A. General Management. Assess patient quickly for level of distress and perform ECG to diagnose rhythm abnormality. Obtain IV access, if necessary. Support airway and circulation, as necessary. If possible, obtain multilead rhythm strips during termination of tachycardia.
B. Specific Management. Management of specific tachycardias centers on stabilizing patient by changing rhythm or by making rhythm more tolerable. If patient is hemodynamically unstable due to tachycardia, electrical cardioversion is treatment of choice for any of these dysrhythmias (synchronized unless a pulseless tachycardia). Pay special consideration to patient with congenital heart disease who has atrial flutter or fibrillation because of possibility of clot formation in left atrial appendage and risk of subsequent stroke following cardioversion. Digoxin and calcium channel blockers are contraindicated in patients with Wolff-Parkinson-White syndrome because of risk of rapid conduction down accessory pathway, promoting ventricular fibrillation.
1. AV and AV-nodal tachycardias. Generically thought of as SVT, these tachycardias use the AV node as a critical part of tachycardia circuit. Therefore, blocking the AV node should terminate tachycardia. However, effectively blocking AV-nodal conduction without producing high-grade block is sometimes difficult.
a. Adenosine. Causes significant AV block for a very transient amount of time; drug is deactivated by enzymes of RBCs and, therefore, has a very short half-life (~9 seconds). SVTs that involve the AV node typically respond to IV adenosine, 100-300 mcg/kg, up to maximum of ~12 mg. Administer as rapid bolus followed by saline push (~10 mL). IV access should be as large and as close to the heart as possible to allow for rapid delivery of drug to myocardium (ie, arm is better than foot). Doses may be repeated incrementally as needed. Effect should be seen within a few seconds after administration. Potential side effects include mild bron-chospasm, atrial fibrillation, asystole (dependent on dose relative to size of patient and level of catecholamines), brief hypotension, chest pain, headaches, and flushing.
b. Vagal maneuvers. May also be tried; among these are bag of ice to face (best as slush), Valsalva, gag, and cough.
c. Verapamil, procainamide, amiodarone. Other IV agents that have been effective in acute treatment of SVT resistant to adenosine. Verapamil is contraindicated in infants or patients with Wolff-Parkinson-White syndrome. Once termination of tachycardia is achieved, oral therapy can be instituted as necessary.
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