Background Micra transcatheter pacemaker system (TPS) usually achieves low implant pacing threshold (IPT). However, IPT may increase in some patients during follow‐up. Aim To apply implant parameters in predicting long‐term occurrence of very high pacing threshold (VHPT) in patients with Micra‐TPS. Methods A cohort of 110 consecutive patients implanted with a Micra‐TPS from 2014 to 2018 was evaluated at discharge and at 1, 12, 24, 36, and 48 months follow‐up. VHPT was defined as greater than 2 V/0.24 ms. VHPT predictors were identified. Results Micra‐TPS was implanted successfully in 108 patients (98.2%). During a mean follow‐up of 24 ± 16 months, 18 patients (16.7%) died of causes nonpacemaker‐related, and 4 (3.8%) developed VHPT. Patients with VHPT had higher IPT and lower implant impedance than patients with non‐VHPT: 1 ± 0.31 vs 0.55 ± 0.29 V/0.24 ms (P = .003) and 580 ± 59 vs 837 ± 232 Ω (P = .03), respectively. IPT and impedance had excellent discriminative power to predict VHPT (area under the curve: 0.85 ± 0.07 and 0.91 ± 0.05, respectively). Negative predictive value (NPV) of IPT ≤ 0.5 V/0.24 ms was 100%; positive predictive value (PPV) was 8% throughout follow‐up. Implant impedance ≤ 600 Ω had NPV of 99% throughout follow‐up, whereas PPV varied: 16%, 21%, 16%, and 28% at 1, 12, 24, and 36 months, respectively. Sequential combination of IPT greater than 0.5 V/0.24 ms and impedance ≤ 600 Ω improved PPV to 25%, 35%, 27%, and 44%, respectively, whereas NPV remained 99% throughout follow‐up. Conclusion Despite favorable long‐term electrical performance of Micra‐TPS, a small percent of patients developed VHPT during follow‐up. A sequential combination of IPT and impedance could allow the implanter to identify patients who will develop VHPT during long‐term follow‐up.
Introduction Ablation with second‐generation cryoballoon technology evolves as an effective and safe alternative to radiofrequency for atrial fibrillation ablation procedures. Nevertheless, the optimal freezing strategy remains unknown. Our objective was to identify the procedural cryoablation parameters predicting successful peri‐pulmonary vein (PV) lesions by directly analyzing Postablation gaps in late‐gadolinium‐enhanced cardiac magnetic resonance (LGE‐CMR). Methods and Results Forty‐nine consecutive patients (196 PVs) undergoing ablation with second‐generation cryoballoon at our center were included. The number and duration of cryoballoon application to achieve PV isolation were left to operator discretion. Gap number and length were quantified in all patients with a LGE‐CMR performed 3 months postablation. Application time (420 ± 217 seconds), number of applications (2.1 ± 1.2), application time after electrical isolation (311 ± 194 seconds) and minimum temperature (−45.8 ± 6.5°C) were similar in the 4 PVs. Gaps were observed in 148 PVs (76%), averaging 1.3 ± 1 gaps per vein. Gaps were longer and more frequent in the right PVs (91% vs 59% in left PVs, P < .001). Neither the number, total duration of applications, nor postisolation application time predicted relative length or number of gaps. Conclusions After successful PV isolation was achieved in patients undergoing cryoablation, increasing the number of applications, the total application time or application time postisolation did not result in a reduction in the number or the relative length of gaps.
BACKGROUND The Micra transcatheter pacing system (Micra TPS) is often implanted in patients with atrial fibrillation and thus with increased thromboembolic risk. It is unknown whether the use of anticoagulants, associated with the use of a large venous introducer, implies an increased risk of bleeding in this group of patients.OBJECTIVE The purpose of this study was to assess the incidence of bleeding and thromboembolic complications after Micra TPS implantation with and without therapeutic anticoagulation.METHODS This single-center observational study included 107 consecutive patients receiving the Micra TPS from 2014 to 2018. At procedure completion, a figure-of-eight suture was placed at the femoral puncture site after sheath withdrawal and was maintained for 24 hours. In patients receiving enoxaparin or new oral anticoagulants, treatment was discontinued 12 or 24 hours before the procedure, respectively, and was reinitiated 4-6 hours postprocedure. In those receiving vitamin K antagonists (VKAs), dosing was not discontinued and the procedure was performed if the international normalized ratio was less than 3. RESULTS Sixty-four patients (60%) did not receive anticoagulants. Of the 43 (40%) who did, 29 (67%) received VKAs, 8 (19%) received new oral anticoagulants, and 6 (14%) received enoxaparin. Two patients presented hemorrhagic or thromboembolic complications during short-term follow-up: 1 woman receiving VKAs presented hemorrhagic pericardial effusion without tamponade and 1 woman not receiving anticoagulants presented thrombosis of the ipsilateral saphenous vein.CONCLUSION Bleeding and thromboembolic complications after receiving Micra TPSs are infrequent. The use of anticoagulant therapy, regardless of the type, does not increase the complications associated with the procedure.
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