What is the initial management and diagnosis for patients presenting with tachycardia (rapid heart rate) or bradycardia (slow heart rate), including the use of electrocardiogram (ECG)?

From the Guidelines

The initial management of patients with tachycardia or bradycardia begins with a rapid assessment of hemodynamic stability while simultaneously obtaining a 12-lead electrocardiogram (ECG) to guide diagnosis and treatment. For unstable patients with tachycardia (heart rate >100 beats per minute) presenting with hypotension, altered mental status, chest pain, or heart failure, immediate synchronized cardioversion starting at 100-200 joules is indicated 1. In stable tachycardia, management depends on the specific rhythm identified on ECG. Narrow complex tachycardias like supraventricular tachycardia may be treated with vagal maneuvers followed by adenosine (6 mg rapid IV push, followed by 12 mg if needed). Atrial fibrillation may require rate control with beta-blockers (metoprolol 5 mg IV) or calcium channel blockers (diltiazem 0.25 mg/kg IV).

Key Considerations

• For bradycardia (heart rate <60 beats per minute) with hemodynamic compromise, atropine 0.5 mg IV every 3-5 minutes up to 3 mg total is the first-line medication, as indicated by the 2018 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay 1.
• If atropine is ineffective, transcutaneous pacing, dopamine infusion (2-10 mcg/kg/min), or epinephrine infusion (2-10 mcg/min) may be necessary.
• The ECG is crucial for diagnosis, helping differentiate between sinus tachycardia, atrial fibrillation, atrial flutter, ventricular tachycardia, sinus bradycardia, heart blocks, and other arrhythmias, as emphasized in the 2019 guideline 1.
• This differentiation is essential because treatment strategies vary significantly based on the underlying rhythm.

Additional Factors to Consider

• While managing the acute presentation, it's important to identify and address potential causes such as electrolyte abnormalities, medication effects, hypoxia, or myocardial ischemia.
• An abnormal initial ECG is predictive of adverse outcomes in patients presenting with syncope and near syncope, in large part as an indicator of underlying structural heart disease or the presence of systemic disease, as noted in the 2019 guideline 1.

From the FDA Drug Label

Bradycardia Bradycardia, including sinus pause, heart block, and cardiac arrest have occurred with the use of metoprolol. Patients with first-degree atrioventricular block, sinus node dysfunction, or conduction disorders may be at increased risk. Monitor heart rate and rhythm in patients receiving metoprolol. If severe bradycardia develops, reduce or stop metoprolol

• The initial management for patients presenting with bradycardia includes monitoring heart rate and rhythm.
• If severe bradycardia develops, the management includes reducing or stopping the medication, in this case, metoprolol.
• The use of electrocardiogram (ECG) is implied as part of monitoring heart rate and rhythm.
• For tachycardia, the label does not provide direct information on initial management. 2

From the Research

Diagnosis of Tachycardia and Bradycardia

• The diagnosis of tachycardia and bradycardia can be made using a 12-lead surface electrocardiogram (ECG) 3.
• The ECG is of great importance for the diagnostics of cardiac arrhythmias, with a sensitivity and specificity for the correct diagnosis of supraventricular tachycardia or ventricular tachycardia of more than 95% 3.
• Bradycardia is defined as a heart rate of less than 50-60 bpm, and can be observed as a normal phenomenon in young athletic individuals, and in patients as part of normal aging or disease 4.

Initial Management of Tachycardia and Bradycardia

• The initial management of patients presenting with tachycardia or bradycardia includes the use of vagotonic physical maneuvers, such as the Valsalva maneuver or carotid massage 5, 6.
• Adenosine is a useful medication for the treatment of supraventricular tachycardia, and can be used as a first-line treatment in hemodynamically stable patients 5, 7, 6.
• In hemodynamically unstable patients, immediate electrical cardioversion is indicated 5, 6.

Role of ECG in Diagnosis and Management

• The ECG is essential for the diagnosis and management of tachycardia and bradycardia, and should be used in conjunction with clinical evaluation and other diagnostic tests 3, 6.
• The ECG can help to identify the underlying cause of the arrhythmia, and guide treatment decisions 3, 6.
• Continuous ECG monitoring is recommended during the administration of adenosine or other anti-arrhythmic medications 7.