The Tachycardia with a Pulse Algorithm

Assessing Appropriateness for Clinical Condition

In the tachycardia algorithm, the first box asks the clinician to assess whether the heart rate is appropriate for the patient’s clinical condition. A useful term is relative tachycardia, an increase in heart rate above what one might expect for a given condition. 

For example, a patient’s body in shock increases the heart rate to counteract low blood pressure. Thus, in conditions such as shock, a heart rate greater than 90 beats per minute is considered tachycardia.²

There is a lower threshold for treating tachycardia in patients experiencing myocardial infarctions, as tachycardia can result in an increased workload on the heart and increased myocardial oxygen demand. 

If a clinician allows a patient’s heart to remain fast, it can lead to increased heart damage. Therefore, while a heart rate of 110 beats per minute would not be a cause for concern in most patients, it could be very detrimental for someone experiencing acute myocardial infarction.

Fever also increases heart rate. The relationship is an independent one. For every one degree rise in temperature (Celsius), there is an increase in heart rate of approximately 10 beats per minute. A clinician should not be alarmed to see a heart rate of 110 beats per minute in an adult with fever, yet a heart rate of 160 beats per minute should lead the clinician to suspect something else is occurring.

Assess whether the heart rate is appropriate for the patient’s clinical condition. Fever can increase heart rate.

In most tachyarrhythmias, the heart rate will be greater than 150 beats per minute and can be much higher.

Read: Assessing Appropriateness for Clinical Condition

Identify and Treat the Underlying Cause

Next, the clinician must do a rapid evaluation of the patient’s airway, breathing, and circulation. The clinician will ensure the airway is open and the breathing efforts are adequate.

The patient should be placed on a cardiac monitor to assess oxygenation, blood pressure, and cardiac rate and rhythm. Hypoxia will increase heart rate, so supplemental oxygen should be provided to a patient with an oxygen saturation less than 90%. 

A clinician may choose to gain IV access at this point as well.

Related Video – Hs and Ts – Hypoxia

Persistent Tachyarrhythmia Causing Serious Signs and Symptoms

Next, the clinician assesses whether the tachycardia is persistent and whether it is causing serious signs and symptoms such as chest pain, heart failure, altered mental status, low blood pressure, or signs of shock. Is the patient stable or unstable? The clinician will use all the data gathered thus far to make this important determination.

Is the patient stable or unstable? If the patient is unstable, the clinician must correct the abnormal rhythm immediately.

If the patient has persistent tachyarrhythmia causing serious signs and symptoms, the abnormal rhythm must be treated immediately. It is essential to stop the abnormal rhythm to prevent further deterioration in the patient’s condition, and the treatment is synchronized cardioversion.³

If the patient is hemodynamically stable, adenosine can be considered.

Synchronized Cardioversion

Defibrillation and synchronized cardioversion differ in when the shock can be delivered during the cardiac cycle. During defibrillation, the shock may be applied at any time during the cardiac cycle and is meant to “stun” the heart, so the heart’s normal pacemaker can take over. 

During synchronized cardioversion, the electrical shock is delivered at a specific point in the cardiac cycle — the peak of the R-wave in the QRS complex. This administration avoids a delivery of energy on the T-wave, which could cause ventricular fibrillation. Synchronized cardioversion uses a much lower energy dose than defibrillation.⁴

Synchronized cardioversion is a low energy shock delivered at the peak of the QRS complex.

Patients requiring synchronized cardioversion should be sedated if possible. The patient requiring defibrillation is essentially dead. The patient is beyond experiencing pain during defibrillation. 

A patient with unstable tachycardia, however, is more than likely awake and quite capable of feeling the pain of shock delivery. Very unstable patients may not be able to wait the several minutes it takes to draw up, administer, and wait for the drugs to take effect. 

Intravenous access is required to sedate the patient. It is wise to have an intravenous in place before providing synchronized cardioversion, as there is always a small risk of deterioration into a more lethal rhythm such as pulseless ventricular tachycardia or ventricular fibrillation.

The steps to performing synchronized cardioversion:

1. Obtain IV access and sedate the patient when feasible (unless the patient is very unstable and/or rapidly decompensating).
2. Turn on the monitor.
3. Attach the monitor leads to the patient’s chest and ensure the rhythm is being displayed correctly; place the defibrillation pads on the patient’s chest, making sure they are not overlying the monitor leads. If the patient is small, consider anterior-posterior placement of the pads.
4. Press the SYNC button on the monitor and watch for a marker at the peak of each R-wave. Adjust gain as necessary if markers do not appear.
5. Choose the appropriate energy level by referring to the recommendations of the device manufacturer. Note: if the rhythm is unstable polymorphic VT, treat as VF and defibrillate (unsynchronized cardioversion).
6. Inform others around the patient that shock is imminent (“clear” the patient).
7. Press the CHARGE button on the monitor.
8. Clear the patient once more.
9. Press the SHOCK button.
10. Evaluate the rhythm. If the rhythm persists, increase the energy level as recommended in a stepwise fashion.

NOTE: Most monitors will DEFAULT BACK TO THE UNSYNCHRONIZED (defibrillation) MODE, so the clinician must press the SYNC button should they need to attempt synchronized cardioversion a second time.

Related Video – Synchronized Cardioversion for Tachycardia

Adenosine

Adenosine is a naturally occurring drug used to treat specific narrow-complex tachycardias, such as paroxysmal supraventricular tachycardia (PSVT), AV nodal reentrant tachycardia (AVNRT), and AV reentrant tachycardia (AVRT).⁵

Adenosine is not the treatment of choice for hemodynamically unstable patients with tachycardia. In those patients, synchronized cardioversion is the required intervention. 

Adenosine can be highly effective in terminating some tachyarrhythmias. It has a very short half-life, making it tricky to administer. The half-life is seconds, so it is essential the clinician administers this drug in an IV site as close to the heart as possible. It should be given as rapidly as possible, followed by a 20 ml bolus of normal saline to facilitate its entry into central circulation. 

It may cause unpleasant sensations in patients, and the clinician should warn them ahead of time. Patients may have chest pain, dizziness, and an impending sense of doom since adenosine actually causes a brief, unpleasant period of asystole. It is administered as a 6 mg IV bolus and may be followed up with an additional 12 mg bolus if the first dose does not convert the tachyarrhythmia.

Adenosine can be highly effective in terminating some tachyarrhythmias.⁶

Related Video – Adenosine – ACLS Drugs

Persistent Tachyarrhythmia Not Causing Serious Signs and Symptoms

If a patient has persistent tachycardia but tolerates the rhythm well and does not show any serious signs or symptoms, such as shock or hypertension, the clinician should determine whether the QRS complex is wide (> 0.12 seconds) or narrow (< 0.12 seconds). 

A 12-lead ECG can provide a lot of valuable information, so the clinician should order one at this stage. The clinician should also obtain IV access at this point if not yet obtained.

Related Video – Introduction to ECG Interpretation

Medications for Stable Wide Complex Tachycardias

Adenosine is a treatment option for hemodynamically stable patients with monomorphic and regular wide-complex tachycardias.⁷ For patients with irregular or polymorphic wide-complex tachycardias, the clinician may consider an antiarrhythmic, such as procainamide or amiodarone. Both are administered as infusions. Intravenous sotalol is also an option; it is given slowly over five minutes.

Medications for Stable Narrow Complex Tachycardias

There are several treatment options for hemodynamically stable patients with stable narrow-complex tachycardia. Vagal maneuvers should be tried first. Adenosine may be used if the rhythm is regular. Beta-blockers and calcium channel blockers are an option for narrow complex tachyarrhythmias when adenosine and vagal maneuvers do not work.

Related Video – Beta Blockers – ACLS Drugs

Expert Consultation

If the patient is stable and not displaying any worrisome signs or symptoms, there is time for a clinician to consult a specialist, such as a cardiologist, to make a treatment recommendation. It’s never wrong to seek expert consultation, particularly for arrhythmias with no known cause or for rhythms that have been refractory to treatment modalities.

A Word About Vagal Maneuvers

Vagal maneuvers are used to increase vagal tone and slow the heart rate. They can be an option in rapid rhythms, slowing the heart rate enough to diagnose the rhythm. 

In some cases, such as PSVT, vagal maneuvers may abort the arrhythmia. The most commonly used vagal maneuvers are carotid massage (which should only be performed by an expert) and Valsalva maneuvers, such as bearing down against a closed glottis.

Some patients who have frequent episodes of SVT will learn how to abort their own episodes, though they may recur. The self-administration buys the patient time to get to a hospital emergency department.

Conclusion

Tachycardia is present in any patient with a heart rate above 100 beats per minute, and a clinician must diagnose the tachycardia’s severity dependent on the patient’s current or ongoing medical conditions. A tachyarrhythmia should be seriously considered for a patient with a sustained HR > 150 bpm.

Synchronized cardioversion is the treatment for any patient with a pulse and tachycardia who demonstrates signs and symptoms of hemodynamic instability.

When treating hemodynamically stable patients with tachycardia, the clinician must determine whether the QRS complex is narrow or wide, regular or irregular, and monomorphic or polymorphic. That information determines the next steps in medical management. Expert consultation with a cardiologist is always advised if the patient’s clinical condition grants the time to do so.

Related Video – Adult Tachycardia With a Pulse Algorithm