Right Ventricular Coil Research Articles

Additional coils mitigate elevated defibrillation threshold in right-sided implantable cardioverter defibrillator generator placement: a simulation study.

The standard implantable cardioverter defibrillator (ICD) generator (can) is placed in the left pectoral area; however, in certain circumstances, right-sided cans may be required which may increase defibrillation threshold (DFT) due to suboptimal shock vectors. We aim to quantitatively assess whether the potential increase in DFT of right-sided can configurations may be mitigated by alternate positioning of the right ventricular (RV) shocking coil or adding coils in the superior vena cava (SVC) and coronary sinus (CS). A cohort of CT-derived torso models was used to assess DFT of ICD configurations with right-sided cans and alternate positioning of RV shock coils. Efficacy changes with additional coils in the SVC and CS were evaluated. A right-sided can with an apical RV shock coil significantly increased DFT compared to a left-sided can [19.5 (16.4, 27.1) J vs. 13.3 (11.7, 19.9) J, P < 0.001]. Septal positioning of the RV coil led to a further DFT increase when using a right-sided can [26.7 (18.1, 36.1) J vs. 19.5 (16.4, 27.1) J, P < 0.001], but not a left-sided can [12.1 (8.1, 17.6) J vs. 13.3 (11.7, 19.9) J, P = 0.099). Defibrillation threshold of a right-sided can with apical or septal coil was reduced the most by adding both SVC and CS coils [19.5 (16.4, 27.1) J vs. 6.6 (3.9, 9.9) J, P < 0.001, and 26.7 (18.1, 36.1) J vs. 12.1 (5.7, 13.5) J, P < 0.001]. Right-sided, compared to left-sided, can positioning results in a 50% increase in DFT. For right-sided cans, apical shock coil positioning produces a lower DFT than septal positions. Elevated right-sided can DFTs may be mitigated by utilizing additional coils in SVC and CS.

Construction of intracardiac vectorcardiogram from implantable cardioverter-defibrillator intracardiac electrograms

We constructed an intracardiac vectorcardiogram from 3 configurations of intracardiac cardiovertor defibrilator (ICD) electrograms (EGMs). Six distinctive 3 lead combinations were selected out of five leads: can to right ventricular coil (RVC); RVC to superior vena cava coil (SVC); atrial lead tip (A-tip) to right ventricular (RV)-ring; can to RV-ring; RV-tip to RVC, in a patient with dual chamber ICD. Surface spatial QRS-T angle (119.8°) was similar to intracardiac spatial QRS-T angle derived from ICD EGMs combination A (101.3°), B (96.1°), C (92.8°), D (95.2), E (99.0), F (96.2) and median (101.5). Future validation of the novel method is needed.

The Relationship Between Cardiac Vulnerability and Restitution Properties of the Ventricular Activation Recovery Interval

The restitution of the action potential duration (APD) is an important contributor to ventricular fibrillation (VF) initiation by a single critically timed ectopic beat. We hypothesized that a steep slope of the activation recovery interval restitution curve was related to the upper limit of vulnerability (ULV). Fifty-four consecutive patients with implantable cardioverter defibrillators (ICDs) implanted between April 2012 and July 2013 were included. At the implantation, pacing from the right ventricular (RV) coil to an indifferent electrode inserted in the ICD pocket was performed, and the unipolar electrograms from the RV coil were simultaneously recorded. We assessed the standard restitution by introducing extra-stimuli, while measuring the activation recovery interval (ARI). Our protocol for the vulnerability test consisted of delivering three 15 J shocks on the T-peak and within ±20 milliseconds of it. If VF was not induced by that procedure, a ULV of ≤15 J was defined. The relationship between the ULV and maximum slope of the restitution curve was analyzed. A restitution curve could finally be obtained in a total of 40 patients. The background characteristics were similar between the two groups. The maximum slope of the restitution curve was steeper in the ULV > 15 J group than ULV ≤ 15 J group (1.55 ± 0.45 vs. 0.91 ± 0.64, P < 0.05). A maximum slope exceeding 1.0 was the optimal point for discriminating patients with a ULV > 15 J from a ULV ≤ 15 J (sensitivity 61.5% and specificity 96.3%). The maximum slope of the restitution curve was significantly related to the ULV. High defibrillation threshold patients could be detected by the ARI dynamics.

Is the pace/sense conductor related to a high voltage short circuit in a dual coil ICD system? An experimental study

BackgroundWe carried out a bench study of implantable cardioverter-defibrillator (ICD) performance in order to investigate whether the right ventricular (RV) ring contributes to the occurrence of a high-voltage (HV) short circuit. MethodsA polycarbonate water bath with 0.18% saline was prepared. An ICD lead was connected to an ICD device and both were placed into the water bath. The impedance of each electrode and coil was measured. In the first experiment, the RV ring was shorted to the RV coil using an alligator clip. The impedance of each electrode and coil at shorting was measured. A maximum energy defibrillation shock was delivered. The therapy log confirmed the HV short circuit and the delivery conditions. In the second experiment, a short circuit was established between the RV ring and the superior vena cava coil and a similar procedure was followed. ResultsNo HV short circuit was observed in either experiment. Scheduled shock energies were delivered without problems. Some changes in pace–sense impedance or coil impedance were observed, but they remained within the normal range. ConclusionsThe RV ring conductor is not related to HV short circuits, even if the RV ring and/or RV ring conductor is placed in contact with HV electrodes.

Implantable intravascular defibrillator: Defibrillation thresholds of an intravascular cardioverter-defibrillator compared with those of a conventional ICD in humans

A percutaneous intravascular cardioverter-defibrillator (PICD) has been developed with a right ventricular (RV) single-coil lead and titanium electrodes in the superior vena cava (SVC)-brachiocephalic vein (BCV) region and the inferior vena cava (IVC). To compare defibrillation thresholds (DFTs) of the PICD with those of a conventional ICD in humans. Ten patients with ischemic cardiomyopathy and ejection fraction ≤35% were randomized to initial testing with either PICD or conventional ICD. A standard dual-coil lead was positioned in the RV apex. If randomized to PICD, the device was placed into the vasculature such that 1 titanium electrode was positioned in the SVC-BCV region and the second in the IVC. For PICD DFTs, the RV coil of the conventional ICD lead was connected to the PICD mandrel [shock vector: RV (+) to SVC-BCV (-) + IVC (-)]. When testing the conventional ICD, a subcutaneous pocket was formed in the left pectoralis region and the ICD was connected to the lead system and positioned in the pocket [shock vector: RV (+) to SVC (-) + active can (-)]. Each device was removed before testing with the other. A step-down binary search protocol determined the DFT, with the initial shock being 9 J. The mean PICD DFT was 7.6 ± 3.3 J, and the conventional ICD system demonstrated a mean DFT of 9.5 ± 4.7 J (N = 10; paired t test, P = .28). The intravascular defibrillator has DFTs similar to those of commercially available ICDs.

Implantable Intravascular Defibrillator: Evaluation of Defibrillation Waveforms with Inferior Vena Cava Electrode System

A percutaneously placed, totally intravascular defibrillator has been developed that shocks via a right ventricular (RV) single-coil and titanium electrodes in the superior vena cava (SVC) and the inferior vena cava (IVC). This study evaluated the defibrillation threshold (DFT) with this electrode configuration to determine the effect of different biphasic waveform tilts and second-phase durations as well as the contribution of the IVC electrode. Eight Bluetick hounds (wt = 30-40 kg) were anesthetized and the RV coil (first-phase anode) was placed in the RV apex. The intravascular defibrillator (PICD®, Model no. IIDM-G, InnerPulse Inc., Research Triangle Park, NC, USA) was positioned such that the titanium electrodes were in the SVC and IVC . Ventricular fibrillation was electrically induced and a Bayesian up-down technique was employed to determine DFT with two configurations: RV to SVC + IVC and RV to SVC. Three waveform tilts (65%, 50%, and 42%) and two second-phase durations (equal to the first phase [balanced] and truncated at 3 ms [unbalanced]) were randomly tested. The source capacitance of the defibrillator was 120 μF for all waveforms. DFT with the IVC electrode was significantly lower than without the IVC electrode for all waveforms tested (527 ± 9.3 V [standard error], 14.5 J vs 591 ± 7.4 V, 18.5 J, P < 0.001). Neither waveform tilt nor second-phase duration significantly changed the DFT. In canines, a totally intravascular implantable defibrillator with electrodes in the RV apex, SVC, and IVC had a DFT similar to that of standard nonthoracotomy lead systems. No significant effect was noted with changes in tilt or with balanced or unbalanced waveforms.

Achieving low defibrillation thresholds at implant: pharmacological influences, RV coil polarity and position, SVC coil usage and positioning, pulse width settings, and the azygous vein

Approximately 30% of implantable cardioverter defibrillator (ICD) patients still die of sudden death. A major cause of these sudden deaths is the failure to defibrillate because of failure to achieve a low defibrillation threshold (DFT). Anti-arrhythmic drugs can have a profound positive or negative effect on the DFT. Unfortunately, present clinical practice continues to feature many procedures and tactics that have minimal to negative DFT benefit. In addition, many demonstrated helpful tactics are not understood or followed. This review covers the optimal RV (right ventricular) coil position and polarity, superior vena cava (SVC) coil positioning and usage, pulse width settings, and azygous vein coil implants. Specifically, the RV coil should be set to an anodal polarity and never 'reversed'. The optimal RV coil position appears to be along the mid-septum. The SVC coil should be kept out of the right atrium and placed in the innominate vein junction. The SVC coil should be always on for high impedance patients. For low impedance patients, the SVC coil should be set on or off depending on which setting gives the lowest DFT. Pulse widths should be set to correspond to optimally charging and discharging a cardiac membrane time constant of between 3.5 and 4.5 ms. For the highest DFT patients, a separate coil should be placed in the azygous vein and connected to the ICD 'SVC' port. Anachronistic approaches such as the use of polarity reversal, apical RV coil tip forcing, and subcutaneous arrays are also discussed.

Influence of pacing configurations, body mass index, and position of coronary sinus lead on frequency of phrenic nerve stimulation and pacing thresholds under cardiac resynchronization therapy

Phrenic nerve stimulation (PNS) can affect, and in some cases considerably limit, the long-term success of cardiac resynchronization therapy (CRT) therapy. To address this common problem, the manufacturers of CRT devices offer a range of configurations aimed at preventing high left ventricular pacing thresholds (LVPTs) and PNS. In 101 consecutive patients who had undergone implantation of a CRT system, we investigated prospectively the parameters LVPT and PNS threshold in relation to coronary sinus (CS) lead position, CS lead configuration, body position, and body mass index. With the configurations LV tip to right ventricular (RV) coil, LV tip to LV ring, and LV ring to RV coil, the LVPT and PNS threshold of patients with LV pacing were measured in the supine and left lateral body positions. The overall mean LVPT was lowest in LV tip to RV coil and highest in LV ring to RV coil configurations. The lowest PNS thresholds were measured in LV tip to RV coil and the highest in LV tip to ring configurations. The LVPT was not affected by body position and was stable in the standard supine and left lateral positions. Flexible LV pacing configurations are a useful feature of CRT systems for preventing PNS. The optimal LV pacing configuration should be determined on the basis of individual patient testing.

Activation Sequence Modification During Cardiac Resynchronization by Manipulation of Left Ventricular Epicardial Pacing Stimulus Strength

Success of cardiac resynchronization therapy (CRT) depends on altering electrical ventricular activation (VA) to achieve mechanical benefit. That increases in stimulus strength (SS) can affect VA has been demonstrated previously in cardiomyopathy patients undergoing ablation. To determine whether increasing SS can alter VA during CRT. In 71 patients with CRT devices, left ventricle (LV) pacing was performed at escalating SS. Timing from pacing stimulus to right ventricular (RV) electrogram, ECG morphology, and maximal QRS duration on 12 lead ECG were recorded. Baseline QRS duration 153 +/- 25 ms, ischemic cardiomyopathy 48%, ejection fraction 24%+/- 7%. With increased SS, conduction time from LV to right ventricle (RV) decreased from 125 +/- 56 ms to 111 +/- 59 ms (P = 0.006). QRS duration decreased from 212 +/- 46 ms to 194 +/- 42 ms (P = 0.0002). A marked change in QRS morphology occurred in 11/71 patients (15%). The RV ring was the anode in 6, while the RV coil was the anode in 5. Sites with change in QRS morphology showed decrease in conduction time from LV to RV from 110 +/- 60 ms to 64 +/- 68 ms (P = 0.04). Twelve patients (16%) had diaphragmatic stimulation with increased SS. Increasing LV SS reduces QRS duration and conduction time from LV to RV. Recognition of significant QRS morphology change is likely clinically important during LV threshold programming to avoid unintended VA change.

Present Understanding of Shock Polarity for Internal Defibrillation: The Obvious and Non‐Obvious Clinical Implications

Uncertainty about the best electrode configuration has combined with the programming flexibility in modern implantable cardioverter-defibrillators (ICDs) to result in routine polarity reversal during an implant to deal with a high defibrillation threshold (DFT). We feel that this practice is not always supported by the clinical data and the present scientific understanding of defibrillation. A meta-analysis of the clinical studies on ICD shock polarity was performed. Subgroup analyses were also performed to test the impact of high DFTs, various tilts, and the use of the hot can electrode. A review of the basic research surrounding the effects of polarity in defibrillation is also presented. A total of 224 patients were studied. The use of an anodal right ventricular (RV) coil lowers the mean DFT by 14.8% (P = 0.00001). It provides thresholds equal to or lower than cathodal defibrillation in 83% of patients. The fraction of patients with lower anodal DFTs was 94/224 versus 38/224 for cathodal polarity. This phenomenon may be explained by virtual electrode effects. In particular, anodal electrodes tend to produce collapsing wavefronts while cathodal electrodes tend to produce expanding proarrhythmic wavefronts. In an ICD implant, the RV coil should be the anode. Furthermore, DFT testing beginning with cathodal defibrillation is most likely unnecessary and needlessly extends the procedure's duration and increases the risks for the patient.

Improved lung edema monitoring with coronary vein pacing leads: a simulation study

This computer simulation study compared the ability of left ventricular coronary vein (LV) pacemaker leads against right ventricular (RV) and right atrial (RA) leads to monitor lung edema using electrical impedance measurements. MRI images were used to construct electrical models of the thorax. Four lead configurations were tested with increases of pulmonary edema, intravascular fluids and heart dilation. The impedance changes observed at end systole with severe lung edema were 8.5%, 11.2%, 12.3% and 26.8% for the RA, RV, RV coil and LV configurations, respectively. Sensitivities in ohms per litre of lung fluid were 19.15, 19.15, 25.07 and 52.11 for the same configurations. The impedance changes for intravascular fluid overload with constant lung status were 1%, 1.3%, 9.2% and 6.4% while the sensitivities were 2, 2, 17 and 11 ohms per litre of intravascular fluid, respectively. Regional analysis of the thoracic sources of impedance revealed a high sensitivity near pacing electrodes and generator, and a low sensitivity to the right lung and all pulmonary vessels. Simulations showed that LV leads have a threefold advantage in sensitivity when monitoring lung edema in comparison to conventional RV leads. To monitor vascular and lung fluids independently, combined impedance configurations may be used. Regional sensitivities must be taken into account for proper clinical interpretation of impedance changes.

767-3 Reverse Polarity Biphasic Defibrillation with Three Biphasic Waveforms Using a Unipolar Defibrillation System

In ten dogs we assessed the impact on defibrillation success of reverse polarity biphasic shocks, using the CPI, Medtronic and Ventritex biphasic waveforms delivered through a right ventricular (RV) coil/CAN system. In each animal the three biphasic waveforms were tested in random order. Similarly with each waveform the defibrillation threshold (DFT) achieved using the standard and reverse polarity were randomly determined. A 5 cm long coil with 426 mm2 surface area was advanced in the RV through the jugular vein and the 80 cm2 defibrillator can was placed in the subcutaneous tissue of the left superior chest wall. Shocks were delivered between the RV coil as cathode and the CAN as anode (standard polarity) and vice versa (reverse polarity). Triplicate defibrillation thresholds were obtained with each biphasic waveform. DFT values are shown below:Empty CellCPIMedtronicVentritexDFT Standard (J)70 ± 2.28.3 ± 3.593 ± 4.3DFT Reverse (J)4.6 ± 1.25.2 ± 2.56.7 ± 3.7CPI Standard vs Reverse p &lt; 0.01; Medtronic Standard vs Reverse p &lt; 0.01; Ventritex Standard vs Reverse p &lt; 001 CPI Standard vs Reverse p &lt; 0.01; Medtronic Standard vs Reverse p &lt; 0.01; Ventritex Standard vs Reverse p &lt; 001 When defibrillation shocks are delivered through a single right ventricular lead/defibrillator can system reverse polarity provides better defibrillation efficacy regardless of the biphasic waveform used.

10265-84 Impact of the Defibrillating Surface Area of an Additional Superior Vena Cava Electrode on the Unipolar Right Ventricular Coil/Defibrillator Can System

We assessed the hypothesis that the surface area of an additional superior vena cava (SVC) defibrillation electrode may impact on the defibrillation efficacy of a right ventricular (RV) coil/CAN system. In ten dogs we randomly compared the energy requirements for defibrillation (DFT) using the RV/CAN configuration and three triple lead systems employing an additional lead in the SVC with a defibrillating surface area of 90 mm 2 , 160 mm 2 and 617 mm 2 respectively. Biphasic shocks with 65% fixed tilt were used for defibrillation. Triplicate defibrillation thresholds were determined with each lead system. With every electrode system the RV coil was used as cathode. Energy (J), peak voltage (VI and impedance at defibrillation threshold are shown below: RV/CAN 90 mm 2 160 mm 2 617 mm 2 DFT(J) 8.6 ± 3.3 8.1 ± 2.6 8.2 ± 2.5 4.9 ± 1.9 * Voltage(V) 373 ± 73 365 ± 58 367 ± 65 284 ± 53 * Impedance 74 ± 24 53 ± 13 + 48 ± 11 + 52 ± 10 + * 617 mm 2 vs RV/CAN p &lt; 0.01 + 90 mm 2 160 mm 2 , 617 mm 2 vs RV/CAN p &lt; 0.01 These results indicate that the surface area of an additional SVC defibrillating electrode may be critical to improving the energy requirement for defibrillation achieved with a single lead right ventricular coil/defibrillator can system.

A Long Thin Electrode Is Equivalent to a Short Thick Electrode for Defibrillation in the Right Ventricle

We hypothesized that a long thin right ventricular (RV) electrode would have equivalent defibrillation threshold (DFT) performance to a short thick electrode with approximately the same surface area. This could lead to thinner transvenous lead systems, which would be easier to implant. A thin (5.1 French) lead was compared to a standard control (10.7 French). The thin lead had an 8-cm RV electrode length with a surface area of 4.26 cm2. The standard lead had a RV electrode length of 3.7 cm and a surface area of 4.12 cm2. A 140-mu French capacitor 65%/65% tilt biphasic defibrillation shock was delivered between the RV electrode and a 14-cm2 subcutaneous patch. DFTs were determined following 10 seconds of fibrillation in 11 dogs by a triple determination averaging technique. The thin lead had a lower resistance (77.1 +/- 27.4 omega vs 88.9 +/- 30.3 omega, P < 0.001) than did the thick lead. There was no significant difference in stored energy DFTs (9.9 +/- 2.5 vs 10.3 +/- 2.7, P = 0.098 2-sided, P = 0.049 1- sided). This was in spite of the fact that the long thin lead had a portion of its RV coil extending above the tricuspid valve and, thus, not contributing efficiently to the ventricular gradients in the small dog heart. We conclude that a long thin right ventricular electrode and a standard short thick electrode had equivalent defibrillation performance. This preliminary result should be confirmed in clinical studies as it could lead to significantly thinner transvenous lead systems.