Left Ventricular Patch Electrodes Research Articles

Cosmetic approach for placement of the automatic implantable cardioverter-defibrillator in young women

A surgical approach is described for a more cosmetically acceptable placement of the automatic implantable cardioverter-defibrillator in young women. The transvenous sensing lead and the vena caval spring electrode are placed through a small subclavicular incision. The left ventricular patch electrode is placed through an anterior minithoracotomy in the crease under the left breast. A small transverse incision in the left lower quadrant is used to place the generator under the external oblique fascia in the low abdominal wall. Minimal cosmetic impairment from incisions and hardware results.

PH-dependent effects of lidocaine on defibrillation energy requirements in dogs.

Lidocaine increases the energy required for ventricular defibrillation in dogs. Because sodium channel-blocking agents that are weak bases have pH-dependent electrophysiologic effects, we investigated the pH dependence of lidocaine (pKa, 7.9) on internal defibrillation energy requirements in 28 dogs with atrial spring and left ventricular patch electrodes. Results of defibrillation testing were used to derive 50% and 90% successful energy requirements (ED50 and ED90) using logistic regression and were compared with analysis of variance. Acidosis produced by hydrochloric acid infusion decreased the arterial pH from 7.40 +/- 0.05 (SD) to 7.18 +/- 0.03 (n = 8, p less than 0.01), but no significant change in ED90 was observed (14 +/- 4 to 16 +/- 6 J). Lidocaine infusion to therapeutic levels (4.2 +/- .07 micrograms/ml) at normal pH (7.42 +/- 0.02) increased ED90 from 13 +/- 3 to 17 +/- 3 J (n = 6, p less than 0.05), and subsequent acidosis (pH 7.19 +/- 0.02, p less than 0.01) exacerbated this effect of lidocaine on ED90 (22 +/- 5 J, p less than 0.05). Alkalosis produced by respirator hyperventilation increased the arterial pH from 7.41 +/- 0.03 to 7.60 +/- 0.03 (n = 8, p less than 0.01), with a fall in ED90 from 13 +/- 4 to 8 +/- 3 J (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

The Effect of Chronic Oral and Acute Intravenous Amiodarone Administration on Ventricular Defibrillation Threshold Using Implanted Electrodes in Dogs

The effect of acute intravenous administration and chronic oral loading of amiodarone on defibrillation threshold was evaluated in normal anesthetized dogs using implanted superior vena caval spring and left ventricular patch electrodes. The effect of oral loading with amiodarone was evaluated by comparing three groups of six dogs each that received either no drug, 200 mg/day for 9 days, or 400 mg/day for 9 days. Defibrillation threshold was evaluated by administering a fixed sequence of shocks with increasing energies until defibrillation was successful. Defibrillation was determined 13 times in each animal. The mean defibrillation threshold (plus or minus standard error of the mean) was 7.5 +/- 0.3 J in the control group, 15.4 +/- 0.6 J in the group receiving amiodarone 200 mg/day, and 17.9 +/- 0.8 J for the group receiving 400 mg/day. These values are significantly different using analysis of variance and Tukey's test. The acute effect of intravenous amiodarone, 5 mg/Kg was evaluated in five dogs using each dog as its own control. The mean defibrillation threshold during control period was 10.8 +/- 0.4 J, and during the first two hours after amiodarone administration was 10.8 +/- 0.4 J. There was no significant difference. Thus, in this study oral administration of a loading dose of amiodarone comparable to that used in patients produced a dose dependent increase in defibrillation threshold, whereas no change in defibrillation threshold was observed acutely after intravenous administration.

Evaluation of Global and Regional Left Ventricular Function Using Two‐Dimensional and M‐Mode Echocardiography in Patients With an Automatic Implantable Cardioverter Defibrillator

The effects of glued epicardial patch electrodes of the automatic implantable cardioverter defibrillator on the left ventricular function was studied by two-dimensional and M-mode echocardiography in 15 patients. Pre- and postoperative end-diastolic and end-systolic left ventricular cross-sectional areas were evaluated using planimetry. Regional left ventricular wall motion at the level of the left ventricular patch electrode was analyzed by two end-diastolic and end-systolic perpendicular axes. Left ventricular end-diastolic and end-systolic diameters as well as E-point-septal-separation and fractional shortening were analyzed using M-mode echocardiography. The mean time interval between preoperative echocardiograms and implantation of the automatic defibrillator was 0.3 X 1.3 (less than 1-2) months. Postoperative echocardiograms were recorded 6.6 +/- 6.9 (0.5-24) months after implantation of the device. There were no significant differences between pre- and postoperative mean values of end-diastolic and end-systolic areas and axes as well as M-mode echocardiographic parameters. Our data show that left ventricular patch electrodes do not significantly alter global or regional left ventricular function in patients after implantation of the automatic defibrillator.

Effect of recainam on the energy required for ventricular defibrillation in dogs as assessed with implanted electrodes

The effect of recainam (WY-42,362), a new class IC antiarrhythmic drug, on ventricular defibrillation was evaluated with use of implanted superior vena cava and left ventricular patch electrodes in 17 normal dogs anesthetized with sodium pentobarbital. The energy required for a 50% probability of successful defibrillation (E50) was used as the index of ventricular defibrillation threshold. The dogs were classified into three groups: a saline group (n = 6), a low dose recainam group (n = 6) and a high dose recainam group (n = 5). The low dose infusion involved an intravenous loading dose of 3.75 mg/kg body weight over 20 min followed by a maintenance infusion of 0.0375 mg/kg per min. The high dose infusion was double those rates.The low dose recainam infusion produced a plasma recainam concentration of 3.1 ± 0.3 μg/ml and significantly increased QRS duration by 11.3 ± 3% during sinus rhythm. The high dose recainam infusion produced a plasma concentration of 7.7 ± 0.9 μg/ml and significantly increased QRS duration by 27 ± 7% in sinus rhythm. Recainam did not change ventricular effective refractory period or sinus cycle length. The mean change in E50between control and infusion periods was 1 ± 5% in the saline group (8.5 ± 1.4 versus 8.6 ± 1.6 joules); 42 ± 11% in the low dose recainam group (8.1 ± 1.0 versus 11.3 ± 1.3 joules) and 92 ± 17% in the high dose recainam group (11.2 ± 2.1 versus 20.5 ± 2.5 joules). The changes in E50in the two recainam groups were significantly different from those in the saline group and from each other (p < 0.05). It is concluded that recainam elevates the energy required for ventricular defibrillation in a dose-dependent manner.

Intraoperative comparison of sequential-pulse and single-pulse defibrillation in candidates for automatic implantable defibrillators

Sixteen survivors of cardiac arrest underwent intraoperative comparison of the effectiveness of sequential-pulse and single-pulse defibrillation. Defibrillation was tested alternately with the single-pulse or sequential-pulse technique 10 seconds into an episode of ventricular fibrillation that was induced with alternating current, the sequential-pulse defibrillation technique using truncated exponential pulses was performed with a right ventricular endocardial catheter and a left ventricular epicardial patch electrode. The first pulse was delivered between the right ventricular apical and the superior vena caval electrode on the right ventricular endocardial catheter. The second pulse was delivered between the right ventricular apical electrode and the left ventricular patch electrode 0.2 ms after termination of the first pulse. Single-pulse defibrillation was performed with a standard intracardiac defibrillation system in which a single truncated exponential pulse was delivered across 2 epicardial patch electrodes positioned over the anterolateral right ventricle and the posterolaterai left ventricle. During defibrillation threshold determination, voltage and current waveforms were recorded and integrated to determine delivered energy. Average defibrillation threshold leading-edge voltage for the sequential pulse technique was 496 ± 140 V, compared with 365 ± 157 V for the single-pulse technique (p < 0.005). Defibrillation threshold leadingedge current for the sequential-pulse technique was 6.0 ± 2.3 A, compared with 10.6 ± 5.1 A for the single-pulse method (p < 0.0005). The defibrillation threshold delivered energy for the 2 methods was not significantly different: 13.0 ± 8.1 J for the sequential-pulse technique and 12.0 ± 8.9 J for the single pulse technique. In survivors of cardiac arrest, the single-pulse system delivers higher current and lower voltage, reflecting the lower impedance of the patch-patch lead system. Energy to terminate ventricular fibrillation successfully, however, was similar using either the sequential-pulse catheterpatch or single-pulse patch-patch method.