InterAtrial Block
David Didlake, EMT-P, RN, ACNP
@DidlakeDW
An early 80’s Female was transported to the ED with new-onset facial droop, slurred speech, and focal deficit. No previous medical history was reported. My colleauges and I (interventional cardiology) were asked to consult during workup.
MRI Brain demonstrated Left MCA acute/subacute infarct, MCA/PCA watershed, and no hemorrhagic transformation. Based on last known normal she was deemed outside the thrombolytic window, and equally a poor candidate for thrombectomy.
Here is the admission ECG.
Examples of cardioembolic stroke etiology include:
1. Atrial Fibrillation
2. Cardiomyopathy with mural thrombus
3. Patent Foramen Ovale
4. Severe calcific Aortic (valve) Stenosis
5. Mechanical prosthetic valve
Severe carotid artery stenosis is also implicated in embolic stroke.
In the pre-hospital setting the varying modalities needed to rule-in/rule-out these causative factors are not available (eg, Chest X-ray, Echocardiogram, etc). This is further complicated if no reliable source of history can be found, such as a family member, or paperwork containing pertinent medical history.
We do have the ECG. And since common things are common, the statistical probability favors Atrial Fibrillation (AFib) as the culprit.
But the ECG is Sinus!
AFib can come and go. The technical term here is paroxysmal AFib (PAF). In general, the longer an AFib episode the more increased risk of stroke. (This is further nuanced based on CHADSVASc scoring).
During graduate school internship an interventional cardiologist stated: “The most common symptom of AFib is no symptom at all.” This means that, more often than not, people are experiencing AFib and don’t even know it. Thus, making a PAF differential diagnosis based solely on the presence/absence of palpitations is not reliable.
Does the ECG in today's case predict PAF? Yes, it does.
Here I have blown up Lead III. Notice how the P-wave morphology is wavy, jagged, and (most importantly) prolonged.
The green lines demonstrate the complete P-wave duration, which is 160ms.
This is InterAtrial Block (IAB).
The following link provides a robust, and comprehensive, review of this entity. But for now I would like to focus on two items of interest that are pertinent to this case.
Advanced IAB is a risk factor for:
1. The development of AFib
2. Ischemic stroke during Sinus Rhythm
Not unexpected, a secondary ECG later captured the following rhythm change.
My initial consult during ED admission (when all I had available for review was the 12 Lead ECG) included the following dictation in the chart:
"12 Lead ECG reviewed. Continuous Tele demonstrates Sinus Rhythm with high-burden PAC's. Given infarct pattern on imaging, and obvious Advanced IAB on P-wave morphology, this is likely embolic PAF."
