ACC/AHA classification of indications for pacing3
| Class I | Conditions for which there is evidence and/or general agreement that a given procedure or treatment is beneficial, useful and effective |
| Class II | Conditions for which there is conflicting evidence and/or a divergence of opinion about the usefulness/efficacy of a procedure or treatment |
| Class IIa | Weight of evidence/opinion is in favour of usefulness/efficacy |
| Class IIb | Usefulness/efficacy is less well established by evidence/opinion |
| Class III | Conditions for which there is evidence and/or general agreement that a procedure/treatment is not useful/effective and in some cases may be harmful |