After a bit of "time off" (working), it is time for another post. Today we will be talking about cardiodiagnostics. This may be a bit of a dry subject, but it will hopefully serve as a resource for people so they can understand what the heck their doctor is trying to figure out.
First off, what is cardiodiagnostics?? These are tests that can be performed upon the heart for a variety of reasons, but essentially they are designed to find out something specific about a particular function of the heart. There are several different kinds of tests, so here are the most common ones you may have to undergo.
Exercise Stress Test (EST): Run Homer, Run!
The EST, or commonly called a "stress test", is probably one of the most common tests of cardiac function. Now, the "stress" portion of the test is not like mental stress, or sweating on a witness stand while a prosecutor drills you with questions ("I want the truth"...."You can't handle the truth!"). No, the stress referred to here is a physical stress on the heart. And what exactly does that mean? Well, for most of our everyday lives, our heart is not under a particularly significant amount of stress. Pumping blood throughout our system for everyday activities is not particularly taxing on the heart muscle. Blood flow through the coronary arteries is sufficient enough to provide oxygen to the muscle and it pumps away at 70 beats a minute without a bother.
Now, what if you suspected that someone may have some underlying (or not quite apparent) coronary disease? What if you were to think that one of these arteries may have a narrowing in it that may limit the amount of blood flow to a portion of the muscle (or one of the villages - see previous post on coronary arteries). This narrowing may not be significant enough to cause any trouble during everyday life, but if we were to ask the heart to work just a bit harder, the muscle would need to pump faster and stronger, it would demand more oxygen, and this narrowing may be enough to limit this increased demand and cause problems. This is where the stress test is useful.
During a stress test, patients are hooked up to a blood pressure machine as well as cardiac monitor and asked to step on a treadmill. The cardiac monitor is all of the stickers on the chest with the wires going to a screen that displays the electrocardiogram.
First off, what is cardiodiagnostics?? These are tests that can be performed upon the heart for a variety of reasons, but essentially they are designed to find out something specific about a particular function of the heart. There are several different kinds of tests, so here are the most common ones you may have to undergo.
Exercise Stress Test (EST): Run Homer, Run!
The EST, or commonly called a "stress test", is probably one of the most common tests of cardiac function. Now, the "stress" portion of the test is not like mental stress, or sweating on a witness stand while a prosecutor drills you with questions ("I want the truth"...."You can't handle the truth!"). No, the stress referred to here is a physical stress on the heart. And what exactly does that mean? Well, for most of our everyday lives, our heart is not under a particularly significant amount of stress. Pumping blood throughout our system for everyday activities is not particularly taxing on the heart muscle. Blood flow through the coronary arteries is sufficient enough to provide oxygen to the muscle and it pumps away at 70 beats a minute without a bother.
Now, what if you suspected that someone may have some underlying (or not quite apparent) coronary disease? What if you were to think that one of these arteries may have a narrowing in it that may limit the amount of blood flow to a portion of the muscle (or one of the villages - see previous post on coronary arteries). This narrowing may not be significant enough to cause any trouble during everyday life, but if we were to ask the heart to work just a bit harder, the muscle would need to pump faster and stronger, it would demand more oxygen, and this narrowing may be enough to limit this increased demand and cause problems. This is where the stress test is useful.
During a stress test, patients are hooked up to a blood pressure machine as well as cardiac monitor and asked to step on a treadmill. The cardiac monitor is all of the stickers on the chest with the wires going to a screen that displays the electrocardiogram.
Now, start walking. Not bad, the heart can handle this. The electrocardiogram (ECG) looks the same as it did before, but maybe starts to speed up as the heart rate increases. Over the course of the test, the speed of the treadmill as well as the incline (slope) start to increase, all while the ECG is being watched closely. You can imagine as these two things are increased, so is the heart rate, contraction strength, and demand for oxygen by the heart muscle. If there is any significant narrowing to any of the coronary arteries, oxygen/blood delivery will be limited by this narrowing, the heart muscle downstream from this will become "unhappy", and two things will occur: (1) a heart muscle that is not getting enough oxygen will start to cramp (like any other muscle) and produce chest pain, and (2) the electrical pattern of the ECG will begin to change in a way that can indicate to the cardiologist what portion of the heart is suffering, and thus which section of the coronary arteries are being compromised.
Is it a perfect test? No. But, it's cheap to perform and is a great screening test for people with risk factors for cardiovascular disease.
Echocardiogram: Hollywood Heart
Now, notice the spelling - ECHOcardiogram. Not to be confused with ELECTROcardiogram. These two tests are very different. We've already learned a bit about the electro version, now let's talk about the echo.
Echo, as you may have guessed, refers to sound waves, and thus an echocardiogram is a test performed upon the heart using sound waves. Sound waves are the basis of an ultrasound machine, and so an echoocardiogram is really just an ultrasound of your heart.
Ultrasound? Those things are for babies! (literally). Like the obstetrical ultrasounds, pictures generated of the heart are not really pictures, but rather real-time movies of the heart as it is working.
Is it a perfect test? No. But, it's cheap to perform and is a great screening test for people with risk factors for cardiovascular disease.
Echocardiogram: Hollywood Heart
Now, notice the spelling - ECHOcardiogram. Not to be confused with ELECTROcardiogram. These two tests are very different. We've already learned a bit about the electro version, now let's talk about the echo.
Echo, as you may have guessed, refers to sound waves, and thus an echocardiogram is a test performed upon the heart using sound waves. Sound waves are the basis of an ultrasound machine, and so an echoocardiogram is really just an ultrasound of your heart.
Ultrasound? Those things are for babies! (literally). Like the obstetrical ultrasounds, pictures generated of the heart are not really pictures, but rather real-time movies of the heart as it is working.
As you can see from these images, we can visualize not only the four chambers of the heart, but also portions of some of the valves separating these chambers as they open and close. This is very important. An echocardiogram allows us to watch the function of the heart valves in real time, and using different settings on the ultrasound machine, the blood flow across these valves can be measured and analyzed. Problems with the valves like stenosis (too tight) or regurgitation (too loose) can be detected and monitored, and the valves could then be repaired then if needed.
Holter Monitor: The Murphy/Nolte
So far we have been able to get a good sense of the state of the coronary arteries (stress test) and the valves (echocardiogram), but what about the electrical system? The electrocardiogram is a great test for this, but it literally only lasts for about 10 seconds. What if we wanted to monitor the heart rhythm for a longer period?
We can do that! The Holter monitor is essentially a portable electrocardiogram machine. You put the stickers on your chest as per usual, but the monitor stays attached for much longer than 10 seconds. You can walk around and go about your daily activities knowing that every electrical impulse your heart is generating is being captured and stored for analysis......
Holter Monitor: The Murphy/Nolte
So far we have been able to get a good sense of the state of the coronary arteries (stress test) and the valves (echocardiogram), but what about the electrical system? The electrocardiogram is a great test for this, but it literally only lasts for about 10 seconds. What if we wanted to monitor the heart rhythm for a longer period?
We can do that! The Holter monitor is essentially a portable electrocardiogram machine. You put the stickers on your chest as per usual, but the monitor stays attached for much longer than 10 seconds. You can walk around and go about your daily activities knowing that every electrical impulse your heart is generating is being captured and stored for analysis......
Now, this may seem like a long time, and it is when you have to sleep with this thing and can't shower! However, the information that can be gathered in this time can be invaluable. Abnormalities in the heart rhythm that may not be captured in a 10 second ECG could be found with this device, and problems like blacking out or lightheadedness or dizziness may have a cardiac cause.
These tests are the big three, the ones most commonly ordered and utilized by cardiologist and family doctors in the community to help diagnose potential problems with the heart, whether it be the coronary arteries, valves, or electrical system.
Now, there are many more tests that we have not touched on, all of which are very important. However, we can't go through all of these individually or else this post would go on forever. Some of these are just a variation on one of the above (like a nuclear medicine stress test). Some are highly invasive (like a cardiac catheterization or angiogram) and nothing like these three. However, no matter what test you are being sent to have done, keep in mind that they all have an important role in trying to figure out what's happening with your ticker.
These tests are the big three, the ones most commonly ordered and utilized by cardiologist and family doctors in the community to help diagnose potential problems with the heart, whether it be the coronary arteries, valves, or electrical system.
Now, there are many more tests that we have not touched on, all of which are very important. However, we can't go through all of these individually or else this post would go on forever. Some of these are just a variation on one of the above (like a nuclear medicine stress test). Some are highly invasive (like a cardiac catheterization or angiogram) and nothing like these three. However, no matter what test you are being sent to have done, keep in mind that they all have an important role in trying to figure out what's happening with your ticker.