Dual coil

Dual Coil Actuator. 1 Alternating. 2 Standby Open. 3 Standby Closed ... 

Some MAS probes are single-coil, allowing proton-only acquisition, and some are dual-coil, allowing the acquisition of 2-D proton-carbon data. Note that MAS probes can be used for ordinary solution work and though very labour-intensive to use, can give excellent sensitivity where the available compound is limited and signal to noise is at a premium. 

Figure 11 Description of dual microcoil probe. (A) Two coils wrapped around a polyimide sleeve (B) Dual-coil probe mounted on top of the probe head. (C) Schematic of balanced tank circuit used for each microcoil. Coil (L), series capacitors (Cs) 3.3 pF, tuning capacitors (CT) 0.6-4.5 pF, matching capacitor (CM) 0.6-4.5 pF, bridge capacitors (CB) 24 pF. (Reproduced with permission from Ref. 41. Copyright 2002 American Chemical Society.)...

FIGURE 15.3 (a) A dual-coil, true bipolar ICD lead system, (b) Tips of two leads one active fixation (helix at tip) and one passive fixation (tines at tip). (Reproduced with permission of Medtronic, Inc.)... 

Transvenous ICD leads are anchored in the right ventricle by small flexible tines at the lead tip that intertwine in small structures in the chamber ( passive fixation ) or by a helix at the lead tip that can be screwed into the myocardial tissue ( active fixation ). The distal defibrillation coil rests within the right ventricle. Dual coil leads are designed such that the proximal coil is positioned in the superior vena cava. 

Although no clear risk factors have been identified, several predictors of venous occlusion in PM/ICD carriers have been reported [55, 56, 59, 61]. These include a history of device upgrades, the presence of temporary endocardial PM wires before implantation of a permanent device, the presence of multiple endocardial leads, retention of severed leads, lead infection, use of dual-coil leads, female hormone therapy, history of venous thrombosis, and gene-based predisposing factors for thrombophilia. In contrast, long-term anticoagulation therapy seems to offer a protective effect. 

Polarity and coil unipolar vs multipolar, single coil vs dual coil... 

Rinaldi CA, Simon RD, Geelen P et al (2003) A randomized prospective study of single coil versus dual coil defibrillation in patients with ventricular arrhythmias undergoing implantable cardioverter defibrillator therapy. Pacing Clin Electrophysiol 26 1684-1690... 

As reviewed in the section on endocardial lead extraction, the irregularity of a shocking coil may promote tissue ingrowth and will iuCTease risk of adhesion (53). In dual coil systems, the proximal coil has the potential to be placed with tissue tension along the SVC, a risk factor for adhesion. For this reason, the... 

When an ICD system is inspected radiographically, it is possible to determine whether the ICD lead has a single coil (Fig. 18.9) or a dual coil (Fig. 18.22) and whether any additional leads are associated with the ICD. Although additional leads are not commonly used, they may include a superior vena cava lead, subcutaneous array (Fig. 18.23), or subcutaneous patch. 

The purpose is simple — to increase the contact time of vapor with cooling coils. This is not the normal purpose of a set of cooling coils installed at the top of the freeboard section. The dual coil apparatus is shown in Figure 1.65. 

As suggested earlier the proximal coil in a dual coil lead is optimally positioned in the SVC. Some patients hearts may be so large that the proximal coil would not wind up there. One way to manage this situation, when a dual coil system is initially desired, is to rather utilize a single coil lead, but adding a lead called an "SVC coil" to the system. This is a separate lead that is connected to the proximal shocking coil port of the ICD and is independently positioned to float in the SVC. In other patients who develop an elevated defibrillation threshold (DFT) after initial implant of only a single coil lead, the SVC coil may also be subsequently added. 

Should a single coil lead configuration not yield an adequate DFT even after polarity reversal, or it is felt by the physician that the proximal coil of a dual coil lead would not be optimally placed in the SVC, a separate SVC coil can be added to the system. Here both coils and the ICD can may participate in the shock pathway and lower the DFT. 

With a dual coil lead similar deflbrillation shock pathways can be duplicated as with a single coil lead plus SVC coil. This assumes, as mentioned before, that the proximal coil is in the SVC. 

Even with an appropriately positioned dual coil system and attempts using both shock polarities the DPT may rarely remain unacceptably high. In this instance the implanting physician has the option of taking the proximal coil out of the defibrillation circuit and adding a subcutaneous array or patch as a means of improving the DPT. 

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