Determinants of Heparin Dosing and Complications in Patients Undergoing Left Atrial Ablation on Uninterrupted Rivaroxaban

Development and Validation of a Nomogram Model Affecting the ACT Targeting Rate During Radiofrequency Ablation of Atrial Fibrillation in China

CONTEXT

A nomogram model affecting the activated clotting time (ACT) targeting rate during radiofrequency ablation of atrial fibrillation (RFCA) in China.

PURPOSE

The aim of this study is to develop and validate a nomogram model for predicting the activated clotting time targeting rate after the initial bolus heparin dosages during the radiofrequency catheter ablation of atrial fibrillation in China.

METHODS AND RESULTS

A retrospective observational study was conducted on the data of 465 patients with atrial fibrillation who underwent radiofrequency catheter ablation (RFCA) from October 2019 to June 2022. All patients were randomized into a training cohort (70%; n = 325) and a validation cohort (30%; n = 140). Independent risk factors were identified using univariate and multifactorial logistic regression analysis. The predictive nomogram model was established using R software. The nomogram was developed and evaluated based on differentiation, calibration, and clinical efficacy using concordance statistic (C-statistic), calibration plots, and decision curve analysis (DCA), respectively. The nomogram was established using three variables, including sex (OR 1.01, 95% CI 0.29-1.76, P = 0.007), heparin dose (OR 0.04; 95%CI 0.02-0.05, P < 0.001), and the baseline ACT (OR 0.03; 95%CI 0.02-0.04, P < 0.001). The C-statistic of the nomogram was 0.736 (95%CI 0.675-0.732) in the training cohort and 0.700 (95%CI 0.622-0.721) in the validation cohort. The calibration plots showed good agreement between the predictions and observations in the training and validation cohorts. The clinical decision curve also proves that the map is useful in clinical settings.

CONCLUSION

The nomogram model has good discrimination and accuracy, which can screen attainment groups intuitively and individually, and has a certain predictive value for the probability of ACT reaching the target after the adequate dosage of initial heparin in Chinese patients with atrial fibrillation.

Protocol driven periprocedural anticoagulation for left atrial ablation

INTRODUCTION

A weight-based heparin dosing policy adjusted for preprocedural oral anticoagulation was implemented to reduce the likelihood of subtherapeutic dosing during left atrial catheter ablation procedures. We hypothesized that initiation of the protocol would result in a greater prevalence of therapeutic activated clotting time (ACT) values and decreased time to therapeutic ACT during left atrial ablation procedures.

METHODS

A departmental protocol was initiated for which subjects received intravenous unfractionated heparin (UFH) to achieve and maintain a goal of ACT >300 s. Initial bolus dose was adjusted for pre-procedure oral anticoagulation and weight as follows: 50 units/kg for those receiving warfarin, 75 units/kg for those not anticoagulated, and 120 units/kg for those on direct oral anticoagulants (DOACs). A UFH infusion was initiated at 10% of the bolus per hour. One hundred consecutive left atrial ablation procedures treated with Protocol Guided heparin dosing were compared with a retrospective consecutive cohort of Usual Care heparin dosing.

RESULTS

When the Usual Care and Protocol Guided cohorts were compared, significant findings were limited to those on pre-procedure DOAC. The initial UFH bolus increased from 99.3 ± 24.8 to 118.2 ± 22.8 units/kg (p < .001), the proportion of therapeutic ACT on the first draw after heparin administration increased from 57.7% to 76.6% (p = .010), and the time to therapeutic ACT after UFH administration decreased from 37.8 ± 19.8 to 30.2 ± 16.4 min (p = .032).

CONCLUSION

A weight-based protocol for periprocedural UFH administration resulted in a higher proportion of therapeutic ACT values and decreased the time to therapeutic ACT for those on pre-procedure DOAC.

Effects of rivaroxaban on activated clotting time in catheter ablation for atrial fibrillation in Chinese patients

PURPOSE

It has been observed that patients on rivaroxaban require more heparin and frequent activated clotting time (ACT) monitoring throughout the catheter ablation of atrial fibrillation, but the strategy of heparin injection varies in different studies. We sought to examine the determinants of heparin dosage in Chinese patients on rivaroxaban.

METHODS

We reviewed consecutive patients who received rivaroxaban before atrial fibrillation ablation and compared them to patients on no anticoagulant. The dosage of heparin required to achieve ACT > 300 s was evaluated. We then tested determinants of heparin dosage prospectively.

RESULTS

There were 124 patients on rivaroxaban (R group) and 42 on no anticoagulant (NA group) in retrospective study. Heparin dosage required to achieve target ACT was 0.89 ± 0.01 mg/kg in R group and 0.60 ± 0.01 mg/kg in NA group, P < 0.05. The bolus heparin dosage required was 0.77 ± 0.01 mg/kg (96.1 ± 1.1 U/kg) when baseline ACT > 200 s. In the prospective study, 80/90(88.9%) of patients in R group and 79/90(87.8%) in NA group achieved an ACT > 300 s after initial bolus injection of heparin. The ACT 60 min after target ACT (ACT60) in R group was higher than that in NA group (287.5 ± 28.3 VS 238.9 ± 29.5, P < 0.05). Rivaroxaban was the only independent predictor of ACT60. There was no significant difference in ACT or heparin dosage in patients with different duration on or withdrawal of rivaroxaban.

CONCLUSIONS

In patients undergoing atrial fibrillation ablation on rivaroxaban, the effective duration of heparin is prolonged and the procedural heparin requirement is significantly greater. Heparin dosage can be predicted by baseline ACT, but not influenced by duration on or withdrawal of rivaroxaban.

Development and Implementation of a Standardized Heparin Protocol for Left-Sided Pediatric Electrophysiology Procedures

Heparin is used to decrease the risk of thromboembolic complications during electrophysiology studies (EPS); however, there is wide practice variation and minimal evidence to guide heparin dosing, particularly in pediatric patients. This study retrospectively analyzed heparin dosing and response, measured via activated clotting time (ACT), in patients undergoing EPS and used these data (pre-protocol cohort, n = 40), as well as guidance from available literature to implement a standardized heparin protocol (phase 1, n = 43). We utilized quality improvement methodology to refine this protocol (phase 2, n = 40) to improve therapeutic heparin response. Prior to the protocol, patients achieved therapeutic ACT levels (250-350 s) only 35% of the time which improved to 60% during phase 1 (p < 0.05) and to 73% during phase 2 (p < 0.001 compared to pre-protocol). There were no thromboses or significant adverse events in any group. These results demonstrate the effectiveness of a standardized heparin protocol in achieving effective antithrombotic therapy during left-sided pediatric EPS.