Implantable Loop Recorder


Article Author:
Viliane Vilcant
Omar Kousa


Article Editor:
Ofek Hai


Editors In Chief:
Stacy Mandras


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Avais Raja
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Carrie Smith
Abdul Waheed
Khalid Alsayouri
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Radia Jamil
Erin Hughes
Patrick Le
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Saad Nazir
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Beenish Sohail
Nazia Sadiq
Hajira Basit
Phillip Hynes
Komal Shaheen
Sandeep Sekhon


Updated:
7/16/2019 9:51:39 PM

Introduction

Ambulatory electrocardiogram (ECG) monitoring is an invaluable tool to assess and establish a diagnosis of a patient’s symptoms. There are a variety of possible ambulatory ECG monitors to choose from. Holter monitors are used to record 24 to 48 hours of activity. Event monitors can record 2 to 4 hours of activity. Implantable loop recorders can record for up to 3 years. The choice among these technologies is usually based on the suspected monitoring duration that will be required to capture a spontaneous event. Thus, if symptoms occur daily, a Holter monitor may be adequate. If symptoms occur weekly or monthly, an event monitor may be best. If symptoms occur less than monthly or even a few times per year, then an implantable loop recorder is likely the best option. Typical event recorders may not be useful at all if the patient collapses and cannot activate the device. Because of such, a device that can activate on its own and/or has memory to retain information for later download is preferred. This article will cover implantable loop recorders.[1][2][3]

The implantable loop recorder (ILR) is a subcutaneous monitoring device used to monitor electrical activity of the heart over an extended period, compared to the fixed picture of electrical activity that is seen with ECGs.[4]

Indications

An implantable loop recorder is most commonly used for the evaluation of recurrent palpitations, syncope of unknown etiology or when other ambulatory monitoring devices of shorter duration are unrevealing.[5][6][7] It may also be useful for the following:

  • Identifying asymptomatic occult episodes of atrial fibrillation following a stroke
  • Assessing the average heart rate and adequacy of rate control in a patient with atrial fibrillation
  • Assessing bradycardic episodes before implanting a permanent pacemaker
  • Screening for asymptomatic ventricular premature beats or nonsustained ventricular tachycardia in patients with congenital or acquired cardiac syndromes
  • Evaluating prognosis following an acute coronary event

Contraindications

An absolute contraindication to implanting a loop recorder is when there is no indication for its use. Relative contraindications include active infection or a bleeding diathesis which may preclude its implantation for a certain period.

Equipment

The implantable loop recorder is a small leadless box, about the size of a USB memory stick, with two self-contained electrodes. As stated previously, current implantable loop recorder devices have a battery life of up to 3 years.[8][4]

Technique

A small incision is made on the left side at about the level of the second or third rib. A pocket is created under the skin, and the device is inserted in that pocket, and then the incision is closed. The device is usually implanted by an electrophysiologist as an outpatient procedure using local anesthesia. Conscious sedation can be used but is generally not required. Once implanted, the device is activated by passing a magnet over it.

Complications

The most common complication is a pain at the implant site. Risks of the procedure include a local pocket infection that may require removal of the implanted device or a local skin reaction to the device.  Poor R-wave sensing is a rare complication that may require moving the device to another location.

Clinical Significance

An implantable loop recorder can store patient activated episodes, automatically activated episodes or a combination of the two. A typical loop recorder report includes information about the captured ECG tracings, the technician’s interpretation of the ECG tracing and any reported symptoms and their respective duration, which can assist the physician in diagnosing the underlying problem.

Implantable loop recorders have the best yield (up to a 75% detection rate for the cause of syncope at 3 years). They do not need to be removed during certain activities such as showering or swimming and may identify significant cardiac rhythm abnormalities when the patient is sleeping. Patients can continue with their normal activity of everyday living and exercise freely. An identification card is usually given to the patient with the make and model of their implantable loop recorder device. This information is valuable should the patient with recurrent symptoms present to the emergency department and need to have their device checked. The main purpose of the device is to record electrical activity and is therefore safe to travel with and it is not affected by other electrical devices. Event recorders are the next most productive and Holter monitors are the least effective unless events occur daily, which is not the case for most patients.

Following the monitoring period, there are three possible combinations of patient symptoms and ECG findings. The first possibility is that the patient had symptoms with corresponding ECG abnormalities, in which case appropriate therapy should be initiated. Possible recommendations include implantation of a permanent pacemaker, implantation of an implantable cardiac defibrillator, or a diagnostic electric study of the heart that may or may not be followed by a therapeutic procedure. If an arrhythmia is detected, such as atrial fibrillation, the patient may need to start a blood thinning medication to decrease the risk of a cerebral vascular accident. The second possibility is that the patient had symptoms without corresponding ECG abnormalities, in which case the diagnosis is unlikely cardiac in nature, and other etiologies for the patient’s symptoms should be investigated. The patient can be referred to other more appropriate specialist if necessary. The third possibility is that the patient had no symptoms and no ECG abnormalities during the monitoring period and a cardiac etiology is unlikely, and no further ECG monitoring is required. If a diagnosis is made or no abnormalities were discovered during the monitoring period, the patient can have the device removed in a similar fashion that it was implanted.

Implantable loop recorders are a safe and effective way to identify arrhythmias and other cardiac abnormalities. It should be considered only after a thorough history and physical examination are performed. Family history and medication use should also be discussed with the patient. Initial imaging should include ECG and echocardiogram which may reveal structural heart disease. Other testing such as a stress test or a tilt table test, may be beneficial if indicated. If the patient continues to have symptoms and all workup is unrevealing, then electrophysiology testing and an implantable loop recorder is the best approach in select patients.[1][5]

Enhancing Healthcare Team Outcomes

Healthcare workers including the nurse practitioner who deal with patients with syncope and arrhythmias should be familiar with the implantable loop recorder. Unlike the traditional holter monitor, the implantable loop recorder is far more efficient and reliable at identifying abnormal rhythms. However, they should be considered only after a thorough history and physical examination are performed. Family history and medication use should also be discussed with the patient. Initial imaging should include ECG and echocardiogram which may reveal structural heart disease. Other testing such as a stress test or a tilt table test, may be beneficial if indicated. If the patient continues to have symptoms and all workup is unrevealing, then electrophysiology testing and an implantable loop recorder is the best approach in select patients.


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Implantable Loop Recorder - Questions

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Which of the following is not an indication for an implantable loop recorder?



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A 50-year-old male with a history of two ischemic cerebrovascular accidents three and five years ago respectively presented to the hospital with left-sided weakness. Vital signs showed blood pressure of 174/92 mm/Hg; pulse rate was 76 beats/min, oxygen saturation was 95% on room air. Chest examination showed bilateral air entry, and cardiac examination reveals regular S1, S2 with no murmurs or added sounds. Pulses are equal in the upper and lower extremities. The neurological examination of the left side showed 3/5 in both upper and lower extremities with no sensory loss. The rest of the examination was unremarkable. Initial labs showed a blood glucose level of 112 mg/dl. CT head without contrast excluded hemorrhagic stroke. All previous workups including electrocardiograms, echocardiograms and a hypercoagulable workup have been unrevealing. He denies any cardiac-related symptoms. Which of the following is the next best step in the management of this patient?



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A 45-year-old female presents to the office for a follow-up. She has had intermittent palpitations for the last several years. Physical examination is unremarkable. She was seen by an electrophysiologist and subsequently had an implantable loop recorder implanted. It has been three years since she had the device implanted, and it has revealed rare premature beats and no significant explanation of palpitations. Which of the following is the next best step in management?



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What is an absolute contraindication to an implantable loop recorder?



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A 47-year-old female came to the clinic because of a 1-week history of fever, night sweats, chills, and malaise. She has a past medical history of chronic bronchitis, recurrent syncope which required loop recorder implantation one year ago. She denies any sore throat, cough, vomiting, dysuria, or diarrhea. Her vital signs showed blood pressure dropped to 123/65 mm/Hg, heart rate of 97 beats per minute, the temperature of 37.6 C, and oxygen saturation was 94% on room air. Physical examination showed erythematous skin changes over her left upper chest, tenderness to palpation and fluid filled pocket over the cardiac device. The rest of the examination was unremarkable. She was sent to the emergency department for further evaluation and management. Blood workups revealed leukocytosis with neutrophils predominant. What is the best next step in management?



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A 49-year-old male, with no significant past medical history, presented to the emergency department because of slurred speech, which was noticed when he woke up. Initial vital signs showed blood pressure of 139/89 mm/Hg, pulse rate 87 beats/min, and oxygen saturation 99% on room air. Chest examination revealed bilateral air entry, cardiac examination, regular S1, S2 with no murmurs or added sounds. Neurological examination showed 5/5 motor power in both upper and lower extremities, with No sensory deficit and reflexes were 2+ bilaterally. Initial labs showed normal CBC, CMP, and blood sugar. EKG showed sinus rhythm. She underwent an urgent CT head stroke protocol was normal. The patient was given 324 mg of aspirin and 80 mg of atorvastatin. He was admitted for further evaluation and management. Ultrasound of the carotid artery, transthoracic echocardiogram with bubbles studies, A1C, and lipid panel are normal. Repeated CT head after 48 hours shows a finding of ischemic infarction. What is the next best step in the management of this patient?



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A 33-year-old male is previously healthy with no significant past medical history presented to the emergency room because of acute witnessed loss of consciousness. The patient had a sudden onset palpitation a few seconds before the episodes, and he regained his consciousness within two minutes. He had similar incidents last week, but he did not seek medical evaluation. Initial vital signs showed blood pressure of 139/89 mm/Hg, pulse rate 87 beats/min, and oxygen saturation 99% on room air. Chest examination revealed bilateral air entry with mild erythematous skin changes over his left chest, which is suggestive of a superficial skin infection. Cardiac examination demonstrated regular S1, S2 with no murmurs or added sounds. Neurological examination showed 5/5 motor power in both upper and lower extremities. No sensory deficit and reflexes are 2+ bilaterally. Initial labs showed normal CBC, CMP, and blood sugar. EKG showed sinus rhythm. An urgent CT head was normal. He was admitted for further evaluation and management. He has a normal transthoracic echocardiogram with bubbles studies, and the electroencephalogram shows no epileptiform discharges. Which of the following best explains why an implantable loop recorder is least likely to be appropriate in this patient?



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Implantable Loop Recorder - References

References

Arcinas LA,McIntyre WF,Hayes CJ,Ibrahim OA,Baranchuk AM,Seifer CM, Atrial fibrillation in elderly patients with implantable loop recorders for unexplained syncope. Annals of noninvasive electrocardiology : the official journal of the International Society for Holter and Noninvasive Electrocardiology, Inc. 2019 Jan 7;     [PubMed]
Roca-Luque I,Francisco-Pascual J,Oristrell G,Rodríguez-García J,Santos-Ortega A,Martin-Sanchez G,Rivas-Gandara N,Perez-Rodon J,Ferreira-Gonzalez I,García-Dorado D,Moya-Mitjans A, Syncope, conduction disturbance, and negative electrophysiological test: predictive factors and risk score to predict pacemaker implantation during follow-up. Heart rhythm. 2018 Dec 18;     [PubMed]
Sakhi R,Theuns DAMJ,Szili-Torok T,Yap SC, Insertable cardiac monitors: current indications and devices. Expert review of medical devices. 2018 Dec 6;     [PubMed]
Santini M,Santini L,Di Fusco SA, Update on cardiac implantable electronic devices: from the injectable loop recorder to the leadless pacemaker, to the subcutaneous defibrillator. Minerva cardioangiologica. 2018 Dec;     [PubMed]
Dwivedi A,Joza J,Malkani K,Mendelson TB,Priori SG,Chinitz LA,Fowler SJ,Cerrone M, Implantable Loop Recorder in Inherited Arrhythmia Diseases: A Critical Tool for Symptom Diagnosis and Advanced Risk Stratification. JACC. Clinical electrophysiology. 2018 Oct;     [PubMed]
Yeung C,Drew D,Hammond S,Hopman WM,Redfearn D,Simpson C,Abdollah H,Baranchuk A, Extended Cardiac Monitoring in Patients With Severe Sleep Apnea and No History of Atrial Fibrillation (The Reveal XT-SA Study). The American journal of cardiology. 2018 Dec 1;     [PubMed]
Padmanabhan D,Kancharla K,El-Harasis MA,Isath A,Makkar N,Noseworthy PA,Friedman PA,Cha YM,Kapa S, Diagnostic and therapeutic value of implantable loop recorder: A tertiary care center experience. Pacing and clinical electrophysiology : PACE. 2019 Jan;     [PubMed]
Kanjwal K,Qadir R,Ruzieh M,Grubb BP, Role of implantable loop recorders in patients with postural orthostatic tachycardia syndrome. Pacing and clinical electrophysiology : PACE. 2018 Sep;     [PubMed]

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