Case:
76 year old female, presents with lightheadedness and lethargy. She is complaining of mid-scapular pain & is syncopal at triage.
She has cold hands & clammy skin. Systolic BP 70 mmHg. Crackles to mid-zones of her chest. Distended JVP.
PMHx: AF (on metoprolol) & rheumatic heart disease (?mitral stenosis)
This is her ECG.
Narrow complex bradycardia @ 30/min. Normal axis.
No visible P-waves. QRS (narrow ~ 80msec). QTc ~430msec (Bazett). ST-segments isoelectric.
Tall, symmetrical T-waves V3-6
- Junctional Bradycardia.
- Bradycardia & peaked T-waves raising possibility of hyperkalaemia.
- No evidence of ischaemia.
Now I do like Mel Herbert’s approach to bradycardia & it’s a list I rattle off each time I see a case similar to this;
- Ischaemia (not suggestive on this ECG)
- Drugs (she is on metoprolol, 25mg BD – no suggestion of OD or self-harm).
- Potassium … ??
Also helpful is the DIES mnemonic (Drugs, Ischaemia, Electrolytes, Sick Sinus Syndrome).
This lady has a venous potassium of 6.2 mmol/L (formal later 6.4); and her ED course went as follows…
- Atropine 0.6mg IV (x2) –> some transient improvement (HR to 70, BP 105; but only for minutes at a time)
- Cautious IV fluid boluses
- I elected to treat the K+ due to those T-wave changes. (Calcium gluconate / Insulin-Dextrose / Resonium).
- Not entirely sure this made a difference…
- Cardiology insistent upon an isoprenaline infusion (which worked well for her & avoided need for temporary pacing).
- She went off to Coronary Care with warm hands and a pink face….
These are here progressive ECGs.
My thoughts on this case:
For all symptomatic & unstable bradycardias; identify & correct any possible causes…
Atropine remains first line in symptomatic bradycardia (recommended 0.5mg q3-5min to a max of 3mg) (Class IIa).
Isoprenaline vs Adrenaline
- The potential beta-2 effects on skeletal muscle vasculature (leading to further hypotension) with isoprenaline seem counterintuitive to me (particularly in this case).
- Having the beta-1 and alpha response to adrenaline seems to make more sense.
- I cannot find any overwhelming evidence to support either (either head-to-head in RCTs or otherwise).
ILCOR suggests second-line agents including; adrenaline (‘particularly if associated with hypotension’), dobutamine & isoprenaline (‘resulting in vasodilatation’).
Transthoracic Pacing
Useful for those resistant to medical therapy. Not known to have a survival benefit; but more consistent effect on heart rate.
Be kind; sedate & analgese appropriately…
If this is unsuccessful, transvenous pacing is indicated.
References.
- Neumar et al. Part 8: Adult Advanced Cardiovascular Life Support: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular …. Circulation (2010)
- DON’T LET YOUR BRADYCARDIC PATIENT D.I.E. @ medialapproach.com
