BOSTON — Patients who received implanted cardiac devices in routine practice during recent years had much better survival rates than did patients who received the same devices in the pivotal trials of the early 2000s, based on data from nearly 86,000 patients.
This first analysis of a huge amount of data from patients with implantable cardioverter defibrillators (ICDs) or cardiac resynchronization therapy-defibrillators (CRT-Ds) collected in a device-monitoring network also showed that a substantial number of “inappropriate” shocks that patients received might actually be clinically appropriate, Dr. Leslie A. Saxon said at the Heart Rhythm Society's annual meeting.
“We traditionally program [these devices] to just shock patients for malignant ventricular arrhythmias. But about 20% of the inappropriate shocks were for atrial fibrillation with more than 200 beats per minute. The clinical appropriateness of shocks for heart rates of more than 200 bpm is an interesting question, and intriguing data. We're suddenly looking at data from [many] shocks; it will help us understand this field a lot better,” said Dr. Saxon, chief of cardiovascular medicine at the University of Southern California, Los Angeles. “We will redefine what is an appropriate shock.”
The improved survival rate seen in the new series compared with earlier results in randomized, controlled trials might reflect differences in patient selection, improved contemporary patient management, more frequent patient monitoring, or other factors, Dr. Saxon added.
The ALTITUDE clinical science program sponsored by Boston Scientific collected data through the company's LATITUDE patient management system on 47,032 patients who received an ICD and 38,967 who received a CRT-D during 2006-2009. Dr. Saxon, chair of the ALTITUDE physician panel, said she has financial ties with Boston Scientific and other companies that market cardiac devices.
As of February 2009, the average age of patients with ICDs in the database was 64 years, with an average implant duration of 40 months. The average age of the CRT-D patients was 69 years, with implants in place for an average of 32 months. Three-quarters of patients in both subgroups were men.
During the first year of follow-up, the survival rate was 99% in the ICD patients and 96% among those with a CRT-D. These rates compare favorably with the 91%-94% survival rates with ICDs from the two major randomized, clinical trials, the Multicenter Automatic Defibrillator Implantation Trial II (MADIT-II) (N. Engl. J. Med. 2002;346:877-83) and the Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT) (N. Engl. J. Med. 2005;352:225-37), and with the 89% survival rate with CRT-D in the major randomized trial for that device, Comparison of Medical Therapy, Pacing, and Defibrillation in Heart Failure (COMPANION) (N. Engl. J. Med. 2004;350:2140-50).
The results also confirmed that patients who receive shocks have worse survival than do patients who remain shock free. (See box.) During follow-up, 19,522 patients received an ICD or CRT-D shock. An adjudication committee reviewed a representative sample of 1,272 shocks. Shocks for an “appropriate” reason—a ventricular arrhythmia—occurred 57% of the time; “inappropriate” shocks made up the remaining 43%. Within the inappropriate group, 83% were for atrial fibrillation or flutter, 12% were for “noise,” and 5% occurred after an appropriate arrhythmia had stopped.
A final analysis presented by Dr. Saxon focused on patients who received a device during 2007-2009. Before 2007, some patients received their devices but did not enter monitoring until several months later, possibly skewing the survival findings. By 2007, the delay between device implantation and the start of monitoring was always less than 3 months. Within the most contemporary subgroup, the 1-year survival rate was still higher than in the earlier trials, with a 97% rate for ICD patients and a 94% rate for CRT-D patients, Dr. Saxon said.
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