Predicting Early Mortality After ICD Implantation
Predicting Early Mortality After ICD Implantation
Background: Patients with advanced heart disease are at risk from sudden death; however, benefit from implantable cardioverter defibrillators (ICDs) may be limited as a result of early mortality from other causes. The objective of this study was to develop a model to predict mortality within the first year after ICD implantation.
Methods and Results: A retrospective analysis was performed of 469 consecutive patients who underwent ICD implantation at a single tertiary-care center from 1999 to 2002. Vital status was determined from the Social Security Death Index. Patients were randomized into prediction and validation cohorts. A risk score was derived from the prediction cohort by multivariate logistic regression and applied to the validation cohort. One point was assigned for each variable in the risk score (age >80 years, history of atrial fibrillation, creatinine >1.8 mg/dL, New York Heart Association class III or IV). One-year mortality significantly increased with increasing risk score in both the prediction and validation cohorts. Validation cohort mortality was 3.4% for 0 points, 4.3% for 1 point, 17% for 2 points, and 33% for ≥3 points (P for trend <.0001). A risk score ≥2 predicted a 1-year mortality rate of 21%, whereas a risk score <2 predicted a mortality rate of 4% at 1 year (P < .0001).
Conclusion: A risk score using simple clinical criteria may identify patients at high risk of early mortality after ICD implantation. This may be helpful in consideration of ICD risk/benefit for individual patients. Further studies conducted in a prospective manner using these clinical criteria are warranted.
Indications for implantable cardioverter defibrillator (ICD) implantation have greatly expanded in the recent years. Secondary prevention of sudden cardiac death is a well-established indication for ICD implantation. Mortality benefit has now been proven for primary prevention of sudden cardiac death in selected patients with ischemic cardiomyopathy, and there is increasing evidence that patients with nonischemic cardiomyopathy may also benefit.
Expanding ICD use introduces new challenges. Unlike therapy with drugs that slow progression of heart failure and prolong survival, ICDs extend survival only for those patients who experience an arrhythmia that would have been fatal was it not terminated by the ICD. Thus, the majority of patients who receive the device do not benefit during short-term follow-up. Indeed, survival is essentially the same for ICD and non-ICD patients alike for the first 10 months of follow-up in the MADIT-II trial and for 18 months of follow-up in SCD-HeFT. Lack of early survival benefit could be caused by a relatively low early risk of sudden cardiac death in primary prevention populations or higher nonsudden cardiac death rate in the ICD group during the first year after implant. This hypothesis is supported by results of the DINAMIT study, examining benefit of prophylactic ICD implantation immediately after myocardial infarction. It showed no benefit with ICD over a follow-up of 30 months and a proportionally higher nonsudden death rate in the ICD group. As ICDs are offered to expanding patient populations outside clinical trials, pump failure and other comorbid conditions are common considerations that may limit ICD benefit.
Increasing use of implantable defibrillators for expanding indications has significant resource implications for the health care system. Identification of those patients at high risk of early mortality who may not derive benefit from ICD implantation is important for optimal patient selection of this therapy. The objective of this study is to develop and validate a risk score using baseline clinical characteristics to predict early mortality inpatients with an indication for ICD implantation.
Abstract and Introduction
Abstract
Background: Patients with advanced heart disease are at risk from sudden death; however, benefit from implantable cardioverter defibrillators (ICDs) may be limited as a result of early mortality from other causes. The objective of this study was to develop a model to predict mortality within the first year after ICD implantation.
Methods and Results: A retrospective analysis was performed of 469 consecutive patients who underwent ICD implantation at a single tertiary-care center from 1999 to 2002. Vital status was determined from the Social Security Death Index. Patients were randomized into prediction and validation cohorts. A risk score was derived from the prediction cohort by multivariate logistic regression and applied to the validation cohort. One point was assigned for each variable in the risk score (age >80 years, history of atrial fibrillation, creatinine >1.8 mg/dL, New York Heart Association class III or IV). One-year mortality significantly increased with increasing risk score in both the prediction and validation cohorts. Validation cohort mortality was 3.4% for 0 points, 4.3% for 1 point, 17% for 2 points, and 33% for ≥3 points (P for trend <.0001). A risk score ≥2 predicted a 1-year mortality rate of 21%, whereas a risk score <2 predicted a mortality rate of 4% at 1 year (P < .0001).
Conclusion: A risk score using simple clinical criteria may identify patients at high risk of early mortality after ICD implantation. This may be helpful in consideration of ICD risk/benefit for individual patients. Further studies conducted in a prospective manner using these clinical criteria are warranted.
Introduction
Indications for implantable cardioverter defibrillator (ICD) implantation have greatly expanded in the recent years. Secondary prevention of sudden cardiac death is a well-established indication for ICD implantation. Mortality benefit has now been proven for primary prevention of sudden cardiac death in selected patients with ischemic cardiomyopathy, and there is increasing evidence that patients with nonischemic cardiomyopathy may also benefit.
Expanding ICD use introduces new challenges. Unlike therapy with drugs that slow progression of heart failure and prolong survival, ICDs extend survival only for those patients who experience an arrhythmia that would have been fatal was it not terminated by the ICD. Thus, the majority of patients who receive the device do not benefit during short-term follow-up. Indeed, survival is essentially the same for ICD and non-ICD patients alike for the first 10 months of follow-up in the MADIT-II trial and for 18 months of follow-up in SCD-HeFT. Lack of early survival benefit could be caused by a relatively low early risk of sudden cardiac death in primary prevention populations or higher nonsudden cardiac death rate in the ICD group during the first year after implant. This hypothesis is supported by results of the DINAMIT study, examining benefit of prophylactic ICD implantation immediately after myocardial infarction. It showed no benefit with ICD over a follow-up of 30 months and a proportionally higher nonsudden death rate in the ICD group. As ICDs are offered to expanding patient populations outside clinical trials, pump failure and other comorbid conditions are common considerations that may limit ICD benefit.
Increasing use of implantable defibrillators for expanding indications has significant resource implications for the health care system. Identification of those patients at high risk of early mortality who may not derive benefit from ICD implantation is important for optimal patient selection of this therapy. The objective of this study is to develop and validate a risk score using baseline clinical characteristics to predict early mortality inpatients with an indication for ICD implantation.
