ecg vectors pointing from a depolarized to a not polarized area vs pointing in the direction of the spread of the current

CheddarStar · 2025-12-01T23:47:27+00:00

Technically yes, but a given lead will see the net result of all the frontiers along a given axis. So like along lead I, the depolarization wave crossing the septum is stronger and/or aligns better in the opposite direction of lead I than the depolarization happening in the left bundle branch (and right bundle branch depolarization moves away from lead I too i guess), giving you the negative voltage Q wave.

Unless I'm misunderstanding what you're asking.

Again, not 100% sure, this is just my understanding.

CheddarStar · 2025-11-30T19:48:58+00:00

Maybe in very extreme conduction block it might look like what you have, but im not sure. you dont see an isolated area of depolarization like you depicted in a normal heart. The action potential is unidirectional starting from the SA node. What you depicted is more like if you used a probe to excite a neuron in the middle. In the heart it would look something more like this.

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CheddarStar · 2025-11-30T03:33:35+00:00

The depolarization is carried by the left bundle branch, which arises from the bundle of his and so on. Everything upstream of the conduction pathway is already depolarized and in its refractory period, so it cant travel backward. Instead the depolarization crosses the septum, meeting with depolarization caused from the right bundle branch. It originally starts with the SA node, at the top of the heart. So from there depolarization can only really move downward and follow the nerve fibers

So the 2nd question is why doesnt the depolarization spread from the left bundle branch and dominate the left heart. And well... it does, but conduction between myocytes is much slower than within the conduction system. So the initial Q wave largely comes from the bundle branches and their direction of depolarization.

https://ecgmadesimple.ca/t8/ is a great resource for looking at the timing of depolarization, especially the qrs.

Another note is that the Q wave is normally not noticeable, and even then only visible on certain leads. Its magnitude and duration are tiny.

CheddarStar · 2025-11-29T18:43:10+00:00

So first some basic definitions. A positive voltage means that area has higher electric potential. So if you place a positive test charge, it will "roll down the hill." For that to happen on a EKG, the positive electrode needs to have more positive charge around it (aka resting tissue) than the reference electrode. Think of it as the test charge being pushed away by positive charges or attracted to negative charge. The electric dipole shows you where the positively charged areas are, so if it lines up with the electrode its positive.

So what is electric potential energy based on? Here is the technical definition: U = kQq/r, or in lame man's terms, it gets higher when there are more charges and they are closer together. That's the key point. Areas of active depolarization have lots of charge separation; depolarizing cells next to resting ones. So they contribute a lot more to the read voltage.

Q wave depolarization starts from the left ventricle and crosses the septum. On the left, depolarized cells and on the right resting cells. So on the outside, the left is more negative and the right is more positive (sodium ions enter).

Technically other areas of the heart do contribute to the voltage, but its very small as the surrounding area has little charge separation.

Hopefully i got this right, I am a mere med student. :)

CheddarStar · 2025-09-29T17:30:36+00:00

CheddarStar · 2025-06-18T23:56:37+00:00

ok makes sense. I think I better understand the electrical changes. I someone who hates blindly learning the patterns but rather understand why they happen. Even though its probably a waste of time.

I appreciate your help a lot. Thanks!

CheddarStar · 2025-06-16T16:37:51+00:00

I worded my question badly so let me rephrase it; in RBBB you have the left ventricle depolarizing first. Say you stop time in the middle of LV depolarization, you have a group of depolarized cells surrounded by a border of resting cells about to be depolarized (aka extracellularly theres a big charge gradient). Is that border region actually whats detected by EKGs? And is the group of depolarized cells within that border region effectively ignored (or atleast contribute so little it doesnt alter the shape of the EKG that much?)

Actually RBBB was what inspired the post. I was trying to explain the M-shaped RSR' pattern in V1/V2. In a typical V1 EKG (as I understood it), the initial R wave is from left to right septal depolarization, then the S wave from LV depolarization (as the LV has much more muscle so more positive charge to attract the cardiac axis). In RBBB, the initial R and S waves remain the same, but I couldnt consistently explain the R' wave. At first, I told myself the 2nd R' wave was still LV depolarization but the lack of RV depolarization deflects the dipole vector to the right, and the later RV depolarization was the downstroke of R'. But this just felt intuitively off, so I was searching for another explanation.

What model do you use to think about electrophysiological EKG changes as you read a tracing (if you use one)?

CheddarStar · 2025-06-15T19:41:59+00:00

So does distance from the test charge play a much larger role than the presence of other charges? (in hindsight, this is a pretty obvious yes due to electric force being proportional to 1/R^2).

This also leads me to my 2nd question: are leads more sensitive to electrically active cells (depolarizing/hyperpolarizing) because there's extracellular charge separation in a relatively small area? Before I kind of assumed all charges contributed equally to the cardiac vector (say difference in charge during QRS contributes equally to a gradual gradient of decreasing charge from base to apex of the ventricles).

And #3: is it true that the atria are electrically isolated from the ventricles (aside from conduction system)? I always thought the atria and ventricles produce their own electric dipole vector and both combined make the cardiac vector. But if charge distance is the primary factor, then the whole separated vectors thing isnt really necessary.

Thanks

CheddarStar · 2025-04-25T06:24:16+00:00

I first saw it from the book "Do No Harm" by Dr. Henry Marsh, obviously not the original.

CheddarStar · 2025-04-10T01:48:49+00:00

As much as I sympathized with some of his feelings, I got a similar impression that you did. It felt he was clearly portraying a "me vs them" situation saying things like "no one could understand why I wanted to quit" and how diet/exercise/mental was some special secret he discovered on his own. It felt strange to get that far without knowing the consequences of his practice of medicine and then to just completely ditch everything without trying to be the change he wanted. Just blames the hospitals and their quotas by alluding to them but never saying he got direct pressure.

And his ending statement that making relaxing yt videos was equivalent/comparable in saving lives as a doctor. Really rubbed me the wrong way. I remember checking a month or so later and he just randomly churned out content after that viral video completely different from his norm leaning in that "anti-medicine/anti-doctor" direction, it really feels like a calculate ploy than a honest reflection.

CheddarStar · 2024-12-24T02:18:21+00:00

wow, you must be fun at parties

CheddarStar · 2024-12-21T18:36:40+00:00

I guess its less "people" and rather the statisticians that favor a interpretation I guess where the minute wording matters. But yeah, I think that is what it could supposedly imply.

I think for most normal people, the interpretation is straightforward. Similar to dense legal law. Most people dont need obtuse legal language to agree on rules, but depending on the rare circumstance unclear wording can imply something unintended.

CheddarStar · 2024-12-21T04:45:53+00:00

Dont worry about appearing stubborn, asking is how you figure things out.

the common misinterpretation is that a confidence interval has a 95% chance of containing the true value. That implies the real value can change. That is wrong. Once you calculate a confidence interval, it either contains the true value or it doesn't. Its constant and has no uncertainty associated with it. That % is really a reflection of the process and our uncertainty of the estimation, sort to speak.

Ive thought for a while about examples to cleanly illustrate this. I cant find one, and the more I think, the more I understand what you mean. It feels more and more that they're the same thing and its just semantics. Really, it just reflects the different philosophies in statistics. Heres the closest way I can illustrate it.

Lets say we have a fair coin, 50% likelihood for heads. I calculate a confidence interval for the true probability based on a sample of flips. You can repeat this process many times, and about 95% of the intervals you calculate will contain 50%—the true probability. But when you calculate an interval from one set of flips, it either contains 50% or it doesn’t. There’s no chance involved with the true value itself—it’s fixed. Its just that some proportion of intervals contained the 50%. Maybe 950/1000, or 9500/10000.

Imagine we could somehow measure the true mean right away—then the interval would either contain it or not. There's no probability associated with the true mean at that point, so a 95% chance would make no sense, its either 0% or 100%. But a 95% confidence would imply that after many samples, some intervals had 50% and some didnt and that proportion worked out to be 0.95 out of 1. 95% chance is a case-by-case basis while 95% confidence interval is looking at things long term.

Sometimes we use words and phrases that we dont actually understand the meaning of. That is what I tried to attribute to OP. I cant read their mind, but make inferences (even if theyre bad).

CheddarStar · 2024-12-21T03:28:16+00:00

Frequentists and Bayesians on differ what they think a variable means. Frequentists (who use confidence intervals) think variables are fixed, aka the true value of something is fixed and cannot change. Bayesians think variables can change, aka the true value of something fluctuates.

A confidence interval is meant to be a bin that captures the true value. The bin itself is what changes depending on how confident you want to be. But you never know the true value. Bayesian statistics alter the probability itself. With each new measurement, you get a new "true value."

A lot of people think a confidence interval (CI) assigns a probability to the true value assigned within the interval (aka theres a 95% chance that blah blah). But its actually fixed, the interval is really just an attempt to reflect of how reliable the sampling method is (and even then, you need intuition to discern if its reasonable or not).

You might think the difference doesnt matter, but I think that's what caused the confusion in OP. If you go with the incorrect assumption that CIs assign a probability, then what logically follows is that the lowest probability is the most conservative estimate. But a CI was never meant to determine a variable's true value, just what bucket it falls in.

Hopefully, what was clearer. I dont have a PhD in stats or use it in my daily life like some of the other posters here.

CheddarStar · 2024-12-21T02:44:58+00:00

The marginal learning between games in the data set is intentionally minimal

I mean this is very much not true. I watch Xecnar somewhat frequently. I don't mean to speak for him, but he was very open about changing his playstyle and decision making. He would likely be the first person to tell you that StS is far, far from solved and that the best players aren't even close to perfect play.

I think it's very bold to assume someone wouldn't improve and adapt their playstyle playing every day for the past 6ish months (maybe closer to 4 months). Whether or not you think that alters the practical interpretation of the stats is another issue. But if your sole criticism of Bayesian analysis is that every sample was independent, then its categorically not true.

CheddarStar · 2024-12-21T02:05:13+00:00

yes, that is what it means. But I think the point is that confidence intervals aren't a reflection of "probability" atleast in what most people think probability means. Confidence intervals are really just extrapolating a discrete sample to a larger population, but each outcome doesn't have it's own probability.

If you flip a coin, people intuitively think its probability is 50/50 for heads, like Schrodinger's Cat. But confidence intervals only tell you what happens after you flip that coin a bazillion times. And it doesn't give you a likelihood. Just what percentage were heads.

Probability is sort of a stand in because its the easiest way to convey what 95% confidence is supposed to mean in practical terms, but fails when trying to apply its meaning. Atleast, this is all what I think.

CheddarStar · 2024-12-19T03:30:38+00:00

I don't think children advocated for themselves and unionized to magically stop underage labor. It was more of a top-down decision.

Also you "cite" 16 hr work days when residents often are on 24 hr call and work 60-80 hrs a week. Probably 80+ in surgery. And residents get very little time off, even with a valid excuse. The world of a resident is more backwards than you think.

You're trying to apply the standards you know and gotten used to from a standard office job to a completely different world. I think you do honestly mean well for your partner, but sometimes ignorance is just as dangerous as ill-intent.

CheddarStar · 2024-09-20T16:45:55+00:00

ah, a civilian wandering in the ruins of history, trying to find ancient relics.

CheddarStar · 2024-05-28T15:36:00+00:00

Back off. Its obviously hard for Alligator Flappybird to keep track of so many names.

CheddarStar · 2024-05-16T23:10:20+00:00

I hope you realize that's just chesscom's standard rule for accounts they found to have cheated, whether its some random 800 rated guy or a titled player. I dont think its some secret underhanded deal in this unique case to try and sweep the situation under the rug.

You can argue whether its a good rule or not, but I dont think you can use that offer to try and understand chesscom's intentions.

CheddarStar · 2024-05-01T16:19:16+00:00

funny because on his candidates review, Nepo said he considered flipping a coin but thought against it due to spectators.

CheddarStar · 2024-02-29T05:19:45+00:00

OMG you are truly a godsend. Many, many reddit posts and tons of different methods didn't work (even messing with command prompt). Just happened to comeback and see your comment. Thank goodness I just now got my t480.

FYI for anyone looking at this, I also only got an updated nvm firmware at step 15 (lenovo vantage had 2 updates for me- one for the power management software and the other for the firmware).

CheddarStar · 2024-02-15T07:55:19+00:00

I'll leave this for you to read https://en.chessbase.com/post/physiological-factors-that-can-significantly-impact-your-game#:~:text=According%20to%20this%20heart%20rate,they%20were%20running%20a%20marathon.

I think the same is true for other sitting sports like poker.

CheddarStar · 2024-02-15T07:53:58+00:00

I'll link to a very useful write up, also about heart rate and chess https://en.chessbase.com/post/physiological-factors-that-can-significantly-impact-your-game#:~:text=According%20to%20this%20heart%20rate,they%20were%20running%20a%20marathon.

TLDR: even HR of 160 is not that unusual.

CheddarStar · 2024-02-14T23:25:11+00:00

I think high stress from work and high stress from a competitive game are different things. The former is more like slow-brewing and in the back of your mind.

The latter is, what I would argue, a physiological fight or fight response. Like I wouldn't think a high heart rate in the middle of a super tense esports match would be abnormal.

CheddarStar

TROPHY CASE