Response to Letter Regarding Article, “Death Without Prior Appropriate Implantable Cardioverter-Defibrillator Therapy: A Competing Risk Study”
We appreciate and welcome the remarks of Boriani and colleagues on our competing risk study published in Circulation.1 Boriani et al point to heart transplantation as an outcome that occurs in competition to appropriate implantable cardioverter-defibrillator (ICD) therapy or death before appropriate ICD therapy. We agree on this point and report that 7 patients underwent heart transplantation (5 with dilated cardiomyopathy and 2 with coronary artery disease). Two of these patients died in the postoperative period and before ever using the ICD device. Both were thus classified as cardiac death (Table 2). Of the 5 transplantation survivors, 2 never used their device before undergoing transplantation and both observations were censored at the time of transplantation. The other 3 transplantation survivors all had either ventricular tachycardia or fast ventricular tachycardia episodes before undergoing transplantation and thus experienced the event of interest. As a result, only 2 subjects had contributed to the competing risk event “heart transplantation.” However, in countries with larger organ availability, heart transplantation might contribute in a more relevant manner.
Patients with an ICD implanted for secondary prevention experienced appropriate ICD therapies more frequently than patients with an ICD implanted for primary prevention. Boriani et al argue that this larger “benefit” might be an artifact due to the potentially lower cutoff rates for ventricular tachycardia detection in secondary prevention patients. Although this might be a potential explanation for the association of secondary prevention with ventricular tachycardia occurrence, it is of interest to report that this association was also found for ventricular fibrillation occurrence, even though the association was less strong. The rate for the detection of primary ventricular fibrillation was standardized to at least 200 bpm and was less subject to individual programming. A similar trend with larger benefits in the secondary prevention setting was found in the more recent Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT)2 and the Second Multicenter Automated Defibrillator Implantation Trial (MADIT II).3
Lastly, we think that risk stratification and consideration of ICD replacement will be crucial in the future. Although only half of our population had >3.6 years of follow-up, none of the patients free of appropriate ICD therapy up to 6 years used the device to terminate ventricular fibrillation thereafter. Rethinking of device replacement is needed in patients who have never used their device and who have undergone ICD implantation for primary prevention of sudden cardiac death. Major research efforts are needed to develop rational replacement strategies in the growing number of older patients with changing risk profiles for appropriate ICD therapy and for prior death.
Sources of Funding
Drs Koller, Wolbers, and Bucher are supported by Santésuisse and by the Gottfried and Julia Bangerter-Rhyner-Foundation. Dr Osswald has received research grants from the Swiss National Science Foundation, Medtronic, Boston Scientific, Biotronik, and St Jude Medical.
Dr Osswald has served as a consultant and on the speakers’ bureau for and has received honoraria from Medtronic, Boston Scientific, and Biotronik. Dr Schaer has received honoraria from Boston Scientific and St. Jude Medical. Dr Sticherling has served as a consultant to Medtronic and has served on the speakers’ bureau for and received honoraria from Medtronic and Boston Scientific. The other authors report no conflicts.
Koller MT, Schaer B, Wolbers M, Sticherling C, Bucher HC, Osswald S. Death without prior appropriate implantable cardioverter-defibrillator therapy: a competing risk study. Circulation. 2008; 117: 1918–1926.
Bardy GH, Lee KL, Mark DB, Poole JE, Packer DL, Boineau R, Domanski M, Troutman C, Anderson J, Johnson G, McNulty SE, Clapp-Channing N, Vidson-Ray LD, Fraulo ES, Fishbein DP, Luceri RM, Ip JH. Amiodarone or an implantable cardioverter-defibrillator for congestive heart failure. N Engl J Med. 2005; 352: 225–237.