Table 2.

OPERA Endpoints.

Endpoint	Definition	Characteristics
Atrial Fibrillation * (primary endpoint)	Any documented atrial fibrillation (AF) or atrial flutter (AFL) of at least 30 seconds duration and documented by rhythm strip or 12-lead ECG. If only a shorter duration ECG is available, then the diagnosis of AF/AFL is based on the arrhythmia being present at onset or termination.	AF - Irregular ventricular response independent of rate, with the following characteristics: QRS complex unchanged from baseline or functional bundle branch block, and absence of P waves, or presence of fibrillatory waves in isoelectric periods of the ECG. AFL - With variable block, 2:1, 3:1, or 4:1, but not sinus tachycardia, with the following characteristics: QRS unchanged from baseline or functional bundle branch block, and absence of sinus P waves, and presence of flutter waves in isoelectric periods of the QRS complex of the ECG. AF/ AFL (unable to distinguish) - Presence of RR interval irregularity will favor AF diagnosis. SVT/ suspect AF - Paroxysmal SVT not consistent with AFL or sinus tachycardia, with characteristics of SVT (see below) except >0.02 second variation in successive cardiac cycles, but not definite AF.
Sustained or Symptomatic Atrial Fibrillation * (secondary endpoint)	AF/AFL meeting all requirements for the primary endpoint, plus being either sustained, symptomatic, or both.	Sustained: Presence for at least one hour duration. Symptomatic: treated with electrical or pharmacological cardioversion, or temporally associated with new or worsening chest pain or shortness of breath, or treated with fluid or pressor treatment for hypotension (drop in blood pressure requiring escalation of treatment).
Other Arrhythmias *	Other supraventricular tachycardia (SVT)	SVT/ suspect not AF - Paroxysmal SVT not consistent with AFL or sinus tachycardia, with the following characteristics: mean ventricular rate ≥ 100 beats per minute, and QRS complex unchanged from baseline or functional bundle branch block, and <0.02 second variation in successive cardiac cycles unless cycle length alternans is seen, and no evidence of atrioventricular dissociation, and absence of sinus P waves.
	Ventricular tachycardia (VT)	Wide complex QRS (>120 msec), rhythm > 100/min, with AV dissociation, capture or fusion beats.
	Ventricular fibrillation (VF)	Completely disorganized ventricular electrical activity.
Utilization Endpoints	Unit and hospital length-of-stays	Total intensive/coronary care unit length-of-stay Total days of telemetry monitoring Total hospital length-of-stay
Mortality and Safety Endpoints	Mortality	30-day mortality, including cause-specific mortality: † cardiac arrhythmic cardiac nonarrhythmic vascular non-cardiovascular unknown 1-year mortality, all-cause
	Major adverse coronary events (MACE)	Myocardial infarction, stroke, and cardiovascular death †
	Bleeding	Chest tube output during the first 24 hours after cardiac surgery. Total RBC transfusions from enrollment to hospital discharge or post-operative day 10 (whichever sooner). Any bleeding requiring re-exploration or surgery. All other episodes of minor and major bleeding. Composite TIMI bleeding indices, including major, minor, and loss no site bleeding.
	Other adverse events and serious adverse events	Coded as appropriate using the MedDRA dictionary.

^*From the time of cardiac surgery until hospital discharge or post-operative day 10, whichever occurs first.

^†Standardized definitions, available from the authors upon request.