Neurocardiogenic Syncope

KEY FEATURES

ESSENTIALS OF DIAGNOSIS

• Most common mechanism of syncope in the young

• Bradycardia (vagal) and profound hypotension (vasodepressor) may occur either alone or in varying proportions

• Pain, fear, or emotion may precipitate syncope

• Many spells over several years are suggestive of this disorder

• Tilt testing is useful in the diagnosis

GENERAL CONSIDERATIONS

• Generally occurs with no structural heart disease

• Prolonged standing may precipitate this disorder

• Usually associated with prodrome such as nausea and diaphoresis

• Bezold-Jarisch reflex triggered by mechanoreceptors of the inferoposterior myocardium leads to sympathetic withdrawal and unopposed vagal input

• This reflex may be a contributor to syncope due to aortic stenosis and hypertrophic cardiomyopathy

• Fatigue, pallor, and diaphoresis after syncope are common

CLINICAL PRESENTATION

SYMPTOMS AND SIGNS

• Recurrent syncope with prodromal symptoms

PHYSICAL EXAM FINDINGS

• Generally normal in between syncopal episodes

DIFFERENTIAL DIAGNOSIS

• Sick sinus syndrome

• Orthostatic hypotension

• Iatrogenic syncope caused by antihypertensive medications

DIAGNOSTIC EVALUATION

LABORATORY TESTS

• CBC, basic metabolic panel

ELECTROCARDIOGRAPHY

• ECG to evaluate baseline intervals

IMAGING STUDIES

• Echocardiogram to exclude structural heart disease

DIAGNOSTIC PROCEDURES

• Head-up tilt-table testing

• If regular tilt testing is negative, consider provocative tilt testing with isoproterenol or carotid sinus massage

• Rare patient benefits from implantable loop recorder

TREATMENT

CARDIOLOGY REFERRAL

• Patient with frequent syncope should be referred to a cardiologist

HOSPITALIZATION CRITERIA

• Hospitalization seldom required

• Recurrent syncope especially with injuries

MEDICATIONS

• Salt and fluid loading; avoidance of dehydration

• Fludrocortisone 0.2 mg PO daily

• Beta blockers, such as metoprolol 50 mg/day

• Adrenergic agonist midodrine 10 mg 3 times daily

• Serotonin reuptake inhibitors, such as paroxetine 20 mg/day

• Disopyramide 600 mg/day in divided doses

THERAPEUTIC PROCEDURES

• Dual-chamber pacemaker with rate-drop feature is rarely performed as it only addresses bradycardia (vagal) and not the profound hypotension (vasodepressor)

SURGERY

• None required

MONITORING

• After initiation of therapy, tilt test may be repeated to document efficacy

DIET AND ACTIVITY

• Additional salt intake

• Avoid dehydration

ONGOING MANAGEMENT

HOSPITAL DISCHARGE CRITERIA

• After therapy is started

FOLLOW-UP

• Three months after initial assessment

• If symptoms are frequent, earlier follow-up may be ...