It’s how my A&P professor used to classify the problems that could happen to the human body. It was either OK, or not a good thing. I’ve learned all sorts of things that surely fall into the latter category, hell, we see that all the time. Then there times where you foresee the worst possible, but the reality is that it isn’t that bad. All things considered.
Case in point. Complete (3rd degree) Atrioventricular [Heart] Block. Just saying makes my heart rate speed up a bit. All sorts of bad situations run through my mind. The ACLS algorithim for bradcardia and PEA jump to the forefront of my memory as I see it pop up on the monitor screen as the “Oh SHIT!” alarm starts ringing for bradycardia. You run into the patient’s room and they’re sitting there, alert, talkative and having a fine time. “Do you feel weird?” I ask.
“No, why?” he says.
“Your heart is doing something funny. Sure you feel OK?” I continue.
“Oh, that,” totally nonplussed, “Naw it happens all the time. I’m used to it. That’s why I’m getting a pacemaker tomorrow.” he finishes.
Then I remember the words of my EKG teacher: sometimes we treat the monitor, others we treat the patient. The key is to figure out which one is which.
So here’s the first strip:
Atrial rate: 80’s
Ventricular Rate: 60’s
Notice how the P-waves march through without any regard to the QRS complexes, except in beats 2 & 6. Beat 6 appears to be preceded by a compensatory pause, where the conduction system appears to reset. One could argue that this may be an extreme case of 1st Degree AV Block, but if you measure the P-P ratio you can see the march of the P’s, into and through the QRS complexes. While it’s not a complete block, as some impulses do seem to carry through and you do have some time spent in sinus rhythm that I couldn’t scan in, you can tell the conduction system in not well.
Now a second strip:
Again, the atrial rate is in the 80’s, and the ventriclar rate is inthe 50’s. Notice how the overall strip seemes to be stretching out, or slowing down. The 5th beat is a PAC, but again, no reset happens. After that you have a lone P-wave followed by a second P-wave with no QRS to be seen.
Pretty much in this case, the atria and ventricles are not working together at all. At times there appears to be some synchrony, but whether that is coincidence can’t be seen in short rhythm strips like this. For some reason I really dig on the heart blocks. Some of my colleagues have a hard time getting their heads around the concept, but it makes perfect sense to me. The short of it is that the top of the heart and the bottom are not communicating effectively, kind of like a dysfunctional family, or couple. (really, AD’s description of the heart blocks is both incredibly informative and hilariously funny, but it makes so much sense. Maybe I just have a dirty mind though.) By the time you get to 3rd degree (or complete) heart block, the atria just does its own thing, usually clicking along at the normal rate for the SA node (60-100 bpm) while the ventricle clips along at its own rate, usually either junctional (40-60 bpm) or idioventricular (20-40 bpm). The ventricular rhythm is determined by which escape pacemaker site is supplying the impulse, the AV node or the His-Purkinje system.
In cases where the patient is asymptomatic, the are several things nurses can do. First, keep them on tele for crying out loud. Don’t let them leave the floor without an ACLS certified nurse. You say, “Well, duh.” To which I say, “You think this hasn’t happened?” Second, either have transcutaneous pacer pads on the patient, or at the very least at the bedside. Third, make sure they don’t get any nodal blocking agents, like metoprolol or diltiazem. Once again, “Well, duh.” Again, “You think, aww screw it…it has happened.” Fourth, make sure they have at least 1 IV site, that works, preferably 2. Finally, make sure Cardiology is involved as the ultimate fix is a permanent pacemaker.
Lucky for us the gent in question stayed hemodynamically stable through the night and ended up getting a new brigh and shiny pacemaker implanted the following morning. It could have been far worse, for sure.
Emedicine’s article: Heart Block, Third Degree
The ECG Blog has a great couple of case studies of this phenomenom, complete with 12-Lead tracings. The latest, Complete (Third Degree) Atrioventricular Block with Junctional Escape Rhythm, is pretty darn cool, and it has our most common complaint in folks with this, “tiredness.” Classic.
Dedicated to Sidney Sinus Node and Viginia Ventricle…