Fröhlig G, Bolz A, Ströbel J, Rutz M, Lawall P, Schwerdt H, Schaldach M, Schieffer H
Medizinische Universitätsklinik, Innere Medizin III, Homburg, Germany.
Pacing Clin Electrophysiol. 1998 Jun;21(6):1239-46. doi: 10.1111/j.1540-8159.1998.tb00183.x.
Minimizing the geometric surface area of pacing electrodes increases impedance and reduces the current drain during stimulation, provided that voltage (pulse-width) thresholds remain unchanged. This may be feasible by coating the electrode surface to increase the capacity of the electrode tissue interface and to diminish polarization. Ten unipolar, tined leads with a surface area of 1.3 mm2 and a "fractal" coating of iridium (Biotronik SD-V137) were implanted in the ventricle, and electrogram amplitude (unfiltered), slew-rate, pacing threshold (0.5 ms), and impedance (2.5 V; 0.5 ms) were measured by the 5311 PSA (Medtronic). On days 0. 2. 5. 10, 28, 90, 180, 360 postimplant, sensing threshold (up to 7.0 mV, measuring range 1-14 mV on day 360 only) and the strength duration curve (0.5-4.0 V; 0.03-1.5 ms; steps: 0.5 V; 0.01 ms, respectively) were determined, the minimum charge delivered per pulse (charge threshold), and the impedance were taken from pacemaker telemetry (Intermedics 294-03). Data were compared with those of an earlier series of 20 unipolar, tined TIR-leads (Biotronik) with a surface area of 10 mm2 and a @actal" coating of titanium nitride. With the model SD-V137 versus TIR, intraoperative electrogram amplitudes were 15.1 +/- 6.1 versus 14.4 +/- 3.9 mV (NS), slew rates 3.45 +/- 1.57 versus 1.94 +/- 1.06 V/s (P < 0.05), pacing thresholds 0.16 +/- 0.05 versus 0.52 +/- 0.15 V (P < 0.01) and impedance measurements 1,136 +/- 175 versus 441 +/- 73 omega (P < 0.0001), respectively. During follow-up, sensing thresholds were the same with both leads. Differences in pulse width thresholds lost its significance on day 28 but resumed on day 360 (SD-V137; 0.08 +/- 0.04 ms; TIR: 0.16 +/- 0.06 ms at 2.5 V; P < 0.01). With an electrode surface of 1.3 mm2, charge per pulse and impedance consistently differed from control, being 0.15 +/- versus 0.66 +/- 0.20 microC (P < 0.001) and 1,344 +/- 376 versus 538 +/- 79 omega respectively, one year after implantation (P < 0.0001). In summary, "fractally" coated small surface electrodes do not compromise sensing; by more than doubling impedance against controls they offer pacing thresholds (mainly in terms of charge) that are significantly lower than with the reference electrode.
在刺激过程中，将起搏电极的几何表面积最小化可增加阻抗并减少电流消耗，前提是电压（脉宽）阈值保持不变。通过在电极表面进行涂层处理以增加电极与组织界面的电容并减少极化，这或许是可行的。将10根表面积为1.3平方毫米且带有铱“分形”涂层的单极、带倒刺导线（百多力SD-V137）植入心室，并用美敦力5311 PSA测量心电图幅度（未滤波）、上升速率、起搏阈值（0.5毫秒）和阻抗（2.5伏；0.5毫秒）。在植入后的第0、2、5、10、28、90、180、360天，测定感知阈值（最高7.0毫伏，仅在第360天测量范围为1 - 14毫伏）和强度-时间曲线（0.5 - 4.0伏；0.03 - 1.5毫秒；步长分别为0.5伏；0.01毫秒），从起搏器遥测数据（Intermedics 294 - 03）中获取每个脉冲输送的最小电荷量（电荷阈值）和阻抗。将数据与早期一组20根表面积为10平方毫米且带有氮化钛“分形”涂层的单极、带倒刺TIR导线的数据进行比较。对于SD-V137与TIR模型，术中心电图幅度分别为15.1±6.1毫伏与14.4±3.9毫伏（无显著差异），上升速率分别为3.45±1.57伏/秒与1.94±1.06伏/秒（P<0.05），起搏阈值分别为0.16±0.05伏与0.52±0.15伏（P<0.01），阻抗测量值分别为1136±175欧姆与441±73欧姆（P<0.0001）。在随访期间，两种导线的感知阈值相同。脉冲宽度阈值的差异在第28天失去显著性，但在第360天恢复（SD-V137；2.5伏时为（0.08±0.04毫秒；TIR：0.16±0.06毫秒；P<0.01）。电极表面积为1.3平方毫米时，植入一年后每个脉冲的电荷量和阻抗与对照组持续存在差异，分别为0.15±与0.66±0.20微库（P<0.001）和1344±376欧姆与538±79欧姆（P<0.0001）。总之，“分形”涂层的小表面积电极不会影响感知；与对照组相比，它们的阻抗增加了一倍多，其提供的起搏阈值（主要在电荷量方面）显著低于参考电极。
