Here's a difficult case that one of our EM residents, Dr Corinne Lau, encountered. What would you do?
73 y/o
PMhx: DM , HTN , HL
Presented to the ED for palpitations , non vertiginous giddiness and chest discomfort. \
ECG:
Decision was made for trial of vagal manoeuvres as standby adenosine was being prepared.
Post vagal manoeuvres patient became hypotensive . However patient was still alert.
ECG repeated showed persistent SVT.
IV fluids was given and trial of adenosine was given 6mg–>12mg –>12mg ,
However patient reverted back to SVT after a few seconds post adenosine.
Repeat BP was 80/60 and patient was still alert.
What would you do now?
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With failure of adenosine , decision was made for synchronised cardioversion with sedation.
50J –>100J–>100J , each time the patient reverted back to SVT within a few seconds and remained hypotensive.
Repeat BP 70/50 despite IV fluids . HR ranged between 180-200.
Cardiology on call was consulted:
- IV diltiazem (bolus) + IV fluids + electrical cardioversion was given
- Patient again reverted back to SVT after a few seconds and remained hypotensive.
- A second attempt of diltiazem ( infusion) + IV fluids + electrical cardioversion was given.
- With the continuous diltiazem infusion patient converted to sinus rhythm.
Q1 :How to correct the hypotension? Is noradrenaline or dobutamine an option ?
Ans :
Management of hypotension always starts with fluid resuscitation. Rate control agents are all vasodilatory and therefore some fluid resuscitation would be helpful.
If decision is made to start vasopressors . Aim is to maintain good blood pressure but not counteract the rate controlling drugs. i.e. amiodarone.
Noradrenaline can be used as a temporising measure , as it has vasoconstriction with limited impact on heart rate (chronotropy) .
Dobutamine is a potent ionotrope with weak chronotropy but it significantly increases myocardial oxygen consumption ,
BOTTOMLINE : Fluids remains the first line of treatment ,and if decision is made to start vasopressors noradrenaline is the drug of choice for most physicians.
Q2 What is the drug of choice when adenosine and electrical cardioversion fails and patient remains hypotensive?
Ans :
Amiodarone is considered first line in this case , as it is believed to have less hypotensive effects compared to calcium channel blockers (CCB). Also CCB should be used in caution in those with unknown EF.
If amiodarone fails, CCB can be tried and diltiazem is preferred to verapamil .
Use diltiazem , not as a push but a slow bolus . Drip it in at 2.5 mg/minute until HR < 100 or you get to 50 mg. Diltiazem can be converted to a conventional dose when patient is more stable.
