Pacemaker in ICD Follow up
The number of implanted pacemakers and ICDs is ever increasing, in part due to the aging of the population and due to expanding device indications. While the follow-up of these devices requires regular device clinic visits, we would like to present basic concepts that you might find useful in the care of your patients with pacemakers or ICDs.
Early postoperative period (approximately weeks 1 – 8):
Here we worry primarily about pocket related complications such as hematoma and pocket infection and early lead dislodgement (< 2% incidence). A small pocket hematoma is fairly common (many patients are on aspirin or plavix, or require coumadin therapy). It most often does not require any specific therapy. A large and tense hematoma almost always requires pocket revision with evacuation of the hematoma. Early pocket infection, while uncommon, presents with progressive pocket pain, swelling and erythema. Almost always the entire hardware has to be removed. Lead dislodgment occurs in less than 2% of cases and may present with unusual pacing behavior and altered pacing and sensing parameters. A chest x-ray may show an unusual lead position that requires repositioning.
Late postoperative period: Here we primarily monitor proper device function, and need to optimize device parameter programming based on the patient’s cardiac/rhythm situation. Typically lead dislodgment and pocket hematoma are rare. Late pocket/device infections are still possible.
Routine device follow-up: Typically pacemaker patients are seen in the pacemaker clinic every 6 to 12 months, ICD patients are seen every 3 to 6 months. Additional visits are scheduled if clinically warranted.
Web-based device follow-up: Essentially all device manufacturers offer a web-based follow-up strategy. This was initially rolled out for biventricular devices and ICDs, and is now also available in newer pacemaker models. Basically, a data module is supplied to the patient, this module interrogates the patient’s device either automatically (via wireless technology) or through a wand (applied to the device by the patient). The data collected by the module, which is very similar to the data that would be obtained at a regular clinic visit, is then sent to a secure website, which is accessed by our pacemaker clinic staff. These data downloads can take the place of a routine clinic visit (thus avoiding patient travel, and easing device clinic workflow), and can be commanded to evaluate symptoms/troubleshoot device problems. Device programming is currently not possible with this technology. This technology has been helpful in dealing with recent device lead recall/alert actions – allowing close device/lead surveillance.
There have been efforts to include heart-failure-related information in these routine data downloads – such as weight, BP, CHF questionnaires, non-invasive assessment of pulmonary fluid status etc. The use of such data, in close collaboration with the treating cardiologist, has been shown to reduce heart failure admissions.
Interested physicians can get access to such websites to assist in their patient management.
Pacemaker/ICDs and magnets: Applying a doughnut-shaped magnet over the device generator affects device function in very specific ways:
(1) In pacemakers, application of a magnet closes a reed switch, resulting in asynchronous pacing (no sensing of intra-cardiac or extra-cardiac signals) at a pre-specified “magnet rate.” The “magnet rate” (which varies between vendors) changes at the end of battery life and is one measure to time generator change. Magnet application allows verification of proper atrial or ventricular capture, and is a method to avoid intra-operative pacemaker inhibition during electrocautery (although temporary device reprogramming to a non-sensing mode is the preferred option).
(2) In ICDs, magnet application does not affect Brady-pacing behavior, however inhibits sensing, and thus therapy, of ventricular tachycardia/ventricular fibrillation. Clinically this can be useful if the patient has atrial fibrillation with fast heart rates triggering VT therapy (shocks). Furthermore the magnet application prevents intra-operative sensing of electrocautery signals as VT/VF (although temporary device reprogramming to a non-sensing mode is the preferred option).
Pacemaker/ICD diagnostic tools: With the increase in computer power, in addition to relevant battery lead parameters, these devices keep track of a multitude of cardiac rhythm parameters; here are some examples:
(1) The device can display a heart-rate histogram; this can be useful if one wants to evaluate proper heart rate response in the ambulatory setting. For example, in evaluating for chronotropic incompetence (the majority of the heart rate is in the low-rate bin,) or concerns about atrial fibrillation with fast heart rates (a large proportion of the ventricular heart rate is in the high-rate bin,).
(2) Another useful parameter relates to episodes of atrial fibrillation, these are detected by the device as episodes with rapid atrial rates (typically > 185 bpm) and stored with regard to time of occurrence, duration, maximum and average ventricular rates during atrial fibrillation. Such data can be helpful to evaluate symptoms and guide medical management with regard to anti-arrhythmic drug therapy and anti-coagulation.
(3) ICDs (and pacemakers) keep track of episodes of ventricular tachycardia (a ventricular rate cut off is programmable). This may be useful in evaluating symptoms such as pre-syncope or syncope. Certain biventricular devices (cardiac resynchronization therapy) also allow a noninvasive evaluation of the pulmonary fluid content, a surrogate marker which has been shown to precede heart failure decompensation, and may allow therapeutic adjustments to prevent hospital admissions for heart failure.