The 12 Leads of Christmas: V5

This article is the ninth in our latest series, The 12 Leads of Christmas, where each day we examine a new finding particular to an individual electrocardiographic lead.

Lead V5

We’re getting into the home-stretch in our little series. I wasn’t entirely sure if we were going to make it through since a few of the leads, though they are useful, don’t bring much that is particularly unique to the table. V5 is one of those—like aVF and V4—and while there is still plenty to discuss, it’s not as exciting as lead III, aVL, or aVR.

Don’t lose faith, however, as I have saved three of my favorites—V2, V3, and V6—for last.

Anyway, let’s get on with this V5 business.

One of my favorite tricks for showing off to new techs (and letting them know that I’m keeping an eye on their work) is to guess that they were sloppy with their precordial lead placement without even seeing the patient. How do I do that?

V1 is a good place to start, looking for signs of incomplete right bundle branch block that could mean the lead was placed too high on the chest.

Another common error, however, is to bunch up leads V4-V6 on the anterior chest. Despite personally training many of the techs in my department, I still see this setup way too often:

Crazy precordial electrode placement. V1 and V2 are way too high (cephalad) and wide (lateral), V4–V6 are bunched up on the anterior chest, and V3 is in no man’s land. Image source.1

 

It’s hard to make a 2D diagram that displays proper electrode placement—especially when you can’t directly visualize the ribs—but a much better setup is shown below:

Correct precordial electrode placement. V1 and V2 are parasternal, in the 4th ICS; V4 is in the mid-clavicular line, 5th ICS; V3 is halfway between V2 and V4; V5 is on the same horizontal level as V4, in the anterior-axillary line; V6 is on the same horizontal level as V4 and V5, in the mid-axillary line. Image source.1

03 - Axillary Lines Torso Electrodes Perspective Correct

A lateral view of V4–V6, showing their relationship to several anatomical landmarks. Image source.

 

How does V5 fit into the picture?

When you follow the R-wave progression across the precordial leads, in a normal adult ECG there should be a tiny R-wave in V1 with a larger S-wave. Though V2 usually has a larger S-wave than V1, as you move from V2 to V6 the S-wave will get smaller and often disappear while the R-wave will grow in height—these transitions should be rather smooth from one lead to the next.

20 - R-wave Progression

Notice how the R-wave reached its maximum height between V4 and V5, and while there will still be a sizable R-wave in V6, it is not as large as V5’s. Below are a few normal ECG’s with proper electrode placement:

04 - 1424 - 20yo M

Note the smooth precordial R-wave progression that reaches its maximum in V5. Also not the disappearance of the S-wave by the time we get to V6. This won’t happen every time but when present it’s a good sign that the electrode has been place far enough posterior.

05 - 0816 - 10yo M

Again there is a smooth precordial R-wave progression with the maximum R-wave amplitude in V5.

06 - 1265 - 13yo M - 01

Again there is a smooth R-wave progression with the tallest R-wave in V5 and no S-wave in V6.

 

When V4–V6 are bunched up on the front of the chest you end up with V5 close to where V4 is supposed to be and V6 ends up where V5 was supposed to be. As a result, the maximum R-wave height occurs in V6 instead of V5 and there will often be a residual S-wave still present in V6 as well. Here are some examples:

07 - 0575 - 63yo M - 01

There is a normal, if somewhat early, R-wave transition on this EKG. This is the baseline for the same patient as the next tracing.

08 - 0575 - 63yo M - 03

This is the same 63yo male as the prior tracing but notice how much slower the R-wave develops across the precordium. The maximum R-wave size is in V6 and there is still an S-wave present there.

09 - 0042 - 70yo F

There is a very poor R-wave progression on this EKG with no sign of old anterior infarction, LAFB, or other abnormalities. It is pretty safe to assume the PRWP is due to electrode placement.

10 - 0020 - 58yo F

Not only is there a poor R-wave progression, there is an rSr’ complex in V1, suggesting this technician made multiple errors when performing the EKG.

11 - 0045 - 49yo M

This is the EKG of a morbidly obese patient showing a poor R-wave progression. Most of the time this would simply be attributed to the patient’s body habitus, but in this case there is a subsequent tracing showing a normal R-wave progression. The PRWP here is just due to improper electrode placement.

13 - 0056 - 16yo M

Poor R-wave progression due to improper electrode placement (confirmed with direct observation) in a 16yo. There is also a large first degree AV-block, unrelated to the PRWP.

15 - 0025 - 21yo F

Another case where the largest R-wave is in V6 with no good reason for this 21yo to show a PRWP. There is also a subtle rSr’ in V1, again suggesting more than one electrode placement error.

16 - 0007 - 53yo M

More of the same.

17 - 0218 - 17yo M

Again an unexplained PRWP, and again there is an rSr’ pattern in V1 that is highly suggestion of improper electrode placement. Noticing a pattern?

18 - 0869 - 14yo M

Yet another young person with no reason to show this poor of an R-wave progression. Lead V4–V6 are practically identical, suggesting that they were placed very close together.

 

We also refer to this finding of a poor R-wave progression as “clockwise rotation.” If you imagine you’re looking at a transverse cross-section of the heart from below, it’s as if the heart has been rotated in a clockwise direction. In the above cases the heart hasn’t been rotated clockwise, the electrodes have been rotated counter clockwise, resulting in the same net-effect.

21 - 800px-Rwaveprogression

Normal R-wave progression. Image source.

22 - 800px-Reduced_rwaveprogression

Clockwise rotation of the transition-zone. Image source.

There are a lot of causes of poor R-wave progression (aka “clockwise rotation”) aside from improper precordial electrode placement. One of the most common is obesity, but that is also a common reason for placing the left-precordial leads too close together on the anterior chest, so it’s hard to determine which obese patients have a true PRWP unless you perform the EKG yourself. It is also seen with COPD, left anterior fascicular block (LAFB), anterior myocardial infarction, among other things.

All of the cases shown above were performed on patients with no other cause for their PRWP progression, leaving improper precordial electrode placement as the most likely culprit. Additionally, you may notice that most of the EKG’s are a bit faded. That’s because most of these cases were collected several years ago, before my hospital instituted a somewhat structured EKG training program. While I still see sloppy EKG’s from time to time, they are nowhere near as common as they were when I first started and, as a result, I’m glad to see most of the examples in my collection are several years old.

 

References

  1. By Unknown (original by Onatas?) (User:Bibi Saint-Pol, own work, 2007-02-08) [Public domain], via Wikimedia Commons.
  2. Häggström, Mikael. “Medical gallery of Mikael Häggström 2014“. Wikiversity Journal of Medicine 1 (2). DOI:10.15347/wjm/2014.008. ISSN 20018762.

 

I hope you’re enjoying our 12 Leads of Christmas series. You can check out the rest of the posts below (updated as new posts come out):

12 Leads of Christmas: Lead I
12 Leads of Christmas: Lead II
12 Leads of Christmas: Lead III
12 Leads of Christmas: aVL
12 Leads of Christmas: aVF
12 Leads of Christmas: aVR
12 Leads of Christmas: V1
12 Leads of Christmas: V2
12 Leads of Christmas: V3
12 Leads of Christmas: V4
12 Leads of Christmas: V6

 

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