Pacing systems pacemaker dependency

After venous access, some consideration should be given to the sequence of lead placement. Some operators prefer to place the RV electrode first for emergency RV pacing, should heart block ensue because the heart failure patients commonly have a left bundle branch block and any trauma to the conduction system or right bundle may result in complete heart block. Other operators choose to place the coronary sinus lead first and, if necessary, depend on heart rate support via a temporary transvenous pacemaker placed via the femoral vein. The issue of failure speaks for placing the coronary sinus lead first. Should the procedure fail with unsuccessful left-sided left ventricular lead placement and the patient has already received right-sided electrodes, a pacing system may be left without an indication unless a future second attempt is considered. As more and more systems are placed for a primary prevention indication like MADIT II, this has become less problematic (153). 

Pacing system inhibition from interference is more important in the pacemaker-dependent patient. If inhibition is observed in a pacemaker-dependent patient, electrocautery application should be limited to 1-2 s with a rest period of approximately 10 s. This will allow the pacemaker to function properly for a greater portion of the time. In some cases back-up temporary transvenous or transcutaneous pacing will be required, or the pacemaker can be programmed to the asynchronous mode of function. 

An integral part of many pacing system follow-up programs is transtelephonic monitoring (TTM) (72-74). This can be initiated by the physician and support staff out of an individual office or provided by a commercial service based on a specific prescription by the physician. Reports of each periodic evaluation are sent to the patient s physician. TTM provides a cost-effective means for frequent monitoring as the implanted device is getting older and there is concern about approaching RRT. It also provides a link between the patient and the physician for those patients who hve alone, who are very anxious, or pacemaker dependent. 

As an aide to the evaluation so that nothing is overlooked, we have developed a worksheet that is then used to generate the final summary note. This is shown in Fig. 19.24. The front side of the sheet has clinical data based on history and the examination while the reverse side has the detailed measurements from the pacing system including capture and sensing thresholds. As noted at the bottom (Fig. 19.24), special information that may impact the follow-up schedule such as unstable threshold, pacemaker dependency, on advisory, and for devices that have been implanted for many years, a indication of their age can be identified. 

There are various types of PPM that pace different chambers of the heart. The choice of pacemaker system used depends very much on the patient s condition and the underlying rhythm of the patient. Most systems are inserted in theatre or a cardiac catheterization lab using fluoroscopic imaging to position the leads, which are inserted through a vein (i.e. the cephalic or Subclavian vein). There are several different modes a pacemaker can be set to. To distinguish between these different settings pacemakers are given a code to define their type and function. Table 8.1 summarises these pacemaker codes. 

Some authors recommend contralateral reimplantation as early as 36 h after extraction in patients with local symptoms only of device-related infection [10]. In some instances, it is considered safe to perform a contralateral same-day reimplantation [11]. The reasons for a same-day reimplantation are usually pacemaker (PM) dependency or hemodynamic need for CRT in case of biventricular pacing. In fact, the risk of subsequent CIED infections and venous thrombosis increases while maintaining a transvenous temporary device, and for this reason, it cannot be used indefinitely [12]. Same-day reimplantation is considered safe if the patient is clinically proven not to have active systemic bacteremia or infection by blood culture at the time of extraction and there is a lack of transesophageal echocardiographic evidence for endocarditis and the presence of a normal white blood cell count. 

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