This is the conclusion to our case 24 year old male: "Anxiety Attack". Be sure to read Part I before the conclusion!
When we left off, our providers were on scene with a young man, in custody, who was pale and had a radial pulse too fast to count. A narrow complex tachycardia was present on the monitor to which our patient helpfully pointed out, "it's SVT".
Let's find out if our patient is right!
The initial rhythm strip shows a regular, narrow complex tachycardia at approximately 200 bpm. Differentials include SVT (e.g. AV Nodal Reentrant Tachycardia and Orthodromic AV ReciprocatingTachycardia), atrial tachycardia, atrial flutter, and atrial fibrillation. However, given the rate, it would seem unlikely to be flutter, and given the near dead-on regularity it excludes atrial fibrillation.
The 12-Lead ECG confirms much of what we saw in the initial rhythm strip. We have a regular, narrow complex rhythm at 200 bpm. Retrograde P-waves are appreciable in leads II, III, aVF, and V1. These P-waves are often termed pseudo-S or pseudo-R' waves, and are most commonly seen in AVNRT. However, ST-elevation in aVR during SVT is a sign of orthodromic AVRT.
Regardless of mechanism, it is safe to say that our patient was right! He is currently experiencing SVT.
The treating paramedic also came to this conclusion and began treatment by lying the patient down and attempting vagal maneuvers. The patient was coached to bear down and then to blow through an empty 10 cc syringe, both without effect:
An 18 gauge IV was established in the left antecubital fossa. 6 mg of adenosine was then administered rapid IV push followed by a 20 cc normal saline bolus flush. The following was captured:
This rhythm strip shows an interruption in the AV nodal reentry circuit with a conversion to a sinus tachycardia.
A repeat 12-Lead was obtained by the crew:
The post-conversion 12-Lead shows a sinus rhythm without delta waves, epsilon waves, or acute ST/T-wave changes. The computerized interpretation notes a short PR interval of 98 ms, however, this author reads the PRi as normal at ~120ms. If an accessory pathway is present, conduction is concealed on the patient's baseline 12-Lead.
The patient was transported by the crew without incident and was lost to follow-up by EMS. However, this case shows that sometimes our patients will know exactly what is wrong, which underscores the importance of obtaining a good history.
- What conditions could this patient have which caused his SVT?
- What treatments may this patient receive if he continues to suffer from SVT?