How can heart rate be controlled in cases of tachycardia?

Heart Rate Control in Tachycardia

For acute rate control in tachycardia, beta blockers (metoprolol, esmolol, propranolol) or nondihydropyridine calcium channel blockers (diltiazem, verapamil) are first-line intravenous agents in hemodynamically stable patients without heart failure, while IV digoxin or amiodarone should be used in patients with heart failure or decompensated states. 1

Acute Management Algorithm

Step 1: Assess Hemodynamic Stability

• If hemodynamically unstable (symptomatic hypotension, ongoing ischemia, pulmonary edema): proceed immediately to electrical cardioversion 1
• If stable: proceed with pharmacologic rate control based on underlying cardiac function 1

Step 2: Determine Heart Failure Status

For patients WITHOUT heart failure or preserved ejection fraction (HFpEF):

• IV beta blockers are recommended as first-line therapy 1
  • Metoprolol: 2.5-5 mg IV bolus over 2 minutes, up to 3 doses 1
  • Esmolol: 500 mcg/kg IV bolus over 1 minute, then 50-300 mcg/kg/min infusion 1, 2
  • Propranolol: 1 mg IV over 1 minute, up to 3 doses at 2-minute intervals 1
• Alternative: IV nondihydropyridine calcium channel blockers (diltiazem, verapamil) 1
• Exercise caution with hypotension 1

For patients WITH heart failure (reduced ejection fraction):

• IV digoxin or IV amiodarone are recommended as first-line agents 1, 3
• Digoxin: 0.25 mg IV every 2 hours up to 1.5 mg total loading dose 4
• Amiodarone: 300 mg IV over 30-60 minutes, then 900 mg IV over 24 hours 4
• AVOID beta blockers and calcium channel blockers in decompensated heart failure, overt congestion, or hypotension (Class III: Harm) 1, 3, 5

Step 3: Special Clinical Scenarios

Atrial fibrillation with gross volume overload/decompensated HF:

• Use IV digoxin or IV amiodarone only 3, 5
• Beta blockers and calcium channel blockers are contraindicated (Class III: Harm) as they can precipitate cardiogenic shock 1, 5
• Address volume status with diuresis while controlling rate 5

Atrial fibrillation with mild hypotension:

• IV amiodarone is preferred due to lower risk of worsening hypotension compared to beta blockers or calcium channel blockers 4
• Verify degree of hypotension; systolic BP <90 mmHg requires cardioversion rather than pharmacologic rate control 4

Pre-excitation syndromes (WPW with AF):

• AVOID digoxin, calcium channel blockers, and IV amiodarone (Class III: Harm) as they may accelerate ventricular response and cause ventricular fibrillation 1

Rate Control Targets

• Lenient rate control: resting heart rate <110 bpm is reasonable as initial approach in asymptomatic patients with preserved LV function 1
• Strict rate control: 60-80 bpm at rest, 90-115 bpm during moderate exercise for symptomatic patients 4
• Assess heart rate control during exercise and adjust therapy to keep rate in physiological range 1

Long-Term Oral Management

First-line oral agents:

• Beta blockers (metoprolol 25-100 mg BID, atenolol 25-100 mg daily) 1, 6
• Nondihydropyridine calcium channel blockers for HFpEF 1
• Digoxin for sedentary patients or those with HF 1

Combination therapy:

• Digoxin plus beta blocker (or calcium channel blocker in HFpEF) is reasonable to control both resting and exercise heart rate 1

Refractory cases:

• Oral amiodarone may be considered when other agents fail (Class IIb) 1
• AV node ablation with ventricular pacing is reasonable when pharmacologic therapy is insufficient or not tolerated 1
• Never perform AV node ablation without first attempting pharmacologic rate control (Class III: Harm) 1

Critical Considerations for Tachycardia-Induced Cardiomyopathy

• Sustained uncontrolled tachycardia can cause reversible LV dysfunction (tachycardia-induced cardiomyopathy) 1, 7, 8
• LV function typically improves within 6 months of adequate rate or rhythm control 1, 7, 8
• For suspected tachycardia-induced cardiomyopathy, either aggressive rate control or rhythm control strategy is reasonable 1, 3
• Recurrent tachycardia after initial recovery causes rapid decline in LV function (within 6 months vs. years for initial development) and carries risk of sudden death 8
• Long-term follow-up is essential even after recovery 7, 8

Common Pitfalls to Avoid

• Never use beta blockers or calcium channel blockers in decompensated heart failure - this can worsen hemodynamics and precipitate shock 1, 5
• Never use digoxin, calcium channel blockers, or IV amiodarone in pre-excitation with AF - risk of accelerated ventricular response and ventricular fibrillation 1
• Do not rely on digoxin alone for acute rate control - onset is delayed 60 minutes to 2 hours 4
• Do not overlook tachycardia-induced cardiomyopathy - requires different management approach and has risk of recurrence 3, 7, 8
• Do not delay cardioversion in hemodynamically unstable patients while attempting pharmacologic rate control 1