Management of Atrial Fibrillation and Heart Failure

Introduction to Contraindications

The American College of Cardiology/American Heart Association guidelines for SVT management list "drugs with SA and/or AV nodal-blocking properties" as a precaution when using either diltiazem or beta-blockers, due to the risk of severe bradycardia, heart block, and hypotension 1
The American College of Cardiology/American Heart Association guidelines also support this contraindication, as reported in another journal 2
The European Society of Cardiology guidelines for heart failure management specifically advise that "calcium-channel blockers should be discontinued unless absolutely necessary, and diltiazem and verapamil are potentially harmful because of their negative inotropic effect" 3

If diltiazem is ineffective, discontinue it completely before starting metoprolol, as an alternative rate control strategy 5
In patients with atrial fibrillation, consider digoxin as an alternative (if no pre-excitation), according to the American Heart Association 5
For patients with heart failure, amiodarone may be considered as an alternative rate control strategy, as suggested by the American Heart Association 5

Standard diltiazem infusion can be maintained for 6-24 hours, and sufficient time should be allowed between discontinuing diltiazem and starting metoprolol, as recommended by a medical guideline 4
Ensure complete clearance of IV diltiazem before starting Toprol XL, and begin with a lower dose of Toprol XL than typically used, with close monitoring for bradycardia and hypotension 5

Heart failure patients should be aware that both medications can worsen heart failure, although recent research suggests diltiazem may be similarly effective to metoprolol in AF with heart failure with no significant safety differences, as reported in a study (note: this is not a direct citation, but rather a mention of a study)
Continuous cardiac monitoring is essential during and after the transition period if sequential therapy is planned, to minimize the risk of adverse effects 5