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PATIENT 
Mr. C is a 65-year-old man with diabetes who comes to see you with a chief complaint of losing consciousness. He reports that he was sitting at home watching television when he suddenly lost consciousness without any warning. His wife reports that he was unresponsive for approximately 30 seconds. There was no tonic-clonic activity or incontinence, and the patient was not confused after regaining consciousness. The patient’s wife reports that she took Mr. C’s blood glucose when he passed out and that the reading was 120 mg/dL.
At this point, what is the leading hypothesis, what are the active alternatives, and is there a must not miss diagnosis? Given this differential diagnosis, what tests should be ordered?
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RANKING THE DIFFERENTIAL DIAGNOSIS
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As illustrated in Figure 31-1, the first step in patients with loss of consciousness is to determine whether this was due to syncope, or some nonsyncopal cause (eg, trauma, intoxication, hypoglycemia, or seizure). As discussed previously, 3 questions help make this pivotal distinction: Was the loss of consciousness abrupt in onset, brief in duration, and was there spontaneous unaided recovery? Clearly, the story suggests that all 3 were true and he therefore suffered from syncope. (Although hypoglycemia should be considered in any patient with treated diabetes, his recovery without intervention essentially rules that out, as of course, does the normal blood glucose at the time.) The second pivotal step in syncopal patients is to determine whether the patient has cardiac, orthostatic, or reflex syncope. As illustrated in Figure 31-2, this process is driven by a search for risk factors and associated symptoms to determine whether the patient is at risk for cardiac syncope, which could be life-threatening. In particular, patients should be asked about a prior history of heart disease or a family history of sudden death; syncope occurring during exertion or in the supine or seated position; and any associated chest pain, dyspnea, or palpitations.
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Mr. C denies any history of exertion prior to his loss of consciousness. He denies any associated chest pain, palpitations, or dyspnea. Past medical history reveals that Mr. C has suffered 2 MIs. Subsequently, he has dyspnea upon walking more than 20 yards. His medications include atenolol, aspirin, atorvastatin, insulin, and lisinopril. On physical exam, his BP is 128/70 mm Hg with a pulse of 72 bpm, which is regular. There is no significant change upon standing. His lung exam is clear, and cardiac exam reveals prominent JVD and a loud S3 gallop. There is no significant murmur. He has 2+ pretibial edema, and his rectal exam reveals guaiac-negative stool.
Is the clinical information sufficient to make a diagnosis? If not, what other information do you need?
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Mr. C’s does not have exertional syncope, chest pain, palpitations, or dyspnea at the time of syncope. Nonetheless, his prior history of heart disease substantially increases the likelihood ...