Holiday Heart Strikes Again – Part 2

Posted by Patrick Lickiss on Dec 6, 2010 in Assessment, General, Treatment | 6 comments

So I presented a scenario earlier this week and had a few ideas for differential diagnoses.  Click here to read the original post.  Basically it comes down to a patient who eats a huge dinner and while having a few sips of wine (her first of the evening), has a syncopal episode which has not resolved by the time EMS arrives, but which fully resolves en route to the hospital.

DIFFERENTIAL DIAGNOSIS
When looking at possible causes for this syncopal episode a few ideas come to mind:

• Increased Vagal Tone
• Dysrhythmia
• CVA/TIA

After doing some research, a few less obvious causes are possible as well:

• Holiday Heart Syndrome
• Nitrate Sensitivity
• Sulfite Sensitivity

So which could it be?  Let’s look at each cause.

INCREASED VAGAL TONE
Most responders are likely familiar with the idea of a vasovagal episode.  The vagus nerve (cranial nerve number 10 for those of you keeping track), when stimulated, increases the activity of the parasympathetic nervous system and decreases the activity of the sympathetic nervous system.  What results is a drop in heart rate (due to the increased parasympathetic  activity) and a drop in blood pressure (due to vasodilation from the decreased sympathetic activity).  This combination often results in a syncopal episode and may have accounted for the patient’s bradycardia and low blood pressure.  There are a variety of causes of vasovagal episodes including abdominal straining which would certainly fit with the large meal.  On a personal note, I actually witnessed a friend’s father have a syncope after a large meal.  He had a history of MI and developed increased vagal tone as a result.  Definitely a weird thing to witness.

Increased vagal tone should certainly remain on the list of possible diagnoses for this patient.  Interestingly though, the patient’s vagal symptoms resolve without the cause for the increased vagal tone resolving (i.e. no vomiting or bowel movement).

DYSRHYTHMIA
In the comments of the original post, Christopher suggested the possibility of several dysrhythmias as causes of the patient’s syncopal episode.  Two of these suggestions seemed like they would be worth reviewing:  Stokes-Adams Syndrome and paroxysmal SVT.

Stokes-Adams Syndrome is generally characterized by a sudden onset of syncope lasting for less than a minute, possibly with seizure activity.  Prior to the syncopal episode, the patient presents as profoundly pale.  The interesting thing about Stokes-Adams Syndrome which sets it apart from other types of syncopes is that it is non-positional.  The syncopal episode can occur when seated rather than exclusively when changing position, like you would see when a dehydrated patient stands up quickly.  The syncope episodes are caused by what amounts to a brief cardiac arrest.  Stokes-Adams syncopes are caused by complete heart block (sometimes periodic which explains the short duration of symptoms) and may present with either ventricular fibrillation or asystole.  Sometimes, a slow ventricular rhythm will present.

While the patient’s slow heart rate and sudden syncope (particularly with a history of previous episodes) lends itself to a Stokes-Adams episode, the fact that the patient presents in sinus bradycardia makes it unlikely that this was such a syncope.  A complete heart block would not allow the electrical impulses from the atria continue down the heart and into the ventricles at all.  While Stokes-Adams Syndrome is a condition to be aware of in patients that present with syncope, it does not appear to be the cause here.

On the other end of the dysrhythmia spectrum is paroxysmal SVT.  Just as a review, a supraventricular tachycardia can be any rhythm which originates above the ventricles (i.e. atrial or coming from the SA or AV nodes).  The qualifier of paroxysmal indicates that the SVT is episodic in nature.  These abrupt starts and stops of dysrhythmia can certainly create syncopal episodes.  What, in my mind, rules this out as a potential cause for our patient is the fact that she presents in a bradycardia upon EMS arrival.  It also takes quite a while for her other symptoms to resolve during transport.  If we were looking at a PSVT, it seems reasonable to assume that her symptoms would resolve shortly after the resolution of the dysrhythmia.

CVA/TIA
The last suggestion for this post (and the last of the “obvious” rule outs) is a stroke or TIA.  Stroke is one of those differential diagnoses which is considered “can’t miss” and should be considered for any episode of altered level of consciousness.  While it is certainly possible that the patient is experiencing a stroke which caused her to lose consciousness, it seems unlikely when compared to the remainder of her presentation.  The patient does not present with the “typical” CVA symptoms (Cincinnati Prehospital Stroke Scale findings) and while her bradycardia could be from a significant bleed, her hypotension does not fit that pattern.  Additionally, her vital signs improve over time whereas one would expect them to get progressively worse as the bleed increases.

WHAT’S LEFT?
So we have one probable differential diagnosis (increased vagal tone), but what’s left?  Later this week, we’ll tackle some of the exotic causes of holiday syncope and see if we can’t get to the bottom of this.

Image via Flickr