Problem-Solving in Lead Extractions

the operator must define a strategy for the procedure, including all possible alternative 

2nd Cardiovascular Department AOUP, Santa Chiara University Hospital, Pisa, Italy 

All the following critical points during pacing and implantable cardioverter-defibrillator (ICD) transvenous lead removal and their solutions are summarized in Table 10.1. 

The intravascular position of the leads or lead fragments is relatively common in patients undergoing transvenous lead extraction. Lead to remove can be free floating either as (1) the result of lead fracture in its intravascular course or (2) the result of an intervention. 

Spontaneous fracture of a lead is not common, and the most frequent cause is subclavian crush (Fig. 10.1). 

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The evolution of the management of transvenous leads has been born out of the furnace of clinical care and the pathophysiology of lead dysfunction. Transvenous lead extraction is only one tool in the management tool chest. At first it wasn t much of a tool, just a rag tag group of ideas used by a few people trying to solve problems for patients without a solution. However, over the last 25 years and particularly with the visionary efforts of Dr. Charles Byrd and his creative collaboration with Cook Pacemaker Inc. (now Cook Vascular Inc.), transvenous lead extraction is not only a tool but an armory of techniques. 

At least three approaches have been proposed to solve for the mean pressure field that avoid the noise problem. The first approach is to extract the mean pressure field from a simultaneous consistent39 Reynolds-stress model solved using a standard CFD solver.40 While this approach does alleviate the noise problem, it is intellectually unsatisfying since it leads to a redundancy in the velocity model.41 The second approach seeks to overcome the noise problem by computing the so-called particle-pressure field in an equivalent, but superior, manner (Delarue and Pope 1997). Moreover, this approach leads to a truly... 

The traditional approach for structure solution follows a close analogy to the analysis of single-crystal XRD data, in that the intensities 1(H) of individual reflections are extracted directly from the powder XRD pattern and are then used in the types of structure solution calculation (e.g. direct methods, Patterson methods or the recently developed charge-flipping methodology [32-34]) that are used for single-crystal XRD data. As discussed above, however, peak overlap in the powder XRD pattern can limit the reliability of the extracted intensities, and uncertainties in the intensities can lead to difficulties in subsequent attempts to solve the structure. As noted above, such problems may be particularly severe in cases of large unit cells and low symmetry, as encountered for most molecular solids. In spite of these intrinsic difficulties, however, there have been several reported successes in the application of traditional techniques for structure solution of molecular solids from powder XRD data. 

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