Guidelines largely based on closed-tip catheters recommend activated clotting times (ACTs) >300 to 350 seconds during atrial fibrillation (AF) ablation to prevent thrombus and char formation. Open irrigated tip catheters (OITC) may decrease complications and permit lower ACTs. This study evaluated factors contributing to vascular and hemorrhagic complications during AF ablation with emphasis on catheter type, anticoagulation level, procedural and clinical variables, and gender. In 1,122 AF ablations we examined catheter used, ACT level, gender, and complications. Target ACTs initially were >300 seconds and were decreased to 225 seconds for the OITC. Average ACT ranges were created: <250, 250 to 299, 300 to 350, and >350 seconds. Average ACT was <250 seconds in 557 ablations (complication rate 1.62%). Cochran–Armitage analysis showed that complications increased linearly as ACT increased and peaked at 5.55% for ablations with ACTs >350 seconds (p = 0.038). Women were older (66 ± 10 vs 60 ± 10 years, p <0.001) and had more paroxysmal AF (43% vs 28%, p = 0.007) and more hypertension (50% vs 40%, p = 0.013). Women received less heparin but were over-represented in higher ACT ranges (p <0.0001) consistent with a pharmacokinetic gender difference. There was no difference in vascular or hemorrhagic complications between men and women (2.3% vs 2.9%, p = 0.668). Multivariate logistic regression showed that only use of the OITC was associated with lower complication rates (p = 0.024). In conclusion, AF ablation with the OITC is safe with a target ACT of 225 seconds.
Consensus guidelines on catheter ablation recommend an intraprocedural activated clotting time (ACT) of 300 to 350 seconds and a longer time of 350 to 400 seconds in patients with spontaneous echocardiographic contrast noted on transesophageal or intracardiac echocardiogram. These recommendations are largely based on intracardiac echocardiographic observation of apparent thrombus and not actual clinical events. These studies were performed before the introduction of the open irrigated tip catheter (OITC). Animal studies have shown that OITCs have lower tissue interface temperature to achieve deeper tissue heating than closed-tip catheters (CTCs) and closed irrigated tip catheters, which results in less or no local thrombus formation. Because of decreased thrombus formation with the OITC in animal models, after the introduction of OITCs we decreased our target ACT to 225 seconds during atrial fibrillation (AF) radiofrequency ablation. This study reports our experience with the OITC for AF ablation at lower target ACTs and examines factors associated with vascular and hemorrhagic complications.
Methods
Subjects were consecutive patients undergoing AF ablation at Sequoia Hospital, Redwood City, California from October 10, 2003 through December 31, 2009. All patients had symptomatic AF and signed written informed consent for ablation. Data analysis was retrospective and approved by the Sequoia Hospital institutional review board. AF type was categorized as paroxysmal (type 1, lasting <1 week), persistent (type 2, lasting >1 week and <1 year or requiring pharmacologic or electrical cardioversion in <1 week), and longstanding persistent (type 3, lasting >1 year).
General anesthesia was used in 96% of ablations. Venous access was from the groin and most patients had all sheaths placed in the right groin. A 63-cm 8Fr transseptal sheath (St. Jude [St. Paul, Minnesota] Fast Cath or Biosense Webster [Diamond Bar, California] Preface SL1), a 23-cm 9Fr sheath (St. Jude Ultimum), and a 12-cm 8Fr sheath (St. Jude Fast Cath) were used. A 7Fr duodeca catheter (St. Jude Livewire) was placed through the 8Fr sheath and around the tricuspid annulus with the distal poles in the coronary sinus. A 9Fr Boston Scientific (Natick, Massachusetts) Ultra Ice intracardiac ultrasound catheter was inserted through the 9Fr sheath for transseptal puncture, which was done using a 71-cm St. Jude BRK or a Baylis (Montreal, Quebec, Canada) NRG needle. All patients had a femoral or a radial arterial line placed. The St. Jude NavX system was used in all cases.
Before January 2006, all ablations were done with a CTC (Boston Scientific Blazer II, n = 8, or Webster Celsius 8 mm, n = 110) until January 2006 after which all ablations were done with an OITC (Webster Thermocool 3.5 mm or St. Jude Cool Path 4.0 mm, n = 1,004). From January until August 2006 the OITC power was gradually increased from 35 to 50 W after which all received 50-W ablations. No special effort was made to keep the transseptal sheath in the right atrium. All patients underwent circumferential atrial ablation around all pulmonary veins and a left atrial roof line ablation. The 50-W ablations were done with a technique of “perpetual motion” where the catheter was moved back and forth across a small area and was not left at a single site for extended periods. The ultrasound catheter was removed and the ablation catheter placed into the left atrium with a circumferential mapping catheter (7Fr Webster Lasso or St. Jude Reflexion Spiral) across the single transseptal puncture site to confirm pulmonary vein isolation. Touchup was done as needed to isolate all pulmonary veins, which was the primary end point of the study. Patients with atrial flutter also underwent ablation of a mitral or caval-tricuspid isthmus line, and many patients had ablation at sites of complex fractionated electrograms in the atria or coronary sinus, ablation of a low posterior left atrial line, and isolation of the superior vena cava. Patients with more persistent AF received more aggressive ablation protocols. Ablation was avoided near the esophagus, which was marked by a thermistor catheter.
Patients receiving warfarin continued it until 5 days before the procedure. Three days before the ablation patients started enoxaparin 1 mg/kg every 12 hours with the last dose 24 hours before ablation. Patients not already receiving warfarin did not receive anticoagulation drugs before the procedure. Patients with persistent or frequent paroxysmal AF underwent transesophageal echocardiography. When the transseptal sheath was in the left atrium an intravenous heparin bolus was given followed by a 1,000-U/hour infusion through the transseptal sheath (protected by an air filter) at a concentration of 10 U/ml. Mapping and ablation were begun immediately and the first ACT was obtained 15 minutes later. ACTs were drawn every 20 to 30 minutes during the procedure. Additional heparin was given and the drip rate adjusted depending on the ACT. The OITC was infused with normal saline containing a heparin concentration of 2 U/ml at 2 ml/min at baseline increased to 30 ml/min while ablating. Our initial target ACT was 300 to ≥350 seconds. After the OITC became available in January 2006 we gradually decreased our target ACT to 225 seconds. Enoxaparin 0.5 mg/kg every 12 hours was started when the sheaths were removed and discontinued when the international normalized ratio was 2.0. Warfarin was started the evening of the procedure and continued for ≥3 months.
Vascular or hemorrhagic complications were defined as pericardial tamponade (or effusion requiring pericardiocentesis), groin or other bleeding requiring transfusion or surgical intervention, groin pseudoaneurysms and arteriovenous fistulas, systemic thromboembolism, and stroke or transient ischemic attack. All strokes, tamponades, and groin complications requiring surgery were considered major and transient ischemic attacks or complications requiring transfusion only or treated noninvasively or with a thrombin injection were considered minor. A single major protamine reaction was also included because it was related to anticoagulation. Most patients were discharged the morning after the procedure but all were contacted by telephone every few days for the first month after the procedure. For all ablations we recorded start (lidocaine injection), procedure end (sheath suture or removal), and left atrial times, heparin bolus, patient weight, and all ACT values. For each ablation mean ACT was calculated from individual ACTs. For data analysis a series of average ACT ranges was defined: <250, 250 to 299, 300 to 350, and >350 seconds. Percentage of patients with a complication in each ACT range was calculated. Heparin bolus, heparin bolus normalized for body weight, use of OITCs, and number of groins/procedure were calculated for each ACT range. Procedure time, left atrial time, heparin bolus, heparin bolus normalized for body weight, age, type of AF, number of antiarrhythmic drugs failed, and presence of hypertension were analyzed separately for men and women.
Statistical analysis was done using XLSTAT 2010 (Paris, France). Continuous data were described as mean ± SD and counts and percentages if categorical. Student’s t test, chi-square test, and Fisher’s exact test were used to compare differences between men and women. The Cochran–Armitage trend test was used to evaluate complication rates and representation of women across ACT ranges. Logistic regression analysis was done to examine factors associated with procedural complications. Factors examined were age, left atrial size, average ACT, gender, irrigated versus CTC, duration of procedure, and paroxysmal versus nonparoxysmal AF. All tests were 2-sided and a p value <0.05 was considered statistically significant.
Results
There were 1,122 ablations performed in 843 patients including 258 second ablations and 21 third ablations. Women accounted for 235 of patients (28%) and 307 (27%) of ablations. Average age at first ablation was 62 ± 10 years and AF types were type 1 in 270 patients (32%), type 2 in 423 patients (50%), and type 3 in 150 patients (18%). Average procedure time was 138 ± 48 minutes.
For all 1,122 ablation procedures mean heparin dose was 8,799 ± 1,606 U and mean heparin dose per kilogram of body weight was 98 ± 20. Table 1 lists mean heparin bolus and dose per kilogram, which increased sequentially across ACT ranges. Among the 557 procedures with an average ACT <250 seconds, 41 had an average ACT <200 seconds.
| ACT Ranges (seconds) | ||||
|---|---|---|---|---|
| <250 | 250–299 | 300–350 | >350 | |
| Number of ablations | 557 | 331 | 196 | 36 |
| Heparin bolus (units) | 8,240 ± 1,539 | 8,952 ± 1,336 | 9,843 ± 1,493 | 10,333 ± 1,394 |
| Heparin bolus (U/kg) | 90 ± 12 | 99 ± 16 | 115 ± 22 | 135 ± 30 |
| Average activated clotting time/ablation (seconds) | 224 ± 16 | 272 ± 15 | 319 ± 14 | 389 ± 29 |
| Nonirrigated tip catheters | 0.2% | 4.8% | 42% | 50% |
| Number of groins | 1.09 ± 0.28 | 1.23 ± 0.42 | 1.26 ± 0.44 | 1.25 ± 0.44 |
| Women | 23.5% | 27.5% | 33.1% | 55.6% |
| Severe protamine reaction | 0 | 1 (0.30%) | 0 | 0 |
| Tamponade/pericardiocentesis | 3 (0.5%) | 3 (0.9%) | 3 (1.5%) | 1 (2.8%) |
| Arteriovenous fistula | 2 (0.4%) | 1 (0.3%) | 1 (0.5%) | 0 |
| Groin pseudoaneurysm | 3 (0.5%) | 2 (0.6%) | 1 (0.5%) | 0 |
| Hematoma (transfusion or surgery) | 0 | 2 (0.6%) | 0 | 1 (2.8%) |
| Stroke | 1 (0.2%) | 1 (0.30%) | 1 (0.5%) | 0 |
| Transient ischemic attack | 0 | 0 | 1 (0.5%) | 0 |
Table 1 presents vascular or hemorrhagic complications, which occurred in 28 of 1,122 procedures (2.5%). Seventeen of the 28 complications were major and 11 were minor. Cochran–Armitage test showed a significant increase in total complication rate ( Figure 1 ) from 1.62% for procedures with ACTs <250 seconds to 5.55% among those procedures with average ACTs >350 seconds (p = 0.038). There were no deaths, atrial-esophageal fistulas, or pulmonary vein stenoses requiring intervention. Char was never seen on any irrigated tip catheter.
At the time of first ablation the women were older (66 ± 9 vs 60 ± 10 years, p <0.001) and had more hypertension (50% vs 43%, p = 0.013), more AF type 1 (43% vs 28%, p = 0.007), and less AF type 3 (11% vs 20%, p = 0.002) than men. Procedural data by gender are presented in Table 2 . Procedure times were similar for women and men; however, left atrial times were slightly shorter for women. Number of groins used was similar for men and women. Despite a lower initial heparin loading bolus, women ended up with a higher dose than men when adjusted for body weight. Women were under-represented in the group with lower ACTs and over-represented in the groups with the longer ACTs ( Table 1 ). Only 23.5% of procedures with ACTs <250 seconds were in women. However, women represented 33.1% of procedures in the ACT range of 300 to 350 and 55.6% of procedures with ACTs >350 (p <0.0001). Of the 28 complications 9 occurred in women (2.9%) and 19 occurred in men (2.3%, p = 0.668).
