Syncope and Faintness

Syncope is a transient loss of consciousness due to reduced cerebral blood flow.

Syncope is associated with postural collapse and spontaneous recovery. It may

occur suddenly,without warning, or may be preceded by presyncopal symptoms

such as lightheadedness,weakness,nausea, dimming vision, ringing in ears, or

sweating. Faintness refers to prodromal symptoms that precede the loss of consciousness in syncope. The syncopal pt appears pale,has a faint, rapid,or irregular pulse,and breathing may be almost imperceptible; transient myoclonic

or clonic movements may occur. Recovery of consciousness is prompt if the pt

is maintained in a horizontal position and cerebral perfusion is restored.

Features Distinguishing Syncope from Seizure

The differential diagnosis is often between syncope and a generalized seizure.

Syncope is more likely if the event was provoked by acute pain or anxiety or

occurred immediately after arising from a lying or sitting position. Seizures are

typically not related to posture. Pts with syncope often describe a stereotyped

transition from consciousness to unconsciousness that develops over a few seconds.

Seizures occur either very abruptly without a transition or are preceded

by premonitory symptoms such as an epigastric rising sensation,perception of

odd odors,or racing thoughts. Pallor is seen during syncope; cyanosis is usually

seen during a seizure. The duration of unconsciousness is usually very brief

(i.e.,seconds) in syncope and more prolonged (i.e., _5 min) in a seizure. Injury

from falling and incontinence are common in seizure,rare in syncope. Headache

and drowsiness,which with mental confusion are the usual sequelae of a seizure,

do not follow a syncopal attack.

Etiology

Transiently decreased cerebral blood flow is usually due to one of three general

mechanisms: disorders of vascular tone or blood volume including vasovagal

syncope and postural hypotension,cardiovascular disorders including cardiac

arrhythmias,or uncommonly cerebrovascular disease (Table 38-1). Not infrequently the cause of syncope is multifactorial.

Neurocardiogenic (Vasovagal and Vasodepressor) Syncope The common

faint,experienced by normal persons and accounting for approximately

half of all episodes of syncope. Frequently recurrent and may be provoked by

hot or crowded environment,alcohol,fatigue,pain, hunger, prolonged standing,

or stressful situations.

Postural (Orthostatic) Hypotension Cause of syncope in 30% of elderly;

polypharmacy with antihypertensive or antidepressant drugs often a contributor;

physical deconditioning may also play a role. Also occurs with autonomic nervous

system disorders,either peripheral (diabetes, nutritional, or amyloid) or

central (multiple system atrophy,Parkinson’s disease). Some cases are idiopathic.

Approach to the Patient

The cause of syncope may be apparent only at the time of the event,leaving

few,if any,clues when the pt is seen by the physician. First consider causes

that represent serious underlying etiologies; among these are massive internal

hemorrhage or myocardial infarction,which may be painless, and cardiac arrhythmias.

In elderly persons,a sudden faint without obvious cause should

arouse the suspicion of complete heart block or a tachyarrhythmia,even if all

findings are negative when the pt is seen. Loss of consciousness in particular

situations,such as during venipuncture or micturition,suggests a benign abnormality of vascular tone. The position of the pt at the time of the syncopal

episode is important; syncope in the supine position is unlikely to be vasovagal

and suggests an arrhythmia or a seizure. Medications must be considered,including

nonprescription drugs or health store supplements,with particular attention

to recent changes. Symptoms of impotence,bowel and bladder difficulties,

or disturbed sweating, or an abnormal neurologic exam, suggest a primary

neurogenic cause. An algorithmic approach to syncope is presented in Fig.

38-1.

TREATMENT

Therapy is determined by the underlying cause. Pts with vasovagal syncope

should be instructed to avoid situations or stimuli that provoke attacks. Episodes

associated with intravascular volume depletion may be prevented by

salt and fluid preloading. _-Adrenergic antagonists (metoprolol 25–50 mg

bid; atenolol 25–50 mg qd; or nadolol 10–20 mg bid; all starting doses) are

the most widely used agents; serotonin reuptake inhibitors (paroxetine 20–

40 mg qd,or sertraline 25–50 mg qd) and bupropion SR (150 mg qd) are

also effective. The mineralocorticoid hydrofludrocortisone (0.1–0.2 mg qd)

or the           -agonist proamatine (2.5–10 mg bid or tid) may be helpful for refractory

pts with recurrent vasovagal syncope but side effects,including increases

in resting bp,limit their usefulness. Permanent cardiac pacing is effective

for pts whose episodes of vasovagal syncope are frequent or associated

with prolonged asystole.

Pts with orthostatic hypotension should be instructed to rise slowly from

the bed or chair and to move legs prior to rising to facilitate venous return

from the extremities. Medications that aggravate the problem should be discontinued when possible. Other useful treatments may include elevation of the head of the bed,elastic stockings,antigravity or g suits,salt loading, and

pharmacologic agents such as sympathomimetic amines,monomine oxidase

inhibitors,and beta blockers.