Read about the latest news on ECG / EKG Machines

Time means heart muscle in a cardiac emergency. Anything that can speed up the cascade of clinical intervention is a good thing when chest pain is involved. To improve clinical intervention times, EKG machines are now being placed in ambulances and carried by first responders. But there is a new twist on this idea that may speed up cardiac care even more.

Little research exists about care received by patients while they are being transported in the ambulance. It is often assumed that such first responders are providing transportation only. They are being shortchanged, quite frankly. They, and their EKG data, are a vital part of the care process, and that link is now being proven.

In Sweden, a study is currently underway that is looking into cases of chest pain, and studying what benefit, if any, there is to transmitting EKG machine data obtained at the scene to the hospital before the patient arrives. The technology is sound. Current EKG machines are being paired with wireless data transfer protocols to make it possible for an emergency room doctor to see the data from the heart of a patient miles away and minutes before the ambulance transporting that patient arrives at the hospital.

Remember that chest pain alone does not necessarily indicate a cardiac event. It is the diagnostic effectiveness of the EKG that determines cardiac involvement with the greatest speed. Preliminary data from the Swedish study found that cardiac care began as much as four hours sooner with the transmitted EKG data than without. This is happening because a triage determination—a decision as to how fast care should start and what kind of care it should be—can be made before a patient arrives in the ER.

The study will be completed in 2010, and should involve over 2000 cases, but the benefits found in the initial study were so dramatic that preliminary data is being released now. The exciting thing is that this is an improvement in care can be accomplished with existing technology.

Some EKG machines have transmitting technology built in. Others can be connected to phones or other communication devices. This new protocol can be implemented with out any additional front end costs, an added benefit for cash strapped hospitals and trauma centers.

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According to a new research study published online in the Journal of Stroke and Cerebrovascular Diseases, an EKG given to a patient receiving emergency treatment for an ischemic stroke can help doctors predict that patient’s likelihood of surviving for the next three months. Each year, there are about 795,000 people in the United States who suffer a stroke, either their first, or a recurrent stroke, according to the American Stroke Association. The majority of these strokes are ischemic strokes, in which blood vessels supplying blood to the brain become obstructed.

As the EKG machine records the electrical activity of the heart, it produces a drawing, or tracing, with a distinctive wave shape. The different parts of this wave are given letter names. In the case of ischemic stroke patients, it is the QTc interval, which measures how long it takes the electrical signals of the heart to pass through the ventricles, that is significant.

If the QTc interval is longer than normal, meaning that the time it is taking for the electrical signal to pass through the ventricles is too long, the stroke patient is at high risk of death during the next three months. The study found that the threat of dying was highest for women with a QTc interval over 440 milliseconds and for men with a QTc interval over 438 milliseconds. Ischemic stroke patients who do not show abnormal electrical activity in the heart when they present for emergency treatment do not have as high a risk of death during the coming three months.

According to study author Dr. Latha G. Stead, there have been few studies that have examined abnormal QTc intervals and patient survival particularly in the context of ischemic stroke. Dr. Stead, supported by the Mayo Foundation Emergency Medicine Career Research Career Development Award, is professor and chair at the University of Rochester Medical Center’s Department of Emergency Medicine. Medical records of 345 patients suffering from ischemic stroke who were treated between 2001 and 2004 were studied during the course of Dr. Stead’s research. The patients were followed for a three month period after the stroke.

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When a patient has a heart attack, the goal of hospitals is to provide emergency angioplasty as rapidly as possible, and within one hour of the patient’s arrival at their facility. This hour is known as the Golden Hour, because during that hour, restoration of arterial blood flow can maximize the patient’s recovery and minimize any permanent damage to the heart muscle. An emergency angioplasty can restore blood flow, even in arteries that are 100 percent blocked.

Time, however, is crucial. Director of Loyola University Hospital’s Cardiovascular Institute, Dr. David Wilber puts it succinctly: “Time is heart muscle.”

Loyola is the first hospital in Illinois to develop a Heart Attack Rapid Response Team, or HARRT. This will consist of having a staff of board certified, experienced cardiologists, nurses, and technicians available at the hospital at all times. Most hospitals do not have these interventional specialists on site at all times, which can cause valuable time and heart muscle to be lost as these on call professionals make their way to the hospital.

One key component in reducing the time it takes for a patient to receive an emergency angioplasty is the presence of 12 lead mobile EKG machines in local ambulances. Paramedics can administer EKGs and transmit the results to the hospital while en route with the patient. A diagnosis can be made, and preparations can take place so that the patient may be immediately taken up to the cardiac cath lab for an emergency angioplasty if one is required. Not all ambulances are currently equipped to administer EKGs, but that number is constantly increasing.

So too is the number of hospitals that are developing 24-hour availability of angioplasty teams. One such hospital, Detroit Medical Center, has been able to reduce the time it takes for a patient to receive emergency angioplasty to only 47 minutes after arrival. This is almost half of the 90 minute window that a combined American College of Cardiology and American Heart Association task force recommends. Vanderbilt Medical Center, Nashville, Tennessee, and Aurora St. Luke’s Medical Center, Milwaukee, Wisconsin, also have angioplasty teams available around the clock.

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This article in the three-part series on EKG electrodes discussed the electronics of EKG electrodes. Be sure to read the other parts regarding chemistry and physics.

In the first two installments in this series, we discussed how the electrical signal of the heart is picked up by the lead and reaches the machine. Now that the signal from the heart has arrived at the EKG machine, there is still one problem to solve. The electric signal from the heart is still small, so small in fact that it would be hard to detect, much less interpret. And it is, after all, the interpretation that is the most important thing.

Today, there is a computer that assists with the final product. But even in the early days of EKG machine, the signals alone were too small to see enough variation to be clinically relevant. There had to be a solution, and that solution was found with electronics.

Electronic signals of all types are waves. Even a small signal is in wave form. If this signal is passed though a device called an amplifier, power is taken from another source and added to the small signal. The shape of the wave is maintained, but the power and size of the wave made larger. It is like setting the enlargement button on a copy machine.

This is the basis of musical amplifiers. The signal strength can be varied according to the needs and wishes of the performers. But on an EKG machine, there is no reason to vary the signal across a range. No one sets EKG machines to eleven, or anywhere else for that matter. There needs to be a constant amplification. This is done with a type of amplifier called a differential amplifier. It multiplies the difference between the input signal and the expected output by a set factor. The accuracy of these factors can be increased by adding additional circuits with additional factors wired in. An appropriate layer of the circuits gives a very high level of accuracy, with little variation or interference that would negatively affect the output of an EKG machine.

These multi-circuit differential amplifiers are called instrument amplifiers. In addition to all these circuits, there are buffers which eliminate the need for so much additional power to match the input wave. It is as these buffers clean up the signal before the additional circuits take over. This increases the overall accuracy of the signal and ultimately the accuracy of the EKG machine, allowing it to produce a tracing that can then be used to diagnose electrical problems in the heart.

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This article in the three-part series on EKG machine electrodes discussed the physics, or conductivity, of EKG electrodes. Be sure to read the other parts regarding chemistry and electronics.

In our last article, we talked about the passage of electrons along a metal wire, or lead. It is not enough to pass the electrons along a lead; they must be passed along with little or no interference. It the physical nature of the lead that will determine the fidelity of the signal that reaches the EKG machine. The wrong choice of material, even if it is a metallic substance, can make the EKG useless. It would be like trying to make an EKG lead out of a piece of twine.

Metal has resistance, and it is that resistance that can transform the electricity into other energy forms, heat for example, and alter the output on the other end.

Think of it this way: we are not talking about wires, but tubes. And the tubes are carrying water, as tubes are wont to do. Let the water be analogous to the electricity. If there is a tube filled with wax, there would be no water coming through. This is a twine based EKG lead, a non-conductive lead. Its use is so limited as to be absurd.

But what about something not so outlandish, a metal lead, but a high resistance metal. Our tube is now filled with rocks, but they are sharp, jagged rocks. Water passes through, but does so slowly and the water that comes out the other end is turbulent and filled with bubbles. This is better than our non-conductor, but the electricity is too different from the input to be of any use in an EKG.

What we need is a tube that is as good a conductor as we can find. The best would be a tube with no filling. But that, extending our metaphor, is superconductivity. And that currently cannot occur at room temperature. Super cooling the patient to minus 423 degrees Fahrenheit, which is the necessary range for superconductivity, would give negative clinical outcomes to an EKG, not to mention increasing the price.

What is used, and functions well, are good conductors. Aluminum, copper and in some instances silver or gold are good choices. Going back to the tube analogy; these are tubes filled with smooth rocks, the water (electricity) will pass through with little turbulence and come out the other end will some, but not many, bubbles.

So, the signal has gone from the heart to the EKG machine, but there is one last part that must be played. The signal must be loud enough to be interpreted.

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All the technical developments behind the EKG machine would be meaningless if not for one thing: the electrode connecting the EKG machine to the patient. Electrode technology is a mixture of chemistry, physics and electronics. In this part of this three part series, we will be discussing the chemistry.

The electric currents that an EKG machine is concerned with are minuscule, especially when compared to the amounts of electricity that we deal with on a daily basis. Given that, how can they be picked up, much less detected and interpreted?

It begins with chemistry, not the biochemistry of the human body, but the chemistry of electrons. All atoms have electrons, either tightly bound to the rest of the atom, or loosely bound. The looser the binding, the easier these electrons can move from one atom to another. This is the reason behind the formation of chemical compounds, whether slowly as in rust, or quickly as in combustion, or, for that matter, very rapidly, as with an explosion. But what we are concerned with is the electron capacity of metals.

Metals are in part defined by a particular state of electrons called delocalized electrons. They are neither tightly bound or loosely bound, but extend across several atoms in an orbit. This is not just a footnote of chemistry. This is the basis of metals’ ability to conduct electricity.

When the electron orbit of one group of atoms is lined up with another orbit from another group of atoms, it forms an even bigger orbit. Multiply this over the length of a piece of metal, a wire for example, and you have now a giant cloud of electrons. The great thing about this cloud is the way it can pass electrons along from one end to another. The passing of electrons is a good model: it is as much a pull from the electrons in the metal itself as it is a push from an outside source.

What all this means for an EKG machine is that certain metals with a high degree of electron activity can pass along very small charges, and pass them along will little change. This is the chemistry that begins the EKG process.

Be sure to read the two additional articles in this series on Physics and Electronics.

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The EKG machine remains a singularly elegant piece of medical technology. A few electrodes are placed on the patient’s skin, a few twists of the controls, and the clinician has a representation of the electrical activity of the heart. But like every piece of technology, the EKG machine has its strengths and its limitations. Here, a quick review of what an EKG can, and can’t, do.

Using an EKG machine, a trained clinician can determine the following.

• Evidence of damage to different parts of the muscle of the heart, either from a prior myocardial infarction or one that is currently developing
• Evidence of impaired or blocked blood flow to the muscle of the heart, useful in diagnosing unstable angina or a myocardial infarction
• Tachycardia, bradycardia, or irregular heart beat
• Evidence of hypertrophy of the muscle of the heart
• Evidence of some congenital heart abnormalities
• Evidence of myocarditis or pericarditis
• How the heart is oriented in the chest cavity
• Rate and rhythm of the heart’s muscular contractions
• Patterns of atypical or abnormal electrical activity, possibly from underlying cardiac disorders
• Damage to the heart from chronic disease including hypertension, emphysema, etc.

With all that an EKG machine can do, it is sometimes difficult to remember its limitations. First among these limitations is that the EKG is a picture of cardiac activity only at the moment the EKG is taken. Some underlying heart problems can be severe and yet not show any symptoms on a routine EKG. For example, a patient with severe coronary artery disease may be asymptomatic and have a normal EKG under routine testing. Only an EKG recorded during a stress test can give an accurate picture of this type of condition.

But the greatest risk with the use of EKG is that by some patients, it is considered the ultimate measure of heart health. Not all cardiac conditions can be discovered during a routine EKG. In the patient with heart symptoms or a familial history of heart disease, additional cardiac testing is required for a thorough assessment.

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If there is a right way to do something, you can bet there is a wrong way to do it as well. If you are in the market for an EKG machine, whether it is a first time purchase or a replacement machine, here are some buying strategies that you should be sure to avoid, lest they cause you grief and disappointment.

Do not wait until your existing EKG machine is beyond repair to begin shopping. If you wait until the last minute, you will not be able to take your time in making a decision and may be pressured into making a bad one. It takes time to consider what you need and compare prices, so start shopping before you absolutely have to for best results.

Do not test drive a machine you have no intention of purchasing. The last thing you need to do is test drive a machine that you cannot afford to buy. You and your staff will only fall in love with the machine, and then be disappointed when it has to go back to the store.

Do not automatically buy expensive medical equipment from your local equipment representative. These days it would be foolish not to take advantage of the many sellers of used medical equipment that you can access and evaluate over the Internet. No longer are you at the mercy of the local supplier, who may trade more on your relationship than the price and service he can offer.

Do not buy a used EKG machine that does not come a service warranty. Also check to see where your local authorized repair shop is located; you don’t want to have to ship your machine across the country if it needs repair. You want relatively local repair options to minimize downtime.

Do shop around for prices on supplies, just as you shop around for the machine itself.

If you keep these considerations in mind, then your EKG machine buying experience will be a pleasant one, and you will find the right machine for your practice at just the right price.

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Most of us associate having an EKG with a frantic trip the emergency room, or lying flat on our back in our doctor’s or cardiologist’s office having a diagnostic procedure. But you can have an EKG test while you are at home or out and about doing your normal activities.

This type of EKG is called an ambulatory EKG, or more commonly a Holter monitor, after its inventor Dr. Norman J. Holter. A Holter monitor is a device which is designed to be worn for an extended period of time, from 24 hours up to a month. Like a standard EKG machine, it uses electrodes to record the electrical activity of the heart, though it may use a smaller number of electrodes for data capture, even as few as three.

Unlike a normal EKG test, however, the Holter monitor is designed to allow doctors to observe and diagnose conditions which may be difficult to observe using a normal EKG. For example, a patient may having occasional arrhythmias. The chance of catching the patient during that time, at a facility equipped to perform an EKG, setting up the EKG, and catching the arrhythmia while it is happening is so small as to be nonexistent.

In contrast, if a patient is wearing an ambulatory EKG machine or Holter monitor, the instant recording of data is only the push of a button away. For example, patients wearing this cardiac monitor are instructed to start the device recording any time they feel a symptom of what is expected may be a cardiac event. Many patients are also instructed to keep a journal, recording any medically significant information, including date and time of experiencing symptoms, symptoms experienced, activity at time of symptom onset, duration of symptoms, etc. Not only do you then have subjective information, but you have the objective record of the patient’s heart’s electrical activity while symptomatic.

This can provide clinical data useful in diagnosing—and ruling out—a variety of cardiac conditions, including:

• Atrial fibrillation
• Multifocal atrial tachycardia
• Paroxysmal supraventricular tachycardia
• Ventricular tachycardia
• Bradycardia

Holter monitors are also used to observe the way the heart reacts to normal every day activity and stress, or as a more thorough assessment of heart functioning.

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