Rho Robert W, Patel Vickas V, Gerstenfeld Edward P, Dixit Sanjay, Poku Joseph W, Ross Heather M, Callans David, Kocovic Dusan Z
Section of Electrophysiology, Division of Cardiovascular Medicine, Hospital of the University of Pennsylvania, 3400 Spruce Street, Ninth Floor Founders Pavillion, Philadelphia, PA 19104, USA.
Pacing Clin Electrophysiol. 2003 Mar;26(3):747-51. doi: 10.1046/j.1460-9592.2003.00127.x.
Cardiac resynchronization therapy (CRT) is a new and promising therapeutic option for patients with severe heart failure and intraventricular conduction delay. Patients who are candidates for CRT and have a previously implanted device may utilize a "Y" IS 1 connector to accommodate the coronary sinus lead. This modification has the potential to alter biventricular pacing thresholds. During an 18 month period, successful biventricular pacemaker implantation was performed in 72 patients (age: 67 +/- 11 years, left ventricular ejection fraction: 20.5 +/- 5.6%). All of these patients had severe symptomatic congestive heart failure (NYHA Class III and IV). In 20 patients a special "Y" adaptor that bifurcates the ventricular IS 1 bipolar output to two bipolar outputs or one unipolar and one bipolar output was utilized. During initial implantation, LV thresholds obtained in a unipolar configuration prior to connecting to the "Y" adaptor were significantly lower than thresholds obtained after connecting to the "Y" adaptor (1.7 +/- 1.11 V at 0.5 ms pulse width versus 2.8 +/- 1.5 V at 0.5 ms pulse width [P = 0.01]). Two patients (10%) required left ventricular lead revisions due to unacceptably high left ventricular thresholds during device follow-up. The difference in measured left ventricular thresholds between the two configurations is best explained by a resistive element that is added to the circuit when performing threshold measurement of the LV lead through the "Y" adaptor (combined tip to RV ring configuration) versus measurement of the LV lead in a unipolar configuration. This resistive element represents multiple factors including anode surface area, resistive polarization at the tissue-electrode interface, and transmyocardial resistance. LV thresholds should be measured in an LV tip to RV ring configuration or ideally in a combined tip (LV and RV) to shared ring configuration in order to accurately assess LV thresholds. This observation has significant clinical implications as loss of capture may occur as a result of improper measurement of left ventricular thresholds at the time of implantation.
心脏再同步治疗（CRT）是重度心力衰竭合并室内传导延迟患者一种新的且有前景的治疗选择。符合CRT标准且先前已植入装置的患者可使用“Y”型IS 1连接器来容纳冠状窦导联。这种改良有可能改变双心室起搏阈值。在18个月期间，72例患者（年龄：67±11岁，左心室射血分数：20.5±5.6%）成功植入双心室起搏器。所有这些患者均有重度症状性充血性心力衰竭（纽约心脏协会III级和IV级）。20例患者使用了一种特殊的“Y”型适配器，该适配器将心室IS 1双极输出分为两个双极输出或一个单极输出和一个双极输出。在初次植入期间，连接“Y”型适配器之前单极配置下获得的左心室阈值显著低于连接“Y”型适配器之后获得的阈值（脉宽0.5 ms时为1.7±1.11 V，而脉宽0.5 ms时为2.8±1.5 V [P = 0.01]）。两名患者（10%）因在装置随访期间左心室阈值过高而需要对左心室导联进行修订。两种配置下测得的左心室阈值差异最好通过以下情况来解释：当通过“Y”型适配器（联合尖端至右心室环配置）对左心室导联进行阈值测量时，与单极配置下测量左心室导联相比，电路中会增加一个电阻元件。这个电阻元件代表多种因素，包括阳极表面积、组织 - 电极界面处的电阻极化以及跨心肌电阻。应在左心室尖端至右心室环配置下测量左心室阈值，或者理想情况下在联合尖端（左心室和右心室）至共用环配置下测量，以便准确评估左心室阈值。这一观察结果具有重要的临床意义，因为在植入时左心室阈值测量不当可能导致捕捉失败。
