Understanding Digoxin

 Most of us have heard of, or encountered a patient taking Digoxin at some point in our carreers. But, do we understand what it is and how it affects our patient?
 

 Digoxin (Lanoxin), is a Cardiac Glycoside, derived from the foxglove plant, Digitalis. This medication is often seen in the pre-hospital setting, used for the treatment of:

 

  •  Heart Failure (HF) with reduced Systolic Function

 

  • Atrial Fibrillation (AF) and Atrial Flutter (A-flutter) associated with Rapid Ventricular Response (RVR)

 

  • Cardiomyopathies

 

  • Often combined with Calcium and Beta Channel Blockers, Angiotensine Receptor Blockers (ARBs) and diuretics

 

 Why does the rate matter?

 Well, as ventricular rates increase, ventricular filling times (Preload) during rest (Diastole) decrease. This can lead to reduced Stroke Volume (SV) and Cardiac Output (CO). This decrease in CO can lead to further complications like Reflex Tachycardia (further increasing oxygen demand), Chest Pain, Dyspnea and other related symptoms.

 

Remember the basics?

 

 

CO = SV x HR
 

 

Digoxin pharmacology:

 

  •  Inhibition of Sodium (Na+) Potassium (K+) ATPase Pump  leads to increased Na+ and decreased K+ intracellular

 

  •  This increased intracellular Na+ influx then triggers Calcium (Ca+) channels to open and increase Ca+ influx, while at the same time, some Na+ is removed from the cell

 

  •  Since Ca+ is responsible for increased contractility (Positive Inotropic effect), there is an increased myocardial contractility leading to greater CO without increased Myocardial Oxygen Consumption (MVO2)

 

  •  Slight Parasympathetic stimulation leads to reduced AV Nodal conduction which leads to increased Preload, improving Stroke Volume (SV) and CO, however, it can lead to decreased Pulse Rate since there is a decrease of impulses entering the ventricles

 

***Digoxin has a prolonged Half-life, between 35-40 hours average, which in the patient with decreased kidney function or metabolism, increases the Bioavailability (the amount of medication available in the bloodstream for use) which will lead to cardiac toxicity.***

***Digoxin also has a narrow Therapeutic Index (the gap between good treatment and toxic effect) which leads to the cardiac toxicity.***

 

 

Digoxin and ECG changes:
 

 

 

  •  ST segment “scooping”, similar to an ice cream scoop shape, with a rounded negative ST segment. This is also know as "Reverse Check" or "Reverse Tick"

 

  • Atrial arrhythmias like AF with slow RVR

 

  • Junctional, Accelerated Junctional and Junctional Tachycardias

 

  •  Decreased AV Nodal conduction can lead to AV blocks and Ventricular Escape Beats since the above conduction is delayed

 

  •  Bi-directional Ventricular Tachycardia (BVT) which is seen as alternating ventricular beats,  e.g.  LBBB pattern beat followed by a RBBB pattern beat which continue alternating.

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EMS 12-Lead

Cardiac Rhythm Analysis, 12-Lead ECG Interpretation, Resuscitation
Comments
Brooks Walsh MD
“Bad heartburn” – 82 y.o. female without chest pain.
The option was indeed turned on! As for non-CP presentations of ACS, I absolutely believe that these warrant the same level of urgency as the "typical" presentations. Both men and women, young and old, all commonly present without classic chest pain. Besides, how much difference is there between "burning in the epigastrium," and "pain in…
2014-08-21 17:10:37
Austin
“Bad heartburn” – 82 y.o. female without chest pain.
You took the words right off of my keyboard, Jason! A little bit of critical thinking works wonders when faced with "protocol versus best interests of the patient" type decisions. Not to encourage deviation from protocols and such, but it is a much less severe trespass if you bend the rules a bit as long…
2014-08-21 16:33:27
Brooks Walsh MD
“Bad heartburn” – 82 y.o. female without chest pain.
My uninformed opinion? I pretty much agree with AHA - if they aren't hypoxic, no need. I'm not sure how terrible superoxia really is, short-term, but why bother if it doesn't help?
2014-08-21 16:31:05
jason
“Bad heartburn” – 82 y.o. female without chest pain.
Chris Watford- as you probably know the "acute MI suspected" detection function in the LP12/15 is a programable option. I suspect the software didn't miss this but rather it wasn't turned on. As for treatment everyone has pretty much got it down. Finally as for activation. Absolutely! Don't real care if the protocol allows for…
2014-08-21 16:30:34
Austin
“Bad heartburn” – 82 y.o. female without chest pain.
There's not much I think I can add at this point, but I will comment on a couple of things. The reciprocal changes indicate to me that there is likely RCA involvement. Also, I've recently been hearing quite a bit about withholding O2 in ACS patients like this. Dr. Walsh, do you have any opinions…
2014-08-21 16:23:21

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