Unexplained syncope: clinical management

Loss of Consciousness in the Young Child

In the very young child (less than eight years of age), transient loss of consciousness represents a diagnostic and management dilemma for clinicians. While most commonly benign, syncope may be due to cardiac dysfunction which can be life-threatening. It can be secondary to an underlying ion channelopathy, cardiac inflammation, cardiac ischemia, congenital heart disease, cardiomyopathy, or pulmonary hypertension. Patients with genetic disorders require careful evaluation for a cardiac cause of syncope. Among the noncardiac causes, vasovagal syncope is the most common etiology. Breath-holding spells are commonly seen in this age group. Other causes of transient loss of consciousness include seizures, neurovascular pathology, head trauma, psychogenic pseudosyncope, and factitious disorder imposed on another and other forms of child abuse. A detailed social, present, past medical, and family medical history is important when evaluating loss of consciousness in the very young. Concerning characteristics of syncope include lack of prodromal symptoms, no preceding postural changes or occurring in a supine position, after exertion or a loud noise. A family history of sudden unexplained death, ion channelopathy, cardiomyopathy, or congenital deafness merits further evaluation. Due to inherent challenges in diagnosis at this age, often there is a lower threshold for referral to a specialist.

Syncope in Children and Adolescents

In the pediatric age group, most cases of syncope represent benign, neutrally-mediated alterations in vasomotor tone. Due to the global cerebral hypoperfusion, syncope is defined as a transient loss of consciousness followed by spontaneous recovery and/or a state of presyncope, including dizziness, lightheadedness, pallor, diaphoresis and palpitations which may precede the loss of consciousness. These symptoms could be a sign of a life-threatening event in a small subset of patients, even though most causes of syncope in childhood are benign, and life-threatening causes of syncope generally have cardiac etiology. In all these cases, routine evaluation includes history, physical examination and a 12-lead standard electrocardiogram which should be performed. Further investigation is indicated by worrying features which include syncope that occurs without warning, syncope during exercise, history of familial sudden death, and abnormalities on clinical exam or electrocardiography. The fact is that syncope generates great fear of injury or sudden death among parents and doctors, and the main aim of the present paper is to help the physician involved in the care of children to differentiate the life-threatening causes of syncope from the common, more benign neutrally-mediated syncope.

Syncope during exercise: just another benign vasovagal event?

In general, syncope in children and adolescents is a benign event. Syncope during exercise may identify patients with a potentially fatal condition. Catecholaminergic polymorphic ventricular tachycardia is characterized by life-threatening ventricular arrhythmias, usually polymorphic ventricular tachycardia or ventricular fibrillation, occurring under conditions of exercise or emotional stress. Catecholaminergic polymorphic ventricular tachycardia is a familial condition that presents with exercise-induced syncope or sudden death in children or young adults. Detailed evaluation should be considered for patients who have syncope during exercise, injure themselves during the fall (i.e., unprotected faint with no antecedent warning prodrome), or who have a family history of syncope, early sudden cardiac death, myocardial disease, or arrhythmias.

Syncope in children and adolescents: Evaluation and treatment

Syncope in children is most often neurally mediated and usually has a natural history of spontaneous resolution or improvement. Syncope is defined as the temporary loss of consciousness resulting from a reversible disturbance of cerebral function. It is characterized by a loss of consciousness due to a lack of cerebral blood flow, rapid or sudden onset, falling of the patient, if not supported, and transiency of the attack. In children, it is most often benign, but may sometimes herald a more serious, potentially life-threatening cause. The main purpose of the present paper is to propose an evaluation scheme that will allow the physician involved in the care of children to differentiate the life-threatening causes of syncope with potential for injury or sudden death from the common, more benign neurally mediated syncope. Secondarily, the present article facilitates the identification of the patient with neurally mediated syncope who may benefit from medical therapy and distinguishes syncope from the more frequent noncardiac 'spells' of childhood.

Endothelial function and peripheral vasomotion in the brachial artery in neurally mediated syncope

BACKGROUND

Paradoxical peripheral vasodilation is one of the suspected mechanisms of neurally mediated syncope. Parasympathetic stimulation following sympathetic activation during orthostatic stress mainly contributes to this vasodilation.

HYPOTHESIS

Since endothelial function modulates peripheral vascular tone, this study aimed to determine whether endothelial function and inappropriate peripheral vasomotion has a significant role in the pathogenesis of neurally mediated syncope.

METHODS

To investigate whether endothelial function is augmented or whether abnormal peripheral vasomotion exits, flow-mediated dilation (FMD, endothelium-dependent vasodilation) and sublingual glyceryl trinitrate-induced dilation (0.3 mg, GTN-D, endothelium-independent vasodilation) were measured in the brachial artery in 16 patients with neurally mediated syncope, aged 33 +/- 10 years, by using high-resolution ultrasound. All patients underwent positive head-up tilt testing. These measures were compared with those in 16 control subjects matched with the patients by age, gender, and coronary risk factors. For FMD, percent diameter changes were obtained from baseline to hyperemic conditions (1 min after 5 min occlusion of the forearm artery). There were five smokers in both the patient and the control groups, but there was no structural heart disease in either group.

RESULTS

Baseline brachial artery diameters were comparable (3.8 +/- 0.6 vs. 3.8 +/- 0.7 mm, NS). Flow-mediated dilation in patients with neurally mediated syncope had a normal value of 9.8 +/- 5.0% despite the inclusion of five smokers. Flow-mediated dilation and GTN-D in patients with neurally mediated syncope were significantly greater than those in controls (9.0 +/- 5.0 vs. 3.0 +/- 3.5%, p<0.05; 18.4 +/- 5.5 vs. 14.1 +/- 4.4%, p<0.05).

CONCLUSIONS

Augmented endothelial function and/or abnormal peripheral vasomotion in peripheral arteries are important in patients with neurally mediated syncope in selected populations.

Tilt training for recurrent neurocardiogenic syncope: effectiveness, patient compliance, and scheduling the frequency of training sessions

Unsatisfactory results obtained with medical therapy and dual-chamber pacing for prevention of recurrent neurocardiogenic syncope necessitated the development of new treatment modalities. Tilt-training, a novel treatment for recurrent neurocardiogenic syncope based on exercise sessions with prolonged upright posture (either on a tilt-table or standing on foot against a wall), was shown to be effective in preventing the recurrence of neurocardiogenic syncope. The purpose of this study was to demonstrate the long-term beneficial effects of a transient tilt training program lasting 2 months. Thirty-two patients with recurrent neurocardiogenic syncope (mean number of syncope episodes in the last 6 months was 3.4 +/- 2.3) constituted the study group. All of the patients were tilt test positive. The patients were taught a tilt training program with 2 phases (in-hospital training with repeated tilt procedures until 3 consecutive negative results were obtained and home exercises with standing against a wall) and home exercises lasted a maximum of 2 months. After this training program, the patients received no treatment and were followed for the recurrence of syncope. At the end of the follow-up period (376 +/- 45 days), 81% of the patients were free of recurrent syncope. This study revealed that similar successful results can also be obtained with a transient tilt training program as a first line treatment strategy. Less interference with the daily activities of the patients is the major advantage of this strategy. The ease of performance and high effectiveness rate will most likely result in more frequent utilization of this treatment modality.

Malignant vasovagal syndrome?

We present the management of a patient with nasopharyngeal carcinoma with a history of recurrent syncopal attacks diagnosed as malignant vasovagal syndrome. We discuss clinical presentation as well as the resolution of disease symptoms. The importance of metastatic nasopharyngeal malignancy in relation to syncope is discussed.

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.

Tilt training: a treatment for malignant and recurrent neurocardiogenic syncope

The treatment of neurocardiogenic syncope is insufficient in many cases. We hypothesized that the repeated exposure of the cardiovascular system to orthostatic stress could have a therapeutic effect on the regulation of cardiovascular reflex mechanisms. We have started a program of tilt training for heavily symptomatic patients. After hospital admission, patients were tilted daily (60-degree inclination), until syncope, or until a maximum of 45-90 minutes. The patients were instructed to continue a program of daily tilt training at home: two 30-minute sessions of upright standing against a vertical wall. No medication was prescribed. A total of 260 tilt table sessions were performed in 42 patients. The first tilt test was positive after 21 +/- 13 minutes. The syncope was cardioinhibitory in 14 cases, vasodepressor in 19, mixed in 9. At the time of hospital discharge, 41 patients could support 45 minutes of head-up tilting. After a mean follow-up time of 15.1 (SD 7.8) months, 36 patients remained completely free of syncope. Syncope still occurred in one patient and presyncope in four patients. One patient died from an extensive myocardial infarction. The abnormal autonomic reflex activity of neurocardiogenic syncope can be remedied by a program of continued tilt training without the administration of drugs. This new treatment has proven to be effective for the vasodepressor and the cardioinhibitory type of syncope.

Pediatric echocardiography: applications and limitations

Echocardiography is an extraordinarily useful imaging technique in fetuses, infants, children, and adolescents. Recent technologic innovations have expanded its versatility in the pediatric population. However, limited societal resources, limitations inherent to ultrasound imaging, and numerous imaging options even within the field of pediatric echocardiography necessitate the discriminate and thoughtful use of echocardiography in children. The clinical assessment remains a critical prelude to echocardiographic examination of the pediatric cardiovascular system.