Ambulatory Electrocardiographic Monitoring

Ambulatory Electrocardiographic Monitoring

History

• Circa 1947, Norman Jefferis "Jeff" Holter first broadcast a radioelectrocardiogram (RECG). He wore it on his back while riding a stationary bicycle.
• His interest in the electrical activity of the human body led to the idea of monitoring heart signals.
• The technique involved recording and transmitting ambulatory electrocardiograms via radio-electrocardiograph and audiovisual superimposed ECG presentation, enabling faster review of ECG data.
• Initially (in 1947), the device consisted of two heavy batteries and an ECG radio transmitter, weighing a total of 38 kg (85 pounds).
• Holter was issued a US Patent on November 2, 1965, for the Electrocardiographic Means.
• The Holter Research Foundation sold exclusive rights to the patent to Del Mar Engineering Laboratories, which became a leader in Holter monitoring technology for over 40 years.
• Dr. William Thornton (B.S. Physics ’52 and M.D. ’63, University of North Carolina) was a NASA Scientist Astronaut and later a Professor of Medicine, Cardiology, at the University of Texas Medical Branch.

Introduction to Heart Monitor Device (AECG)

• The 12-lead electrocardiogram (ECG) has been the “gold standard” for arrhythmia diagnosis for over a hundred years.
• Limitations of ECGs have long been recognized; arrhythmias can be paroxysmal and asymptomatic, making a baseline resting ECG insufficient for diagnosis.
• A “heart monitor” is used when a patient reports palpitations, syncope, or has a history of arrhythmia to track the heart rhythm.

Indications for AECG Monitoring

1. Determine the cause of palpitations and syncope.
2. Identify ventricular ectopy or nonsustained ventricular tachycardia in patients at potential risk for sudden cardiac death.
3. Monitor the efficacy and safety of pharmacological and nonpharmacological therapies.
4. Identify asymptomatic AF as a potential source of cryptogenic stroke.

Considerations for Palpitations

• Frequency and regularity: Palpitations lasting a few seconds and occurring randomly are often due to premature beats. Rapid, irregular palpitations are common in atrial fibrillation.
• Associated symptoms: Dizziness and loss of consciousness might suggest idiopathic ventricular tachycardia in structurally normal hearts.
• Precipitating factors: Exercise, caffeine, alcohol, or cocaine can precipitate palpitations. Supraventricular arrhythmias can be induced by exercise and may appear at the end of intense physical activity.
• Comorbid medical conditions: Psychiatric illness might indicate anxiety, while heart disease might suggest arrhythmias.
• Cardiovascular examination: Murmurs or abnormal heart sounds might reveal valvular or structural heart disease. Look for signs of congestive heart failure.

Types of Available AECG Monitors

• The 1999 practice guidelines categorized AECG monitors as either continuous short-term recorders (24 to 48 hours) or intermittent longer-term recorders (patient-activated event and loop recorders).
• Holter monitors are about the size of a large deck of cards and continuously record rhythm for 24-48 hours.
• Event monitors only record rhythm at certain times.
• Continuous loop recorders continuously record and erase data every few minutes.

Types of AECG Recorder

• Continuous Recorder
  • 24/48/72 hours Holter
  • King of Heart
• Event Recorder
  • Symptom Event Recorder: Store a brief recording of ECG activity when activated by the patient in response to symptoms.
  • Loop Memory Recorder: Record the ECG in a continuous fashion but store only a brief record when activated by the patient. Includes external and internal loop recorders, and rhythm card.

Holter Monitors

• Ambulatory electrocardiography is a noninvasive procedure that continuously records the heart’s activity during normal routines, usually for 24 to 72 hours or up to one month.
• Monitoring uses a portable external monitor worn around the waist or over the shoulder to measure and record heart electrical impulses.
• The monitor has a clock for accurate time monitoring.
• The patient keeps a diary to record daily activities and any cardiac symptoms experienced during the testing.
• The diary documents the time and description of symptoms.
• ACC/AHA guidelines recommend Holter monitoring for patients with palpitations and syncope, near syncope, and recurrent palpitations.

Holter Monitors Also Can:

1. Determine the average heart rate and heart rate range.
2. Quantify atrial and ventricular ectopy counts.
3. Determine whether AF is present.
4. Provide information about the shortest and longest duration of AF, burden of AF, and heart rate during AF.
5. Determine the pattern of initiation and termination of AF.

• Ambulatory telemetry monitoring was developed to overcome limitations inherent to Holter, event, and loop monitoring by offering long-term monitoring and the ability to capture information about symptomatic and asymptomatic arrhythmias.

Indications of Holter Monitoring

• To detect arrhythmias in patients without palpitations or syncope:
  • High-risk cardiac patients (recent myocardial infarction, low left ventricular ejection fraction, hypertrophic cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy, or congenital heart disease).
  • Monitoring of previously diagnosed arrhythmias after treatment or intervention.
  • Detection of occult atrial fibrillation in patients presenting with stroke of uncertain etiology.
  • Monitoring rate control in patients with treated atrial fibrillation.
  • Detection of new-onset arrhythmias in selected patients under pro-arrhythmogenic drugs.
  • Patients with pacemakers or implantable cardioverter defibrillators where dysfunction is suspected, especially with new symptoms such as syncope or palpitations.

Holter in Recent Myocardial Infarction

• After Myocardial Infarction survivors are at an increased risk of sudden death, with the
  incidence highest in the first year after infarction.
• The major causes of sudden death are ventricular tachycardia and ventricular fibrillation.
• The risk of developing an arrhythmic event has declined with the increasing use of
  thrombolytic agents and coronary revascularization.
• AECG monitoring usually is performed over a 24-hour period before hospital discharge.
• Some studies suggest that 4 hours of AECG monitoring provides as much information as 24 hours. In many studies, AECG monitoring was performed at least 6 and often approximately 10 days after the acute MI.

Holter in Congestive Heart Failure

• Patients with congestive heart failure (CHF) often have complex ventricular ectopy and a high mortality rate.
• Ventricular arrhythmias are sensitive but not specific markers of death and sudden death.

Holter in Hypertrophic Cardiomyopathy

• Sudden death and syncope are common among patients with hypertrophic cardiomyopathy.
• The relation between ventricular arrhythmias or Heart Rate Variability and outcomes for patients with hypertrophic cardiomyopathy remains open to question.
• AECG monitoring may add to the prognostic information provided by known risk factors.
• Treatment of ventricular arrhythmias has not consistently been shown to increase life expectancy.
• The specific role of AECG in the day-to-day treatment of these patients remains unclear.

Holter in Valvular Heart Disease

• A few studies have examined the relation between valvular heart disease and Heart Rate Variability or ventricular ectopy.
• The presence of mitral valve prolapse chronic mitral regurgitation or aortic valve prosthesis without other symptoms does not establish the need for AECG monitoring nor for assessing Heart Rate Variability.

Holter in Diabetic Neuropathy

• Diabetes is associated with diffuse degeneration of sympathetic and parasympathetic small nerve fibers.
• Heart rate and rhythm are under the control of the autonomic nervous system, several groups have studied the relation between HRV and diabetic neuropathy.
• High-frequency measures of HRV can detect small changes in cardiac autonomic function in diabetic subjects and can distinguish diabetic subjects with neuropathy from those without neuropathy.
• Although these tests are reliable and sensitive for cardiac parasympathetic function, their clinical utility is limited for 2 reasons.
• First, large numbers of diabetic subjects have reduced HRV.
• Second, there is no evidence that early identification of subclinical diabetic neuropathy will lead to improved patient outcomes.
• In a report on the natural history of diabetic neuropathy, more than half the deaths were due to kidney failure and not cardiac arrhythmias.

Holter in Hemodialysis Patients

• Patients with kidney failure who are receiving hemodialysis are at increased risk of dying from a cardiovascular event and have an increase in ventricular ectopy during dialysis.
• In a minority of these patients, significant ventricular arrhythmias develop .Those most at risk of having an abnormal AECG recording are patients with known coronary artery or peripheral vascular disease.
• Patients with Lown grade 3 or higher arrhythmia have decreased survival compared with patients without ventricular ectopy.
• Whether this prognostic information justifies performing AECG monitoring on these patients is unknown.

Holter in Systemic Hypertension

• Systemic hypertension is the most common cause of LV hypertrophy
• Hypertensive patients with either ECG or echocardiographic criteria of LV hypertrophy have an increased incidence of complex ventricular arrhythmias.
• There is an increased risk of ventricular arrhythmias, MI, and sudden death in patients with LV hypertrophic.
• Monitoring of asymptomatic patients with LV hypertrophy is of uncertain value because those patients with complex or frequent arrhythmias have only a marginally significant risk of dying after adjusting for age, sex, and other clinical factors.

Holter in Monitoring Pharmacological Management

• Several medications used in the treatment of patients with cardiac conditions affect either directly or indirectly the autonomic nervous system.
• Analysis of R-R variability may provide a tool for understanding these various pharmacological manipulations.
• To date, the prognostic implications of the noted alterations are unknown.
• In drug development, analysis of R-R variability may provide insights into mechanisms of action.

Advantages of Continuous Holter Monitoring

1. Possibility of quantifying the real burden of an arrhythmia and detecting rhythm disturbances outside algorithm limits.
2. Quantification of arrhythmic events may aid therapeutic decisions, especially for frequent/disabling arrhythmias.

ECG OF THE HEALTHY HEART

• 1:1 AV synchrony (one atrial event for each ventricular event)
• Stable rhythm with repeating patterns
• Similar morphologies of beats from complex to complex
• Appropriate rate

HOLTER SUMMARY – What to Look For

• HR trend
• Abnormal finding
• Pause
• NSVT
• SVT
• PVC
• PAC
• AF
• Total number of beat
• Minimum HR
  • What time?
  • If at night during sleeping:
    • Normal (High vagal tone)
• Maximum HR
  • What time?
  • Any arrhythmia?

SIGNS OF ARRHYTHMIC ACTIVITY ON AN ECG

• Abnormal shaped waves
• Lack of 1:1 AV synchrony
• Rapid cardiac activity, even if otherwise stable
• Very slow cardiac activity, even if otherwise stable
• Irregular cardiac activity
• Variability in PR interval
• “Missing” cardiac events
• Premature beats
• Pauses

Pause

• How many episodes?
• What time?
• Longest?
• What happened before the pause episode?
• Is it ventricular standstill or SApause?

NSVT / SVT

• What is patient underlying disease?
  • Ischemic or not?
• How many episodes?
• Longest?
• What initiate the NSVT / SVT episode?
• How it terminate?
• Is there any ablation done previously?

PVC / PAC

• How many episodes?
• Monomorphic or polymorphic?
• How much the Burden?
• Is there any RFAdone previously?

AF

• How many episodes?
• Maximum and minimum duration?
• How much the Burden?
• Patient taking any anticoagulant drugs?
• Is there any ablation done previously?

Loop Recorder

• Can be divided into two categories: loop recorders, which include external loop recorders (ELRs) and implantable loop recorders (ILRs); and post- event recorders (non-looping recorders).
• Loop recorders are event recorders with a ‘loop memory’: they continually analyse the ECG and retain information pertaining to relevant arrhythmias that are automatically detected.
• As the patient pushes a button signifying that symptoms have occurred, an event marker is placed on the tape for later correlation with the cardiac activity recordings and the daily event diary.
• As event recorders can be activated by the patient when he or she experiences symptoms, they can reliably document a correlation between symptoms and an arrhythmia, as well as excluding a causative role of heart rhythm disturbances in determining syncope or palpitations when such symptoms occur without any arrhythmia
• ELRs can monitor the ECG for a maximum of 30 days.
• ILRs, can continue monitoring for up to 3 years.

Post-Event Recorders

• Can be used for 14–30 days.
• The monitoring function starts when the patient puts the device on his or her chest as symptoms commence.
• The diagnostic yield of post-event recorders is limited by the potential loss of events causing disabling symptoms that prevent patients from activating the device
• There is also the risk that patients may forget to activate the device.
• Some post-event recorders have an extended backward memory, e.g. 15 minutes, which allows time to handle the patient before pressing the button to save a recording

Strategy

• The optimal monitoring strategy has not been defined, although expert consensus documents endorse the importance of periodic AECG.
• There is a continuum of monitoring that can be entertained, ranging from the minimal, 12-lead ECG recording at follow-up outpatient visits, to the ideal that does not yet exist, a permanently implanted and accurate wireless monitoring system.

Diary in Ambulatory Monitoring

• Patient is asked to keep a diary of all symptoms, activities, and events during the period of AECG monitoring.
• When carefully recorded and timed correctly, the log is valuable in diagnosing the complaint of the patient.
• Patients should record symptoms such as, palpitations, dyspnea, fatigue ,dizziness, chest pain/discomfort, arm pain, nausea, presyncope or syncope.
• The diary is also an essential tool to exclude false positive or false negative findings.
• The patient should be instructed to grade symptoms as severe, moderate or slight.
• It is also important that the patient should note the following carefully at the time of occurrence:
  1. Meals
  2. Taking of any stimulants such as coffee, chocolate, smoking,
  3. Taking medication
  4. Stress such as anger, frustration, sorrow, depression, anxiety,
  5. Exercise and sexual activity
  6. Bowel movement, straining and any valsalva maneuvers
  7. Heavy lifting, and hyperventilation.