Dual-chamber pulse generator

Fig. 1 A dual-chamber pulse generator and two leads. The pulse generator is a hermetically sealed titanium can containing an Lil power source, circuitry (including microprocessor), niobium or tantalum/sapphire feed throughs, and a connector to receive two leads. The lead with the straight distal tip is inserted in the right ventricle while that with the J shape is placed in the right atrial appendage. Both leads are bipolar (two electrodes within the heart). The tiny projections (tines) at the tip help provide fixation for the distal stimulating electrode...

Figure 18.5 shows pulse generators with three different polarities. In A, a single connector pin identifies the device as unipolar. In B, the two connector pins indicate either a unipolar dual-chamber pacemaker or an older singlechamber pacemaker that accepts a bifurcated bipolar lead. (Although these leads are no longer implanted, some are still in service.) In C, two leads with two pins each represent a bipolar in-Une lead and therefore a dual-chamber bipolar generator. 

One should always consult the physicians manual to determine the specific behavior that indicates the need for elective replacement. A mode conversion from dual-chamber to single-chamber (e.g., DDD to VVI), rate response to nonrate response or a change in magnet rate behavior may be observed when the ERI is triggered. Some pulse generators also provide an additional pre-ERI alert known as an intensified foUow-up indicator (IFI), a safety feature that... 

Implantation of transvenous ICD systems employs techniques similar to those used for permanent pacemaker implantations, and is discussed in detail in a separate chapter in this book. Connecting ICD leads to the device is slightly different than connecting pacemaker leads to pacemaker generators. All ICD pulse generators have at least three ports for single chamber devices (four ports for dual chamber devices, and five ports for CRT-D). One LV port is for the pace/sense IS-1 terminal pin, and two are for the defibrillation coil (usually DF+ and DF-). The second DF port may be capped if a single coil... 

Fig. 18.1 Posteroanterior (A) and lateral (B) chest radiographs of a dual-chamber pacing system. The pulse generator is located in a left prepectoral position. The position of both atrial and ventricular leads is acceptable. The J on the atrial lead is adeqnate. The ventricnlar lead is not positioned in a true apical position but is well seated with adequate slack.

The approved Medicare follow-up schedule is detailed in Table 19.4. It is slightly different for dual-chamber and single-chamber devices and whether the pulse generator has a known track record or not. Most of the devices which are being implanted today are relatively new model series and do not have a track record. By the time they do, it is likely that they would have been supplanted by the next generation of device. As such, it is probably reasonable to conclude that while individual manufacturers may have a track record for the overall performance of their systans, their currently released models will not yet have withstood the proverbial test of time. 

---