Adult Tachycardia Management Algorithm

Initial Assessment and Management

The American Heart Association recommends determining hemodynamic stability as the first critical decision in managing adult tachycardia, which determines whether to proceed with immediate cardioversion or stepwise pharmacologic management 1, 2
Signs of hemodynamic instability, such as acute altered mental status, ischemic chest discomfort, acute heart failure, hypotension, or signs of shock, indicate the need for immediate cardioversion 1
The American College of Cardiology suggests that if the heart rate is <150 bpm without ventricular dysfunction, the tachycardia is more likely secondary to an underlying condition rather than the primary cause of instability 2

The American College of Cardiology recommends proceeding directly to synchronized cardioversion without attempting vagal maneuvers or medications in unstable patients 4
The initial energy for synchronized cardioversion should be 50-100 J biphasic, with a stepwise increase in dose if the initial shock fails 6

The American Heart Association suggests classifying the tachycardia as narrow-complex or wide-complex, and obtaining a 12-lead ECG to determine QRS duration 2
For narrow-complex tachycardia, vagal maneuvers are the recommended first-line intervention, with a success rate of 27.7% when switching between techniques, and the modified Valsalva maneuver achieving ~43% success 5, 6, 8, 3
If vagal maneuvers fail, adenosine is the next intervention, with 90-95% effectiveness for terminating SVT, and a dosing protocol of 6 mg rapid IV push via large peripheral vein, followed by 20 mL saline flush 2, 6, 8, 4, 3

The American College of Cardiology recommends using intravenous diltiazem, verapamil, or beta blockers if adenosine fails or is contraindicated, with calcium channel blockers having a 64-98% conversion rate for SVT 7, 8, 4
Diltiazem is more effective than beta blockers for terminating SVT, but may cause hemodynamic collapse, accelerated ventricular rate, or precipitate ventricular fibrillation 7, 4

The American Heart Association suggests assuming ventricular tachycardia until proven otherwise, and treating accordingly, as improper treatment can be lethal 1
For stable ventricular tachycardia, antiarrhythmic therapy with amiodarone, procainamide, or sotalol is recommended, with amiodarone being the most effective for preventing recurrent monomorphic VT 1
For pre-excited atrial fibrillation, ibutilide or IV procainamide should be used, and calcium channel blockers, beta blockers, or digoxin should be avoided, as they may enhance accessory pathway conduction and precipitate ventricular fibrillation 5, 6

The American College of Cardiology recommends referring all patients treated for SVT to a heart rhythm specialist, and considering oral verapamil or diltiazem for ongoing AVNRT management, and catheter ablation as a potentially curative option for recurrent SVT 4, 3, 7