Byrne‐Quinn 1970.

Methods	RCT Double‐blind Loss to follow‐up reported: yes
Participants	Persistent AF (mean duration: 12 months). n = 74 Men: 53% Age (mean): 54 (range 30–70) years Structural heart disease: 80%. LAD: NS. LVEF: NS
Interventions	Quinidine 1.2 g/day vs placebo Method of AF cardioversion: electrical Warfarin discretionary
Outcomes	At 12 months: Mortality Proarrhythmia Adverse effects AF recurrence
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	No information given on the method employed to generate the random sequence.
Allocation concealment (selection bias)	Unclear risk	Participants "were randomly allocated to two groups". No details provided.
Blinding (performance bias and detection bias) All outcomes	Low risk	Identical tablets. Participants and investigators blinded.
Incomplete outcome data (attrition bias) All outcomes	High risk	High proportion of participants withdrawn, unbalanced between groups.
Selective reporting (reporting bias)	Low risk	All study's prespecified outcomes of interest were reported. All main outcomes expected were reported.
Other bias	Low risk	No other bias apparent.