Introduction
Syncope is a common and important medical problem resulting from a transient reduction in cerebral blood flow to the parts of the brain that control consciousness. Individual episodes of syncope may lead to death or serious injury, and recurrent episodes of syncope or presyncope can be disabling.
Syncope and recurrent presyncope are common, and poorly understood, problems in pregnancy. Pregnant women have long been said to be “fainters” with little thought given to the underlying pathophysiology. Very little systematic research had been done to evaluate these symptoms among pregnant women. A postpartum survey identified a prevalence of syncope in pregnancy of 4.6% [1]. Furthermore, 28.2% of women reported at least one episode of presyncope during pregnancy, and 10.3% reported troublesome recurrent presyncope. These symptoms often have a dramatic effect on these women’s quality of life.
The causes of syncope and recurrent presyncope are diverse (Table 43.1). Among nonpregnant patients presenting to an emergency room with syncope, the most common etiologies were neurally mediated (vasovagal), arrhythmia, seizures, orthostasis and situational syncope [1]. At least one-third of these patients did not have a definite cause of syncope identified despite appropriate investigations. During pregnancy, the differential diagnosis of syncope is relatively unchanged, although the physiologic changes of pregnancy make certain causes more likely.
Table 43.1 Causes of presyncope and syncope in pregnancy
| Cause of presyncope or syncope | Investigations | Comments |
| Cardiac and circulatory causes | ||
| Neurally mediated (vasovagal) syncope and presyncope (most common) | History Physical exam 12-lead EKG | Features that suggest vasovagal syncope include: gradual onset; accompanying nausea, hot flushes, diaphoresis, mild dyspnea and palpitations, visual graying; onset while sitting, standing or lying flat in late pregnancy; improvement with assumption of a lateral recumbent position; and absence of postevent confusion after syncope. Most women who experience vasovagal syncope do not suffer injury, as the onset of symptoms is gradual, and following resolution of the episode they feel exhausted |
| Situational syncope (cough syncope, micturition syncope, carotid sinus hypersensitivity, etc.) | History | Situational syncope is usually apparent on a careful history |
| Cardiac arrhythmias: bradyarrhythmias tachyarrhythmias (SVT, VT, WPW, long QT syndrome with torsades) | EKG 24- or 48-hour Holter monitor Event monitor | Cardiac arrhythmias, particularly supraventricular [10] and ventricular tachycardia [11,12] , occur with increased frequency during pregnancy. While these arrhythmias more typically present with palpitations characterized as a rapid and regular heart beat, they may precipitate presyncope or syncope with rapid rates. Tachycardia-induced syncope is a particular risk in women with pre-existing cardiac conduction abnormalities such as pre-excitation [13] (e.g. WPW or Lown-Ganong-Levine syndromes) or long QT syndrome [14]. Bradycardia provoking syncope is rare in pregnancy but may be precipitated by medications such as beta-blockers or nondihydropyridine calcium channel blockers (such as verapamil and diltiazem) |
| Structural cardiac disease (aortic stenosis, atrial myxoma, cardiac tamponade, obstructive cardiomyopathy, massive pulmonary embolism) | History Physical exam Echocardiogram | A history or physical findings suggestive of cardiac disease would indicate a primary cardiac cause for syncope. Cardiac syncope is more likely to be sudden in onset, associated with severe palpitations of a fast regular heart beat and result in injury. Suspicious findings should be pursued with a detailed cardiac echo |
| Endocrine causes | ||
| Hypoglycemia | Review diabetic monitoring record | Pregnant diabetics are at enhanced risk of hypoglycemia, which may progress to syncope or seizures if unrecognized or untreated |
| Hyperventilation | History | |
| Neurologic/psychiatric causes | ||
| Seizures | Collateral history EEG MRI | A collateral history of convulsive activity, particularly with a history of epilepsy or neurologic disease, would support a diagnosis of seizure as the cause of syncope. This diagnosis would be supported by transient confusion following the episode, tongue biting or incontinence. Pregnant women with epilepsy may experience a worsening of their seizure disorder during pregnancy, most often due to either medication noncompliance or pregnancy-related changes in the pharmacokinetics of their anticonvulsant drug leading to subtherapeutic levels |
| TIA/CVA (rare) | History Physical exam CT/MRI brain | TIA and CVA are rare causes of syncope and will generally be associated with some focal neurologic deficit |
| Subclavian steal syndrome | History | Rapid or vigorous upper extremity movement may precipitate presyncope or syncope in susceptible individuals |
| Generalized anxiety disorders and panic attacks | History Psychiatric consultation | Among women with a history of psychiatric illness and/or atypical or inconsistent symptoms, a psychiatric etiology should be considered [15] |
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