Title of Trial
ORBIT trial

Date and Location of Presentation
Presented at the November 2003 American Heart Association Annual Scientific Session in Orlando, Florida

Purpose of the Trial
The aim of the ORBIT trial was to evaluate the safety and efficacy of biphasic versus monophasic defibrillation in the termination of ventricular fibrillation (VF) and pulseless ventricular tachycardia (VT) in victims of out-of-hospital cardiac arrest.

Study Category
Sudden Cardiac Death & Syncope

Patient Population
Victims of out-of-hospital cardiac arrest

Inclusion Criteria

• Spontaneous, hemodynamically unstable, sustained ventricular tachycardia or fibrillation

Exclusion Criteria

• Age < 18 years
• Traumatic cardiac arrest
• Enrollment in other studies

Study Design
Randomized clinical trial of monophasic (200 J, 300 J, 360 J) versus biphasic (120 J, 150 J, 200J) defibrillation

Primary Endpoint

• Conversion to organized electrical activity with first shock

Secondary Endpoints

• Conversion with 1-3 shocks
• Energy required for conversion

Baseline Characteristics
Patient number: 436
Mean Age: 67 years
Gender: % female; 28%
Other characteristics: Down times of patients were 10.6 minutes for the monophasic group and 10.9 minutes for biphasic group.

Time to Follow-up
one year

Results
There was no difference in the primary endpoint of conversion with first shock (26% with monophasic versus 32% with biphasic, p=0.2). There was also no difference in conversion with 1-3 shocks (45% with monophasic versus 54% with biphasic, p=0.06). Conversion for the first highest energy setting shock was higher with monophasic (14%) versus biphasic (23%, p=0.02). Prior defibrillation had occurred more frequently in the monophasic arm (23% vs. 16%, p<0.05). A similar proportion of patients arrived at the emergency department alive (57% each) and remained alive through discharge (22% vs. 23%) and 30 days (7% each).

Trial Status: Completed

Review written by Samir Saba, MD