Asymptomatic Bradycardia

[Fire Nurse 39]

90 yoF presents to ER by ambulance with asymptomatic brady. 911 call prompted by "feeling off" so her son checked her heart rate. EMS patches to receiving hospital with confirmation of asymptomatic bradycardia with a heart rate of 22 wide complexes, blood pressure 160 palp. Requests to deviate protocol and give atropine denied by physician due to asymptomatic.

Patient arrives and it's exactly as it sounds. Confirmed HR in low 20's without treatment and a blood pressure of 176/48! Rhythm presents as 2nd degree mobitz II. Relatively no cardiac history with exception of some hypertension and hyperlipidemia. Relatively no other medical complaints. ER treats with dopamine drip maxed at 20 mcg/kg/minute which raised HR to 34, 1 Liter NSS and continuation of monitoring. Admission orders continue dopamine drip and fluids and an echo to be performed.

Discussion:

What's the lowest HR you've seen in a conscious patient? How about lowest in an asymptomatic?

What are your states protocols? Can you give atropine if asymptomatic?

What other treatment options can you think of?

What are your theories for cause of this?

 

[Gurby]

Would really like to see a 12-lead...

I'm interested by the fact that she apparently has no cardiac history, and is in a wide complex 2nd degree AV block. It seems possible that she had / is having a cardiac event of some sort, maybe an infarct affecting the AV node and/or some other part of the conduction system. Worth remembering that women often present atypically when having an MI compared to the chest pain/etc that you see with men.

Also just a random thought, hypertension with widened pulse pressure + bradycardia... Reminiscent of Cushing reflex. I doubt this is the case, but it's the first thing that comes to mind after seeing those vital signs. Something cardiac seems a lot more likely to me.

Could also be an electrolyte issue.

 

[STXmedic]

Interesting. Why did the ED opt to treat her, vs just admission for cards?

The lowest heart rate I've seen conscious with a pulse was 18-20, but she was having recurrent syncopal episodes while supine. When she was awake, she could hold regular conversations though.

The lowest asymptomatic bradycardia I've seen was around 26bpm, which was actually a bradycadic, variable A flutter. She didn't have any complaints and had actually called us for her mother. Her mother got us to check the caller because she had been saying she felt more tired than usual over the last few days. I didn't treat her other than putting pads on her.

I personally regularly run as low as the mid 30s.

We don't have state protocols. Under the protocols I work under, I certainly could give it if I deemed necessary- but if they were asymptomatic I doubt I would. There are guys much smarter than me with fellowships under their belt that these patients can see.

As to your patient, my first thought was a ventricular escape rhythm, since it was reported to be wide-complex in that range. Possibly a sick sinus or sinus arrest.

 

[STXmedic]

I must have missed reference to a 2* block...

 

[Fire Nurse 39]

Electrolytes were pretty good, potassium of 3.3 and everything else WNL or just a hairline off.

ED treated after calling admitting cardiologist who advised the dopamine (so treated by admitting intensivist - just in ER).

As for Cushing's, good point to remember. All neurologic functions remained at baseline as per patient's family. We had questioned as well - no falls/trauma's and no thinners. If the patient was hypertensive with a HR in 20's, imagine her systolic at 60+ beats? Very well could've blown an aneurysm.

I was also thinking some sort of atypical MI given her age and sex. Just the most bizarre thing I've ever seen. I've never done so many manual pressures on an ER patient because the machine wouldn't register the beats being so far apart. Which also led to an extended time taking them manually which the patient had trouble tolerating with the HTN.

Thanks for the input so far!

 

[Carlos Danger]

My very first call as a cleared paramedic was right at shift change on an otherwise quiet Sunday morning in the inner city for a guy in his late 40's whose implanted pacer/defibrillator was malfunctioning. We met him standing on a street corner waving us down. His HR was in the 20's (clearly the pacer wasn't working), and his only complaint was pain when the defib fired every couple of minutes. It was a short ride to the tertiary center where he'd had the device placed, and the only treatment I gave him was oxygen.

 

[Bullets]

if she says shes "feeling weird" is that really asymptomatic? I feel like unless the patient says "nothing is bothering me" that would be asymptomatic. How do you define that?

 

[Tigger]

My understanding is that atropine is not likely to be useful in Mobitz II anyways. If she's symptomatic (altered, chest pain, profound hypotension) I would pace her. Incidentally our medical director wants any third degree block paced, regardless of rate or symptoms.

 

[Nova1300]

I can't really think of a scenario in which a stable bradycardia requires pre-hospital intervention beyond placement of pads.

The mean arterial pressure is clearly sufficient to provide end-organ perfusion, let it ride and transport.

This presentation screams ischemic injury, though usually the rhythm would be a complete heart block. I have seen very few mobitz 2 patients with a ventricular rate that low.

We're that the case, that this patient (a 90yo female) was actually having an cardiac ischemia, the worst possible things you could do to her are as follows:
1. Cause tachycardia
2. Screw around with her autonomic nervous system
3. Cause delirium
Atropine will do all of those things, and well

If a 90 year old lady has that blood pressure with a heart rate of 20 and is speaking to you, I can tell you a couple things:
1. It's probably not a result of high ICP.
2. That heart is probably failing.
A 90 year old heart must still abide by the laws of physiology. That means cardiac output = heart rate x stroke volume. A stiff, century-old heart is NOT going to have a stroke volume to make up for that kind of loss in heart rate. Look at the equation again. She is going to have a low cardiac output. She is not a 30 year old athlete who can balance the equation out with stroke volume.

So why is her blood pressure high? Because her body has increased the afterload to maintain end-organ perfusion. Her systemic vascular resistance is high so her kidneys will continue to get blood flow despite this decreased output from the heart.

Atropine will cause a tachycardia against that high afterload, in a failing heart. Yuck.

In this scenario, the bradycardia is actually protective by minimizing the heart's oxygen needs. But a dose of atropine will put a swift end to that.

These patients need inotropes, hence the dopamine. He wasn't using it to increase the heart rate. He suspected that, because CO=HRxSV even in a 90 year old, that this lady was likely in heart failure and needed inotropes and an echo.

 

[mttbdtd]

One night about 3 years ago my mom calls and wakes me up. She had been taking her own bp with one of those cheap auto wrist cuffs. She checked my dads just for fun and it said his pulse was 30. I told her to palp a radial and she got somewhere around 30. I told to call an ambulance. I drove 5 hours to meet them at the hospital where I finally got some history on the situation. Looking back on it after we put the peices together he had been symptomatic for months. He is 60, medium frame, runs every day, was having erectile dysfunction and increased dizziness on standing quickly in the evenings. His 12 lead showed an obvious junctional rhythm with no signs of infarct or ischemia. His bp had stayed around 120 systolic throughout. The first ER he was in had been giving him Atropine per ACLS to no effect a nurse eventually had to almost smack the other nurse to get them to stop. Personally I don't feel a need to give anything like Atropine unless you need it. Also, a second to the post above mine hypertensive bradycardia that is not increased ICP plus atropine equals a potential disaster.

 

[mttbdtd]

Addition to my above post. He ended up with a pacemaker and was back to running daily 2 days after discharge.

 

[Code 3]

What are your states protocols? Can you give atropine if asymptomatic?

We only treat symptomatic bradycardia, which is defined as SBP < 90 and CP, SOB or ALOC.

From there, we categorize them into narrow or wide complex bradycardia and treat accordingly. For narrow complex brady we start off with fluids + atropine while for wide complex brady we do fluids + pacing. If the SBP is refractory to fluids, we can titrate dopamine to maintain SBP > 90.

What are your theories for cause of this?

I think Nova1300 hit the nail on the head – this is most likely a protective brady in an effort to decrease myocardial demand for a failing heart.

 

[Daniel G]

This might be a dumb question, but what was the GCS? I understand she's 90, but still relevant.

Was the patient alert?(i dont imagine so) Stranger things have happen.

 

[Summit]

I would not treat that with atropine. What would I hope to fix? A number? And what would the real result be and for how long?

I've seen symptomatic brady in the 20s, 30s, 40s. Lowest palpable pulse I've seen asymptomatic was 18 (sinus with bigeminal pvc couplets).

Interesting choice dopamine at the max alpha/beta. I would have thought isoproterenol and maybe a cath.

What did the cardiac enzymes show?