Implantable Device Complications: Avoid Being Shocked

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QVlQMjgwMDA2MC1NUjIwMTEtMDQtMTIgMTg6NTE6MDM=.jpg - electrophysiology

While complication rates associated with implantable cardiac devices have decreased, they remain problematic for patients and cardiologists. Better patient selection, physician training and improved device software and/or programming can help improve implantation and reduce complications, including inappropriate shock therapy.

Is it all about the numbers?

Stanford University Medical Center researchers may have provided some insight surrounding the question of how to improve outcomes with implantable cardioverter-defibrillators (ICDs) when they  found that ICD patients treated at high-volume hospitals had fewer complications compared with low-volume hospitals (J Am Coll Cardiol 2010;56:1134-1139). There was a "roughly linear trend that said the more procedures you perform, the better the outcomes," says lead author James V. Freeman, MD, MPH, a clinical fellow in cardiovascular medicine at Stanford in Stanford, Calif. This volume-outcome association was consistent no matter the ICD subtype—single-chamber, dual-chamber or biventricular devices.

While more data are needed to understand what low-volume hospitals can do to improve their outcomes, Freeman advocated one option. If hospitals perform below a certain threshold, they should not get reimbursed for device implants. This could potentially help raise the bar on procedural complications and outcomes, he says.

But if a facility doesn't have the option to increase volume, can operator experience and training improve outcomes? A study by Curtis et al showed that complication rates associated with ICD implants were highest in patients whose ICDs were implanted by thoracic surgeons (5.8 percent), followed by non-EP cardiologists (4 percent) and then EPs (3.5 percent (JAMA 2009;301:1661-1670).

In addition, nearly one-third of the more than 111,000 patients in the study met criteria for cardiac resynchronization therapy with defibrillation (CRT-D). However, patients who had devices implanted by non-EPs were less likely to receive CRT-Ds.

While the Heart Rhythm Society (HRS) has published guidelines for minimum training for physicians, it is not mandated that only EPs implant these devices.

Inappropriate shocks

While increased operator training and volume certainly can help improve procedural outcomes, how can device-related complications improve?

Researchers from the Minneapolis Heart Institute (MHI) recently found that the recalled Sprint Fidelis ICD lead (Medtronic) failed more often in younger patients, women and patients who had a history of heart disease. The suggested benchmark for these failures is 0.6 percent per year. The MHI researchers found a 2.81 percent failure rate for the Fidelis and a 0.43 percent failure rate for Quattro leads (Medtronic).

While these lead fractures were not linked to injury or death, most of these patients experienced inappropriate shocks. "We need to test leads more vigorously before they are released onto the market," says Robert G. Hauser, MD, a cardiologist at MHI and lead author of the above study.

The first question to consider when an ICD delivers a shock is whether or not the shock was delivered in response to a real rhythm disturbance, says Charles D. Swerdlow, MD, a cardiac electrophysiologist at Cedars-Sinai Heart Institute in Los Angeles.

A recent trial led by Swerdlow found that downloadable software (Medtronic) can slash the risk of inappropriate shocks caused by lead fractures by almost 50 percent compared to conventional impedance monitoring (Circulation 2010;122:1449-55). Researchers found that the software can decipher when leads break and help to reduce unnecessary shocks caused by lead fractures. In fact, 72 percent of the 213 patients in the software arm did not receive an inappropriate shock, or had at least three days or more warning prior to shock, compared to 50 percent of the 213 patients without the software. St. Jude Medical and Boston Scientific have similar alert algorithms.

Devices also must be appropriately programmed and adjusted from the manufacturer's nominal settings to increase the duration required to detect an arrhythmia that would help avoid shock therapy for many arrhythmias that will stop on their own, Swerdlow says.

While these adjustments can improve patient safety, the most important aspect to reduce complications remains patient selection, he says.

Temporal Changes in Non-Evidence-Based Implantable Cardioverter-Defibrillators