Narrow complex tachycardia assessment, treatment

SVT is a general term for all narrow complex tachycardias, but it is important to perform a 12-lead ECG to determine the exact underlying rhythm

Article updated July 24, 2017

You are transporting a 36-year-old male who complained of a racing heart (read the EKG case) for about 30 minutes prior to your arrival. He was not in distress, had a weak, thready radial pulse of 146, respiratory rate of 20, BP of 106/65 and had no pain.

Upon obtaining a 12-lead EKG, you noted that he had a narrow complex tachycardia without ectopy that was unresponsive to a valsalva maneuver and vagus stimulation. After contacting medical control, you administered 6mg of adenosine with a conversion to sinus tachycardia without ectopy. The patient is resting comfortably on 4 lpm of oxygen via nasal cannula and you'll arrive at the hospital in less than 10 minutes.

The EKG Club experts created this case for these learning objectives: 

  • Basic: Recognition of narrow complex tachycardia.
  • Intermediate: Identifying the range of therapies available to treat this rhythm (e.g. valsalva, drugs).
  • Advanced: Awareness of possible contraindications to adenosine and the co-administration of adenosine. Being prepared for that period of "asystole" that often occurs during treatment.

The first EKG shows a regular, narrow-complex tachycardia at 143 bpm. The broad term for these rhythms is supraventricular tachycardia which, if analyzed, only means a rhythm originating above the ventricles that has a rate of more than 100 bpm. Although many rhythms fall into this category and it is correct to label all as "supraventricular tachycardia," some distinctions are in order. Note the regularity of the rhythm and the seeming lack of P waves. On a closer look, you may see retrograde P waves following the QRS on leads I and V1-V5.

While using the general term of supraventricular tachycardia (SVT) for all narrow complex tachycardia is common, it is important to perform a 12-lead EKG and determine the exact rhythm that you are dealing with.

The American Heart Association guidelines recommend different treatment modalities based on the specific rhythm. It is important for EMS professionals to understand the pacemaker location as well as the conduction pathways that are in use for any tachycardia.

There are two primary reasons to consider:

  1. The best drug for one rhythm may prove to be deadly for the next rhythm.
  2. There are different causes for different rhythms. Using the wrong medication will not correct the problem and in some cases using any of the medications you have available may only make matters worse.

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