If you’ve been befuddled by all the different types of heart block, today is your lucky ducky day. After reading this post, you will be able to easily and quickly identify and differentiate between the various types of heart block and keep them all straight in that gorgeous head of yours.
For this lesson, we are going to make an analogy between the atria/ventricles and a wife/husband. Recall that the atrial contraction (depolarization actually) is represented by the P wave, and ventricular contraction (depolarization) is represented by the QRS. So for our analogy, the atria (represented by the P wave) is our wife; the ventricles (represented by the QRS) is our husband. See what happens as their relationship goes south. Ready?
First-Degree Block: The husband comes home late every day. Granted, it’s at the same time every day, but he’s still late. This is represented by a longer-than-normal PR interval that is consistently the same length. Every P results in a QRS….but the QRS is “late.” Maybe the husband is just going out after work for a beer with the guys, but he feels slightly bad about it so he always tries to be home by 9pm. Yes, he’s late, but he’s consistent.
Second-Degree Block Type 1: So, the husband starts noticing a cute little brunette waitress at the local sports bar…but he’s trying to still be a good husband. So, he comes home on time on Monday like he’s supposed to. But, on Tuesday he stops by the bar and comes home a little late. On Wednesday he hangs around the bar until the brunette gets off work, so he gets home even later. On Thursday, he says, “to heck with this” and doesn’t come home at all. He feels terrible about this, so on Friday he comes home on time like a good husband (heck, he even brings flowers). But he can’t stop thinking about that cutie, so the cycle continues…Saturday he comes home a little late, on Sunday a little later, then on Monday he doesn’t come home at all. The cycle repeats itself over and over. In a second-degree block Type 1, you have a progressive lengthening of the PR interval followed by a missed beat.
Second-Degree Block Type II: In this relationship, the husband/QRS randomly picks days to not come home at all. No warning, just doesn’t come home. Maybe the brunette’s work schedule is all over the place (kind of like a nurse’s schedule!) All the other days, he comes home right on time…no delay. On the EKG you’ll see regular PR intervals and then out of nowhere you’ll have a missing QRS.
Third Degree Block: This is also called a “complete heart block.” In this relationship, things have gotten really bad for our couple. The wife is doing her own thing, and the husband is doing his own thing…the two aren’t even talking to each other anymore. They’re essentially living separate lives until the divorce negotiations can be worked out. On the EKG you will see the P waves march out beautifully, and the QRS will march out beautifully, but they will have nothing to do with one another. P waves that appear randomly, QRS without Ps…it’s chaos…and it’s very
very bad. The patient will absolutely need a pacemaker because the next stop after a complete heart block is dead (or divorce, if you want to think about it that way!).
So there you have it…the quick and dirty guide to heart blocks (and dysfunctional relationships). And just to show I don’t think all men are jerks like our guy in the example, here’s a picture of one of my favorite guys…Oliver the cat 🙂
Get this on audio in podcast episode 101.