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Longitudinal Studies of Implantable Cardioverter Defibrillators for Primary Prevention in Community Practice: Clinical Characteristics, Shocks, Outcomes, and Cost 
(CVRN ICD) Study
Atria Project


Alan S. Go, MD, Co-Principal Investigator 
Kaiser Permanente Northern California
David Magid, MD, Co-Investigator Kaiser Permanente Colorado
David Smith, RPh, PhD, Investigator
Kaiser Permanente Northwest
Frederick Masoudi, MD, MDPH, Co-Principal Investigator
Kaiser Permanente Colorado
Robert Greenlee, PhD, Co-Investigator
Marshfield Clinic Research Foundation

Study Summary 

The CVRN ICD dataset is comprised of patients with left ventricular systolic dysfunction (LVSD) (ejection fraction <50%) who received an Implantable Cardioverter Defibrillator (ICD) for primary or secondary prevention of sudden cardiac death (SCD) between January 1, 2006 and December 31, 2009. Dataset members were followed for a minimum of four months and monitored for the occurrence of device shocks in response to arrhythmic events through December 31, 2011. The CVRN ICD dataset provides a contemporary real-world assessment of the patients who meet guidelines for ICD placement, practice patterns, and outcomes associated with implantation. The CVRN ICD study utilizes patient data from seven participating sites across the US. The dataset was compiled using standardized programs that convert local source data extract into a common dataset structure with the same mapped variables and corresponding definitions. 


The CVRN ICD consists of adults aged 18 years or older at the time of ICD implantation between January 1, 2006 through December 31, 2009. The mean age of ICD placement was 66.6 years. 70.3% were male an 33.0% were nonwhite.

Table 1. CVRN ICD Dataset Member Counts by Site

Number of Members​ ​Percent of Dataset
​Henry Ford Health System 
​Kasier Peranente Colorado
​Kaiser Permanente Northern California
​Kaiser Permanente Northwest
​Kaiser Permanente Southern California
​Marshfield Clinic Research Foundation
​Meyers Primary Care Institute of Fallon Health Plan

Cohort Characteristics

Figure 1. Distribution of New York Heart Association (NYHA) Functional Class at Time of ICD Placement in CVRN ICD Cohort

Figure 1 Legend

​NYHA Class
​Class I
​No limitation of physical activity. Ordinary physical activity does not cause undue fatigue, palpitation, dyspnea (shortness of breath).
​Class II
​Slight limitation of physical activity. Comfortable at rest. Ordinary physical activity results in fatigue, palpitation, dyspnea.
​Class III
​Marked limitation of physical activity. Comfortable at rest. Less than ordinary activity causes fatigue, palpitation, or dyspnea.
​Class IV
​Unable to carry on any physical activity without discomfort. Symptoms of heart failure at rest. If any physical activity is undertaken, discomfort increases.


Data Source

All member data was extracted using the Virtual Data Warehouse (VDW). The VDW is a standardized resource comprised of: (1) computerized datasets stored behind separate security firewalls, including variables with identical names. formats, and specifications; (2) informatics tools that facilitate storage, retrieval, processing, and managing the datasets; and (3) detailed data documentation. All data are lined by a unique identifier so that data elements can be rolled up to the individual person-level. The database was merged with detailed NCDR-ICD Registry data. The NCDR-ICD Registry houses detailed baseline clinical data for patients undergoing ICD implantation. This registry was adopted nationwide in April 2006.

Key Publications

Masoudi, F. A., Go, A. S., Magid, D. J., Cassidy-Bushrow, A. E., Doris, J. M., Fiocchi, F., ... & Gurwitz, J. H. (2012). Longitudinal study of implantable cardioverter-defibrillators: methods and clinical characteristics of patients receiving implantable cardioverter-defibrillators for primary prevention in contemporary practice. Circulation: Cardiovascular Quality and Outcomes5(6), e78-e85.

Masoudi, F. A., Magid, D. J., Go, A. S., Cassidy-Bushrow, A. E., Gurwitz, J., Reynolds, K., ... & Greenlee, R. T. (2010). The Cardiovascular Research Network Longitudinal Study of Implantable Cardioverter Defibrillators: ICD Therapy in a Community Population.