Editor’s note: We asked columnist Tom Bouthillet to pick a winner to this month’s challenge and he wrote: “For this month’s column I chose CW. He really knows his stuff! It takes a real ECG geek to differentiate between AVNRT and orthodromic AVRT! He even pointed out some features that I hadn’t mentioned. Namely, the pseudo-R in lead V1 and pseudo-S in lead II. Get this guy (or gal) his own column STAT! Seriously, though. Good job and enjoy the bottle opener and t-shirt!” Read their diagnoses in the comment block.
Haven’t read the initial case presentation? Read: ECG Challenge: Es muy rapido
Let’s take another look at the patient’s 12-lead ECG.
Here is the computerized interpretation.
This 12-lead ECG shows a narrow complex tachycardia. The first step when evaluating a narrow complex tachycardia is to determine whether or not the rhythm is regular or irregular. The second step is to determine whether or not the patient is stable or unstable.
This is not always simple or straight forward. For example, at very fast rates atrial fibrillation can give the illusion that the rhythm is regular. In addition, it’s not enough to say that a patient is unstable! You have to ask yourself a question that is even more important.
Is the instability causing the tachycardia or is the tachycardia causing the instability?
Consider these comments from the 2010 AHA ECC Guidelines:
“In both unstable and symptomatic cases the provider must make an assessment as to whether it is the arrhythmia that is causing the patient to be unstable or symptomatic. For example, a patient in septic shock with sinus tachycardia of 140 beats per minute is unstable; however, the arrhythmia is a physiologic compensation rather than the cause of instability. Therefore, electric cardioversion will not improve this patient’s condition. Additionally, if a patient with respiratory failure and severe hypoxemia becomes hypotensive and develops a bradycardia, the bradycardia is not the primary cause of instability. Treating the bradycardia without treating the hypoxemia is unlikely to improve the patient’s condition. It is critically important to determine the cause of the patient’s instability in order to properly direct treatment. In general, sinus tachycardia is a response to other factors and, thus, it rarely (if ever) is the cause of instability in and of itself.”1
In this case the patient appeared to be relatively stable. There was no obvious underlying cause for the patient’s tachycardia. Hence, the treating paramedic attempted vagal maneuvers. However, perhaps due to the language barrier the patient was not particularly cooperative and they were unsuccessful.
An 18 G IV was established and 0.9% normal saline was run wide open. 6 mg adenosine was given rapid IV push. Wisely, the treating paramedic pressed the PRINT button prior to administering the drug.
The patient converted to normal sinus rhythm.
Since the 12-lead ECG electrodes were already placed it was a simple matter to push the 12-lead button again.
A little bit of ST-depression immediately following conversion of a tachycardia is not particularly troublesome. The fact that 6 mg of adenosine successfully converted this regular narrow complex tachycardia to sinus rhythm suggests that it was a reentrant tachycardia, most likely AV nodal reentrant tachycardia (AVNRT).
This call was very well executed by the EMS crew. They documented the patient’s tachycardia in 12 leads prior to treatment, considered possible underlying causes, remembered to push the PRINT button prior to giving the adenosine, converted the rhythm to sinus, and then captured a post-conversion 12-lead ECG.
It doesn’t get much better than that!
Reference:
Part 8: Adult Advanced Cardiovascular Life Support: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Circulation. 2010;122:S729-S767
