Metoprolol Use for Tachycardia: Heart Rate Thresholds

Heart Rate Thresholds for Metoprolol Use

Tachycardia is defined as a heart rate >100 beats per minute, but clinical significance typically occurs at higher rates 1, 2
Heart rates ≥150 beats per minute are more likely to be attributable to an arrhythmia rather than a physiologic response 1
When heart rate is <150 beats per minute, symptoms of instability are unlikely to be caused primarily by the tachycardia unless there is impaired ventricular function 1

Avoid use in patients with asthma, obstructive airway disease, decompensated heart failure, and pre-excited atrial fibrillation or flutter 3, 4
Use with caution in patients with AV block greater than first degree or sinus node dysfunction (in absence of pacemaker) 5

For intravenous administration: 5 mg over 1 to 2 minutes, repeated as required every 5 minutes to maximum dose of 15 mg 6, 3
For oral administration: Starting with 25-50 mg daily, with maintenance doses up to 200 mg BID for metoprolol tartrate or 400 mg daily for metoprolol succinate 5

Effective for narrow-complex supraventricular tachycardias (SVT) 3, 4
Useful for controlling ventricular rate in atrial fibrillation or atrial flutter 3, 4

First, determine if tachycardia is the primary cause of symptoms or secondary to an underlying condition 1
Assess for and correct hypoxemia, which is a common cause of tachycardia 1
For heart rates ≥150 beats per minute with symptoms of instability, consider metoprolol if no contraindications exist 1, 3
For heart rates <150 beats per minute, metoprolol may still be considered if there is evidence of impaired ventricular function or if the tachycardia is symptomatic 1
The American College of Cardiology recommends considering synchronized cardioversion for hemodynamically unstable patients with tachycardia when pharmacologic therapy is ineffective or not feasible 7, 8

The American College of Cardiology recommends vagal maneuvers as the first-line treatment for hemodynamically stable patients with SVT, including AVNRT, which is the most common form of SVT 9, 10
AVNRT commonly occurs in young adults without structural heart disease and can be provoked by alcohol consumption 9

Oral beta blockers, including metoprolol, may be reasonable for acute treatment in hemodynamically stable patients with AVNRT, with a Class IIb recommendation 9, 10
The American College of Cardiology notes that oral beta blockers have a lower class of recommendation compared to IV formulations, but remain a viable option when IV access is not immediately available or preferred 9, 10

Absolute contraindications to metoprolol include decompensated heart failure or acute heart failure exacerbation 9
Severe bronchospastic disease or active asthma exacerbation is also a contraindication to metoprolol 10
The American College of Cardiology advises against using beta blockers in patients with underlying bronchospastic pulmonary disease without first correcting hypoxia 9, 10

If metoprolol is contraindicated or ineffective, calcium channel blockers, such as diltiazem or verapamil, are preferred as Class I recommendations for ongoing AVNRT management 10