RISK FACTORS: Patients with heart disease, Patients taking following drugs: Antihypertensives, Vasodilators (including calcium channel blockers, ACE inhibitors, and nitrates), Phenothiazines, Antidepressants, Antiarrhythmics, Diuretics
Medical Care: The treatment strategy in patients with syncope depends entirely on the etiology of the syncope in the given patient.
" Neurocardiogenic (vasovagal or reflex) syncope
o A number of therapeutic strategies are available.
o Patients with rare episodes with a specific trigger (eg, drawing blood) generally do not require specific therapy.
o In some patients with more frequent symptoms, nonpharmacologic measures may be adequate. These include fluid and sodium loading, avoidance of triggering situations (eg, hot tubs), support stockings to reduce venous pooling, and others. Discontinuation of offending medications (eg, nitrates) that are not necessary also may be helpful.
o Drug therapy for patients with neurocardiogenic syncope may include beta-blockers, selective serotonin reuptake inhibitors, fludrocortisone, midodrine, theophylline, disopyramide, scopolamine, and hyoscyamine.
o Permanent pacemakers have been shown to be effective in patients whose syncope is refractory and has a significant cardioinhibitory component. Pacemakers are frequently useful in patients with carotid sinus hypersensitivity.
" Orthostatic hypotension
o In younger patients, orthostatic hypotension may be reflective of a dysautonomia.
o In elderly patients, orthostatic hypotension may be due to other medical conditions such as diabetes mellitus or medications. Nonpharmacologic measures, such as dangling the legs over the side of the bed before slowly arousing and use of support stockings, may be helpful.
o In young patients and in those without a history of hypertension, fluid and sodium expansion may improve symptoms; fludrocortisone and midodrine are frequently helpful in this setting.
o If hypertension is present, modification of the medical regimen may improve symptomatic orthostasis. Blood pressure must be monitored carefully if therapy with fludrocortisone or midodrine is undertaken.
" Bradyarrhythmias: Unless the sinus node or AV conduction abnormality is attributable to a medication that can be discontinued safely, a permanent pacemaker is generally indicated for patients with symptomatic bradycardia.
" Ventricular tachyarrhythmias
o In patients with significant structural heart disease, ventricular tachyarrhythmias are possible potentially life-threatening causes of syncope. In these patients, the documentation of a sustained episode of VT, ventricular fibrillation, or EP testing results documenting a high risk for ventricular tachyarrhythmias is generally an indication for ICD implantation.
o For patients in whom ICD implantation is not appropriate or desired, medical therapy with amiodarone is also an option.
" Supraventricular tachycardia: In patients with supraventricular tachycardia causing syncope or patients with preexcitation (WPW syndrome) and syncope, radiofrequency catheter ablation is generally suggested.
" Structural heart disease: For patients with syncope attributable to structural heart disease (eg, aortic stenosis, hypertrophic cardiomyopathy, pulmonary hypertension), treatment is generally directed at the underlying organic cardiovascular condition.
Surgical Care: Pacemakers and ICDs are frequently implanted in patients with syncope.
" Pacemaker implantation
o Pacemakers are implanted in patients with syncope due to bradyarrhythmias (sinus node dysfunction or AV block).
o Pacemakers may be of benefit in patients with refractory neurally mediated (ie, reflex or vasovagal) syncope with a prominent cardioinhibitory component, but this remains controversial.
" ICD implantation
o ICDs are implanted in patients with syncope in whom ventricular tachyarrhythmias are determined to have caused the syncope or in those who have structural heart disease and a high risk for life-threatening ventricular arrhythmias, but they are generally not implanted to prevent syncope.
o Patients with idiopathic VT and cardiac arrest due to WPW syndrome are not treated with ICDs. Patients with idiopathic VT may be treated with drugs or catheter ablation; the prognosis is excellent if the heart is structurally normal. Patients with WPW syndrome and syncope (or sudden death) should undergo EP studies and radiofrequency catheter ablation.
Diet: Dietary recommendations depend on the underlying conditions. Patients with neurocardiogenic syncope in the setting of structurally normal hearts are generally recommended to increase their intake of fluid and sodium. Dehydration predisposes patients to vasovagal episodes.
Activity: Activity recommendations depend on the patient's underlying conditions. For patients with recurrent syncope, working at heights, scuba diving, and driving are generally proscribed until the syncope is treated successfully. In some US states, physicians are required to report patients with syncope to the state's drivers' license bureau.
DRUG TREATMENT : PHARMACOLOGIC THERAPY IS USED MOST COMMONLY IN PATIENTS WITH VASOVAGAL SYNCOPE.
1. BETA BLOCKERS : These agents inhibit chronotropic, inotropic, and vasodilatory responses to beta-adrenergic stimulation. Peripheral venous pooling and cardiac hypercontractility can be avoided through the use of beta-blockers
- PROPRANOLOL
- METOPROLOL
2. SELECTIVE SEROTONIN REUPTAKE INHIBITORS :
- FLUOXETINE
- PAROXETINE
3. CORTICOSTEROIDS : These agents are used to treat syncope secondary to orthostatic hypotension. They act on fluid and electrolyte balance and enhance sodium reabsorption in the kidney, resulting in expanded extracellular fluid volume. They increase renal excretion of potassium and hydrogen ions.
- FLUDROCORTISONE
4. ALPHA-ADRENERGIC AGONISTS : These agents improve the hemodynamic status by increasing myocardial contractility and heart rate, resulting in increased cardiac output. They also increase peripheral resistance by causing vasoconstriction. Increased cardiac output and increased peripheral resistance lead to increased blood pressure.
- MIDODRINE
5. METHYLXANTHINES :
- THEOPHYLLINE
6. CLASS IA ANTIARRHYTHMICS : Cardiac hypercontractility and the vagal portion of the autonomic reflex can be inhibited with a negative inotropic anticholinergic medication (eg, disopyramide).
- DISOPYRAMIDE
7. ANTICHOLENERGIC AGENTS :
- SCOPOLAMINE
- HYOSCYAMINE
PATIENT MONITORING :
. Frequent followup visits for patients with cardiac causes of syncope, especially patients on antiarrhythmic drugs
. Patients with an unknown cause of syncope rarely (5%) have a diagnosis made during followup
PREVENTION/AVOIDANCE: Avoid Risk factors
POSSIBLE COMPLICATIONS :
. Trauma from falling
. Death - see prognosis
EXPECTED COURSE/PROGNOSIS :
. Cumulative mortality at 2 years:
. Low (2-5%) - young patients (< 60) with a non-cardiac cause or unknown cause of syncope.
. Intermediate (20%) - older patients (> 60) with a noncardiac or unknown cause of syncope.
. High (32-38%) - patients with cardiac cause of syncope.