I’m not looking for specific diagnoses, but general understanding of what an EKG can and cannot show. A guy I know saw his cardiologist with chest discomfort. History of reflux. Doc speculated that’s what it was, sent him home. Two weeks later, he goes in for quintuple bypass. My amateur medical thinking is that with that much blockage, and EKG would likely be abnormal in some ways, and indicate further investigation. But maybe not. Could an EKG totally miss such a situation? His rhythms could be perfectly normal? How to explain this seeming contradiction?
Not a cardiologist, but possibilities include a false-negative EKG (this has been described in up to 10% of heart abnormalities overall), or subtle findings that were missed or incorrectly interpreted.
History, physical exam and evaluation of risk factors along with EKG are major screening tools for ischemic heart disease, but they’re not perfect.
There’s no contradiction, EKGs don’t show things that haven’t happened yet, they only show what’s happening at that moment. They might show old heart attack damage, or might not. They might show ischemia or infarct occurring at the moment, or not. They’ll only show the rate & rhythm present at that time. They may indicate less than normal movement of the heart muscle as a whole (axis), but can’t tell whether that movement is new and abnormal, normal for that individual, etc.
I’ve been reading EKGs for 4 decades, I do it pretty much weekly. They’re just one piece of the complex puzzle that is a particular individual. When they show something definitive, great! When they don’t, it doesn’t mean nothing is going on. They’re also open to mis-interpretation, wish fulfillment of patient and physician, and so forth.
I was hoping to hear from Qadgop! Thanks, doc, you told me exactly what I wanted to know.
An Electrocardiogram shows the electrical activity of the heart. Since the electrical activity drives and is driven by the mechanical activity, ECG can also illustrate mechanical failure.
As it happens, electrical problems with the heart are common: my parent was recently given a pacemaker, which is an electrical solution to an electrical problem. ECG gives a fairly direct indication of those problems if they are present at the time of measurement. My inlaw also has a pacemaker: that was inserted after several weeks of wearing a halter ECG on two occasions.
What it doesn’t do is illustrate blood flow: It doesn’t show what the flow rate is, or what the exit pressure is, or stuff like that. For that, there are other methods. It doesn’t even illustrate oxygen starvation until it starts to interfere with the mechanical action of the heart.
I have a fair bit of experience reading EKGs. The ones used in hospitals have 12 or 15 leads attached to the chest. These ones are good at showing which parts of the heart are not getting enough oxygen, which, when prolonged is called a heart attack.
Preceding this, sometimes blocked arteries can cause changes in blood pressure or oxygenation which manifest in other ways - such as hypertrophy or ischemia. The EKG may or may not show this. The reader may or may not pick up on subtle changes which are often of uncertain significance.
Really, more specific tests to look at the blood vessels are preferred.
My pet peeve is when Iphone apps are called EKGs. These are one lead EKGs. So they can miss an awful lot and are not at all equivalent to a hospital EKG. These rhythm strips can pick up atrial and ventricular fibrillation, however, which ain’t nothing.
@Qadgop_the_Mercotan is obviously dispositive, but I thought I’d share my experience. When I was in cardiac rehab, I watched a guy crash off the treadmill in cardiac arrest right in front of me. He was wearing a 4-lead EKG (as we all were) and it was continuously monitored by somebody who knew what they were looking at. Fortunately, they were able to resuscitate him and, after quadruple bypass, he was apparently fine. I don’t know what had him in rehab in the first place.
I talked to them later, as I was feeling pretty freaked by the whole episode. Wasn’t this why we were all there exercising on a heart monitor in the first place? Paraphrasing, yeah, but sometimes there’s nothing to see until there’s really something to see.
I had been scheduled to have my aortic valve replaced in August of 2012. A month prior to the scheduled surgery, I had a routine heart catheterization. The test showed that I needed quadruple bypass. So I had the bypasses done at the same time as the aortic valve.
The first time I saw my cardiologist post-surgery, he commented that he was surprised I needed the bypasses. He said none of my previous tests, in the 5 years I had been seeing him, indicated any problems except the aortic valve.
This is something I still don’t understand.
Cardiologist here. I’ve seen this in many of my patients who express disbelief that they could have an MI just after seeing their doctor a week prior. As others have mentioned, the EKG is a decent tool but it does not prognosticate future heart attacks well. Like any test, it is most helpful in the context of the patient. An EKG that could look like a heart attack if done on a 75 year old diabetic smoker may look like pericarditis on a 20 year old getting over a cold. I think a key concept to understand is that the MIs that typically bring people into the hospital are due to plaque rupture. The plaques that rupture tend to be smaller in nature, meaning that before they erupt like little volcanoes, they don’t actually obstruct the blood flow much if at all. This is in contrast to more stable plaque that grows in size until it does start to limit the flow. That’s what typically leads to more of a stable angina picture, where symptoms are generally only present with exertion or stress and resolve with rest. There’s a lot of overlap between these, and it’s certainly possible to have both problems present at the same time, but if all you have is a 20-30% narrowing, it’s unlike you would have anything abnormal on an EKG, stress test, or even symptoms.
Sorry, just to add to this; whenever we are planning on opening the chest, we like to tune up everything so as to avoid a need to repeat a sternotomy in the future. So your primary problem was the aortic valve, but likely they would have done an angiogram and maybe saw some narrowing or stenosis of the coronary arteries that weren’t resulting in clinically evident ischemia. Since they’re going to crack you open anyway, might as well bypass those so that they don’t become a problem requiring surgery again in the future.
Could the doctors in this thread also tell us a little something about echocardiograms? What kind of diagnostic information is, or isn’t, available from that?
I had one once a few years ago. I got back a lab report which contained (it seemed to me) an astonishing quantity and resolution of detail (none of which I understood even slightly), except that it came with a summary that said everything looked good.
Good question. Now that we’ve got a cardiologist on board, I’ll leave that to the good Dr. audiobottle to elaborate on, as I’m just a primary care doc, and your basic journeyman when it comes to deep cardiology knowledge.
But I will take the opportunity to gripe about how poor far too many primary care physicians skills are with EKGs and echos. I’m told those skills aren’t encouraged for generalists anymore. I’ve had a few young internists refuse to even give a prelim interpretation of an EKG they ordered, saying they need cardiology to look at it. I find my basic familiarity with EKGs and other things like basic Xrays etc. to be invaluable. End of gripe. For now.
Ooh that’s a big question. The echocardiogram gives us a great structural view of the heart in real time. We use it a lot for things such as function (how well is the heart squeezing, relaxing); valvular function (are the valves leaky? Stenotic? Both?); is there fluid collection around the heart (pericardial effusion); are parts of the heart that don’t move as well (may indicate scar from prior heart attack or maybe just heart muscle that’s not getting enough blood supply); estimates of pressure inside each chamber of the heart and the lungs… the list sort of goes on and on. It’s a great study because the risk to the patient is essentially zero and we can get a lot of information. Certain modalities such as cardiac MRI or CT may give us a more precise idea of the function or scar or other things, but they come with the risk of contrast and/or radiation, and are very susceptible to motion artifacts or abnormal heart rhythms. This doesn’t even get into the use of echocardiograms in the setting of exercise and being able to monitor the effect of exercise on the pressures in the heart.
Dr. Qadgop, as a specialist at an academic center, I like to think that our primary care doctors are pretty good about reading the EKGs, but there is definitely one (I’m looking at YOU Dr. ____!) who are all too happy to write “Refer to cardiology” for any and all things that are even tangentially related to the heart.