Arrhythmia Diagnosis: Clinical Indications and Implications
Andrew H. Locke
Peter Zimetbaum
KEY POINTS
Correlating symptoms with electrocardiographic data is the sine qua non of proper utilization of remote electrocardiography (ECG) monitoring. If a symptom does not correlate with an arrhythmia, a cardiac etiology of that symptom is excluded. If a symptom correlates with arrhythmia, further management should be considered.
A remote ECG monitoring device should be selected based on the following:
Duration of monitoring required (short-term vs long-term)
Mode of data acquisition (complete data during the monitoring period, loop recording, or acquisition only after a trigger is activated)
Data interpretation: real time, immediate availability of data, or post hoc analysis after the device is returned
Profile of the device: attached via wires, a patch without wires, or an implantable device
It is essential to determine duration of monitoring required prior to ordering a remote monitor. Duration of monitoring should be guided by the frequency of symptoms.
Unless symptoms are occurring multiple times a day, the traditional 24- to 48-hour Holter monitor has limited diagnostic utility with the exception of specific indications. Longer term monitoring should be considered.
The most common clinical indications for remote ECG monitoring include palpitations, syncope and presyncope, investigation of a cardioembolic source of cryptogenic stroke, and the evaluation and subsequent management of atrial fibrillation.
Remote monitoring in high-risk conditions can be helpful in determining an arrhythmogenic cause of nonischemic cardiomyopathy or in monitoring for arrhythmias associated with adult congenital heart disease; however, its utility in inherited channelopathies and cardiomyopathies is currently less understood.
INTRODUCTION
The diagnosis of arrhythmia can be challenging given the paroxysmal and unpredictable nature of abnormal heart rhythms. The field of remote ambulatory electrocardiography (ECG) monitoring grew out of the clinical need to assess patients for arrhythmia outside of the directly observed hospital or clinic environments.1 The first form of remote monitoring occurred in the 1940s. Dr Norman J. Holter (1914-1983), an American biophysicist, developed the Holter monitor, a 75-lb backpack that had the ability to record a single ECG lead for several hours.2 This was the first example of ambulatory ECG recording.
Remote monitoring technology has evolved to multiple low-profile options to meet a myriad of clinical needs, where the observation of ECG data is paramount to clinical decision making. This chapter will review the utility of remote monitoring in the diagnosis of arrhythmia, the clinical indications that should prompt a clinician to consider remote ambulatory ECG testing, and various implications of remote arrhythmia diagnosis and monitoring.
APPROACH TO THE PATIENT
Remote Monitoring Devices—Technical Capabilities and Limitations
Prior to the specific evaluation of a patient and the determination of whether remote ECG monitoring is indicated, it is important to have a firm understanding of the available technologies. For a full description, please see Chapter 10, Understanding Technology and Equipment.
A careful history and physical examination as well as a baseline ECG will help a physician determine if remote ECG monitoring is indicated. The following four clinical questions help the clinician determine if ambulatory ECG monitoring is indicated and which type of ECG monitoring device should be utilized:
1. What is the presenting symptom or condition that may require remote ECG monitoring?
2. What is the duration of monitoring that is required?
3. Do we wish to correlate symptoms with an episode of arrhythmia?
4. What is the likelihood of a life-threatening arrhythmia?
If remote ECG monitoring is indicated, the physician must choose the most appropriate technology based on device-specific capabilities and limitations:
Duration of monitoring: allow short-term or long-term monitoring
Data acquisition: acquire complete data during the monitoring period; continuously acquire data (looping) but only record data if a trigger occurs (data are recorded pre- and posttrigger) or only acquire data after a trigger is activated
Data interpretation: real time, immediate availability of data, or availability of data only after the device is returned and analyzed
Profile of the device: attached via wires, a patch without wires, or an implantable device
In the case of symptom evaluation, the specific symptom (ie, palpitations) and symptom frequency (ie, daily, weekly, monthly) will determine the type of device and the need for short-term versus long-term ambulatory ECG monitoring. The desire to correlate symptoms with an episode of arrhythmia should encourage a physician to order a monitoring device where a patient-triggered symptom marker can be recorded. Finally, the potential need for immediate or real-time access to data will also influence device choice. A summary of various ECG monitors and their device characteristics can be found in Table 11.1.
TABLE 11.1 Summary chart describing the characteristics and capabilities of various forms of remote ECG monitoring. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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CLINICAL INDICATIONS
There are several clinical indications where remote ECG monitoring can be helpful in the clinical management of various conditions. The majority of indications for remote ECG monitoring center on the investigation of arrhythmogenic symptoms such as palpitations, presyncope, and syncope.3,4,5 Arrhythmias may also be responsible for more atypical symptoms such as fatigue, dyspnea, chest discomfort, diaphoresis, lightheadedness or dizziness, neck pain, visual changes, abdominal discomfort, and anxiety. In the case of symptom evaluation, there are several possible outcomes of remote monitoring that may assist in the ruling-in or ruling-out of an arrhythmogenic etiology (Figure 11.1).
In addition to palpitations, syncope and presyncope, there are many other clinical indications where remote ECG monitoring plays an important role, including the evaluation of cryptogenic stroke, specifically to determine if paroxysmal atrial fibrillation or atrial flutter is present. Remote ECG monitoring can aid in the clinical management of hypertrophic cardiomyopathy, arrhythmogenic right ventricular dysplasia, and arrhythmia-induced cardiomyopathies such as tachycardia-induced cardiomyopathy. The assessment of the efficacy of rate or rhythm control therapy for various arrhythmias can also be assessed with ambulatory ECG monitors. Ambulatory ECG monitoring may be used to identify asymptomatic arrhythmias in patients with congenital heart disease, channelopathies or cardiomyopathies as a form of risk stratification.
Palpitations
Palpitations are an extremely common chief complaint in the outpatient setting. In one study, palpitations were a component of 16% of outpatient encounters.6 Palpitations can be a challenging diagnosis because the term “palpitation” can have varying meanings to providers and patients. Palpitations generally refer to the undesired sensation and awareness of the heart beating in the chest. Palpitation episodes can vary in duration and in character. Developing a method of communication that allows a patient to clearly describe the sensation of the palpitations can be helpful in determining the etiology. Describing with words such as “fluttering,” “pounding,” or “flip-flopping” may be helpful.7 However, the rhythm of palpitations should also be
investigated, namely are the palpitations regular or irregular. We find that contrasting these rhythms by tapping on a flat surface in the examination room can eliminate the reliance on these nonspecific words and help more accurately describe the episodes (Figure 11.2). Additional approaches to the management of patients with palpitations are summarized in several position papers.7,8,9
investigated, namely are the palpitations regular or irregular. We find that contrasting these rhythms by tapping on a flat surface in the examination room can eliminate the reliance on these nonspecific words and help more accurately describe the episodes (Figure 11.2). Additional approaches to the management of patients with palpitations are summarized in several position papers.7,8,9
 FIGURE 11.1 Chart identifying the four possible outcomes of arrhythmogenic symptom evaluation with remote ECG monitoring. ECG, electrocardiography; VT, ventricular tachycardia. |
 FIGURE 11.2 Various rhythmic patterns of palpitations correlating with arrhythmia subtype. AV, atrioventricular; AVNRT, atrioventricular-nodal reentry tachycardia; AVRT, atrioventricular reentrant tachycardia; SVT, supraventricular tachycardia. |
Etiology of Palpitations
Palpitations can be due to a number of conditions. Etiologies include cardiac, psychiatric, anemia-related, medication-related, and substance-related such as caffeine, amphetamines, and cocaine. A cardiac etiology is the most common cause of palpitations estimated at approximately 43%.10 The specific cardiac conditions that may result in the sensation of palpitations are summarized in Table 11.2. Palpitations are very commonly caused by supraventricular or ventricular ectopy as well as by sustained or nonsustained arrhythmias. However, any change in a patient’s rate or rhythm baseline can result in the sensation of palpitations. For example, a change in the average ventricular rate of a patient with chronic rate-controlled atrial fibrillation may note new palpitations. Valvular heart disease, most commonly left-sided valvular insufficiency and mitral valve prolapse, can also be a cause of palpitations.
Indeed, in many instances, palpitations are associated with a normal cardiac rhythm.
Diagnostic Evaluation of Palpitations
History is a key component of the diagnostic workup of patients with palpitations. For example, adult patients who have a history of sustained palpitations since early childhood are more likely to have a supraventricular tachycardia such as atrioventricular reentrant tachycardia than ventricular tachycardia.
TABLE 11.2 Cardiac Conditions Causing Palpitations | |
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There are several indications for which one should consider remote ECG monitoring in the workup of patients with palpitations9:
1. Findings on the history, physical examination, and/or 12-lead ECG that support a likelihood of arrhythmia
2. Patient with known or suspected structural heart disease
3. Family history of an inherited channelopathy or sudden cardiac death
4. Patient anxiety surrounding possible arrhythmia diagnosis
Palpitations and the Diagnostic Yield of Ambulatory ECG Monitoring
Palpitations are responsible for a significant percentage of all remote ECG monitoring indications, accounting for 31% to 43% in two different studies.11,12 Several studies have evaluated the diagnostic yield of varying forms of remote ECG monitoring in the workup of patients with palpitations.4,13,14,15,16,17,18,19,20,21,22 Remote ECG monitoring has also been found to be a cost-effective test in the evaluation of palpitations.10
The diagnostic yield is dependent on the frequency of symptoms and the ECG monitoring technology selected. Our approach to selecting the proper ECG monitor can be seen in Figure 11.3. In the case of daily symptoms, a 24- to 48-hour Holter monitor may be beneficial. However, the majority of traditional Holter monitors will continuously record ECG tracings without the ability to record an electronic symptom marker. Therefore, the correlation of symptoms with ECG tracings is dependent on a patient’s ability to keep a “symptom diary” detailing the time of each symptomatic episode. Additionally, the likelihood of capturing a palpitation event is limited in a 24- to 48-hour period compared with longer term methods of ECG recording. In one study, a continuous external loop recorder (ELR) successfully provided a diagnostic ECG rhythm strip that correlated with symptoms in 67% of patients versus 35% in a 48-hour Holter monitor.15 ELRs provide longer duration of monitoring. Several prospective studies have shown a diagnostic yield up to 86% for ELR within
a 4-week period.17,20,21 In addition to providing a longer interval of ECG monitoring, ELRs have electronically recorded patient-activated markers that can link an electronic symptom marker to a specific ECG tracing. When a patient is experiencing palpitations, this individual can trigger this symptom marker thereby helping to make the diagnosis without reliance on a “symptom diary.”
a 4-week period.17,20,21 In addition to providing a longer interval of ECG monitoring, ELRs have electronically recorded patient-activated markers that can link an electronic symptom marker to a specific ECG tracing. When a patient is experiencing palpitations, this individual can trigger this symptom marker thereby helping to make the diagnosis without reliance on a “symptom diary.”
 FIGURE 11.3 Approach to selecting the proper remote ECG monitor for a patient presenting with palpitations. ECG, electrocardiography. Adapted from Zimetbaum P, Goldman A. Ambulatory arrhythmia monitoring: choosing the right device. Circulation. 2010;122(16):1629-1636. |
Similarly, the diagnostic yield of continuous mobile cardiac outpatient telemetry (MCOT) devices has also been studied in the evaluation of palpitations. One study showed a 73% diagnostic yield using MCOT as the first remote ECG monitoring system.20
Leadless event recorders, also known as “postevent recorders,” are another option for the evaluation of palpitations. This form of remote ECG monitoring is patient-friendly because no hardware is worn continuously by the patient. The patient applies the event recorder to the skin and records an ECG tracing at the time of symptoms. In the case of short-lived episodes of palpitations, this form of monitoring may not be clinically useful given the arrhythmic event may have completed by the time the monitor is applied to the skin. Additionally, ECG data preceding the symptom will not be available for review. Despite these limitations, studies have shown a diagnostic yield between 40% and 72%.14,22
Implantable loop recorders (ILRs) are appropriate for palpitation episodes that occur rarely and in cases where alternative remote ECG monitoring has failed to determine the underlying cause. In a prospective randomized crossover trial studying patients with rare (≤one episode or less per month) palpitations, 73% of patients who underwent placement of ILR yielded a diagnosis versus 21% in the conventional strategy group, which included a 24-hour Holter monitor, a 4-week external recorder, and an electrophysiology (EP) study.19 A summary of the diagnostic yield of various forms of remote ECG monitoring in the workup of patients with palpitations is summarized in Table 11.3.
TABLE 11.3 Diagnostic yield of various remote ECG monitors in the evaluation of palpitations. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Syncope and Presyncope
Syncope is defined as a transient loss of consciousness caused by either a sudden or gradual period of inadequate cerebral blood flow. This decrease in cerebral blood flow is most often the result of an abrupt decrease of systemic vascular resistance and/or cardiac output.23,24 Presyncope refers to a constellation of symptoms experienced prior to the full loss of consciousness. The most feared implication of syncope is that it has occurred as an aborted lethal arrhythmia, which may ultimately recur in the form of sudden cardiac death.
In general, those who experience cardiac syncope have poorer clinical outcomes than similar individuals who do not. In a prospective trial examining the Framingham Heart Study cohort, the prognosis of patients experiencing syncope was evaluated. In over 2100 patients who were followed for an 8.6-year period, patients with cardiac syncope had a 2-fold increase in risk of death compared with those without syncope. Importantly, it was found that those with vasovagal syncope and orthostatic syncope did not have an increased risk of the major predetermined outcomes, including death from any cause, myocardial infarction, or death from coronary heart disease.25 Given an increased risk of death in those with cardiac syncope, evaluating for an arrhythmogenic cause is essential in the evaluation of syncope and presyncope. An understanding of the possible etiologies of syncope is necessary to determine whether remote ECG monitoring is warranted.
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