The entities in this section constitute relatively frequent referrals to cardiologists and electrophysiologists for suspected arrhythmia. The most accurate way of making or excluding arrhythmia is obviously recording the electrocardiogram (ECG) during a clinical episode, an exercise complicated when symptoms are infrequent and sporadic, and clinical clues are nonspecific or absent. Since the original publication of this book in 1994, technology has moved on providing us with a plethora of ECG monitoring products, including implantable types capable of long-term monitoring in the range of months and years. Ambulatory monitoring of blood pressure has become available and it is likely that ambulatory monitoring utilizing novel sensors will be available in the foreseeable future. This has probably contributed the most to streamlining the current management of most of these patients, leaving us to grapple only with those who have specific unique issues complicating diagnosis or treatment.
TRANSIENT LOSS OF CONSCIOUSNESS (LOC)
The differential diagnosis of transient loss of consciousness is very extensive and covers a broad spectrum of associated cardiac and noncardiac conditions1-3. The more common categories of disorder potentially causing loss of consciousness are listed in Table 14-1. The term syncope is more specific and refers to a transient loss of consciousness due to temporary impairment of cerebral perfusion related to drop of blood pressure for various reasons as per Table 14-1. That said, the term syncope is frequently used as if interchangeable with “transient loss of consciousness.” Fortunately, the differential diagnosis can usually be narrowed considerably by a careful history and physical examination and some simple laboratory assessment.4,5
TABLE 14-1Major categories of loss of consciousness. |Favorite Table|Download (.pdf) TABLE 14-1 Major categories of loss of consciousness.
|A. ||Neurological |
| ||i. Seizure |
|B. ||Cardiogenic/vascular (“syncope”) |
| ||i. Arrhythmic (bradycardia or tachycardia) |
| ||ii. Hemodynamic, such as LV outflow obstruction, left atrial myxoma, pulmonary embolus, ischemia (rare), exertion with fixed cardiac output, pulmonary hypertension |
| ||iii. Reflex peripheral vascular, such as vasovagal (most common), carotid hypersensitivity, micturition, cough and swallow syncope, orthostasis, vasodilating medications |
|C. ||Miscellaneous |
| ||i. Includes hysteria, malingering, hyperventilation, hypoglycemia |
The broad goals of assessment in a patient presenting with LOC are threefold. The key goal, but often the most elusive, is the recording of physiological parameters (especially the ECG) during a spontaneous episode. Under ideal circumstances, the spell is witnessed by a physician, who documents physical findings, blood pressure, ECG, and perhaps even an electroencephalogram (EEG) during the episode! Failure to monitor or witness an actual clinical episode is the fundamental problem and results in diagnosis by inference, with all its potential vagaries. A secondary goal is the documentation of associated medical and, in particular, cardiac disease. This can narrow the diagnostic possibilities and help predict prognosis.6 Finally, the third goal is to identify by laboratory testing abnormalities that suggest a potential diagnosis. ...