Ventricular defibrillator leads

The ICD generator communicates with the heart through a ventricular defibrillator + atrial and LV electrode or "lead." The leads are connected to the ICD via a "header." The header provides holes for insertion of all aspects of the ventricular defibrillator lead and, if also needed, an atrial and LV lead in specific ICD models. As in the pacemaker, set screws in the header may be tightened to fix the leads in place or loosened to allow their removal. 

A contemporary ventricular defibrillator lead consists of multiple internally separated metal wires that are externally encased in silicone rubber or polyurethane insulation. This allows the lead to function similarly to a standard pacemaker lead, i.e. transmission of electrical pacing/sensing signals between the heart and generator, but also structurally provides a separate pathway that participates in the delivery of shocks. This pathway includes what are commonly referred to as the lead "coil(s)." Shocks are delivered across the heart between the coil(s) and potentially the ICD can. Each element of the lead has its own pin that may connect to the ICD header. 

A pacing impedance level of about ventricular defibrillator lead. 

As an SVT causes signal input below the atrio-ventricular (AV) node at progressively more rapid rates one of the bundle branches may cease conducting temporarily due to its refractory period being reached. What can happen then is the R wave morphology recorded by the ventricular defibrillator lead may change due to the alteration in ventricular activation. 

Management Solution Decrease ventricular sensitivity without compromising VF detection. Rarely the ventricular defibrillator lead might even be repositioned to minimize the T wave amplitude on the VEGM. 

H 1. 5-French atrial pacemaker lead I 2. 7-French atrial pacemaker lead B 3. Coronary sinus left ventricular lead F 4. Endocardial rate/sensing lead G 5. Epicardial defibrillator patch D 6. Right ventricular defibrillator lead C 7. Screw-in right ventricular pacemaker lead A 8. Surface ECG lead... 

A ventricular defibrillator lead tip placed at a distance away from the RV apex can result in an elevated. ... 

Fig 1 41 Section of interventricular septum from a patient who underwent cardiac transplantation 676 days after implantable cardioverter-defibrillator lead implantation and 7 days after last defibrillator shock (a). Right ventricular surface of interventricular septum (R) is at the top and left ventricular surface (L) at bottom. Characteristic fibroelastic tissue encircles the lead curved arrow). Trichrome-stained section of tissue (b) band of fibroelastic tissue curved arrow) encircles lead (L), and beneath, in myocardium, lies fibrous connective tissue F). Area of confluent fibrous connective tissue immediately adjacent to lead also extends into surrounding myocardium, forming radial pattern of interstitial fibrosis arrows), suggesting that shocks have caused lines of electrical injury (courtesy [51])... 

Fig. 7.2 Serial anteroposterior fluoroscopic images taken during transvenous removal of a left-sided dual-chamber implantable cardioverter-defibrillator (ICD) system. After placement of a temporary right-ventricular (RV) pacing system

Goldberger JJ, Horvath G, Donovan D, Johnson D, ChallapaUi R, and Kadish AH. Detection of ventricular fibrillation by transvenous defibrillating leads integrated versus dedicated bipolar sensing. J Cardiovasc Electrophysiol 1998 9 677-688. 

Physical contact of a ventricular pacemaker and defibrillator lead can cause. ... 

Ensuring that ventricular pacemaker and defibrillator leads are. space decrease the likelihood of lead chatter. 

Contact of a ventricular defibrillator and pacemaker lead near/close to their tips can produce that may be sensed as events. 

On the other hand, the medical condition where the heart beats too fast is known as tachycardia. If untreated, tliis condition may lead to ventricular fibrillation, that is, a condition in which the heart stops beating and shakes uncontrollably and is usually fatal. In 1980, a special device was developed and implanted in patients. It could sense the condition and provide a shock that would stop the fibrillation and restore the normal sinus rhythm via an electrode sutured onto the heart. The device was first powered by a lithium/vanadium pentoxide system later it was replaced by a system using a cathode material of silver vanadium oxide (SVO or Ag2V40ii). This is the actual system used in modem ICDs (implantable cardioverter/defibrillator). Another material used is the lithium/manganese dioxide system. Also, a new system using a sandwich cathode design with an inner cathode material of carbon monofluoride and an external cathode layer of silver vanadium oxide is in wide use. 

CRT reduces symptoms of CHF and improves cardiac performance in patients with moderate-to-severely symptomatic heart failure, severe left ventricular systolic dysfunction, normal sinus rhythm and a wide QRS complex. Resynchronization therapy significantly reduces hospitalizations in these patients and is highly cost-effective. Perhaps most important, resynchronization therapy for heart failure improves survival for these patients, particularly when employed in conjunction with an implantable defibrillator. However, randomized clinical trials show that a substantial minority of patients are clinical nonresponders. Therefore, critical questions remain with respect to identifying appropriate candidates for CRT, optimal device programming, and left ventricular lead placement. 

Fig 5 14 (a-d) Temporal-sequence fluoroscopic images (same patient as in Figure 5.8) after exposure of the atrial lead from the internal jugular vein showing introduction and sheath advancement over the lead, overcoming binding sites to the tip. (e-h) The same maneuver on an implantable cardioverter-defibrillator (ICD) ventricular lead... 

TLR, transvenous lead removal A, atrial RV, right ventricular LV, left ventricular PL, pacing leads ICD, implantable cardioverter defibrillator L, leads... 

From January 1994 through April 1996, extraction of 3,540 leads from 2,338 patients (mean age 64 years, range 5-96) was attempted at 226 centers. Indications for removal were infection (27%), nonfunctional or incompatible leads (25%), Accufix or Encore leads (46%), or other causes (2%). The leads were implanted for a mean of 47 41 months (maximum 26 years) 53% were atrial leads, 46% ventricular leads, and 1% superior vena cava (SVC) defibrillating coils. The conventional technique for mechanical dilatation with Cook extraction-kit tools (Cook Vascular Inc., Leechburg, PA, USA) was used. Extraction was attempted via the implant vein using locking stylets and dilator sheaths and/or transfemorally... 

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