Second-line Treatments
If vagal manoeuvres fail to terminate the tachyarrhythmia, adenosine is recommended as second-line treatment. Adenosine works by slowing conduction thorough the AV node.
It is given as a rapid IV bolus (6 mg, 12 mg, 18mg) via a large vein and is followed by a rapid flush. Note the recent update in dosing regimen.
Side-effects include:
- Nausea
- Dizziness
- Breathlessness
- Flushing
- Chest tightness
Ensure you alert your patient to adenosines very unpleasant side effects before administration. Be ready to reassure your patient shortly after administration of adenosine.
Adenosine has a success rate in excess of 90%.
Adenosine is contraindicated in heart block and sick sinus syndrome. Heart transplant patients should be given a small dose (3 mg) as the donor AV node may be exquisitely sensitive to adenosine. Asthma is discussed below.
Verapamil is an alternative option and is recommended if adenosine is ineffective. It has a longer onset of action and more potential side effects than adenosine.[5] It can be given IV over 2 minutes at a dose of 5-10 mg in otherwise well patients.
Verapamil is contraindicated in patients with heart block or impaired left-ventricular function. It should also be avoided in patients who take beta-blockers as you risk asystole.
Beta-blockers may be considered if all of the above options are ineffective.