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Two keys to managing patients with unstable tachycardia are, first, quickly recognizing that the patient has significant symptoms and is unstable, and second, quickly recognizing that the patient's signs and symptoms are caused by the tachycardia. You need to decide if the tachycardia is producing the hemodynamic instability and serious signs and symptoms or if the signs and symptoms are producing the tachycardia—for example, the pain and distress of an acute MI could be causing the tachycardia. Making this decision can be difficult. Generally, a heart rate between 100 bpm and approximately 130 bpm is usually caused by an underlying process that is represented as sinus tachycardia (see Stable Tachycardia module for more information on sinus tachycardia). Heart rates > 150 bpm may be symptomatic. The higher the rate, the more likely the symptoms are a result of the tachycardia. Underlying heart disease or other problems can cause symptoms at lower heart rates. Keep in mind the following considerations:

• If the patient is seriously ill or has cardiovascular disease, the patient may have symptoms at lower rates.
• If the patient's heart rate is above 150 bpm and the patient is unstable (has symptoms), cardioversion is often required.
• Sinus tachycardia is usually a response to an underlying condition that creates a need for increased cardiac output. Sinus tachycardia does not respond to cardioversion, and a shock may actually increase the patient's heart rate.
• Atrial flutter typically has a heart rate of 150 bpm, but it is often stable for a patient who does not have heart disease or other serious conditions.

Overview

The ACLS Tachycardia Algorithm is organized around the following four questions:

If the patient does not have a pulse and his or her rhythm is a tachycardia, follow the ACLS Pulseless Arrest Algorithm.

If a pulse is present, answer these three questions to help determine treatment options for tachycardia:

1. Does the patient have a pulse?
• If the patient does not have a pulse and his or her rhythm is a tachycardia, follow the ACLS Pulseless Arrest Algorithm.
• If a pulse is present, answer these three questions to help determine treatment options for tachycardia:
2. Is the patient stable or unstable?
3. Is the QRS wide or narrow?
4. Is the ventricular rhythm regular or irregular?

Steps

Does the patient have a pulse?

If yes:

Assess the patient using the primary and secondary surveys:

1. Check airway, breathing, and circulation.
2. Give oxygen and monitor oxygen saturation.
3. Get an ECG.
4. Identify rhythm.
5. Check blood pressure.
6. Identify and treat reversible causes.

Is the patient stable?

Look for altered mental status, ongoing chest pain, hypotension, or other signs of shock.

Remember: rate-related symptoms are uncommon if heart rate is less than 150 bpm.

If the signs and symptoms continue after you have given oxygen and supported the airway and circulation AND if significant symptoms are due to the tachycardia, then the tachycardia is UNSTABLE and immediate cardioversion is indicated.

If you determine that the patient has an unstable tachycardia, perform immediate synchronized cardioversion.

1. Start an IV.
2. Give sedation if the patient is conscious.
3. Do not delay cardioversion.
4. Consider expert consultation.

If you determine that the patient has a stable tachycardia, start an IV and obtain a 12-lead ECG.

For a patient with a stable tachycardia, decide if the QRS complex is wide or narrow and if the rhythm is regular.

Does the patient's rhythm convert? If it does, it was probably reentry supraventricular tachycardia. At this point you watch for a recurrence. If the tachycardia resumes, treat with adenosine or longer-acting AV nodal blocking agents, such as diltiazem or beta-blockers.

If the rhythm pattern is irregular narrow-complex tachycardia, it is probably atrial fibrillation, possible atrial flutter, or multi-focal atrial tachycardia.

You may not always be able to tell from the ECG whether the rhythm is ventricular or supraventricular. Most wide-complex tachycardias originate in the ventricles (particularly if the patient is older or has underlying heart disease). If the patient does not have a pulse, treat the rhythm as ventricular fibrillation and follow the Pulseless Arrest Algorithm.

If the patient is unstable and has a wide-complex tachycardia, assume the rhythm is VT until you can prove otherwise.