Syncope MUHAMMAD ALI Cardiology Division Department of Child Health University of Sumatera Utara

Prevalence The prevalence of syncope and near syncope in children is unknown, but it may be as high as 3% of emergency room visits in some areas. Definition Syncope is a transient loss of consciousness and muscle tone that by history does not suggest other altered states of consciousness. In near syncope (i.e., presyncope), premonitory signs and symptoms of imminent syncope occur; these include dizziness with or without blackout, pallor, diaphoresis, thready pulse, and low blood pressure, but no loss of consciousness. The complaint could also represent a serious cardiac condition that could cause sudden death.

CAUSES OF SYNCOPE CIRCULATORY CAUSES –Extracardiac causes Common faint or vasodepressor syncope Orthostatic hypotension Failure of venous return (e.g., increased intrathoracic pressure, decreased venous return, hypovolemia) Cerebrovascular occlusive disease –Cardiac causes Severe obstructive lesions (e.g., aortic or pulmonary stenosis, hypertrophic obstructive cardiomyopathy, pulmonary hypertension) Myocardial dysfunction (e.g., myocardial ischemia or infarction, Kawasaki's disease, coronary artery anomalies) Arrhythmias (extreme tachycardia or bradycardia, long QT syndrome) METABOLIC CAUSES –Hypoglycemia –Hyperventilation syndrome –Hypoxia NEUROPSYCHIATRIC CAUSES –Epilepsy –Brain tumor –Migraine –Hysteria or nonconvulsive seizures

EXTRACARDIAC CAUSES OF SYNCOPE Vasovagal Syncope Also called vasodepressor, neurocardiogenic, or common syncope Characterized by a prodrome (warning symptoms and signs) lasting a few seconds to a minute: dizziness, lightheadedness, pallor, palpitation, nausea, diaphoresis, and hyperventilation, followed by the loss of consciousness and muscle tone. The patient usually falls without injury, the unconsciousness does not last more than a minute, and the patient gradually awakens. The syncope usually occurs in association with anxiety or fright, pain, blood drawing or the sight of blood, fasting, hot and humid conditions, crowded places, or prolonged and motionless standing.

Diagnostic Tests ECG, Holter monitoring, neurologic evaluation with EEG, glucose tolerance test, echo, computed tomography, and MRI of the head. These tests are usually negative and have no value in vasovagal syncope. Tilt testing of various protocols is useful in diagnosing vasovagal syncope. The tilting table is placed in an upright position to obtain the necessary pooling of blood to the lower extremities, usually with the patient in a fasting state. The angle of the tilt varies from 60 to 80 degrees, and the duration of the tilt varies from 10 to 60 minutes. If symptoms occur during the upright tilt (positive test), the patient is returned to a supine position and allowed to recover. If the tilt test alone is not positive, the procedure is repeated with an infusion of isoproterenol, starting at 0.02 μg/kg per minute and increasing to 1 μg/kg per minute for 15 minutes.

Management Placing the patient in a supine position until the circulatory crisis resolves may be all that is indicated. Inhalation of ammonia is usually effective. If the patient feels the prodrome to a faint, he or she should be told to lie down with the feet raised above the chest; this usually aborts the syncope. Success in preventing syncope has been reported with the following medications (and mechanisms of action): –Pseudoephedrine (an α-adrenergic stimulant that prevents venous pooling and hypotension), 60 mg, given orally twice a day, has been reported to be beneficial in some older children and adolescents. –Metoprolol (a selective β1 antagonist with negative inotropic effects), 1.5 mg/kg per day given orally in two or three doses, has also been reported to be beneficial in some children.

–Fludrocortisone (Florinef) is a mineralocorticoid that works through volume expansion. –Disopyramide (Norpace) is a class 1A antiarrhythmic agent that is an anticholinergic and negative inotropic agent as well as a peripheral vasoconstrictor. –Scopolamine (an anticholinergic drug that lessens vagal tone during syncope) is given transdermally. Beneficial effects of an implanted pacemaker have been reported by some investigators but not by others. Even though the pacemaker maintains heart rate, blood pressure drops, and symptoms still occur.

CARDIAC CAUSES OF SYNCOPE May be caused by structural heart disease or may be secondary to arrhythmias. Suggested by the occurrence of syncope even in the recumbent position, syncope provoked by exercise, chest pain associated with syncope, a history of unoperated or operated heart disease, or a family history of sudden death. May include obstructive lesions, coronary insufficiency, and arrhythmias, including long QT syndrome

Obstructive Lesions Patients with severe obstructive lesions such as aortic stenosis (AS), pulmonary stenosis (PS), or hypertrophic obstructive cardiomyopathy (HOCM), as well as those with pulmonary hypertension, may have syncope. Patients may also complain of chest pain, dyspnea, and palpitation. Obstructive lesions and pulmonary hypertension can be diagnosed by careful physical examination, ECG, chest x-ray studies, and echo. Surgery is indicated for most of these conditions, with the exception of irreversible forms of pulmonary hypertension. Myocardial Dysfunction Although rare, myocardial ischemia or infarction secondary to congenital anomalies or acquired disease (Kawasaki's disease) of the coronary artery may cause syncope.

Arrhythmias Either extreme tachycardia or bradycardia can decrease cardiac output and lower the cerebral blood flow below the critical level, causing syncope. Commonly encountered rhythm disturbances include supraventricular tachycardia (SVT), ventricular tachycardia, sick sinus syndrome, and complete heart block. Simple bradycardia is usually well tolerated in children, but the combination of tachycardia followed by bradycardia (overdrive suppression) is more likely to produce syncope. Arrhythmias may or may not be associated with structural heart defects.

No Identifiable Structural Defects Syncope from arrhythmias is rare in children with apparently normal hearts, with the exception of children with the following conditions. Long QT syndrome is characterized by syncope caused by ventricular arrhythmias, prolongation of the QT interval on the ECG, and occasionally a family history of sudden death. Congenital deafness is also a component of Jervell and Lange-Nielsen syndrome but not of Romano-Ward syndrome Wolff-Parkinson-White (WPW) syndrome may be associated with SVT. Right ventricular dysplasia (right ventricular cardiomyopathy) is a rare anomaly of the myocardium and is associated with repeated episodes of ventricular tachycardia.

Structural Heart Defects Ebstein's anomaly, mitral stenosis (MS) or mitral regurgitation (MR), and congenitally corrected TGA (L-TGA), may cause arrhythmias preoperatively. CHDs may cause arrhythmias postoperatively, especially after repairs of TOF and TGA) and after the Fontan operation. These children may have sick sinus syndrome, SVT or ventricular tachycardia, or complete heart block. Dilated cardiomyopathy can cause sinus bradycardia, SVT, or ventricular tachycardia. Hypertrophic cardiomyopathy is a common cause of ventricular tachycardia and syncope. Mitral valve prolapse (MVP) is a rare cause of ventricular tachycardia

Most arrhythmias respond to antiarrhythmic therapy. Long QT syndrome responds well to propranolol. Propranolol or other antiarrhythmic drugs may be indicated in patients with symptomatic MVP syndrome. Surgical treatment may be indicated (such as in WPW syndrome causing frequent SVT). Implantation of a pacemaker with a standby mode may be indicated in some patients with sick sinus syndrome.

Differential Diagnosis Epilepsy May have incontinence, marked confusion in the postictal state, and abnormal electroencephalograms (EEGs). Rigid rather than limp and may have sustained injuries. Do not experience the early symptoms of syncope (e.g., dizziness, pallor, palpitation, diaphoresis). Convulsive Syncope Some children may exhibit tonic-clonic movement during loss of consciousness from vasovagal syncope. Normal EEGs and do not respond to antiseizure medications. Hypoglycemia Has characteristics similar to syncope, such as pallor, perspiration, abdominal discomfort, lightheadedness, confusion, unconsciousness, and possible subsequent occurrence of seizures. Differ from syncope in that the onset and recovery occur more gradually, they do not occur during or shortly after meals, and the presyncopal symptoms do not improve in the supine position.

Hyperventilation Hyperventilation spells produce hypocapnia, resulting in intense cerebral vasoconstriction. A typical spell usually begins with an apprehensive feeling and “deep sighing respirations” that the patient rarely notices. Abdominal discomfort, palpitations, lightheadedness, and rarely loss of consciousness. The supine position may help the patient relax and may stop the anxiety-hyperventilation cycle. The syncopal episode can be reproduced in the office when the patient hyperventilates. Hysteria Not associated with injury and occurs only in the presence of an audience. The attacks may last longer (up to an hour) than a brief syncopal spell. Episodes usually occur in an emotionally charged setting and are rare before 10 years of age. Spells are not consistently related to postural changes and are not improved by the supine position.

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