Trends in treated ventricular fibrillation out-of-hospital cardiac arrest: a 17-year population-based study.

OBJECTIVES

The aims of this study were to describe the trends of ventricular fibrillation (VF) out-of-hospital cardiac arrest in Rochester, Minnesota, since 1985 and to determine coexistent trends in implantable cardioverter defibrillator (ICD) placement and termination of potentially lethal ventricular arrhythmias that might explain, at least in part, a declining incidence trend.

BACKGROUND

The incidence of VF out-of-hospital cardiac arrest treated by emergency medical services (EMS) personnel has declined over the past decade. Because VF out-of-hospital cardiac arrest occurs primarily in the setting of severe coronary artery disease, primary and secondary prevention strategies may account in part for the decline. In particular, ICD use in large primary and secondary prevention clinical trials in patients at high risk of sudden death has demonstrated that these devices improve survival.

METHODS

All residents of the City of Rochester, Minnesota, who presented with a VF out-of-hospital cardiac arrest from 1985 to 2002, identified and treated by EMS, were included in the study. In addition, residents of the City of Rochester who received their first ICD implant from 1989 to 2002 were identified. From the ICD records, general demographics, etiology of heart disease, comorbid medical disease, and indication for ICD placement were abstracted. Follow-up data obtained from this population included ICD shocks, the underlying rhythm disturbance, and death.

RESULTS

The overall incidence of EMS-treated VF out-of-hospital cardiac arrest in Rochester during the study period was 17.1 per 100,000 [95% confidence interval (CI) 15.1-19.4]. The incidence has decreased significantly (P < 0.001) over the study period: 1985-1989: 26.3/100,000 (95% CI 21.0-32.6), 1990-1994: 18.2/100,000 (95% CI 14.1-23.1), 1995-1999: 13.8/100,000 (95% CI 10.4-17.9), 2000-2002: 7.7/100,000 (95% CI 4.7-11.9). One hundred ten patients received an ICD. The placement of ICDs also has increased dramatically over the past 10 years: 1990-1994: 5.0/100,000 to 2000-2002: 20.7/100,000 (P < 0.001). ICDs terminated VF or fast ventricular tachycardia (<270 ms) in 22 patients. Termination of these potentially fatal arrhythmias has shown a trend toward an increase over the study period: 1990-1994: 1.1/100,000 to 2000-2002: 3.5/100,000 (P = 0.06).

CONCLUSIONS

The incidence of VF out-of-hospital cardiac arrest is declining. In contrast, the rates of ICD placement and ICD termination of ventricular tachycardia or VF are markedly increasing. Sudden death preventive strategies are multifactorial. These observations suggest that ICD termination of potentially lethal ventricular arrhythmias may contribute to the lower incidence of VF out-of-hospital cardiac arrest.