Single-chamber pacing systems

In many ICD systems, pacing and sensing are hmited to the right ventricle (single-chamber ICDs), and usually, only a single lead is required. More often, a pace-sense lead is also inserted via the same transvenous route and is fixed in the right atrium (dual-chamber ICD). The right atrial lead provides... 

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. 18.28 Posteroanterior chest radiograph (A) and close-up view (B) from a patient with congenital heart disease and an abandoned dual-chamber endocardial pacing system. Two ventricular epicardial leads are connected with a Y connector to a single chamber ventricular pacemaker. On the close-up view (B) the arrow notes a defect in the lead adaptor just as it exits the connector block.

While this testing need not be done on a routine basis with standard dualchamber pacing systems, its utility increases in cardiac resynchronization systems. With respect to single-and dnal-chamber pacing systems, it can be used to optimize the programmed parameters of the pacemaker with respect... 

Levine PA, Electrocardiography of bipolar single and dual-chamber pacing systems, Herzschrittmacher 1988 8 86-90. 

The location of the spikes helps to identify the type of pacemaker system in situ. A spike before a P wave denotes atrial pacing, whereas one before the QRS complex identifies ventricular pacing. Spikes before both P waves and QRS complexes can be either dual chamber (atria and ventricle) or Bi-v pacing. As both chambers are synchronized in the Bi-v system only one spike is usually visible. Figures 8.4 and 8.5 show single and dual chamber pacemaker systems. 

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