Recurrent syncope. Experience with an implantable loop recorder

Trends in Subcutaneous Cardiac Monitoring Technology

Ambulatory cardiac monitoring is a rapidly expanding field and one that is likely to progress beyond electrocardiographic (ECG) and blood pressure recordings. To date, the primary cardiac monitoring focus has been ambulatory ECG (AECG) monitoring. In this setting, AECG monitoring has become a diagnostic tool used daily by physicians of many specialties. In this regard, both wearable and subcutaneous ECG monitoring technologies are now widely available, with the appropriate choice for a given patient being best determined by the frequency with which the patient’s symptom recurrences are expected. In other words, the less frequent the symptomatic events, then the longer the monitoring duration requirement should be. However, multiple factors other than the technology used impact success. For example, wearable AECG systems are only capable of monitoring patients for a period of a few days to several weeks due to limited battery longevity, patient intolerance to cutaneous ECG electrodes, the cumbersome nature of the device, or a combination of these factors. Current-generation insertable cardiac monitors (ICMs), on the other hand, offer three years of monitoring and infrequent skin irritation. Additionally, automatic remote download, a valuable feature in many cases, is only offered by certain wearable technologies, but is an option in all currently available ICMs. This report focuses on the current status of subcutaneous ICMs and their indications and limitations. The goal is to highlight the variety of utility of current ICM technologies and to provide insight into potential future subcutaneous ICM applications.

The Reveal LINQ insertable cardiac monitor

Insertable cardiac monitors (ICMs) are leadless subcutaneous devices that continuously monitor the heart rhythm and record events over a timeframe measured in years, allowing for the diagnosis of infrequent rhythm abnormalities that can be the cause of palpitations, syncope and stroke. To date, ICMs have primarily been used in the work-up and management of syncope; however, their use in other areas of rhythm evaluation, particularly atrial fibrillation monitoring, is increasing. The Reveal LINQ™ is the smallest and most versatile ICM available and represents a dramatic leap forward in ICM technology that has the potential to transform patient care in a number of circumstances. Device miniaturization, simplified implant procedure and enhanced automation vastly increase physician and patient acceptance. The next 5 years can be expected to bring a greatly increased use of ICMs for disease diagnosis and management in a variety of clinical settings.

24 h and prolonged ambulatory ECG recording in patients with ventricular ectopy: Maybe 24 h are not enough?

AIM

To assess whether 24-h ambulatory ECG (AECG) recording underestimates arrhythmic risk in subjects with both ventricular ectopy and cardiovascular risk factors or history of coronary heart disease (CHD).

METHODS

29 consecutive patients with both ECG evidence of premature ventricular contractions (PVCs) and cardiovascular risk factors (n=14) or history of CHD (n=15) underwent 6 days prolonged AECG with an apposite device. Patients were divided according to number of PVCs, Lown's classification and evidence of non-sustained ventricular tachycardia (NSVT). Day by day data were compared with final findings at 6th day.

RESULTS

Significant differences between findings at 24 h and those at 6th day were observed for all considered parameters. Differences became statistically not significant only at 4th day for number of PVCs and Lown's classes, at 5th day for NSVT. Results were significant both among patients with only risk factors and those with history of CHD. Sensitivity for NSVT significantly and progressively increased from 18% at 24 h, up to 82% only at 120 h.

CONCLUSIONS

Twenty-four-hour AECG underestimates the risk of ventricular arrhythmias in patients with cardiovascular risk factors or history of CHD. Prolonged AECG might reduce this underestimation, particularly among patients at low risk. A careful cost-benefit assessment needs to be held in order to identify the most convenient AECG duration and subsets of patients most benefiting from prolonged AECG.

Digital implantable loop recorders in the investigation of syncope in children: Benefits and limitations

BACKGROUND

Conventional diagnostic methods for detecting arrhythmogenic causes of syncope in children are poor. Digital implantable loop recorders are of proven value in adults.

OBJECTIVES

The purpose of this study was to evaluate digital implantable loop recorders in the investigation of syncope in children.

METHODS

We reviewed the clinical and technical records of 18 consecutive patients (6 female and 12 male; age <or=16 years) who received an implantable loop recorder from 1999 to 2005.

RESULTS

Median age at implantation was 11.3 years (range 4.6-16.5 years). Median duration of the device in situ was 18 months (range 5-36 months). Median time to diagnosis was 6 months (range 1 day to 17 months). Two patients had a congenital heart defect. Ten children (56%) had an event, 9 (50%) of whom had diagnostic information; 5 (28%) had profound bradycardia or asystole; 2 (11%) had polymorphic ventricular tachycardia (VT); and 1 child had supraventricular tachycardia. One patient died, but the automatically activated recording was recorded over again after death. One child had sinus rhythm during syncope. One child with polymorphic VT had no auto-activation on two occasions, and the third activation was triggered by asystole after VT terminated. Sixteen patients (89%) had false-positive activations as a result of either artifact or sinus tachycardia.

CONCLUSION

The digital implantable loop recorder is a useful diagnostic modality in children with unexplained syncope. However, the automatic detection algorithm is imperfect, missing genuine polymorphic VT and frequently interpreting muscle tremors as VT. Because of continuous overwriting by automatic detection, genuine arrhythmias may be over-recorded by artifact.

Dysrhythmia as a cause of syncope in children without neurological or cardiac morphological abnormalities

BACKGROUND

Arrhythmias are among the malignant causes of syncope. This study has been undertaken to determine the relative incidence and significance of dysrhythmia in the pathogenesis of syncope among patients referred to a pediatric cardiology unit.

METHODS

Between March 1997 and March 1999, 105 consecutive patients (59 female, 46 male) aged 11.5 +/- 3.6 years without neurologic or cardiac morphologic causes were evaluated for at least one episode of syncope. A pediatric cardiologist and a pediatric neurologist evaluated all the patients. Routine chest X-ray, 12-lead electrocardiogram (ECG), electroencephalography (EEG), 24-h Holter monitoring and echocardiography were carried out. When deemed necessary, further tests were undertaken for the cases of syncope which were unexplained by routine tests.

RESULT

The cause of syncope was identified as vasovagal in 25.7% (n = 27) and related to dysrhythmia in 30.5% (n = 32). The cause was migraine-associated syncope in two children, psychogenic syncope in three children and orthostatic hypotension in one patient. The cause was unknown in 36.2% (n = 38).

CONCLUSION

We conclude that dysrhythmia is a significant and frequent cause in children referred to pediatric cardiology units. The combination of ECG, Holter monitoring, electrophysiologic study, transtelephonic ECG and head-up tilt test can identify the underlying cause of syncope in as many as 58% of these patients that present with syncope.

Use of an implantable loop recorder in the evaluation of children with congenital heart disease

BACKGROUND

A recently developed implantable loop recorder (ILR) has been used in adult patients whose syncope remains unexplained in spite of extensive investigations. Syncope in the patient with congenital heart disease presents a diagnostic challenge. We applied this technology to a cohort of pediatric patients.

METHODS

We reviewed our experience with an ILR in patients with congenital heart disease with syncope or palpitations after conventional investigations failed to identify a cause for the symptoms.

RESULTS

ILRs were implanted in 4 patients with congenital heart disease at 2 centers for investigation of syncope (n = 2), near-syncope (n = 1), and palpitations (n = 1). Implantations were performed at a mean age of 5.9 +/- 0.9 years (4.2 to 7.6 years) and a mean weight of 26.7 +/- 6.6 kg (15.7 to 42.5 kg) with patients under general anesthesia, with no complications. All patients experienced typical symptoms and activated the device appropriately at a median of 86 days (46 to 102) after implantation. Each patient had good-quality data that allowed interpretation of the rhythm. In 2 of 4 cases, a likely cause for the symptoms was identified, with exclusion of more malignant arrhythmic diagnoses in all patients. Escalation of therapy was avoidable in all patients on the basis of the data recorded by the ILR.

CONCLUSIONS

Recently developed loop recorder technology can be implanted in the young child without difficulty. The ILR proved to be very useful for excluding malignant arrhythmias as a cause of symptoms in these patients at high risk.

Long-term EEG monitoring: a clinical approach to electrophysiology

Long-term electroencephalographic monitoring (LTM) is the capability of recording the EEG over long periods of time and not a specific duration. Prolonged EEG recording is used primarily for epilepsy monitoring, but LTM is also used in the intensive care unit, the operating room, and in the emergency department. The purpose of LTM is to expand the limited time sampling associated with shorter "routine" EEG recording. Audiovisual monitoring may also be used in conjunction with LTM to evaluate simultaneously a specific clinical behavior that may or may not be associated with EEG alteration. This is typically performed in a hospital setting for safety and ancillary testing purposes. LTM is used most frequently in the diagnosis and management of seizures and "spells," but has also gained wider application in the evaluation of sleep disorders, cerebrovascular disease, psychiatric conditions, and movement disorders. Computer-assisted LTM systems that process, analyze, compress, and store data digitally have become widely available in clinical practice both in the hospital as well as outside the hospital when the patient is ambulatory.

Misdiagnosis of epilepsy: many seizure-like attacks have a cardiovascular cause

OBJECTIVES

We sought to investigate the value of cardiovascular tests to diagnose convulsive syncope in patients with apparent treatment-resistant epilepsy.

BACKGROUND

As many as 20% to 30% of epileptics may have been misdiagnosed. Many of these patients may have cardiovascular syncope, with abnormal movements due to cerebral hypoxia, which may be difficult to differentiate from epilepsy on clinical grounds.

METHODS

Seventy-four patients (33 men, mean age 38.9 +/- 18 years [range 16 to 77]) who were previously diagnosed with epilepsy were studied. Inclusion criteria included continued attacks despite adequate anticonvulsant drug treatment (n = 36) or uncertainty about the diagnosis of epilepsy, on the basis of the clinical description of the seizures (n = 38). Each patient underwent a head-up tilt test and carotid sinus massage during continuous electrocardiography, electroencephalography and blood pressure monitoring. Ten patients subsequently underwent long-term electrocardiographic (ECG) monitoring with an implantable loop recorder.

RESULTS

In total, an alternative diagnosis was found in 31 patients (41.9%), including 13 (36.1%) of 36 patients taking an anticonvulsant medication. Nineteen patients (25.7%) developed profound hypotension or bradycardia during the head-up tilt test, confirming the diagnosis of vasovagal syncope. One other patient had a typical vasovagal reaction during intravenous cannulation. Two patients developed psychogenic symptoms during the head-up tilt test. Seven patients (9.5%) had significant ECG pauses during carotid sinus massage. In two patients, episodes of prolonged bradycardia correlated precisely with seizures according to the insertable ECG recorder.

CONCLUSIONS

A simple, noninvasive cardiovascular evaluation may identify an alternative diagnosis in many patients with apparent epilepsy and should be considered early in the management of patients with convulsive blackouts.

Differential diagnosis of sleep disorders, non-epileptic attacks and epileptic seizures

Making a correct diagnosis in patients presenting with attack disorders is important. The clinical features of autosomal dominant nocturnal frontal lobe epilepsy and concussive seizures are reviewed. Recent work on the diagnosis and investigation of psychogenic non-epileptic attacks, drop attacks, falls, syncope and sleep disorders is discussed.