Adverse Events With Transvenous Implantable Cardioverter-Defibrillators
ABSTRACT & COMMENTARY
Synopsis: Adverse events are not uncommon in the first year after ICD implantation.
Source: Rosenqvist M, et al. The European 7219 Jewel ICD Investigators. Circulation 1998;98:663-670.
This study reports the systematically collected data on adverse events from 778 patients who received a new transvenous implantable cardioverter defibrillator (ICD), the Medtronic Jewel Model 7219, during clinical trials prior to its full release. Data were collected as part of a prospective clinical evaluation protocol. Events were reviewed and classified by a panel of investigators. Patient follow-up was performed according to a standard protocol.
Among the 778 patients entered into the trial, 259 suffered one or more adverse events. During an average duration of follow-up of four months, 20 of 778 (2.6%) patients died. Six patients died in the immediate post-implant period and were considered to be procedure- related. Causes of death in these six patients included three patients with sepsis, two with severe postoperative hemodynamic compromise, and one with peripheral thromboembolism. Nonfatal adverse events were documented in 161 patients. The most common adverse events related to the surgical procedure were pneumothorax or hemothorax (0.9%), right ventricular perforation or tamponade (0.6%), wound or pocket problems (3.5%), and lead or ICD dislodgement or migration (3.0%). Late adverse events associated with the ICD system included increased defibrillation requirements or failure to terminate clincal arrhythmias (3.2%), inaccurate identification of ventricular tachycardia or ventricular fibrillation (16.4%), sensing problems (1.2%), and pacing threshold elevations (1.8%). Inappropriate shocks were often delivered due to inappropriate identification of a ventricular rhythm with the therapy zone due to atrial arrhythmias or oversensing.
The most common non-device-related adverse events were either worsened congestive heart failure or increased frequency of ventricular tachycardia to the point that it became incessant.
Rosenqvist and associates conclude that adverse events are not uncommon in the first year after ICD implantation. Although the ICD appears to have a beneficial effect on total mortality, many of the complications classified as device-related might occur in any patient receiving an ICD. These data will affect the risk-benefit ratio as ICD therapy is advocated for populations at lower risk for sudden death.
COMMENT BY JOHN P. DiMARCO, MD, PhD
This excellent study presents data from a large prospective study of ICD therapy using a single system limitation of the authors' data on ICD therapy as the time period of the study (1993-1994). The most important ICD problems were with the surgical procedure, ICD generator failures or lead dislodgements, and problems related to inappropriate delivery of therapy. However, ICD technology is rapidly advancing, and steps have already been taken to address most of the problems reported here.
The device used in this study, the Medtronic Jewel Model 7219, was one of the first transvenous systems that was inserted using a pectoral site for the pocket in almost all patients. The device was still bulky compared to current generation pacemakers. Since this model was introduced, available single chamber ICD models have undergone a 40% reduction in volume, and implants are now technically much easier. ICD leads have also evolved, and, with the availability of active fixation devices and other improvements in lead design, the 10% lead dislodgement rate seen here has now significantly been reduced. Over-detection of atrial arrhythmias has remained a problem. Current devices now have sophisticated detection algorithms and dual chamber devices can often effectively differentiate between supraventricular arrhythmias with rapid rates and ventricular arrhythmias in the same heart rate range. This paper is useful, however, in that it documents that transvenous ICD systems can produce excellent one-year survival rates-97% in this series. Newer models should maintain this favorable effect on mortality yet be associated with a significant reduction in the frequency of adverse events.
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