Irastorza Ramiro M, Maher Timothy, Barkagan Michael, Liubasuskas Rokas, Pérez Juan J, Berjano Enrique, d'Avila Andre
Instituto de Física de Líquidos y Sistemas Biológicos (CONICET), La Plata B1904, Argentina.
Departamento de Ingeniería Mecánica, Facultad Regional La Plata, Universidad Tecnológica Nacional, La Plata C1041, Argentina.
J Cardiovasc Dev Dis. 2022 Oct 3;9(10):336. doi: 10.3390/jcdd9100336.
Background: Baseline impedance, radiofrequency current, and impedance drop during radiofrequency catheter ablation are thought to predict effective lesion formation. However, quantifying the contributions of local versus remote impedances provides insights into the limitations of indices using those parameters. Methods: An in silico model of left atrial radiofrequency catheter ablation was used based on human thoracic measurements and solved for (1) initial impedance (Z), (2) percentage of radiofrequency power delivered to the myocardium and blood (3) total radiofrequency current, (4) impedance drop during heating, and (5) lesion size after a 25 W−30 s ablation. Remote impedance was modeled by varying the mixing ratio between skeletal muscle and fat. Local impedance was modeled by varying insertion depth of the electrode (ID). Results: Increasing the remote impedance led to increased baseline impedance, lower system current delivery, and reduced lesion size. For ID = 0.5 mm, Z ranged from 115 to 132 Ω when fat percentage varied from 20 to 80%, resulting in a decrease in the RF current from 472 to 347 mA and a slight decrease in lesion size from 5.6 to 5.1 mm in depth, and from 9.2 to 8.0 mm in maximum width. In contrast, increasing the local impedance led to lower system current but larger lesions. For a 50% fat−muscle mixture, Z ranged from 118 to 138 Ω when ID varied from 0.3 to 1.9 mm, resulting in a decrease in the RF current from 463 to 443 mA and an increase in lesion size, from 5.2 up to 7.5 mm in depth, and from 8.4 up to 11.6 mm in maximum width. In cases of nearly identical Z but different contributions of local and remote impedance, markedly different lesions sizes were observed despite only small differences in RF current. Impedance drop better predicted lesion size (R2 > 0.93) than RF current (R2 < 0.1). Conclusions: Identical baseline impedances and observed RF currents can lead to markedly different lesion sizes with different relative contributions of local and remote impedances to the electrical circuit. These results provide mechanistic insights into the advantage of measuring local impedance and identifies potential limitations of indices incorporating baseline impedance or current to predict lesion quality.
在射频导管消融过程中，基线阻抗、射频电流和阻抗下降被认为可预测有效损伤的形成。然而，量化局部阻抗与远程阻抗的贡献有助于深入了解使用这些参数的指标的局限性。方法：基于人体胸部测量数据，使用左心房射频导管消融的计算机模拟模型，并求解以下参数：（1）初始阻抗（Z）；（2）输送到心肌和血液的射频功率百分比；（3）总射频电流；（4）加热过程中的阻抗下降；（5）25W - 30s消融后的损伤大小。通过改变骨骼肌与脂肪的混合比例来模拟远程阻抗。通过改变电极插入深度（ID）来模拟局部阻抗。结果：增加远程阻抗会导致基线阻抗增加、系统电流输送降低以及损伤大小减小。当ID = 0.5mm时，随着脂肪百分比从20%变化到80%，Z值范围为115至132Ω，导致射频电流从472mA降至347mA，损伤大小略有减小，深度从5.6mm降至5.1mm，最大宽度从9.2mm降至8.0mm。相比之下，增加局部阻抗会导致系统电流降低，但损伤更大。对于50%脂肪 - 肌肉混合物，当ID从0.3mm变化到1.9mm时，Z值范围为118至138Ω，导致射频电流从463mA降至443mA，损伤大小增加，深度从5.2mm增加到7.5mm，最大宽度从8.4mm增加到11.6mm。在基线阻抗几乎相同但局部和远程阻抗贡献不同的情况下，尽管射频电流仅有微小差异，但观察到的损伤大小却明显不同。阻抗下降比射频电流能更好地预测损伤大小（R2 > 0.93）（R2 < 0.1）。结论：相同的基线阻抗和观察到的射频电流可能导致损伤大小明显不同，这取决于局部和远程阻抗对电路的相对贡献。这些结果为测量局部阻抗的优势提供了机制性见解，并确定了纳入基线阻抗或电流来预测损伤质量的指标的潜在局限性。
