Valsalva or other vagal manoeuvre (eg. ice on face) may revert a SVT
blow into a 10ml syringe with plunger in place then immediately lie flat with legs up in air (REVERT trial suggests this doubles the success rate of just a Valsalva - see vide at bottom)
IV boluses of adenosine are usually effective with only occasional prolonged AV block but makes patients feel like they are dying.
only use with full resuscitative facilities on hand (preferably with external pacing for those rare cases)
avoid in severe asthma, patients on theophylline may require higher doses
avoid in severe coronary artery disease as risk of vasodilatation of normal vessels may produce ischaemia in vulnerable territory
dipyridamole potentiates effects of adenosine
carbamazepine increases risk of prolonged AV block
alternative to adenosine is IV verapamil (Isoptin) 3mg over 1-2min then 1mg per minute as needed up to 10mg max in adults (unfortunately it seems iv verapamil will be taken off the Australian market in October 2012)
BUT ONLY IF:
narrow complex tachycardia, and,
BP > 80mmHg systolic, and
no WPW (as rapid ventricular rate in AF may occur), and
not pregnant (greater risk of maternal hypotension and fetal hypoperfusion than adenosine), and
take care if ischaemic heart disease or on beta blockers as risk of profound myocardial depression or AV blockade
AND ensure you can deal with its adverse effects
beta blockers may be used as first-line Rx for those with catecholamine-sensitive tachycardias such as RV outflow tachycardia.
refractory cases should be discussed with cardiology, possible options include:
flecainide if young, no structural heart damage on echo, and not pregnant