Cardiac Surgery:In the last two issues of the newsletter, we've discussed the anatomy of the heart and the things that can go wrong with the heart. (If you have not read them yet, it would be helpful, but not essential, before reading on.) In this issue, we're going to desist our series by examining how your physician unravels the secrets of your heart when you visit his/her office. My goal is not to turn you into doctors, but to take some of the strangeness out of determination so that you know what your physician is looking at, listening to, and analyzing when he/she is looking at your heart -- to arm you with some basic diagnostic knowledge so you are not totally at the mercy of the healing mystique when the results of your next corporal are pronounced.
A definition
Before we inaugurate into our subject, though, we have to define two terms that will be referenced throughout the newsletter: systole and diastole:
Cardiac Surgery:Secrets of the Heart
- Systole refers to the contraction of the chambers of your heart.
- Diastole refers to the relaxation of those chambers.
In fact, you can have systole and diastole in all four heart chambers, but in most cases, doctors focus on the left ventricle -- the accommodation that pumps blood throughout your whole body -- when using the terms. Also, there are two kinds of systole and diastole: electrical and mechanical. Electrical systole is the electrical action that precedes actual contraction. It's what stimulates the heart muscle of the distinct chambers to easily contract. The delay in the middle of electrical stimulation and actual contraction is about a tents of a second.
The same is true of diastole, the relaxation of the heart muscles. Electrical diastole is the recovery and repolarization of the heart in establishment for the next beat. Mechanical diastole is the actual relaxation of the muscle that follows electrical diastole. This inequity becomes foremost when you look at your Ecg.
Incidentally, the increased pressure produced in your circulatory theory by the mechanical systole (contraction) of the left ventricle is referred to as systolic pressure. The reduced pressure while relaxation is called diastolic pressure. These are the two numbers your physician gives you when reading your blood pressure (e.g., 120 over 70). We'll gawk that in detail in the next series of newsletters when we gawk the circulatory system.
The Sounds of Your Heart
The most basic tool your physician has for evaluating the health of your heart is the stethoscope. It is so basic to treatment that it has been around in assorted forms for roughly 200 years and is probably the most recognizable symbol of doctors in the world today. Before the stethoscope, physicians would just listen to the heart by pressing their ears against the patient's chest -- not very efficient, and often very unclean.
And what do doctors hear through a stethoscope?
Surprise! It's easily not the beating of your heart. The heartbeat itself is virtually soundless. That thump...thump your physician listens to is the sound of blood dashing against the inner walls of the heart chambers. This is a very beneficial distinction. Hearing the movement of blood reveals far more than would be the case if all we heard was a mechanical contraction.
More precisely, the thump...thump of your heartbeat is the sound of the turbulence of blood against the walls of the heart and the valves while systole (contraction). In fact, thump...thump is not an entirely literal, description of the sound. As it turns out, each thump is, in reality, comprised of cut off sounds in both the atria and the ventricles. But because the sound in the ventricles is so loud, it drowns out the other sounds...unless there is a problem.
For example, if there's stenosis (hardening) of the mitral valve, part of the heartbeat is slowed down because it takes longer for the stiff valve to close so that the many sounds start to separate. Instead of the general thump...thump, you hear something that sounds more like thump...pa pa. On the other hand, if you have incomplete closer of a valve, as in aortic regurgitation, you lose the clean thump and get sort of a chortling "woosh" sound as in whoosh...thump. (If you're interested, here's a link to more heart sounds.)
Invariably, then, listening to your heart through a stethoscope is one of the basic parts of any checkup. It provides the first clues as to the health of your heart.
Note: for those of you interested in coaching your physician through anyone they may have forgotten in healing school, here's a more detailed tutorial.
The Ecg/Ekg
When most population think of heart tests, they think of the Ecg. Ecg stands for electrocardiogram. It's also called an Ekg, from the German elektrokardiogram. Although it may look like an Ecg is recording heartbeats, it's not. In fact, it records the electrical action (the electrical triggers, if you will) that presage the actual heartbeat. The mechanical beats effect the electrical triggers by about a tenth of a second -- unless, of course, there's a problem. Or to state it in "medicalese," electrical systole and diastole precede mechanical systole and diastole (contraction and relaxation) of the heart by about a tenth of a second.
The Ecg is an foremost tool for your doctor, but is hardly unblemished and comes with any limitations.
It's a static test, which means it doesn't necessarily recognize problems that appear only when the patient's heart is under stress. An example would be a patient complaining of intermittent chest pain. This might easily be an indicator of a severe basic problem, and yet a thorough Ecg could easily read as perfectly normal.
Ecg readings indicate only general problems. In most cases, abnormalities in the reading are non-specific as to cause, and in fact, many times, may mean nothing all.
Bottom line:
- A general Ecg reading doesn't necessarily mean that there is no problem.
- An abnormal reading doesn't necessarily mean that there is.
- It's merely a piece of the puzzle that can help point the physician in a direction.
That said, an Ecg provides four traditional pieces of facts for your doctor.
First, an Ecg can show how fast your heart is beating -- or more accurately, how fast the electrical action is moving through your heart. By measuring the intervals in the middle of beats, your physician can decide if the electrical signal is moving through your heart too slow or too fast.
It also shows the impel and timing of the beat. By measuring the estimate of electrical action passing through your heart muscle, your physician can get an indication as to which parts of your heart are too large or are overworked or if it's not pumping forcefully enough.
It can contribute evidence of damage to assorted parts of the heart muscle caused by:
- previous heart attacks.
- Congenital heart abnormalities.
- Diseases such as thyroid problems, rheumatic fever, diabetes, and high blood pressure.
- Inflammation to either the heart muscle or its lining (inside and out).
- Very low or very high levels of electrolytes along with calcium, magnesium, and potassium.
- And it can indicate problems with impaired blood flow in the coronary arteries supplying oxygen to your heart muscle.
Reading the Ecg
Your physician performs an Ecg by hooking you up to a series of electrodes scattered over your chest, arms, and legs. (Accurate placement is important.) Each electrode reads the same signal, but because of its unique vantage point, provides a distinct view of that signal. Think of it like watching a speeding train from the front arrival at you, from behind racing away, and from the side whizzing by. It's the same train, at the same point in time, but each vantage point provides very distinct facts about the train.
Here's a snippet of an Ekg showing any electrodes tracking a heart. Consideration how the electrodes start providing noticeably distinct facts with regard to the same beat about 2/3 of the way through.
All well and good you might say, but what does it mean? How do I read it? Does it mean I'm wholesome or unhealthy? Can I run a marathon, or do I need bypass surgery? All good questions.
In order to understand great what your physician sees when he looks at an Ecg printout, let's focus on a single beat from a single electrode.
Alright, I agree. That's easily pretty meaningless at first glance. However, with a tiny decoding, it starts to make much more sense. In fact, the heartbeat as represented in an Ecg breaks down into four traditional pieces: the Pr interval, the Q wave, the Qrs complex, and the T wave. Let's gawk them for a bit. (Refer back to the descriptive as needed.)
The Pr interval on the left side of the graph shows the electrical impulse for the contraction of the atria, immediately followed by its depolarization (or clearing of the electrical charge to that part of the heart muscle) so it can relax and gear up for the next contraction. As mentioned earlier, the actual contraction of the muscle follows the signal by about 1/10 of a second -- in this case while the Pr segment.
The Q wave (labeled Q above) is the initial downward (negative) deflection connected to the initial phase of depolarization of the ventricular heart muscle. Again, depolarization is establishment for receiving an electrical stimulus.
The Qrs involved in the center of the descriptive shows the electrical stimulation of the ventricles, immediately followed by their depolarization. Not surprisingly (considering how much more fine ventricular contraction is), the amplitude of the electrical signal for the ventricles is much larger than that of the atria.
The T wave on the right side shows the repolarization of the ventricles in establishment for the next beat. Note: The St segment represents the duration from the end of ventricular depolarization to the beginning of ventricular repolarization. In English, the T wave represents the recovery duration of the ventricle in establishment for the next beat.
Now, if you've easily been paying attention, you might be asking yourself an certain question, "Where's the corresponding T wave for the atria following their Pr interval. Don't the atria have to repolarize just like the ventricles?" And the sass is, "Yes, they do." Good call there! The question is that the repolarization of the atria happens while the Qrs complex, and because the ventricular signal is so much stronger than the atrial signal, you can't see the atrial repolarization -- kind of like a flashlight turned on while the midday sun. Give yourself a pat on the back for catching its existence though.
And lastly, we have the Qt interval. The Qt interval is not a cut off section, but is a combination of the Qrs involved and its following T wave. It represents the time in the middle of the start of ventricular depolarization and the end of ventricular repolarization. It is beneficial as a measure of the duration of repolarization.
So what's your physician looking for when she examines your Ecg? To put it simply, she's looking for general intervals and general amplitudes in all key segments of the wave. For example:
The Pr interval is indicative of the movement of the cardiac impulse from the atria to the ventricles via the atrioventricular node (see The Anatomy of the Heart), which is normally in the middle of 0.12 - 0.20 sec (3 - 5 small boxes wide). If the Pr interval is greater than 0.20 sec, that's an indicator that an Av block is present (see Heart Problems).
The Qt interval will vary depending on the heart rate, age, and gender of the patient. It increases with bradycardia (slow heartbeat) and decreases with tachycardia (rapid heartbeat). Men have shorter Qt intervals (0.39 sec) than women (0.41 sec). The Qt interval is also influenced by the electrolyte balance, drugs, and ischemia. Your physician will be looking for any interval face the norm.
A Qrs interval of 0.04 to 0.10 seconds -- no larger than half a large box -- and of general amplitude.
Differences in the sizes of the Q waves read from distinct electrodes at the same point in time are indicative of previous heart attacks -- the differences are normally caused by areas of dead muscle tissue. A trained cardiologist can accurately pinpoint the area of damage agreeing to which leads are producing which signals.
Inverted T waves may indicate ischemia, or low blood flow to the heart.
Deviations in the St segment can show ischemia and infarction (i.e., lack of blood flow to the heart muscle and dead muscle tissue). In general, a depression in the St segment indicates ischemia while an elevation indicates infarction.
If you got lost in the last few bullet points, don't worry about it. The foremost point is to understand the "kinds" of anomalies your physician is looking for -- not necessarily to recognize them yourself.
However, for those of you interested in keeping up with your doctor, here's a more detailed tutorial.
And for those of you who just want to walk away with something to hold onto, you can use your Ecg to easily reckon your heart rate by counting the estimate of large squares in the middle of R waves (the high point in each beat).
1 square = 300 bpm
2 squares = 150 bpm
3 squares = 100 bpm
4 squares = 75 bpm
5 squares = 60 bpm
6 squares = 50 bpm
The easiest way to do this is find an R wave that coincides with the beginning of a large box and then plainly count over to the next R wave. In our Ecg snippet (two graphics above), we can find such a point in the middle of the graph. A quick count to the right shows 5 large boxes, or roughly 60 beats per minute. Is that cool or what? You can now read a good chunk of an Ecg -- and without going to healing school.
Seeing the Heart
Listening to your heart and monitoring its electrical activity, may not be enough. Your physician may also want to see the heart, and there are any ways to do that.
The most basic heart photograph is the chest X-ray. Skilled doctors can easily justify a great deal from an X-ray, but that's also the question with the technology -- it requires a great deal of interpretation. That means its accuracy, at times, can be less than desirable.
Arteriogram/angiogram
You can think of the arteriogram (Aka angiogram, angiograph, etc.) as an X-ray on steroids. It's a course that uses a extra dye (contrast material) and X-rays to see how blood flows through your heart.
An area of your body, normally the arm or groin, is cleaned and numbed with a local anesthetic. An Iv (intravenous) line is inserted into the area. A thin hollow tube called a catheter is settled through the Iv and considered moved up into one of the heart's arteries. (X-ray images help the physician see where the catheter should be placed.)
Once the catheter is in place, the dye (contrast material) is injected into the Iv. X-ray images are taken to see how the dye moves through the artery. The dye helps highlight any blockages (dark areas) in blood flow.
Thallium Stress Test
Sometimes heart problems do not show up while general activity; they only manifest under stress (i.e., an increased load on the heart). In those cases, an arteriogram won't recite the problem. The thallium stress test, then, is used by your physician to decide either exercise causes a decreased blood flow to the heart muscle. This test incorporates elements from the Ecg, the angiogram, and an Mri. An Iv is inserted into your hand and Ecg wires are hooked up to your chest. You then walk on a treadmill until you caress symptoms such as chest pain or shortness of breath, or until you are too tired to continue walking. while the whole procedure, your blood pressure and Ecg are monitored continuously. roughly one tiny before you stop walking on the treadmill, the thallium is injected. Thallium is an isotope which is "taken up" by the heart and the coronary arteries. (It flows more easily through non-diseased arteries.) You then lie down on a table, and a scanner takes a photograph of your heart. Areas where blood can't flow easily under stress appear dark. (See below, lower left corner.)
The thallium stress test easily provides more facts than a easy Ecg. Unfortunately, stress tests do not detect atheromata present throughout the heart or other body arteries, nor do they recite the vulnerable plaques, which are typically flat against the walls of the arteries and which are the cause of most heart attacks.
Echocardiogram
An echocardiogram uses high frequency ultrasound waves to produce a moving image of your heart. Such an image can help your physician assess:
- The size of your heart -- both the thickness of the heart muscle and the size of the pumping chambers.
- How well your heart is pumping blood.
- Any valve problems: An echocardiogram can easily detect valve leaks and incomplete closure.
- Blood clots or tumors inside the chambers of the heart.
- Any holes in the walls of the heart.
- It's the same technology used to look at babies in the womb. Check it out.
Full petition Mri
The big new gun in heart diagnostics is the moving Mri. Up-to-date advances in the technology now allow for full petition images of the heart that can be done fast adequate to even accommodate accident room patients. This tool is proving to be one of the most literal, heart assessment tools yet.
Sometimes technology easily does work.
Conclusion
The purpose of this newsletter (in fact, this whole series on the heart, face anatomy, physiology, and final in this issue with diagnostics) was not to turn you into a doctor. My goal was merely to take away some of the strangeness and fear that comes from not knowing what's being done to you when it comes to your heart. There's no interrogate that ignorance and the sense of fear and victimization that come with it contribute greatly to both the anxiety and depression so often connected with heart disease and its treatment. Now, though, you should be able to partner to some degree with your physician when it comes to your treatment -- to be proactive, and less anxious.
Keep in mind, there are some doctors who won't like the fact that you can now ask questions and participate in your own healing -- to interrogate a determination or treatment option. Unfortunately, insecurity does not brook a challenge. My guidance is to stop working with those doctors. Find a physician that will work with you. Good doctors welcome informed patients.
And that concludes our consulation of the heart. When we return to our series on the human body, we will take on the circulatory system.
Cardiac Surgery:Secrets of the Heart
