What is the treatment for a patient with an irregular heart rate, specifically tachycardia or arrhythmia?

Treatment of Irregular Heart Rate with Tachycardia or Arrhythmia

For patients with irregular heart rate and tachycardia, immediate treatment depends critically on hemodynamic stability: unstable patients require immediate synchronized cardioversion, while stable patients need rhythm identification via 12-lead ECG followed by rate control with IV beta-blockers or diltiazem for atrial fibrillation, or rhythm-specific antiarrhythmic therapy for other arrhythmias. 1

Initial Assessment and Stabilization

Assess hemodynamic stability first by looking for acute altered mental status, ischemic chest discomfort, acute heart failure, hypotension, or other signs of shock. 1

• Provide supplementary oxygen if oxygenation is inadequate or signs of increased work of breathing are present (tachypnea, intercostal retractions, suprasternal retractions, paradoxical abdominal breathing). 1
• Attach cardiac monitor, evaluate blood pressure, and establish IV access immediately. 1
• Obtain 12-lead ECG to define the rhythm, but do not delay cardioversion if the patient is unstable. 1, 2

Treatment Algorithm Based on Stability

Unstable Patients (Rate-Related Cardiovascular Compromise)

Proceed immediately to synchronized cardioversion if the patient demonstrates signs of shock, acute altered mental status, ischemic chest pain, acute heart failure, or hypotension attributed to the tachyarrhythmia. 1

• Establish IV access and administer sedation if the patient is conscious, but do not delay cardioversion if the patient is extremely unstable. 1
• For atrial fibrillation: use initial biphasic energy of 120-200 J, increasing stepwise if unsuccessful. 1
• For atrial flutter and other SVTs: start with 50-100 J, increasing stepwise if needed. 1
• For monomorphic VT with pulse: use 100 J initially, increasing stepwise if no response. 1

Stable Patients

Step 1: Rhythm Identification

Determine if the rhythm is regular or irregular, and narrow-complex (<120 ms) or wide-complex (>120 ms). 1, 2

Irregular narrow-complex or wide-complex tachycardia is most likely atrial fibrillation (with or without aberrant conduction) with uncontrolled ventricular response. 1

• Other possibilities include multifocal atrial tachycardia (MAT) or sinus rhythm with frequent premature beats. 1
• When rhythm diagnosis is uncertain and patient is stable, obtain 12-lead ECG with expert consultation. 1, 2

Step 2: Treatment Based on Rhythm

For Atrial Fibrillation (Irregular Rhythm):

Rate Control Strategy:

• IV beta-blockers and nondihydropyridine calcium channel blockers (diltiazem) are the drugs of choice for acute rate control in most patients with atrial fibrillation and rapid ventricular response. 1
• For patients with congestive heart failure: use digoxin or amiodarone for rate control. 1
• Critical warning: Consider the risk of conversion to sinus rhythm with amiodarone before using it for rate control. 1

Rhythm Control (Cardioversion) Considerations:

• Do not attempt cardioversion (electric or pharmacologic) in patients with atrial fibrillation duration >48 hours unless the patient is unstable, due to increased risk of cardioembolic events. 1
• Alternative: perform cardioversion after anticoagulation with heparin and transesophageal echocardiography to exclude left atrial thrombus. 1

For Pre-Excited Atrial Fibrillation (Wide-Complex Irregular):

• Avoid AV nodal blocking agents (adenosine, calcium channel blockers, digoxin, possibly beta-blockers) as they may cause paradoxical increase in ventricular response. 1
• These patients typically present with very rapid heart rates and require emergent electric cardioversion. 1
• Seek expert consultation immediately. 1

For Regular Narrow-Complex SVT:

• If not hypotensive, may treat with adenosine while preparing for synchronized cardioversion. 1

For Monomorphic (Regular) Ventricular Tachycardia:

• Amiodarone is effective for preventing recurrent monomorphic VT or treating refractory ventricular arrhythmias: 150 mg IV over 10 minutes, repeat as needed to maximum 2.2 g IV per 24 hours. 1, 3
• Sotalol 1.5 mg/kg over 5 minutes is relatively safe and effective, but avoid in patients with prolonged QT interval. 1
• Lidocaine is less effective than procainamide, sotalol, and amiodarone, and should be considered second-line therapy: 1-1.5 mg/kg IV bolus, maintenance 1-4 mg/min. 1

For Polymorphic (Irregular) VT:

• Requires immediate defibrillation with same strategy as VF. 1
• If long QT interval present (torsades de pointes): stop QT-prolonging medications, correct electrolyte imbalances, consider magnesium. 1

Special Considerations and Critical Pitfalls

Heart Rate <150 bpm:

• When ventricular rate is <150 bpm without ventricular dysfunction, the tachycardia is more likely secondary to an underlying condition rather than the cause of instability. 1
• Focus on identifying and treating the underlying cause (fever, dehydration, anemia, hypotension/shock). 1

Sinus Tachycardia:

• No specific drug treatment is required for sinus tachycardia. 1
• Therapy should be directed toward the underlying cause. 1
• Warning: When cardiac function is poor, cardiac output may be dependent on rapid heart rate; "normalizing" the heart rate can be detrimental. 1

Wide-Complex Tachycardia of Unknown Origin:

• If unable to distinguish between SVT and VT, and the rate is regular with monomorphic QRS, IV adenosine is relatively safe for both treatment and diagnosis. 1
• Do not give adenosine for unstable or irregular/polymorphic wide-complex tachycardia. 1
• Presence of AV dissociation or fusion complexes is diagnostic of VT. 2

Amiodarone Safety Considerations:

• Hypotension is the most common adverse effect (16% of patients), usually related to infusion rate rather than dose. 3
• Monitor for QTc prolongation; combination with other QT-prolonging agents should be reserved for life-threatening arrhythmias. 3
• Drug-related bradycardia occurs in approximately 5% of patients. 3
• Avoid rapid infusion rates and high loading dose concentrations to prevent acute hepatic necrosis. 3

Mandatory Specialist Referral:

• All patients with Wolff-Parkinson-White syndrome (pre-excitation). 2, 4
• Wide-complex tachycardia of unknown origin. 2, 4
• Severe symptoms during palpitations (syncope, dyspnea). 2, 4
• Drug-resistant or drug-intolerant narrow-complex tachycardias. 2, 4