What is the initial approach for treating tachycardia?

Initial Approach to Tachycardia Treatment

The initial approach to tachycardia treatment depends critically on hemodynamic stability: unstable patients require immediate synchronized cardioversion, while stable patients should undergo rhythm assessment (regular vs. irregular, narrow vs. wide QRS) followed by targeted pharmacologic intervention, with adenosine being first-line for regular narrow-complex supraventricular tachycardia. 1

Immediate Assessment and Stabilization

The first priority is determining hemodynamic stability by assessing for acute altered mental status, ischemic chest discomfort, acute heart failure, hypotension, or shock 1. Simultaneously:

• Attach cardiac monitor, establish IV access, and evaluate blood pressure 1
• Assess oxygenation via pulse oximetry and provide supplemental oxygen if inadequate 1
• Identify and treat reversible causes (infection, hypotension, metabolic derangements, hypoxia, hypokalemia, hypomagnesemia) while initiating treatment 2, 1

A 12-lead ECG should be obtained to define the rhythm if the patient is stable enough to wait, but never delay cardioversion in unstable patients while waiting for ECG 1.

Algorithm Based on Hemodynamic Stability

For Hemodynamically UNSTABLE Patients:

Immediate synchronized cardioversion is mandatory when the patient demonstrates rate-related cardiovascular compromise 1. Key points:

• Sedate the patient prior to cardioversion if conscious and time permits 1
• For unstable wide-complex tachycardia, presume ventricular tachycardia and perform immediate cardioversion 1
• Consider precordial thump only for witnessed, monitored unstable ventricular tachycardia if a defibrillator is not immediately ready 1

For Hemodynamically STABLE Patients:

The approach is algorithmic based on ECG characteristics 1:

Step 1: Determine if rhythm is regular or irregular 1

Irregular tachycardias suggest:

• Atrial fibrillation
• Atrial flutter with variable block
• Multifocal atrial tachycardia (most common in pulmonary disease patients) 2

Regular tachycardias proceed to Step 2.

Step 2: Assess QRS width 1

Management of Regular NARROW-Complex Tachycardia (QRS <120ms)

First-Line: Vagal Maneuvers

Attempt Valsalva maneuver or carotid sinus massage first for suspected AV nodal re-entrant tachycardia or AV reciprocating tachycardia, as these can terminate the arrhythmia in many cases 2.

Second-Line: Adenosine

Adenosine is the drug of choice for regular narrow-complex SVT with approximately 93% success rate 3:

• Initial dose: 6 mg rapid IV push followed immediately by saline flush 3
• If no effect after 1-2 minutes: 12 mg rapid IV push 3
• Must be administered in monitored environment due to risk of transient complete heart block 3

Critical contraindication: Avoid adenosine in pre-excited atrial fibrillation or flutter (irregular rhythm with delta waves), as it may precipitate ventricular tachycardia/fibrillation 1, 3.

Alternative Agents if Adenosine Fails:

• Beta-blockers are most effective for controlling ventricular response and accelerate conversion to sinus rhythm compared to diltiazem 2
• Calcium channel blockers (diltiazem or verapamil) 2
• Digoxin is least effective of these options 2

Management of Regular WIDE-Complex Tachycardia (QRS ≥120ms)

Treat as ventricular tachycardia unless proven otherwise 1. Administering verapamil or diltiazem for presumed SVT when the rhythm is actually VT can cause hemodynamic collapse or ventricular fibrillation 1.

For Stable Wide-Complex Tachycardia:

Adenosine can be used for both treatment and diagnosis of regular monomorphic wide-complex tachycardia of uncertain origin 1, but use with caution as it may precipitate ventricular fibrillation in patients with coronary artery disease 1.

For confirmed or presumed ventricular tachycardia:

• Amiodarone 150 mg IV over 10 minutes is the recommended agent 1, 4
• Amiodarone is indicated for frequently recurring VF and hemodynamically unstable VT refractory to other therapy 4
• Avoid sotalol in patients with prolonged QT interval 1

Special Considerations

Sinus Tachycardia

Sinus tachycardia (>100 bpm) requires treatment of the underlying cause rather than specific drug therapy 1. It accelerates and terminates gradually, unlike paroxysmal SVT 2. Common causes include infection, volume loss, pain, anxiety, or other stressors 2.

Rate Thresholds

Heart rates <150 beats/minute are unlikely to cause symptoms unless ventricular function is impaired 1. This helps distinguish pathologic tachycardia from compensatory responses.

Atrial Fibrillation/Flutter Management

For these irregular rhythms, the initial approach involves slowing ventricular response rather than immediate cardioversion 2:

• Beta-blockers are most effective for rate control 2
• Diltiazem is an alternative 2
• Digoxin is least effective 2
• Cardioversion is generally not recommended for asymptomatic or minimally symptomatic arrhythmias until correction of underlying problems 2

Multifocal Atrial Tachycardia

This irregular tachycardia with ≥3 different P-wave morphologies is most commonly associated with underlying pulmonary disease 2. Calcium channel blockers have shown modest success, while beta-blockers are usually contraindicated due to underlying lung disease 2.

Critical Pitfalls to Avoid

• Never delay cardioversion in unstable patients while obtaining 12-lead ECG 1
• Never use AV nodal blocking agents (adenosine, calcium blockers, beta-blockers) in pre-excited atrial fibrillation/flutter, as this can accelerate ventricular response and cause degeneration to ventricular fibrillation 1
• Never administer adenosine for irregular or polymorphic wide-complex tachycardia 1
• Never normalize heart rate in compensatory tachycardias where cardiac output depends on rapid rate (e.g., hypovolemia, sepsis) 1
• Never use multiple AV nodal blocking agents with overlapping half-lives, which can cause profound bradycardia 1
• Never assume wide-complex tachycardia is SVT with aberrancy without definitive evidence—treat as VT 1

Electrolyte Management

Avoid and correct electrolyte abnormalities, especially hypokalemia and hypomagnesemia, as these may reduce perioperative incidence and risk of arrhythmias 2. However, acute preoperative repletion of potassium in asymptomatic individuals may carry more risk than benefit 2.

When to Refer

Refer to cardiac arrhythmia specialist for 2:

• Wide-complex tachycardia of unknown origin
• Clear history of paroxysmal regular palpitations
• Pre-excitation on resting ECG with history of paroxysmal palpitations
• Drug resistance or intolerance
• Patients desiring to be free of drug therapy