Management

1. Rate Control:

    a. Pharmacologic Options

Rate control consists of controlling the ventricular rate to slow down its response.  The different rate control agents act on the atrioventricular (AV) node to prolong its refractory period and to slow its conduction.  By doing so, one avoid the hemodynamic instability associated with tachycardia such as heart failure, and angina, and prevent long term tachycardia-mediated cardiomyopathy.   Unfortunately, one may also have to face unwanted side effects, such as hypotension and bradycardia, for the same reason.  In most situations, medication can be administered through the per os (PO or oral) or intravenous (IV) route.  As expected the intravenous form provides a faster onset of action.  The four main classes of rate control agents consist of; beta-blockers (metoprolol, atenolol, propanolol), calcium channel blockers (diltiazem, verapamil), sodium-potasium ATPase inhibitors (digoxin), and class III antiarrhythmic agents such as amiodarone.   Beta-blockers, and calcium channel blockers are both effective at rest and during exercise, while digoxin is only effective at rest. 

A special consideration should be given to patient with Wolff-Parkinson-White syndrome as administration of a beta-blocker, calcium channel blocker, adenosine, or digoxin would facilate antegrade conduction through the accessory conduction pathway and cause ventricular preexcitation.  In this particular case, class I and III antiarrhythmic agents (amiodarone) become the best treatment option.  The following tables give a list of possible rate control agents, along with their dosing and major side effects.  I would recommend you to carry a version of it for when you are on call.

 

Table 2. Rate Control Pharmacological Options
Drug Loading dose by
route of administration
Onset of action Maintenance dose Major side effect
Metoprolol 2.5 to 5 mg IV bolus
over 2 min, up to 3 doses
5 mins IV infusion n/a Hypotension*, heart block,
asthma/COPD**, heart failure
25-100 mg
PO bid
4 to 6 hrs 25 - 100 mg PO bid Hypotension*, heart block,
asthma/COPD**, heart failure
Propanolol 0.15 mg/kg IV over
1 min
5 mins IV infusion n/a Hypotension*, heart block,
asthma/COPD**, heart failure
80 - 240 mg/day in
divided doses
1 to 1.5 hrs 80 - 240 mg/day in
divided doses
Hypotension*, heart block,
asthma/COPD**, heart failure
Diltiazem 0.25 mg/kg IV over
2 mins
2 to 7 mins 5 - 15 mg/hr infusion Hypotension*, heart block,
heart failure
120 - 360 mg/day in
divided doses
2 to 4 hrs 120 - 360 mg/day in
divided doses
Hypotension*, heart block,
heart failure
Verapamil 0.075 - 0.15 mg/kg
IV over 2 mins
3 to 5 mins IV infusion n/a Hypotension*, heart block,
heart failure
120 - 360 mg/day in
divided doses
1 to 2 hrs 120 - 360 mg/day in
divided doses
Hypotension*, heart block,
heart failure
Digoxin 0.25 mg IV every
2 hrs up to 1.5 mg
2 hrs 0.125 - 0.25 mg/day Digoxin toxicity***,
heart block (bradycardia)
0.25 mg PO every 2 hrs
up to 1.5 mg
2 hrs 0.125 - 0.375 mg/day Digoxin toxicity***,
heart block (bradycardia)
Amiodarone 150 mg IV over
10 mins
days 0.5 - 1 mg/min IV Hypotension*, heart block,
pulm toxicity, thyroid dysfct,
warfarin interaction
800 mg/day for 1 wk
600 mg/day for 1 wk
400 mg/day for 4-6 wks
all PO
1 to 3 wks 200 mg/day Hypotension*, heart block,
pulm toxicity, thyroid dysfct,
warfarin interaction

*     Do not use if systolic blood pressure less than 90 mmHg
**   Severe contraindication
*** Do not use or need careful monitoring in renal failure patient

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