"Arrhythmia" means "irregular heartbeat" in English. The term "arrhythmia," therefore, is not a diagnosis, but a general term describing many different conditions that share the commonality of irregular heartbeat. Some patients, unfortunately, even after extensive diagnostic evaluation, are said to have suffered from an "arrhythmia." Diagnosing someone as having an "arrhythmia" is like saying that the patient has a "heart condition." It is vague and provides little or no useful information for the patient or for the next physician taking care of the patient. For, there are many different types of arrhythmias with widely varying severity of symptoms, and, more importantly, markedly different prognoses.
There are literally dozens of different types of arrhythmias. Some arrhythmias can kill a patient instantly while others are completely benign. Some can cause severe symptoms like racing heartbeat and fainting spells while others may produce absolutely no symptoms whatsoever. Making a specific diagnosis of the type of arrhythmia the patient has, therefore, is of paramount importance.
As a general rule, in order to make a diagnosis of an arrhythmia, some forms of electrocardiographic recording (i.e., EKG, Holter monitor, or event monitor) must be made at the time the arrhythmia is occurring. Evaluation by symptoms alone is inadequate. This is because symptoms from different arrhythmias may feel exactly the same to a patient, and the same arrhythmia may feel differently for different patients. For example, the sensation of palpitation can occur in patients with ventricular tachycardia or with PVCs, two conditions with vastly different prognoses. The physician, therefore, usually can not diagnose one arrhythmia from another based on symptoms alone.
In addition, in between episodes of arrhythmias, the EKG can be completely normal, making the diagnosis quite challenging. A very common scenario is a patient with an SVT (a very rapid arrhythmia) who has an episode of attack once a month, lasting 10 minutes each. Every time this patient runs to the emergency room, the SVT has already stopped and the EKG in the ER is completely normal. Many such patients have been misdiagnosed as "panic attack" or "anxiety" because of the lack of physical evidence (other than patient's subjective report of symptoms) of an arrhythmia. Some patients even leave the ER with a diagnosis of "palpitation," which is a symptom, not a diagnosis. The true diagnosis can be quite elusive until one day when an EKG is finally done at the time an episode is still ongoing.
If an arrhythmia becomes persistent and is present day-in and day-out, as often is the case for atrial fibrillation or atrial flutter, the diagnosis is quite easy with a routine EKG done in the physician's office. The challenge is when an arrhythmia occurs intermittently (on and off) or is self-limiting, whereby a EKG performed in between attacks can be completely normal. To circumvent this problem, one would go to the next level of evaluation with a long-term monitor.
Long-term monitors basically are EKG recorders that patients can take with them. They fall into two major categories. A "Holter monitor" records continuously the EKG of a patient, usually for 24 hours. The advantage of a Holter is that every single heartbeat during that day is recorded and can be analyzed. The disadvantage is that if an arrhythmia did not happen on that particular day, the Holter would not be useful. An "event monitor," on the other hand, is a long-term monitor that can be used for up to 30 days at a time. The advantage is that the longer the recording period, the better chance of "catching" an intermittent arrhythmia. The disadvantage is that an event monitor must be activated by the patient and downloaded through a telephone line, a task that requires certain amount of manual dexterity and may be difficult for some patients.
For certain arrhythmias which are so rare that they occur once or twice a year, the diagnosis can be nearly impossible to make with any of these monitors. In these cases, or in patients who are not capable of handling an event monitor, an implantable monitor is available that can monitor patients' rhythms for up to 2 years, continuously, 24/7. The major advantage of this monitor is the length of time of monitoring compared to other monitors. The disadvantage is that it requires a surgery, though a very minor one that takes about 5 minutes to complete.
For many patients, both Holter monitor or event monitors, or even implantable monitors may be necessary because these different monitors have different capabilities and complement each other. However, if the diagnosis remains elusive after extensive evaluations with these "passive" tests, a "proactive" test may be necessary.
A "passive" test waits for an arrhythmia to occur spontaneously before making a recording. This can be time consuming and sometimes a diagnosis simply can not be made despite extensive evaluation. In those cases, a "proactive" approach may be necessary whereby the physician actively "provokes" an arrhythmia in order to make a recording of it for a diagnosis.
This "proactive" approach may involve simply having patient engage in activities which historically have provoked patient's symptoms, while the patient is wearing a monitor. For example, certain arrhythmias that occur consistently during physical activities or after ingestion of alcohol may be reproduced with these activities during a monitoring period.
For conditions that occur with exercise, a treadmill stress test supervised by your physician sometimes can reproduce an arrhythmia, helping to clench the diagnosis. A similar test monitoring the "T waves" of the EKG can help reveal underlying conditions that can cause serious arrhythmias. For certain conditions that cause fainting spells, a tilt table study can recreate an episode and help reveal a cause.
Lastly, when all else fails and the diagnosis remains uncertain, an electrophysiology study can be done to confirm or exclude certain arrhythmia diagnoses. This invasive test is also done in conjunction with radiofrequency ablation.
In summary, there is an extensive battery of diagnostic tests for patients with symptoms suspicious for arrhythmias. These tests range from simple and routine to complex and invasive. Different tests have different yields for diagnosing an arrhythmia and not all tests are appropriate for every patient. Your physician can made the decision on which tests are appropriate for your particular condition.
While every physician may evaluate patients with suspected arrhythmias differently, a general rule is usually followed. Most physicians would recommend starting with the least invasive (which, incidentally, may have the lowest yield) and progress to the most invasive tests if the diagnosis still remains unclear. On the other hand, for certain patients with serious presentations (e.g., a fainting spell that resulted in a major car accident) or patients whose line of work involves the safety of others (e.g., a commercial airline pilot who suffers from loss of consciousness), the physician may elect to bypass the low-yield, non-invasive tests and go directly to the more invasive evaluations.
The following paragraphs describe in detail some of the most common diagnostic procedures a physician uses in the evaluation of patients with suspected arrhythmias.
Office and Hospital Based Diagnostic Procedures for Arrhythmias
Electrocardiogram (EKG). This is the most basic and standard initial evaluation for patients with a suspected arrhythmia. An EKG is a window into the electrical activities of the heart. Multiple electrodes (stick patches) are placed on the arms, legs, and over the chest area in order to record electrical activities of the heart from different angles of view. The heart generates electrical activities with each heartbeat, which can be detected by the voltage difference between pairs of electrodes and translated into graphical display on paper. Today's standard EKG utilizes 12 electrodes, thus the name "12-Lead EKG." An EKG is most useful in diagnosing an ongoing arrhythmia at the time the EKG is being performed, but it is not useful if the arrhythmia, or the symptoms suspected to be due to arrhythmia, is no longer present at the time of the evaluation. Keep in mind that an EKG is a static picture, or a "snap shot," of what is happening in the heart at the time the recording is made.
Holter monitor. This is an EKG recorder that continuously records every heartbeat of a patient for a period of usually 24 hours. Rather than having 12 leads, most Holter monitors utilizes 3 leads. Patients are usually "hooked up" with a Holter while in the physician's office, wearing it for 24 hours, then returns the next day to have it removed in the office. Patient may not shower and should avoid strenuous activities (unless specifically instructed by the physician) during the recording period. At the end of the 24 hour period, patient may remove the unit on his or her own and bring the unit back to the office for analysis.
The recording of the heart rhythm on a Holter is made in a continuous fashion onto an electronic media, which is then downloaded into a computer and analyzed beat-by-beat. This test is most useful if an arrhythmia is there all the time, or occurs frequently enough to be "caught on tape" during that 24-hour period of recording. It is therefore very important for the patient to write down in the accompanying diary any symptoms that occurred during the recording period, so the physician can correlate the symptoms to actual arrhythmias found on the recording.
One important limitation of a Holter monitor is that it records only during that 24 hours of time and may miss an infrequent arrhythmia. In other words, an arrhythmia that occurs only a few times a year is unlikely to be "caught" by chance during any single 24-hour period of recording. In those cases, a long-term event monitor may be the preferred choice of test.
Event monitor. An event monitor is a long-term (usually 30 days) monitoring device that records "patient triggered" events. Similar to an EKG or a Holter monitor, it records the electrical activities of the heart via electrodes placed on the patient's chest. The electrodes and wires are attached at all time to patient's chest and can be taken off and replaced as needed for shower and other activities where patients may not wish to have the hardware attached.
Unlike a Holter monitor, which records continuously, the event monitor records only when activated by patients. In other words, while the monitor continuously keeps a "loop" memory, the actual recording of the heartbeat and writing of the data onto the electronic media occurs only when patient triggers the recording by pressing a button on the unit. This is so that the physician can correlate patient's symptoms to what is recorded, thus confirming or refuting the cause of patient's symptoms being of arrhythmic origin. A major advantage of a loop-recorder is that it always keeps the preceding 40-60 seconds of data in the loop memory, such that if a patient was not able to trigger the recording immediately at the time of the symptoms, but does so a short time later, the data may still be useful.
Some newer types of event monitor have automatic recording capability. Rather than waiting for patients to make a recording during symptoms, these devices can detect asymptomatic episodes of arrhythmias. This is most useful in patients with suspected atrial fibrillation. However, in contrast to the traditional patient-triggered event-recording, the automatic recording is NOT used to help explain patient's symptoms (as it is not patient-triggered), but to detect sub-clinical, or "silent" arrhythmias.
Another type of event monitor is so-called "non-loop" event monitor. They usually come in the shape of a credit card. Unlike the loop-recorders, this unit does not have to be attached through electrodes to the patient at all time. One simply can keep such a card in his or her pocket or purse, and can apply it to the chest whenever an episode of arrhythmia occurs. Although most patients may prefer this type of event monitor because of comfort and convenience, it does not have "loop" memory since it is not attached to the patient all the time. The recording will start only after it is placed on the chest and activated. For some arrhythmias that are very short in durations, i.e., seconds, by the time the unit is applied appropriately on the chest and recording started, the arrhythmia may have been missed. Furthermore, this type of monitor is not useful for diagnosing syncope, or fainting spells. For, without a loop memory, by the time a recording is made, the event that initially caused fainting may already have passed.
For any type of event monitors, once a recording is made successfully with patient activation, the data can then be downloaded through the telephone to a centralized station, which in turn faxes the EKG tracings to the physician on record. The physician can then correlate findings on the recording with patient's symptoms. After 30 days of monitoring, patients would usually make an appointment with the physician to review the results.
There are two major advantage of the event monitor over the Holter monitor. One is that a patient can keep the event monitor for an extended period of time (usually 30 days and renewable), maximizing the chance of recording an infrequent or intermittent arrhythmia. The yield for a diagnosis is directly proportional to the length of the recording, based on probability and statistics. The other is that because the recording occurs only when triggered by the patient (for the traditional event recorders), the physician can determine whether patient's symptoms are actually caused by an arrhythmia. In other words, if a patient feels severe palpitation while concurrent monitor recording showed only normal regular heartbeats, one can safely conclude that the symptoms are not due to arrhythmias.
One disadvantage of an event monitor compared to a Holter is that, too frequently, patient may "forget" to have the monitor close by during an episode, or that a patient may be in a social situation in which making such a recording (the unit may make loud beeping sounds) may be socially unacceptable. Yet for other patients, making a recording and downloading the information over the phone may be more than the manual dexterities of the patients can handle. This is when an implantable loop recording can be helpful.
Implantable Loop Recorder. When extensive testing fail to identify an arrhythmia and yet arrhythmia is still suspected as the cause of patient's symptoms, the physician may recommend proceeding to insert an Implantable Loop Recorder. The idea of an implantable loop recorder is identical to that of a traditional event recorder. It records specific patient triggered event to help the physician explain patient's symptoms. However, the main difference is that this unit is implanted surgically on the chest so that it is there all the time. Patient simply can not "forget" to bring the unit with him or her, nor would feel uncomfortable "making a scene" in public since the unit can record automatically. The unit is there 24/7 for 2 years and faithfully records the information continuously in a loop memory, and writes onto the hard memory when triggered by patient or when an automatic detection algorithm is met. The automatic algorithm usually triggers a recording when the heartbeat is either too fast or too slow, conditions that can cause symptoms of palpitation, lightheadedness, or fainting spells.
This very small (about 1x3 inches) device is implanted just under the skin on the chest, a surgery that usually takes about 5 minutes to complete and is done on an outpatient basis. The recorder uses its built-in electrodes on the unit to make recording of the heart rhythm. The internal battery can last 18 to 24 months.
The major advantages of this type of recorder are two folds. One is that a patient will never "forget" to bring the recorder with him since it is already implanted under the skin. Secondly, among all monitors, the implantable loop recorder has the best chance of recording an arrhythmia that occurs very infrequently (i.e., once a year).
T-Wave Alternans. This is a treadmill stress test that specifically evaluates patients for risk of serious arrhythmias and sudden cardiac death. It records microscopic changes in the T-Wave (a part of your EKG) not visible to the naked eyes. It has been shown to be very effective in differentiating patients who are at low risk versus those who are at high risk for sudden death.
Tilt table study. This simple and noninvasive test evaluates patients with dizziness and fainting spells (syncope). Specific diagnoses such as vasovagal syncope, neurocardiogenic syncope, postural orthostatic tachycardia syndrome, and carotid hypersensitivity syndrome can be made this study.
The test is usually done on an outpatient setting after an overnight fast. The patient, strapped to a tilt table to prevent accidentally falling off the table, is tilted to about 75 degree angle and monitored with EKG and blood pressure recording continuously for 20 to 45 minutes. For patients with recurring fainting spells, the underlying cause of fainting can be revealed in about 50-75% of the cases.
In order for the diagnosis to be made, however, the fainting or near-fainting episodes must be reproduced during the test. While this may sound disconcerting, this is the only way to confirm a diagnosis. Furthermore, there is no better place to have a fainting spell than when under the direct care of a Cardiac Electrophysiologist.
Electrophysiology study (EPS). This invasive study is generally needed for patients whose cause for fainting or severe palpitation remains unknown despite extensive noninvasive evaluations. It is also useful to differentiate the various causes for a documented episode of arrhythmia. It can be used to risk-stratify certain patients with known or suspected arrhythmias. Lastly, it is performed in conjunction with radiofrequency ablation, as a mean to confirm the mechanism of the arrhythmia before performing curative ablation.
The procedure is performed in a hospital setting in the cardiac catheterization laboratory, the same facility where coronary angiogram and angioplasty are performed. Several catheters are inserted through the veins in the groins into the heart (see picture), after which electrical stimulation of the heart is performed through these catheters by the Electrophysiologist. This provocative test can reveal an underlying electrical conduction problem such as slow heartbeat or heart block, as well as reproducing and confirming the cause of a rapid arrhythmia which the patient chronically suffers from. Therefore, patients do not necessarily have to be in their arrhythmia at the time of the procedure.
If a slow heartbeat is documented, one can prescribe the appropriate treatment, usually a pacemaker. If a fast heartbeat is confirmed, one of several treatment options exist, depending on the type of rapid heartbeat discovered. For some rapid heartbeat that are potentially life-threatening, such as ventricular tachycardia, an implantable defibrillator is indicated. On the other hand, for the more benign forms of rapid heartbeats, such as SVT, the arrhythmias can be "mapped" to determine the their causes and the suitability for ablation. In the majority of cases, ablation can successfully eliminate the culprit of the arrhythmias, resulting in a long-term permanent cure for the patient.
Thus, an Electrophysiology study is a diagnostic study that helps the Electrophysiologists confirm the root of the suspected electrical problem of the heart. As the initial invasive Electrophysiology procedure, it serves as a gateway to other therapeutic modalities available to treat the arrhythmias.
Many patients who have serious symptoms from their rapid heartbeat, such as fainting or near-fainting, are often very reluctant to have a test which can provoke their arrhythmias. Reproducing the arrhythmia, however, may be the only way to confirm the causes of their arrhythmias in most patients. Furthermore, there is no safer place to have an arrhythmia than in the cardiac catheterization laboratory under the direct care of a Cardiac Electrophysiologist and in the presence of an entire team of personnel specializing in the chronic as well as emergency management of arrhythmias.
In contrast to an coronary angiogram, a procedure designed to look for clotted arteries of the heart (coronary arteries), an Electrophysiology study is not meant to evaluate the patency of patient's arteries. But rather, it focuses on the evaluation of the electrical health of the heart.
Exercise Treadmill Test. This is a diagnostic test used to evaluate patients for the health of their coronary arteries. Its most common function is to rule out the presence of hardening of the arteries in the heart in patients with chest pain. However, for the Electrophysiologist, a treadmill can serve additional purposes of evaluating causes for fainting, certain types of rapid heartbeat (e.g. exercise induced VT), slow heartbeat (2:1 heart block), and can help guide appropriate programming of a pacemaker or a defibrillator.
This test involves placing a patient on an exercise treadmill with progressively increasing speed and grade, while monitoring the patient with EKG. An underlying heart condition can frequently be revealed during the test. This test is often combined with other imaging modalities, such as echocardiogram, to improve the accuracy of of the test.
Echocardiogram. A noninvasive test, echocardiogram images the heart in the same way that an obstetrician images an unborn baby in the womb. An ultrasound probe is placed on the chest and a real-time beating-heart picture can be seen immediately on the TV screen. This test is excellent for detecting enlarged heart and abnormal heart valves such as aortic stenosis and mitral valve prolapse. It can also detect abnormalities in the lining of the heart, as well as some areas outside of the heart. Completely noninvasive, the test uses no dye, no radiation, and posts virtually no risk to any patient.
For an Electrophysiologist, an echocardiogram can help evaluate the health of the heart muscle to determine the "ejection fraction" and the suitability of a defibrillator. It can reveal certain conditions associated with arrhythmias, such as Epstein anomaly, hypertrophic cardiomyopathy, and arrhythmogenic RV dysplasia.
Tissue Doppler. This specialized test gives information on how the main pumping chamber of the heart (left ventricle) works (or doesn't work) in patients with heart failure. It is an adjunctive test to a standard echocardiogram. It helps identify patients with severe heart failure who are candidates for cardiac resynchronization therapy (CRT). CRT is a specialized pacemaker or defibrillator capable of "resynchronizing" a failing heart to improve patient's symptoms and heart function.
Stress Echocardiogram. This test combines an exercise treadmill test with an imaging modality, the echocardiogram. This improves the ability to diagnose coronary artery disease (clogged artery of the heart) above and beyond the standard stress EKG test. This test can also be used to evaluate patients with known or suspected arrhythmias.