Value and limitations of noninvasive assessment of syncope

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.

The investigation of syncope

Patients with syncope are usually referred to either neurology or cardiology clinics, yet the facilities for detailed syncope investigation are mostly in cardiac units. The diagnosis rests principally upon the history, but investigations may be required to support the clinical diagnosis. Close collaboration between the epilepsy clinician and a cardiologist is essential for effective investigation and safe management of syncope. It is frequently misdiagnosed and often erroneously treated as epilepsy. Furthermore, it is potentially a marker of sudden death when associated with certain cardiac disorders. Here we review the main syncope types and explore diagnostic approaches.

[Value and limitations of carotid sinus massage in healthy elderly individuals. Evaluation of diagnostic criteria for hypersensitive carotid sinus syndrome]

OBJECTIVE

To study the value and limitations of carotid sinus massage in healthy individuals older then 50 years of age, in order to assess the validity of the widely used criteria for the diagnosis of hypersensitive carotid sinus syndrome.

METHODS

Right and left carotid sinus massage was performed in 120 healthy individuals older then 50 years of age (74 males and 46 females aged 59 +/- 7 years) who had no prior history of syncope, pre-syncope, or abnormal bradyarrhythmia, during EKG monitoring.

RESULTS

Hypersensitivity of the carotid sinus (HSCS) defined as a pause > 3 s, was found in 28 individuals (23.3%). The pause was induced by right carotid sinus massage in 20 cases and by left carotid sinus massage in 8 cases. Patients demonstrating HSCS were older compared to those who did not develop a pause. One or multiple blocked P wave was seen in 16 cases when carotid sinus massage was performed on the left side compared to 8 with right carotid sinus massage.

CONCLUSION

In healthy individuals older than 50 years of age, it is not rare to induce a significant pause following carotid sinus massage. This limits the validity of the widely used criteria for the diagnosis of hypersensitive carotid sinus syndrome. Additional criteria are proposed to make this diagnosis in front of a brief loss of consciousness.

Syncope and orthostatic intolerance

Syncope and orthostatic intolerance remain common and significant clinical problems with many undocumented, misdiagnosed, or cryptogenic cases. Careful clinical assessment and application of advancing laboratory support can further improve diagnosis and treatment. Despite the depth of existing research into these common problems, many underlying mechanisms remain unproven.

Evaluating elderly patients with syncope

Age-related physiologic changes together with high prevalence of chronic illness and the use of multiple medications predispose older adults to syncope. The causes of many of these patients' syncope are unexplained and most remained symptomatic. A thoughtful diagnostic strategy is essential to pinpoint the cause in each patient. The initial assessment includes a comprehensive medical history, preferably with an eye witness account, and a thorough physical examination. The decision for further diagnostic tests often depends on whether there is evidence of underlying structural heart disease. In the absence of heart disease, tilt table testing and the related autonomic function testing are usually most productive. Various cardiac studies will be more appropriate for those with suspected structural heart disease. A cause of syncope can only be concluded if there is a sufficiently strong correlation between syncopal symptoms and the detected abnormalities on investigations. A strategic evaluation of syncope of the elderly subjects should allow a correct diagnosis and appropriate management.

Monitoring devices for falls and syncope

Monitoring devices are an important adjunct to the clinical assessment of patients who experience falls. The use of these devices should be guided by the clinical history, a physical assessment, and routine investigations. Quantitative measures of postural sway should be used in conjunction with clinical measures to provide a more accurate assessment of gait and balance. Assessment of blood pressure changes during the investigation of neurocardiovascular causes of syncope and falls in older adults should be performed with noninvasive digital photoplethysmographic devices, so long as their appropriate use and limitations are applied and understood. Only minimal information can be gained from short-term heart rate and rhythm monitoring in patients with infrequent symptoms. The usefulness of long-term ECG monitoring (with both external and implantable recorders) is well established for the diagnosis of unexplained syncope but requires further assessment in older individuals who experience falls. Twenty-four-hour measurements of ambulatory blood pressure generally are not diagnostically helpful in patients who experience falls or syncope but do have a role in the monitoring of therapeutic interventions.

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.

Diagnostic evaluation and management of patients with syncope

This article focuses on the evaluation of patients with syncope, a symptom not a disease. Syncope is a transient loss of consciousness associated with loss of postural tone with spontaneous recovery. The authors discuss the utility of an indications for different diagnostic tests, the indications for hospital admission, and the management of patients with certain known causes of syncope, including vasovagal and arrhythmic.

Clinical usefulness of cardiac event recording in dogs and cats examined because of syncope, episodic collapse, or intermittent weakness: 60 cases (1997-1999)

OBJECTIVE

To determine the clinical usefulness of cardiac event recording in evaluating dogs and cats with unexplained syncope, episodic collapse, or intermittent weakness.

DESIGN

Retrospective study.

ANIMALS

58 dogs and 2 cats.

PROCEDURE

Medical records and electrocardiographic rhythm strips obtained by cardiac event recordings were reviewed. Cardiac rhythm data from the event recordings were classified as diagnostic or nondiagnostic. Diagnostic yield was calculated by dividing the number of animals for which cardiac event recording was diagnostic by the total number of animals undergoing cardiac event recording.

RESULTS

For 51 animals, cardiac event recording was classified as diagnostic; therefore, overall diagnostic yield was 85%. Diagnostic yield was lower for animals without underlying structural heart disease (75.5%) than for animals with structural heart disease (95.6%). A specific arrhythmia was identified as the cause of clinical signs in 18 of the 51 (35%) animals for which cardiac event recording was diagnostic. Cardiac arrhythmia was definitively excluded as the cause of clinical signs in the remaining 33 (65%) animals in which cardiac event recording was diagnostic.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicate that cardiac event recording had a high diagnostic yield in dogs and cats examined because of unexplained syncope, episodic collapse, or transient weakness and ataxia, regardless of whether animals did or did not have an underlying structural heart disease. Diagnostic yield of cardiac event recording was higher than that reported previously for Holter monitoring.

Evaluation of the patient with syncope: an evidence based approach

The cause of syncope often eludes the clinician despite extensive efforts to make a definitive diagnosis. In that group of patients for whom the cause has eluded the clinician, it is unclear which patients need a rapid inpatient work-up and which patients can be safely discharged for outpatient evaluation. The authors present the results of a systematic literature search to determine the diagnostic value of the emergency department work-up of the patient with syncope.

[Subcutaneous implantable Holter. A new instrument for the diagnosis of syncope of undetermined origin]

We present a recurrent syncope case with no clear origin or not stabilized after complete diagnostic exploration including echocardiogram, Holter, carotid Doppler, electrophysiologic study, computerized tomography, etc. Due to its recurrence and sudden appearance which was presumed to be of cardiac origin we implanted a long recording subcutaneous Holter system, the first unit used in Spain. This device, which has several advantages compared to external recorders previous in use, facilitated the patient's diagnosis (arrhythmic syncope of cardiac origin due to a paroxysmal atrioventricular block) one month after implantation. We describe the system, which includes a recorder and an external activator, its handling and diagnostic capabilities as well as the implantation procedures.