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

Impact of high-power short-duration atrial fibrillation ablation technique on the incidence of silent cerebral embolism: a prospective randomized controlled study

BACKGROUND

High-power short-duration (HPSD) ablation strategy has emerged as a popular approach for treating atrial fibrillation (AF), with shorter ablation time. The utilized Smart Touch Surround Flow (STSF) catheter, with 56 holes around the electrode, lowers electrode-tissue temperature and thrombus risk. Thus, we conducted this prospective, randomized study to investigate if the HPSD strategy with STSF catheter in AF ablation procedures reduces the silent cerebral embolism (SCE) risk compared to the conventional approach with the Smart Touch (ST) catheter.

METHODS

From June 2020 to September 2021, 100 AF patients were randomized 1:1 to the HPSD group using the STSF catheter (power set at 50 W) or the conventional group using the ST catheter (power set at 30 to 35 W). Pulmonary vein isolation was performed in all patients, with additional lesions at operator's discretion. High-resolution cerebral diffusion-weighted magnetic resonance imaging (hDWI) with slice thickness of 1 mm was performed before and 24-72 h after ablation. The incidence of new periprocedural SCE was defined as the primary outcome. Cognitive performance was assessed using the Montreal Cognitive Assessment (MoCA) test.

RESULTS

All enrolled AF patients (median age 63, 60% male, 59% paroxysmal AF) underwent successful ablation. Post-procedural hDWI identified 106 lesions in 42 enrolled patients (42%), with 55 lesions in 22 patients (44%) in the HPSD group and 51 lesions in 20 patients (40%) in the conventional group (p = 0.685). No significant differences were observed between two groups regarding the average number of lesions (p = 0.751), maximum lesion diameter (p = 0.405), and total lesion volume per patient (p = 0.669). Persistent AF and CHA2DS2-VASc score were identified as SCE determinants during AF ablation procedure by multivariable regression analysis. No significant differences in MoCA scores were observed between patients with SCE and those without, both immediately post-procedure (p = 0.572) and at the 3-month follow-up (p = 0.743).

CONCLUSIONS

Involving a small sample size of 100 AF patients, this study reveals a similar incidence of SCE in AF ablation procedures, comparing the HPSD strategy using the STSF catheter to the conventional approach with the ST catheter.

TRIAL REGISTRATION

Clinicaltrials.gov: NCT04408716. AF = Atrial fibrillation, DWI = Diffusion-weighted magnetic resonance imaging, HPSD = High-power short-duration, ST = Smart Touch, STSF = Smart Touch Surround Flow.

Comparing the safety and effectiveness of dedicated radiofrequency transseptal wires to electrified metal guidewires

Background

Application of electrocautery to a metal guidewire is used by some operators to perform transseptal puncture (TSP). Commercially available dedicated radiofrequency (RF) guidewires may represent a better alternative. This study compares the safety and effectiveness of electrified guidewires to a dedicated RF wire.

Methods

TSP was performed on freshly excised porcine hearts using an electrified 0.014″ or 0.032″ guidewire under various power settings and was compared to TSP using a dedicated RF wire with 5 W power (0.035″ VersaCross RF System, Baylis Medical). The primary endpoint was the number of attempts required to achieve TSP. Secondary endpoints included the rate of TSP failure, TSP consistency, the effect of the distance between the tip of the guidewire and the tip of the dilator, and effect of RF power output level. Qualitative secondary endpoints included tissue puncture defect appearance, thermal damage to the TSP guidewire or dilator, and tissue temperature using thermal imaging.

Results

The RF wire required on average 1.10 ± 0.47 attempts to cross the septum. The 0.014″ electrified guidewire required an overall mean of 2.17 ± 2.36 attempts (2.0 times as many as the RF wire; p < .01), and the 0.032″ electrified guidewire required an overall mean of 3.90 ± 2.93 attempts (3.5 times as many as the RF wire; p < .01). Electrified guidewires had a higher rate of TSP failure, and caused larger defects and more tissue charring than the RF wire. Thermal analysis showed higher temperatures and a larger area of tissue heating with electrified guidewires than the RF wire.

Conclusion

Fewer RF applications were required to achieve TSP using a dedicated RF wire compared to an electrified guidewire. Smaller defects and lower tissue temperatures were also observed using the RF wire. Electrified guidewires required greater energy delivery and were associated with equipment damage and tissue charring, which may present a risk of thrombus, thermal injury, or scarring.

Increased Rate of Pump Thrombosis and Cardioembolic Events Following Ventricular Tachycardia Ablation in Patients Supported With Left Ventricular Assist Devices

Ventricular arrhythmias are common following left ventricular assist device implantation (LVAD), and the effects of ventricular tachycardia (VT) ablation on thrombosis and embolic events are unknown. We aimed to assess LVAD thrombosis, stroke, and embolic event rates after VT ablation. Left ventricular assist device implantation patients from two academic centers who underwent endocardial VT ablation between 2009 and 2016 were compared to a control group with VT who were not ablated and followed for one year. The primary composite outcome was confirmed or suspected LVAD thrombosis, stroke, or other embolic event. Survival analysis was conducted with Kaplan-Meier curves, log-rank tests, and Cox regression. Forty-three LVAD patients underwent VT ablation, and 73 LVAD patients had VT but were not ablated. Patients who were ablated were more likely have VT prior to LVAD (p = 0.04), monomorphic VT (p < 0.01), and to be on antiarrhythmics (p < 0.01). Fifty-eight percent of the patients in the ablation group experienced the primary composite outcome (11% had confirmed device thrombosis [DT], 41% suspected DT, 39% had a stroke or embolic event) compared to 30% in the control group (12% with confirmed DT, 11% with suspected DT, 14% with stroke or embolic event) (p = 0.002). In multivariable regression, ablation was an independent predictor of the primary composite outcome (hazard ratios, 2.24; 95% confidence interval, 1.09-4.61; p = 0.03). Patients with LVADs referred for endocardial VT ablation had elevated rates of DT and embolic events.

REduction of THRomboembolic EVents during Ablation using the laserballoon: The RETHREVA registry

INTRODUCTION

Cerebral events (CEs), including silent (SCEs), are a known complication of left atrial catheter ablation (LACA) in patients with atrial fibrillation. The aim of this prospective registry was to gain more information about CEs during laserballoon LACA and to reduce the risk of their occurrence.

METHODS AND RESULTS

We enrolled 74 patients (age 61 ± 11 years; 74% male; CHA₂ DS₂ -VASc 1.9 ± 1.4). Cerebral MRI (1.5 Tesla) was performed to detect CEs. ASPItest identified aspirin-resistant patients (ARPs). All bleeding complications were recorded. Due to an initial high CE rate, we evolved our clinical procedure step-by-step arriving at an optimized protocol: -Group 1: heparin after single transseptal puncture (TP), activated clotting time (ACT) > 300 seconds (CE: 64.3%). -Group 2: heparin after double TP, ACT > 300 seconds; 2a without (CE: 45.5%, RRR: -29.2%) and 2b with additional intravenous aspirin (CE: 36.4%, RRR: -43.4%; excluding ARP: 30%, RRR: -53.3%). -Group 3: heparin before double TP, ACT > 350 seconds; 3a without (CE: 54.5%, RRR: -15.2%) and 3b with aspirin (CE: 18.5%, RRR: -71.2%; excluding ARP: 8.7%, RRR: -86.5%). Larger LA diameter > 44 mm (OR: 1.149, P  =  0.005) and no aspirin use (OR: 4.308, P  =  0.008) were CE risk factors in multivariate logistic regression. In those patients receiving aspirin, aspirin resistance (OR: 22.4, P  =  0.011) was an exceptionally strong risk factor.

CONCLUSION

These data support the use of intravenous aspirin including monitoring of aspirin resistance in addition to ACT-guided heparin. An optimized protocol of heparin before TP, double TP, and intravenous aspirin in non-ARP resulted in a significantly lowered CE incidence and severity.

Influence of cardioversion on asymptomatic cerebral lesions following atrial fibrillation ablation

PURPOSE

Asymptomatic cerebral lesions detected by diffusion-weighted magnetic resonance imaging (MRI) following atrial fibrillation (AF) ablation were reported in recent years. It was reported that cardioversion during the procedure of AF ablation was one independent risk factor of asymptomatic cerebral lesions. However, in some studies, the similar association between asymptomatic cerebral lesions and intraprocedural cardioversion was not observed. Given the inconsistent results, we did a meta-analysis to explore the influence of intraprocedural cardioversion on the asymptomatic cerebral lesions detected by MRI following AF ablation.

METHODS

Studies exploring the association between cardioversion during AF ablation and asymptomatic cerebral lesions following AF ablation were systematically searched in PubMed, Web of Science and the Cochrane Library Databases. Odds ratios (ORs) and 95% confidence intervals (CIs) were pooled. Subgroup and sensitivity analyses were performed to explore the source of heterogeneity.

RESULTS

Nine studies involving 813 participants were included in the present meta-analysis. When we pooled data from nine studies using fixed-effects model, we found cardioversion during the procedure significantly increased the risk of asymptomatic cerebral lesions detected by MRI following AF ablation (pooled OR = 1.793, 95% CI 1.201-2.678, I (2) = 38.8%, P heterogeneity = 0.109).

CONCLUSIONS

Cardioversion during AF ablation significantly increased the risk of asymptomatic cerebral lesions on MRI following the procedure. Additional studies are required to further verify the association.

Illustrated Atlas of Post-AF Ablation Cerebral Abnormalities

Atrial fibrillation (AF) is one of the most common cardiac arrhythmias and relates to high morbidity and mortality due to thromboembolic events, especially ischemic stroke. During the last 15 years, transcatheter ablation has emerged as an effective therapeutic option to treat AF but carries a risk of possible complications. The occurrence of cerebrovascular accidents, both symptomatic and silent, is one of the most frequent and severe. Transcatheter AF ablation entails a relevant risk of silent cerebral ischemia detected by means of magnetic resonance imaging, and many efforts have been directed to improve the safety of this procedure.

Silent Cerebral Embolism during Atrial Fibrillation Ablation:Pathophysiology, Prevention and Management

Although many efforts have been directed to improve atrial fibrillation transcatheter ablation safety, thromboembolism to the brain remains one of the major complications. In fact several studies have confirmed occurrence of silent cerebral embolic lesions by post-procedure magnetic resonance imaging. The present review will focus on the possible mechanisms leading to silent cerebral embolism in an attempt to provide recommendations holding the potential to reduce the incidence of this clinically relevant complication.

Predictors of asymptomatic cerebral infarction associated with radiofrequency catheter ablation for atrial fibrillation using an irrigated-tip catheter

AIMS

Catheter ablation is a potentially curative treatment for atrial fibrillation (AF). However, complications such as ischaemic stroke are more frequent and more severe compared with ablation procedures for other arrhythmias. Irrigated-tip catheters have been reported to reduce the risk of stroke. The present study aimed to evaluate predictors of asymptomatic cerebral infarction (CI) after AF ablation using an irrigated-tip catheter.

METHODS AND RESULTS

A total of 70 consecutive AF patients who underwent catheter ablation were subjected to brain magnetic resonance imaging (MRI) 1 day after the procedure. In 10 (14.3%) of 70 patients, MRI revealed acute CI, but neither symptoms nor abnormal neurological findings were present in these patients. In univariate analysis, a history of persistent AF, left atrial dimension, presence of spontaneous echo contrast (SEC), procedure duration prior to heparin injection, and electrical cardioversion during the procedure differed significantly between the two groups, those with and without CI (P = 0.02, 0.05, 0.01, 0.01, and 0.05, respectively). Multivariate logistic regression analysis identified SEC [odds ratio (OR), 9.39; 1.60-55.2; P = 0.01] and procedure duration prior to heparin injection (OR, 1.19; 1.04-1.36; P = 0.01) as predictive of acute asymptomatic CI after AF ablation.

CONCLUSION

The presence of SEC and procedure duration prior to heparin injection are determinants of asymptomatic CI during AF ablation despite the use of an irrigated-tip catheter.

Cryoablation therapy for atrioventricular nodal reentrant tachycardia in children: a multicenter experience of efficacy

Atrioventricular nodal reentrant tachycardia (AVNRT), a common tachycardia in children, is routinely treated by catheter ablation using radiofrequency or cryothermal energy. Acute success rates of 95-97 % are reported for cryoablation, similar to those achieved with radiofrequency ablation (RFA). However, early studies reported higher recurrence rates after cryoablation for treatment of AVNRT than those reported for RFA. This study evaluated the success and recurrence rates for cryoablation in a current cohort of pediatric patients across several institutions. Patients 21 years old or younger with AVNRT who underwent cryoablation at five participating centers between 2004 and 2009 were retrospectively reviewed. Patient demographics and procedural data were extracted from patient records and analyzed. A total of 434 patients with AVNRT who underwent cryoablation were identified. Cryoablation was used as the exclusive ablation method for 379 patients. For 97 % (368/379) of these patients, cryoablation was acutely successful. A higher acute success rate was found with the 6-mm-tip catheter (99 %) than with the 4-mm-tip catheter (91 %) (p < 0.01). Recurrence was experienced by 7.3 % of the patients. Recurrence was more likely for those treated with the 4-mm-tip catheter (6/42, 14 %) than for those who had the larger catheters (12/204, 6 %) No patient experienced permanent heart block. Success and recurrence rates for this cohort of patients were similar to those reported for RFA used to treat AVNRT in pediatric patients. The findings show a higher success rate and a lower recurrence rate after cryoablation with a 6-mm-tip catheter than after use of the 4-mm-tip catheter, with an associated excellent safety profile.

Incidence of tissue coring during transseptal catheterization when using electrocautery and a standard transseptal needle

BACKGROUND

The application of radiofrequency electrocautery to a standard, open-ended transseptal needle has been used to facilitate transseptal puncture (TSP). The purpose of this study was to determine the incidence of cardiac tissue coring when this technique is used.

METHODS AND RESULTS

A model using excised swine hearts submerged in a saline-filled basin was developed to simulate TSP with electrocautery and a standard transseptal needle. Punctures were performed without the use of electrocautery and by delivering radiofrequency energy to the transseptal needle using a standard electrocautery pen at 3 target sites (fossa ovalis, non-fossa ovalis septum, and aorta). The tissue of the submerged heart was gently tented, and the needle was advanced on delivery of radiofrequency. The devices were retracted, and the needle was flushed in a collection basin. None of the TSPs without cautery caused tissue coring. For TSPs using electrocautery, the frequency of coring was at least 21% for any puncture permutation used in the study and averaged 37% at septal sites (P<0.001 compared with punctures without cautery). Tissue coring occurred in 33 of 96 (35%) punctures through the fossa ovalis and in 38 of 96 (40%) punctures through non-fossa ovalis septum. The frequency of tissue coring at aortic sites was 62 of 96 (65%), which was significantly higher than at the septal sites (P<0.001).

CONCLUSIONS

In an animal preparation, TSP at the level of the fossa ovalis using electrocautery and a standard open-ended Brockenbrough needle resulted in coring of the septal tissue in 35% of cases (33 of 96 punctures).

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.

Radiofrequency Catheter Ablation of Atrial Fibrillation: A Cause of Silent Thromboembolism?

Background—

Radiofrequency left atrial catheter ablation has become a routine procedure for treatment of atrial fibrillation. The aim of this study was to assess with preprocedural and postprocedural cerebral magnetic resonance imaging the thromboembolic risk, either silent or clinically manifest, in the context of atrial fibrillation ablation. The secondary end point was the identification of clinical or procedural parameters that correlate with cerebral embolism.

Methods and Results—

A total of 232 consecutive patients with paroxysmal or persistent atrial fibrillation who were candidates for radiofrequency left atrial catheter ablation were included in the study. Pulmonary vein isolation or pulmonary vein isolation plus linear lesions plus atrial defragmentation with the use of irrigated-tip ablation catheters was performed. All of the patients underwent preprocedural and postablation cerebral magnetic resonance imaging. A periprocedural symptomatic cerebrovascular accident occurred in 1 patient (0.4). Postprocedural cerebral magnetic resonance imaging was positive for new embolic lesions in 33 patients (14). No clinical parameters such as age, hypertension, diabetes mellitus, previous history of stroke, type of atrial fibrillation, and preablation antithrombotic treatment showed significant correlation with ischemic cerebral embolism. Procedural parameters such as activated clotting time value and, in particular, electric or pharmacological cardioversion to sinus rhythm correlated with an increased incidence of cerebral embolism. Cardioversion was also associated with an increased risk of 2.75 (95 confidence interval, 1.29 to 5.89; P =0.009).

Conclusions—

Radiofrequency left atrial catheter ablation carries a low risk of symptomatic cerebral ischemia but is associated with a substantial risk of silent cerebral ischemia detected on magnetic resonance imaging. Independent risk factors for cerebral thromboembolism are the level of activated clotting time and, in particular, the electric or pharmacological cardioversion to sinus rhythm during the procedure.

Influence of radiofrequency catheter ablation on platelet aggregation

The objective of this article was to find out how radiofrequency catheter ablation (RFA) influences platelet aggregation (PA), and the dependence on the total energy (TE) of RFA used and the cause of arrhythmia. We investigated 97 patients. PA was analyzed before, after, and in 24 hours after RFA. ADP- and epinephrine-induced PA significantly decreased after RFA by 5% and 8.9% (P < .001), respectively, and increased in 24 hours close to baseline. PA induced by ADP and collagen did not radically depend on the TE. Epinephrine-induced PA decreased after RFA by 0%, 8% (P < .05), and 16.9% (P < .01) in groups of patients where the TEs used were <4000 J, 4000 to 15,000 J, and >15,000 J, respectively. There were no significant differences in PA between groups based on the cause of arrhythmia. ADP- and epinephrine-induced PA significantly decreased after RFA and returned close to baseline in 24 hours. Epinephrine-induced PA was inversely associated with the TE used for RFA.

Cerebral diffusion-weighted magnetic resonance imaging: a tool to monitor the thrombogenicity of left atrial catheter ablation

INTRODUCTION

Cerebral embolism and stroke are feared complications of left atrial catheter ablation such as pulmonary vein (PV) ablation. In order to assess the thrombogenicity of left atrial catheter ablation, knowledge of both clinically evident as well as silent cerebral embolism is important. The aim of the current study was to examine the use of diffusion-weighted magnetic resonance imaging (DW-MRI) for detection of cerebral embolism, apparent as well as silent, caused by PV catheter ablation.

METHODS AND RESULTS

Twenty consecutive patients without structural heart disease undergoing lasso catheter-guided ostial PV ablation using an irrigated-tip ablation catheter were studied. Cerebral MRI including DW single-shot spin echo echoplanar, turbo fluid attenuated inversion recovery, and T2-weighted turbo spin echo sequences were performed the day after the ablation procedure. Ten patients also underwent preprocedure cerebral MRI. All ablation procedures were performed without acute complications. A mean of 3.2 +/- 0.6 PVs were ablated per patient. No patient had neurological symptoms following the procedure. In 2 of 20 patients (10%), DW-MRI revealed new embolic lesions, which were located in the right periventricular white matter in one and in the left temporal lobe in the other patient. There was no statistically significant difference in age, history of hypertension, left atrial volume, and procedure duration between the 2 patients with and the 18 patients without cerebral embolism following AF ablation.

CONCLUSION

This is the first study using highly sensitive DW-MRI of the brain to detect asymptomatic cerebral embolism after left atrial catheter ablation. Even small, clinically silent, embolic lesions can be demonstrated with this technique. DW-MRI can be used to monitor and compare the thrombogenicity of different AF ablation approaches.

Ten year follow-up after radiofrequency catheter ablation for atrioventricular nodal reentrant tachycardia in the early days forever cured, or a source for new arrhythmias?

BACKGROUND

Radiofrequency (RF) catheter ablation is highly effective with a low complication rate. However, lesions created by RF energy are irreversible, inhomogeneous, and therefore potentially proarrhythmic.

OBJECTIVES

The aim of this study was to examine the magnitude and importance of long-term proarrhythmic effects of RF energy.

METHODS AND RESULTS

Between 1991 and 1995, 120 patients underwent RF ablation for atrioventricular nodal reentrant tachycardia (AVNRT). Patient data were collected by contacting patients and/or filling out a questionnaire, and medical files were screened for recurrent, documented arrhythmias, pharmacological treatment, and repeated EP study. Referring cardiologists were asked about recurrences of tachyarrhythmias. Fourteen patients (11%) were lost to follow-up. During a mean follow-up of 10 years, six patients died. Recurrences of AVNRT were not any more observed after 3 years after ablation. A total of 29 patients (24%) suffered from new arrhythmias, 6 from type 1 atrial flutter, 6 from atrial tachycardia, 9 from atrial fibrillation, and finally 16 from symptomatic premature atrial contractions (PACs), needing medical treatment or a combination of these arrhythmias. Nine patients underwent pacemaker implantation, 4 after developing procedural atrioventricular (AV) conduction disturbances, 2 after His ablation for permanent atrial fibrillation, 1 patient for sick sinus syndrome, and another 2 patients after developing late AV block, respectively, 7 and 9 years after ablation.

CONCLUSION

During long-term follow-up after RF ablation for AVNRT, no AVNRT recurrences were observed, but 29 patients (24%) suffered from new arrhythmias or late AV block. This potential proarrhythmic effect of RF energy promotes the application of alternative energy sources for ablative therapies for cardiac arrhythmias.

Transvenous radiofrequency catheter ablation of atrioventricular nodal reentrant tachycardia and its pitfalls: A rationale for cryoablation?

Today, radiofrequency (RF) catheter ablation of atrioventricular nodal reentrant tachycardia (AVNRT) is accompanied by a high success, a low recurrence, and a low complication rate. Despite the fact that over the years this technique has been refined, several shortcomings still remain. In this overview, the most important pitfalls in the treatment of AVNRT with RF energy are discussed. Cryotherapy has the ability to overcome some of them. Both ice mapping and cryo-adherence are important characteristics of this energy source to study prospective ablation sites before a definitive and irreversible lesion is created. Theoretically, this could lead to less applications with less tissue damage and abolish the risk for permanent conduction disturbances. The early experience with this technique will be described. Until now, it still has to be proven that in a large cohort of patients, cryotherapy is at least as effective, and safer than RF.

Effect of heparin on activation of platelet function in patients during radiofrequency catheter ablation

1. Thromboembolism occurs in 0.4-2.0% of patients undergoing radiofrequency catheter ablation (RFCA). Some studies have shown that treatment with heparin inhibits the activation of coagulation and fibrinolysis. No study has directly measured the activation of platelet aggregation to investigate the effect of heparin on platelet function. The purpose of the present study was to observe the inhibitory effect of heparin on platelet activity in patients undergoing RFCA. 2. Sixty-two patients with supraventricular tachycardia were observed and divided into a heparin-treatment group and a control group. Changes in platelet aggregability (PAG) and thromboxane B(2) (TXB(2)) in the blood samples of all patients at different times (before, after electrophysiological study, immediately after and 10 and 30 min after the RFCA procedure) were observed. 3. No indication of clinically symptomatic thromboembolism and no major differences in baseline characteristics and procedure were apparent in either group. The levels of PAG and TXB(2) were all clearly increased after the electrophysiological study (all P < 0.05). Immediately after RFCA, PAG and TXB(2) levels were significantly increased in both groups and remained elevated 30 min after the procedure (all P < 0.05). In the heparin-treatment group, the increases in PAG (54.69 +/- 3.24%) and TXB(2) (29.01 +/- 1.84%) caused by RFCA were lower than changes observed in the control group (70.92 +/- 3.45 and 44.70 +/- 3.28%, respectively; both P < 0.01). Moreover, treatment with heparin normalized the elevated level of PAG 30 min after RFCA more clearly. 4. The results of the present study suggest that intravenous heparin treatment during the operation inhibits the activation of platelets induced by RFCA.

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.

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.

Decrease in sensitivity of D-dimer for acute venous thromboembolism after starting anticoagulant therapy

D-dimer testing is useful for the exclusion of acute venous thromboembolism (VTE). Anticoagulant therapy is expected to reduce D-dimer levels in patients with thrombosis and, consequently, it may not be safe to use D-dimer levels to exclude VTE after anticoagulant therapy has been started. The objectives of this study were to estimate the decrease in D-dimer levels after 24 h of heparin therapy and, applying this estimate to the results of a recent study, to calculate the expected reduction in sensitivity. Using pre-defined criteria, we first performed a literature review to determine whether, and by how much, D-dimer levels decrease within 24 h of starting heparin therapy in patients with acute VTE. Using D-dimer levels that were measured in a prospective study of patients with confirmed deep vein thrombosis and/or pulmonary embolism as baselines, we then determined the change in sensitivity (and specificity) that would result from the fall in D-dimer levels that the literature review suggested would have occurred after 24 h of heparin therapy. On the basis of the literature review, we calculated that mean D-dimer levels decrease by 25%, 24 h after starting heparin therapy in patients with acute VTE. This 25% decrease in D-dimer levels resulted in a decrease in sensitivity from 95.6% (95% confidence interval, 90.0-98.6) to 89.4% (95% confidence interval, 83.7-95.1). There is a decrease in D-dimer levels in patients with acute VTE 24 h after starting heparin therapy that is expected to result in a clinically important drop in sensitivity.