimed to examine whether immature platelet fraction (IPF) and inflammatory markers differ between AF types and whether they are affected by ablation.

METHODS

A prospective study included patients with atrial fibrillation/flutter (AFL). We excluded patients with hematologic, inflammatory, or acute coronary states. Blood samples for IPF, white blood cells (WBC), neutrophil-to-lymphocyte ratio (NLR), and C-reactive protein (CRP) were collected at baseline, within one-hour postablation in those undergoing ablations, and the day after ablation. IPF was measured by an autoanalyzer (Sysmex 2100 XE).

RESULTS

One hundred and four patients were included (paroxysmal AF-63, persistent AF-36, AF and AFL-7, AFL alone-5), (Mean age 67.7 ± 12.8 years, 54.8% male, CHA₂ D₂ -VASC₂ 3.2 ± 1.8). Seventy-two patients underwent ablation (cryoballoon AF ablation-60, AFL radiofrequency ablation-5, both-7). There was no difference between paroxysmal and persistent AF regarding baseline markers. There was a significant change in the following parameters after ablation: WBC (baseline 6.9 ± 2.0, 1-h post 8.0 ± 2.4, and 1-day post 9.0 ± 2.8 ×10⁹ /L), NLR (2.9 ± 2.2, 3.0 ± 2.4, 4.2 ± 2.9, respectively), and CRP (3.6 ± 3.7, 3.6 ± 3.5, 12.4 ± 9.0 mg/L, respectively) (P < .05 for all). However, there were no differences in immature platelet count (8.6 ± 4.8, 8.5 ± 4.9, 8.4 ± 5.2 ×10⁹ /L) or IPF (4.6 ± 3.2, 4.7 ± 3.3, 4.9 ± 3.6%) from baseline to postablation (p = NS).

CONCLUSIONS

AF persistency does not affect IPF and inflammation. In patients undergoing cryoablation of AF, there is a postablation inflammatory process; however, platelet activation is probably not affected.

Prothrombotic Responses After Catheter Ablation for Atrial Fibrillation During Uninterrupted Oral Anticoagulant Agent Administration

OBJECTIVES

The aim of this study was to evaluate the extent of changes in prothrombotic responses after catheter ablation for atrial fibrillation (AF) under uninterrupted oral anticoagulant agent (OAC) administration.

BACKGROUND

Catheter ablation for AF has a potential risk for prothrombotic activation and silent thromboembolic events.

METHODS

A total of 814 patients (n = 172 [warfarin], n = 153 [dabigatran], n = 134 [rivaroxaban], and n = 301 [apixaban] patients undergoing AF ablation and a control group of 54 patients undergoing non-AF ablation) were included. Uninterrupted OACs were administered during the procedure in patients with AF. Blood samples were collected the day before and 3 days after the procedure.

RESULTS

At baseline, D-dimer levels were within normal limits (≤1.0 μg/ml) in more than 90% of the patients in all groups. However, after 3 days, this proportion decreased to 67%, 73%, 59%, 68%, and 65% in the warfarin, dabigatran, rivaroxaban, apixaban, and control groups, respectively (p = 0.180). Changes in prothrombin fragment 1+2 levels differed (p < 0.001), whereas fibrin monomer complex levels 3 days after ablation at a trough were equivalent within normal ranges among the groups (p = 0.146). Multivariate analysis revealed that age, CHA₂DS₂-VASc score, first session, and radiofrequency ablation were independent predictors of increased D-dimer levels after the procedure. Various changes in prothrombotic markers were observed between the warfarin and direct OAC groups after propensity score matching analyses.

CONCLUSIONS

The coagulation cascade was activated after catheter ablation for AF under uninterrupted OAC administration. The changes in various prothrombotic markers differed among the OAC groups.

Laser catheter ablation of long- lasting persistent atrial fibrillation: Longterm results

Catheter ablation of atrial fibrillation (AF) is a current therapeutic option but its efficacy for the treatment of long-lasting persistent AF (l-lpAF) remains suboptimal. We tested the laser method as an alternative for catheter ablation of l-lpAF by using an open-irrigated electrode laser mapping and ablation (ELMA) catheter. Laser ablation was attempted in 48 patients aged 50-81 years (69 ± 7.6 y, female = 28) with drug resistant (3.5 trials) l-lpAF (≥12 months). All of the patients had comorbidities: congestive heart failure NYHA II-III (100%), hypertension 29 (60%), coronary artery disease 19 (40%), and heart valve defect 17 (35%). None of the patients had diabetes or obstructive sleep apnea. All were in AF at the beginning of the procedure. Continuous wave (cw) 1064nm Nd:YAG laser applications at 15W/10-20s (14-26/patient) were applied via the ELMA catheter until local electrical activity displayed on the monitor in the bipolar focused local electrograms (LEG) recorded via the pin electrodes from the tip of the catheter was abolished permanently and sinus rhythm was achieved. Online monitoring of electrical potential amplitudes in the focused LEG recorded via the pin-electrodes of the ELMA catheter allowed for validation of ablation success. Procedure duration ranged from 82-175 min (118 ± 72 min), number of lesions were14-26 (19 ± 4) per patient and X-ray exposure times ranged from 15-82 min (23.2 ± 12 min). Interventions were without complications. After the ablation procedure all the patients were in sinus rhythm, off medication, however, 12 (25%) needed a repeat study for various arrhythmias. During followup of 9 months to 29.3 years (8.2 ± 6.5 years) patients' quality of life improved significantly and during final follow-up control all except two were off medication still in sinus rhythm (lifelong success rate = 96%). As compared to other catheter ablation methods the laser method is an intriguing alternative for catheter ablation of l-lpAF.

Effects of cryoablation and radiofrequency ablation on endothelial and blood clotting activation

Cryoablation (CA) emerged as an alternative procedure to radiofrequency (RF). The aim of this study was to compare haemostatic system alterations in patients undergoing RF or CA for atrioventricular nodal reentrant tachycardia ablation. von Willebrand factor (vWF), spontaneous whole blood platelet aggregation, prothrombin fragment F1 + 2 (F1 + 2), thrombin-antithrombin complex (TAT), plasminogen activator inhibitor type-1 (PAI-1), and clot lysis time (CLT) were determined in 48 patients (27 CA; 21 RF; 19M/29F, mean age 49.6 ± 17.6 years). Blood samples were obtained before the procedure (T0), immediately after (T1), and 24 h later (T2). At T1 both procedures were associated with a significant increase in levels of the endothelial activation marker vWF. At T2 vWF levels were lower in CA than in RF group. No changes in whole blood platelet aggregation before and after ablation procedures were observed. At T1 both groups determined an increase in blood clotting activation markers, F1 + 2, TAT, and DD. At T2 F1 + 2, TAT and DD levels were similar to baseline values. The comparison between RF and CA showed no significant differences in F1 + 2 and TAT levels, whereas at T1 DD levels were higher in CA group than in RF group. Both procedures induced a significant decrease in CLT, whereas no changes in PAI-1 levels were found. There were no significant differences in CLT and PAI-1 levels. The fibrinolytic efficiency analysis showed that at T1 DD/TAT and DD/F1 + 2 ratios were lower in RF group and remained lower in RF than in CA group at T2. CA procedure may be associated with a lower degree of endothelial damage and with a higher fibrinolytic capacity respect to RF.

Neurologic complications of catheter ablation/defibrillators/pacemakers

Approaches to the management of patients with cardiac arrhythmias have significantly evolved over the last decade, with advancement in catheter ablation and device implantation techniques. As the techniques and tools evolve, so does our understanding of the possible complications from these procedures. The focus of this chapter is discussion of the neurologic complications involved with catheter ablation, pacemaker and defibrillation implantation, with the focus on timely diagnosis, and management strategies.

Open-irrigated laser catheter ablation produces flow-dependent sizes of lesions

BACKGROUND

Growth and sizes of lesions produced during catheter ablation is difficult to control. Laser lesion formation was evaluated during various flow rates and energy settings by using an open-irrigated laser catheter on a thigh-muscle dog model.

METHODS

Laser radiation at 15 W or 20 W was applied in blood for 10 seconds, 20 seconds, 30 seconds, 40 seconds, and 50 seconds during an irrigation flow of 16 mL/min or 35 mL/min, in direct contact, and in a noncontact mode of laser application. Lesions were evaluated morphometrically.

RESULTS

There was a linear increase of lesions with the increase of the level of energy applied. Maximal depth of lesions achieved during a flow rate of 16 mL/min at 15 W/50 seconds increased significantly from 9.9 ± 0.3 mm to 12.1 ± 0.5 mm, and at 20 W/50 seconds from 11.1 ± 0.55 mm to 12.4 ± 0.26 mm, when irrigation flow was 35 mL/min (P < 0.5). However, difference of lesion increase between 15 W and 20 W was not significant (P = 0.30). Lesions were achieved also in a noncontact mode of radiation at a distance of 1-2 mm, but not at 5 mm away. Radiation at 20 W > 40 seconds and a flow rate of 35 mL/min may cause steam pop with intramural cavitation.

CONCLUSIONS

By using an open-irrigated laser catheter augmentation of catheter flow increases lesion sizes. Lesions can be achieved also in a noncontact mode of radiation. In order to avoid unwanted effects the level of energy applied must be limited.

Hemostatic changes before and during electrophysiologic study and radiofrequency catheter ablation

We sought to investigate specific hemostasis activation markers during electrophysiologic study (EPS) with consequent radiofrequency catheter ablation (RFA). Sixty patients were studied prospectively during routine EPS with RFA for paroxysmal supraventricular tachycardia. Blood samples were drawn before the insertion of venous sheaths (T0), at the end of EPS (T1), and 30 min after completion of RFA (T2). To study coagulation and fibrinolytic and platelet activity, we measured concentrations of thrombin-antithrombin III (TAT), D-dimers (DD), plasminogen activator inhibitor type 1 (PAI-1), tissue-type plasminogen activator (t-PA), and circulating platelet aggregates. The results are expressed as median and show 95% confidence levels. Levels of DD increased from 0.24 mg/L at T0 to 0.37 mg/L at T1 (P < 0.001) and to 0.59 mg/L at T2 (P < 0.001). TAT levels increased from 5.29 μg/L at T0 to 35.80 μg/L at T1 (P < 0.001) and decreased to 26.30 μg/L at T2 (P < 0.001). PAI-1 concentration decreased from 30.10 μg/L at T0 to 26.4 μg/L at T1 (P < 0.001). t-PA at T2 increased to 5.10 μg/L from 4.75 μg/L at T1 (P = 0.001). No other differences between corresponding medians were statistically significant (P > 0.05). We found that concentrations of DD at T2 versus T1 depended on the number of radiofrequency energy applications (r (S) = 0.387; P = 0.002). Marked platelet activation was observed from the start of the procedure, without changes during the procedure.

Transvenous Cryoablation Reduces Platelet Activation During Pulmonary Vein Ablation Compared with Radiofrequency Energy in Patients with Atrial Fibrillation

BACKGROUND

Radiofrequency (RF) ablation procedures for atrial fibrillation (AF) are associated with potential risks of thromboembolism, which may be minimized by the use of cryoablation that preserves the integrity of endocardium. The objective of this study was to compare the thrombogenic potential of transvenous cryoablation versus RF ablation during pulmonary vein (PV) isolation.

METHODS AND RESULTS

Thirty consecutive patients with paroxysmal AF were randomized to undergo segmental PV isolation procedure using 4-mm tip RF ablation (n = 15) or cryoablation (CryoCor, San Diego, CA, USA) (n = 15). Blood samples were drawn after sheath insertion (baseline), after transseptal puncture, before ablation (after heparin administration), and after isolation of a superior PV. Activation of coagulation was measured with plasma levels of prothrombin fragment 1 + 2 (F1 + 2) and thrombin-antithrombin III complex (TAT), and platelets by plasma level of beta-thromboglobulin (beta-TG) and flow cytometric enumerating of P-selectin (CD62)-positive platelets. In both groups, the plasma level of beta-TG, F1 + 2, and TAT were elevated after sheath insertion. The percentage changes in plasma level of beta-TG, F1 + 2, and TAT and CD41/62-positive platelets from baseline after transseptal puncture and before ablation were similar (P > 0.05). However, the percentage changes in CD62-positive platelets from baseline were significantly higher in patients treated with RF ablation (82 +/- 20%) than with cryoablation (22 +/- 14%, P = 0.02), although their plasma levels of beta-TG, F1 + 2, and TAT were not different (P > 0.05).

CONCLUSIONS

Significant platelet and coagulation activations were observed during PV ablation procedures, and heparin administration only prevented activation of coagulation but not platelets. Persistent platelets activation was observed during RF energy application, but not during cryoablation.

Feasibility of Catheter Cryoablation in Normal Ventricular Myocardium and Healed Myocardial Infarction

Although novel cryoablation systems have recently been introduced into clinical practice for catheter ablation of supraventricular tachycardia, the feasibility of catheter cryoablation of VT is unknown. Thus, the present study evaluates catheter cryoablation of the ventricular myocardium (1) in healthy sheep and (2) of VT in chronic myocardial infarction (MI). In three healthy sheep, 21 ventricular lesions (12 left and 9 right ventricle) were created with a catheter cryoablation system. Different freeze/thaw characteristics were used for lesion creation. The mean nadir temperature was -84.1 degrees C +/- 0.9 degrees C, mean lesion volume was 175.8 +/- 170.3 mm3, and 5 of 21 lesions were transmural. Lesion dimensions were 7.5 +/- 3.1 mm (width) and 4.2 +/- 2.5 mm (depth). Left ventricular lesions were significantly larger than right ventricular lesions (262 +/- 166 vs 60.5 +/- 91.6 mm3, P=0.0025). There was no difference in lesion volume with respect to different freeze/thaw characteristics. Anatomically (n=3) or electrophysiologically (n=3) guided catheter cryoablation was attempted in six sheep 105 +/- 56 days after MI, three of six animals had reproducibly inducible VT with a mean cycle length of 215 +/- 34 ms prior to ablation. In these animals, five VTs were targeted for ablation. A mean of 6 +/- 3 applications for nine left ventricular lesions were applied, six of nine lesions were transmural. The mean lesion volume was 501 +/- 424 mm3. No VT was inducible in two of three animals after cryoablation using an identical stimulation protocol. Therefore, catheter cryoablation of VT in healed MI is feasible, and no acute complications were observed.

Comparison of hemostatic activation created by right- and left-heart radiofrequency catheter ablation

BACKGROUND

Thromboembolic complications commonly occur in radiofrequency (RF) ablation procedures (0.6-1.3% of cases). Comparison of hemostatic activation between left and right RF ablation is limited.

HYPOTHESIS

The purpose of this study was to evaluate platelet and hemostatic activation before, immediately after, and 48 h following left and right myocardial RF ablation procedures.

METHODS

The subjects were two groups of patients who underwent right-heart (24 patients) and left-heart (20 patients) RF ablation. Blood samples taken before, immediately after, and 48 h after the procedure were tested for changes in platelet and hemostatic activation.

RESULTS

No indication of clinically symptomatic thromboembolism and no major differences in baseline characteristics and procedure were apparent in either group, except for a higher temperature mode setting (p < 0.001) in the left-heart group. The hemostatic evaluation levels increased significantly by the end of the procedure in both groups and the platelet activation level remained elevated for 48 h after the procedure. The platelet activation level increased insignificantly at the end and 48 h after the procedure. Of the other changes in levels of platelet and hemostatic activation, only an increase in one of the hemostatic levels in the right-heart group at 48 h after procedure was significant (p = 0.01).

CONCLUSIONS

Our findings suggest that similar hemostatic activation occurred during and immediately after RF ablation in both groups. Sustained elevation of the hemostatic marker after the ablation procedure in the right-heart group was observed as of significant therapeutic and prognostic implications.

Lower incidence of thrombus formation with cryoenergy versus radiofrequency catheter ablation

BACKGROUND

Radiofrequency (RF) catheter ablation is limited by thromboembolic complications. The objective of this study was to compare the incidence and characteristics of thrombi complicating RF and cryoenergy ablation, a novel technology for the catheter-based treatment of arrhythmias.

METHODS AND RESULTS

Ablation lesions (n=197) were performed in 22 mongrel dogs at right atrial, right ventricular, and left ventricular sites preselected by a randomized factorial design devised to compare RF ablation with cryocatheter configurations of varying sizes (7F and 9F), cooling rates (-1 degrees C/s, -5 degrees C/s, and -20 degrees C/s) and target temperatures (-55 degrees C and -75 degrees C). Animals were pretreated with acetylsalicylic acid and received intraprocedural intravenous unfractionated heparin. Seven days after ablation, the incidence of thrombus formation was significantly higher with RF than with cryoablation (75.8% versus 30.1%, P=0.0005). In a multiple regression model, RF energy remained an independent predictor of thrombus formation compared with cryoenergy (OR, 5.6; 95% CI, 1.7, 18.1; P=0.0042). Thrombus volume was also significantly greater with RF than with cryoablation (median, 2.8 versus 0.0 mm3; P<0.0001). More voluminous thrombi were associated with larger RF lesions, but cryolesion dimensions were not predictive of thrombus size.

CONCLUSIONS

RF energy is significantly more thrombogenic than cryoenergy, with a higher incidence of thrombus formation and larger thrombus volumes. The extent of hyperthermic tissue injury is positively correlated with thrombus bulk, whereas cryoenergy lesion size does not predict thrombus volume, most likely reflecting intact tissue ultrastructure with endothelial cell preservation.

Delayed thrombogenesis following radiofrequency catheter ablation

The cause and duration of the thrombogenesis provoked by radiofrequency catheter ablation (RF-CA) was investigated by measuring the thrombin-antithrombin III complex (TAT) in 43 patients who underwent RF-CA and in 20 control subjects who underwent an electrophysiologic study. Blood samples were collected at 7 different times: before introducing the sheaths, during the ablation procedure and at 30 min, 6 and 24h, and 3 and 6 days after the procedure. Hepatocyte growth factor (HGF) was simultaneously measured in the ablation group. Plasma TAT concentration exhibited a double peaked pattern in the ablation group: the first peak occurred during the ablation procedure (42.8+/-15.5 ng/ml), and the second peak 3 days later. Plasma TAT at 3 days after the procedure was significantly higher than that of the control group (21.3+/-19.0 vs 2.5+/-1.4, p=0.0003). The first peak significantly correlated with the procedure time prior to the administration of heparin (r=0.669), but the second peak did not (r=0.132). A subgroup with a serum HGF >0.40 ng/ml at 6 h after the procedure exhibited a significantly high second peak. The thrombogenesis caused by RF-CA has 2 phases; in the acute phase, there is hemostasis during placement of the catheters, and in the delayed phase thrombogenesis is the result of endothelial damage from the RF current.

Radiofrequency catheter ablation of left-sided accessory pathways in pediatric patients

In many cases, radiofrequency catheter ablation has replaced the long-term use of antiarrhythmic medication for symptomatic tachycardia, and has all but eliminated arrhythmia surgery. The most common substrate for radiofrequency catheter ablation in pediatric patients is atrioventricular (AV) reentry tachycardia due to a concealed or manifest accessory pathway. Accessory pathways are distributed unevenly along the right and left atrioventricular valve annuli, and left-sided accessory pathways are most common. Although some centers advocate an abbreviated diagnostic and mapping approach to both concealed and manifest left-sided accessory pathways, most still use a complete electrophysiological evaluation and complex catheter manipulation for mapping, followed by the application of radiofrequency energy. Left-sided accessory pathways may be approached from the transatrial approach, the retrograde aortic approach, or less commonly from within the coronary sinus. Each approach has proven to be associated with success, but also with a distinct set of risks. Possibly because left-sided accessory pathways are most common, catheter ablation of this substrate has proven highly successful and has the lowest risk of recurrence. However, recent data also suggest that this substrate is associated with greater risk of complications than of right-sided accessory pathways or pathways located in the posteroseptal region. The following report reviews some of the recently described diagnostic and mapping techniques, success rates, risks and follow-up data in pediatric patients undergoing radiofrequency catheter ablation of left-sided accessory pathways.

Mortality following radiofrequency catheter ablation (from the Pediatric Radiofrequency Ablation Registry). Participating members of the Pediatric Electrophysiology Society

Deaths have been reported following radiofrequency catheter ablation (RFCA), but the mortality rate in children has not been defined. This study sought to analyze the incidence and the factors associated with mortality related to RFCA. Ten of 4,651 cases (0.22%) reported to the Pediatric RFCA Registry resulting in death were reviewed and compared with a matched control group (n = 18). Death occurred in 5 of 4,092 children (0.12%, ages 0.1 to 13.3 years) with structurally normal hearts. Death was related to traumatic injury, myocardial perforation and hemopericardium, coronary or cerebral thromboembolism, and ventricular arrhythmia. All cases were left-sided (p = 0.019 vs right or septal) supraventricular arrhythmias with radiofrequency applications in the systemic atrium and/or ventricle, and all procedures were successful. Mortality occurred in 5 of 559 children (0.89%, p = 0.001 vs normals, ages 1.5 to 17.4 years) with structural heart disease. No new pathology except the mural radiofrequency lesions was seen at autopsy. Those with structurally normal hearts who died were smaller (32.7 vs 55.6 kg, p = 0.023) and had more radiofrequency applications (26.3 vs 8.7, p = 0.019) than those who survived. No differences were demonstrated for those with abnormal hearts. Operator experience was not different (deaths 103 +/- 106 vs controls 117 +/- 125, p = 0.41). Mortality associated with pediatric RFCA is rare, but is more frequent when there is underlying heart disease, lower patient weight, greater number of radiofrequency energy applications, and left-sided procedures. Operator experience does not appear to be a factor leading to mortality.

Thrombus formation at the site of radiofrequency catheter ablation

A 55-year-old woman with a history of resected atrial myxoma with residual patched atrial septal defect (ASD) underwent a successful radiofrequency (RF) ablation of reentry atrial tachycardia. She presented with progressive dyspnea 5 days later. Transesophageal echocardiography revealed a 1-cm right atrial mass attached to the intraatrial septum at the ablation site. Repeat study after anticoagulation for 5 weeks showed complete resolution of the thrombus. Thrombus formation at the site of RF ablation is a potential complication that may require aggressive anticoagulation. Patients with patched ASD might be at higher risk.

Initial experience with the radial incision approach for atrial fibrillation

BACKGROUND

Surgery for atrial fibrillation (AF) is performed with the aim of restoring sinus rhythm and atrial transport function, and preventing thromboembolism. The radial incision approach (RIA), in which the atrial incisions radiate from the sinus node toward the atrioventricular annular margins and parallel the coronary arteries, was developed as an outgrowth of and an alternative to the maze procedure in order to preserve a more physiological activation sequence and the atrial transport function.

METHODS

To determine whether the RIA is a promising procedure for AF, 23 patients who had undergone the RIA (n = 10) or the maze procedure (n = 13) for chronic AF associated with valvular heart disease were examined in terms of the postoperative cardiac rhythm and atrial transport function.

RESULTS

AF was cured in 90% of RIA patients and 92.3% of maze patients (not significant). One patient in each group required pacemaker implantation for an insufficient sinus rate postoperatively. The RIA was technically easier than the maze procedure, because the incisions were more linear and there was no isolation incision or "T-shape" incision in the left atrium. The left atrial transport function, assessed by transthoracic Doppler echocardiography, was greater after the RIA than after the maze procedure, while the right atrial transport function was equally preserved by both procedures. The peak atrial filling/early filling waves of the flow-velocity spectra across the mitral valve was significantly larger after the RIA than after the maze procedure (0.58+/-0.17 vs. 0.25+/-0.07, p<0.005). The left atrial filling fraction was significantly larger after the RIA than after the maze procedure (28.5%+/-5.0% vs. 15.1%+/-4.0%, p<0.001).

CONCLUSIONS

RIA provides a greater atrial transport function, and thus may represent a physiological alternative to the maze procedure as a surgical procedure for AF.

Electrophysiologic procedures and activation of the hemostatic system

BACKGROUND

Thromboembolism occurs in 0.4% to 2% of the subjects undergoing radiofrequency ablation (RFA), but its mechanisms remain unclear. Our aim was to evaluate several parameters of the hemostatic system in relation to the electrophysiologic procedure.

METHODS

Thirty consecutive patients were enrolled in the study. Fifteen underwent electrophysiologic study and 15 underwent radiofrequency ablation. Before the ablation procedure, all subjects were given an intravenous heparin bolus (2500 IU). Blood samples were drawn immediately before, at the end of, and 24 hours after the procedures. Spontaneous platelet aggregation in whole blood and in platelet-rich plasma, markers of clotting activation (prothrombin fragment 1+2 and the thrombin-antithrombin complex) and the fibrinolytic system (plasminogen activator inhibitor and D-dimer) levels were evaluated.

RESULTS

At the end of the procedure, spontaneous platelet aggregation in whole blood, prothrombin fragment 1+2, thrombin-antithrombin complex, and D-dimer levels increased significantly in all patients. The hemostatic changes were more marked after RFA than after electrophysiology. Spontaneous aggregation in whole blood, prothrombin fragment 1+2, and thrombin-antithrombin complex levels at 24 hours after the procedure were similar to those observed before the procedure in both groups; D -dimer levels were still elevated with respect to preprocedure levels, with a trend toward higher levels in patients undergoing RFA rather than electrophysiology. A significantly more marked activation of coagulation (prothrombin fragment 1+2, P <.005) was found in patients in whom the mean duration of energy application was higher than 23.5 seconds.

CONCLUSIONS

Our data suggest that antithrombotic prevention with a prolonged administration of heparin and/or the association of antiplatelet agents should be considered in patients undergoing RFA.

The activation of platelet function, coagulation, and fibrinolysis during radiofrequency catheter ablation in heparinized patients

INTRODUCTION

Catheter ablation may be complicated by clinical thromboembolism in about 1% of patients.

METHODS AND RESULTS

We studied the activation of coagulation (prothrombin fragment 1+2 [PF1+2]), platelets (beta-thromboglobulin [beta-TG])) and fibrinolysis (plasmin-antiplasmin complexes [PAP] and D-dimer) during radiofrequency (RF) ablation in 13 patients. They received heparin 100 U/kg intravenously after the initial electrophysiologic study, prior to the delivery of RF current; thereafter 1,000 U/hour throughout the procedure. PF1+2 increased fourfold (P < 0.001) during the diagnostic study, but gradually declined to upper reference value during heparin administration. There was a strong correlation between procedure duration prior to heparin bolus (range 39 to 173 min); and (a) the maximal rise of PF1+2 (r = 0.83, P < 0.001) and (b) the increase of PF1+2 from baseline to end of the procedure (r = 0.74, P = 0.004). There was no correlation between postheparin changes of PF1+2 and (a) postheparin procedure duration (range 40 to 317 min), (b) number of RF pulses (range 1 to 16), or (c) RF current duration (range 46 to 687 sec). Plasma beta-TG concentration showed similar trends. Fibrinolytic activity increased moderately from baseline until heparin administration; then remained around the upper reference values. PAP at the end of procedure and D-dimer at the time of heparin administration both correlated with preheparin procedure duration (r = 0.70, P = 0.007 and r = 0.69, P = 0.01, respectively). All parameters were normal the next morning.

CONCLUSION

Procedure duration prior to heparin administration, and not the delivery of RF current per se, determines activation of hemostasis and fibrinolysis during RF ablation.

Thromboembolic complications of cardiac radiofrequency catheter ablation: a review of the reported incidence, pathogenesis and current research directions

INTRODUCTION

Radiofrequency catheter ablation (RFCA) has become established as an effective therapy for the treatment of many cardiac tachyarrhythmias. The principle limitation of conventional RFCA continues to be the risk of thromboembolism. This risk is of particular concern for the ongoing development of the catheter maze procedure for the treatment of atrial fibrillation, which currently involves the creation of extensive linear lesions in the left atrium.

METHODS AND RESULTS

A Medline search of the literature over the last ten years was performed. Focused review of the reported thromboembolic complications of RFCA indicates an overall incidence of 0.6%. However, the risk is increased when ablation is performed in the left heart (1.8% to 2%) and for ventricular tachycardia (2.8%). It is of concern that intravenous heparin and the use of temperature feedback to control radiofrequency current do not eliminate the risk of thromboembolic events.

CONCLUSION

The thromboembolic complications of RFCA are not eliminated by the treatment of intravenous herapin and mode of temperature control during ablation. Potential approaches to further reduce the risk of thromboembolism include the adjunctive administration of specific inhibitors of platelet activation and aggregation, intraprocedural intracardiac echocardiography, irrigated radiofrequency ablation, and cryoablation catheter systems.

Slow intramural heating with diffused laser light: A unique method for deep myocardial coagulation

BACKGROUND

Catheter ablation of postinfarction ventricular tachycardia (VT) may be limited by insufficient myocardial coagulation or excessive endocardial or epicardial damage. We propose that volumetric heating restricted to intramural sites may improve the outcome and safety of this procedure, especially if delivered at rates that enhance heat conduction and forestall adverse tissue changes.

METHODS AND RESULTS

A novel optical fiber with a diffusing tip for direct intramural, volumetric laser heating was tested via thoracotomy and percutaneously in normal dogs. Low-power (2.0- to 4.5-W) diode laser light (805 nm) diffused within tissue induced large lesions but no visible surface damage, mural thrombi, or transmural perforation. Mean lesion depth approximated tip length (10 mm). Mean lesion widths in the thoracotomy and percutaneous groups were 5.8+/-0.5 to 9.1+/-0.84 mm and 5.2+/-0.85 to 7.9+/-1.1 mm, respectively, depending on the light dose. Mean volumes in the percutaneous group were 1006+/-245 to 2471+/-934 mm. ST-segment depression, appearing in unfiltered bipolar electrograms recorded from the guiding catheter, was specific for lesion induction. All dogs survived the protocol, which included a 1-hour observation period. In cross section, lesions were elliptical to spherical and characterized by extensive contraction-band necrosis abruptly bordering viable tissue. No platelets or fibrin adhered to the endocardium.

CONCLUSIONS

Slow, volumetric, and direct intramyocardial heating induces large, deep lesions without hazardous tissue damage. Such heating might cure postinfarction VT more successfully and safely than present techniques. Further testing and development of this method seem warranted.

Pretreatment with antithrombotic agents during radiofrequency catheter ablation: a randomized comparison of aspirin versus ticlopidine

INTRODUCTION

D-dimer is a product of fibrin degradation and can serve as a biochemical marker of thrombus formation and reactive fibrinolysis. According to our previous observations, and as reflected by elevated plasma D-dimer levels, lesions produced by radiofrequency (RF) ablation have a thrombogenic effect. Pretreatment with combined aspirin and ticlopidine mitigates this thrombogenicity; however, the effect of either agent alone remains unknown.

METHODS AND RESULTS

In this study, 59 patients undergoing RF ablation were randomized to pretreatment with aspirin (group I; n = 30) or ticlopidine (group II; n = 29) for 3 days prior to RF ablation. D-dimer levels were measured by enzyme immunoassay before and after the electrophysiologic study (EPS), and both immediately and at 48 hours after RF ablation. Results also were compared with those of 31 patients (nonrandomized group III) who had received both aspirin and ticlopidine. At all stages, D-dimer levels were higher in groups I and II when compared with group III. Baseline D-dimer (31+/-20 vs 24+/-13 vs 17+/-11 microg/L, respectively; P = 0.002) rose after EPS to higher levels in groups I and II (91+/-100 microg/L and 51+/-35 microg/L) compared with group III (31+/-17 microg/L; P = 0.001). After RF ablation, D-dimer levels increased in all groups, but this increase was much higher in groups I and II (214+/-210 microg/L and 201+/-222 microg/L) than in group III (74+/-60 microg/L; P = 0.005). At 48 hours, D-dimer levels decreased in all groups, but remained higher in groups I and II (91+/-100 microg/L and 95+/-99 microg/L) than in group III (35+/-31 microg/L; P = 0.009). There were no differences among the three groups in the number of RF ablation lesions or the duration of the RF ablation procedure.

CONCLUSION

Pretreatment with aspirin or ticlopidine alone does not decrease the thrombogenic potential of RF ablation. Only combined therapy with aspirin and ticlopidine has a favorable effect, as reflected by the lower degree of D-dimer elevation.

Does radiofrequency ablation induce a prethrombotic state? Analysis of coagulation system activation and comparison to electrophysiologic study

INTRODUCTION

Although thromboembolism is an uncommon complication of radiofrequency (RF) ablation, some preliminary reports have suggested that RF ablation results in activation of the coagulation system, possibly increasing this risk. We hypothesized that the insertion of intravenous catheters and their prolonged intravenous placement rather than RF ablation activates the coagulation cascade.

METHODS AND RESULTS

Thirty-seven patients, group 1 (n = 21) during RF ablation, and group 2 (n = 16) during routine electrophysiologic studies (EPS), were studied prospectively. Blood was drawn for coagulation and fibrinolytic studies following insertion of venous sheaths (T0), following catheter placement (T1), and 1 hour after completion of RF ablation or EPS (T2). Conversion of prothrombin to thrombin was measured using thrombin-antithrombin complex (TAT) and prothrombin activation peptide (F1+2), and fibrinolytic activity was assessed using D-dimer concentration. Levels of D-dimer increased in group 1 from 823.52+/-323.52 ng/mL at T0 to 1,314.28+/-297.63 ng/mL at T2 (P = 0.005), and in group 2 from 658.15+/-161.70 ng/mL at T0 to 1625+/-641.45 ng/mL at T2 (P = 0.064). TAT levels increased from to 27.74+/-5.6 microg/L at T0 to 52.99+/-5.93 microg/L at T2 in group 1 (P = 0.09), and from 19.79+/-5.14 microg/L at T0 to 73.5+/-24.15 microg/L at T2 in group 2 (P = 0.05). F1+2 concentration increased from 1.52+/-0.30 nmol/L at T0 to 3.06+/-0.41 nmol/L at T2 in group 1 (P = 0.004), and from 1.32+/-0.30 nmol/L at T0 to 3.11+/-0.46 nmol/L at T2 in group 2 (P = 0.087). There was no significant difference in the concentration of the three coagulation variables between group 1 and group 2 at any given time point. No correlation was demonstrable between concentration of D-dimers, TAT, or F1+2 and variables of RF delivery such as cumulative energy, number of RF energy applications, or number of impedance rises. However, a significant positive correlation (r = 0.65, P<0.01) was noted between the duration of the RF ablation procedure and the concentration of D-dimers.

CONCLUSION

We conclude that activation of the coagulation cascade in RF ablation procedures is not related to the delivery of RF energy, but is related to the placement of intravascular catheters and to the duration of the ablation procedure.

Pretreatment with aspirin and ticlopidine confers lower thrombogenic potential of radiofrequency catheter ablation

In the present study we pretreated 31 patients undergoing radiofrequency catheter ablation (RFA) with combined aspirin and ticlopidine for 3 days before the procedure, whereas 37 patients did not receive pretreatment. D-dimer levels reflecting the thrombogenic potential of RFA were significantly lower in the pretreated group at each stage before, during, and after the procedure, whereas there were no significant differences between the 2 groups in the number of RFA lesions or duration of the procedure.