This is the feedback I gave the student on this case. (Recall that this was a young adult male who presented with dyspnea, chest pain, as well as pre-syncope, whose initial ECG showed a brisk tachycardia which went up to the 170s at points):
“As you point out, this was sinus tachycardia. When you have sinus tachycardia, you have to look for causes and treat those. I encourage you to read David Baumrindâ€™s excellent essay on this topic for a different explanation. Here’s mine.
“Sinus tachycardia can be caused by hypovolemia, cardiogenic shock, hypoxia, thyroid storm, cocaine intoxication, alcohol withdrawal, or massive pulmonary embolism. Sinus tachycardia is not an arrhythmia, itâ€™s a symptom.Â The patient is telling you â€“ through their vital signs â€“ that their body is being stressed by something. You have to figure out what this stress is, and treat that.
You (the student) did all the right things to address the sinus tachycardia; getting a history and physical to suggest causes, performing a few tests to catch things the exam didn’t reveal, and trying a few interventions (like oxygen and fluids) that can act as therapy as well as being diagnostic.
The patient had a massive PE, as well as moderate thyrotoxicosis. There was little in the exam or ECG to suggest these, so transport to the ED with supportive care was about the best you could have shot for.
The big thing to know about thyrotoxicosis and about PE Â is that adenosine doesnâ€™t help either of those.
“What is adenosine used for? For briefly blocking off the AV node from conduction when the patient has a reentrant rhythm. The most common examples of reentrant rhythms are AVRT and AVNRT, but we usually just lump them together as PSVT. Many people just shorten this to SVT, although this is sloppy medical language.
What is SVT?
â€œBut,â€ you might say, â€œthis was SVT, because it was over 150 bpm!â€ This is not true at all, and not what ACLS says.
- First off, many cases of PSVT/AVNRT/AVRT have a heart rate under 150. There are two examples at my blog â€“ go check it out!
- Second, many patients with sinus tachycardia have a HR over 150, as you well know. If they have severe symptoms, chest pain, feelings of doom, shortness of breath, whatever â€“ you have to figure out the cause, and treat it (E.g. with fluids, oxygen, intubation, benzos – whatever is appropriate for the clinical context).
Heck, when I run up from the cafeteria, my heart rate gets up over 150, just from the unexpected physical effort. The treatment isnâ€™t adenosine; I just have manyto rest for a moment! Go back and look at the ACLS chapter. It suggests that a narrow complex tachycardia is unlikely to be the primary cause of hemodynamic problems if the HR is under 150. That means, if the patient is crashing, a tachycardia of 140 (whether itâ€™s AF, PSVT, MAT, whatever) probably isnâ€™t the reason theyâ€™re crashing. I.e.; the hemorrhage/hypoxia/sepsis is the problem, not the rhythm itself. For some odd reason though, this has been profoundly misinterpreted by some in the EMS community. I assure you, no physician I know believes â€œHR > 150 means SVT.â€
Don’t block the AV node in sinus tach.
“So, this patient had a clear-cut sinus tachycardia. Adenosine was not indicated â€“ in fact it is contraindicated. Your paramedic preceptor should have been encouraging you to look for the cause of the sinus tachycardia. And it isn’t just adenosine – you don’t want to use any AV blockers in this situation.
- Metoprolol is only indicated for the treatment of sinus tachycardia in a few unique circumstances (e.g. thyroid storm).
- Calcium-channel blockers are almost never indicated in sinus tach, and the potential to harm is significant. For example, if you give diltiazem to a patient in cardiogenic shock (and sinus tachycardia), you might as well have shot them in the head. (Yes, I have seen this happen. Not good.)
Thanks anonymous student for your help with this post!
Thank you for being very open about your thinking in this case. I know that you are (were?) very proud about this case, and no one likes to hear that they were off in their judgment. However, when I’ve made mistakes in the past, I’ve endeavored to keep other folks from doing the same thing. You keep doing the same!”
â€œAn expert is a person who has made all the mistakes that can be made in a very narrow field.â€ Bohr