Review Question - QID 213821

This patient is presenting with sudden-onset syncope with a rapid return back to baseline in the setting of QT prolongation, which could support a diagnosis of torsades de pointes as the etiology of his syncope.

Syncope can be due to a cardiac source, neurologic source, or orthostatic source. Syncope from a cardiovascular etiology, an arrhythmia in particular, can lead to rapid onset syncope without a prodrome with a rapid return to baseline. This occurs secondary to a sudden loss of cerebral perfusion followed by the resumption of cerebral perfusion when the arrhythmia resolves. The workup for a cardiac etiology of syncope should include an ECG to evaluate for any arrhythmias or QT prolongation, continuous cardiac monitoring (as arrhythmias may not be present on presentation), electrolytes to look for any derangements, and possibly troponins if there is a concern for an ischemic etiology. Torsades de pointes is a condition associated with QT prolongation that presents with twisting of the QRS complex around an electrical baseline. It can be exacerbated by congenital QT prolongation conditions (such as Romano-Ward or Jervell-Lange Nielson syndrome), QT-prolonging medications, and electrolyte abnormalities such as hypokalemia, hypomagnesemia, and hypocalcemia. The treatment of torsades de pointes is magnesium sulfate and defibrillation if the patient has no pulse. Patients who are intermittently in torsades de pointes may experience syncope, and spontaneously exit rhythm, and have a normal ECG on presentation (or only QT prolongation).

Figure/Illustration A is an ECG demonstrating QT prolongation (note the prolonged space between the red arrows). An easy rule to use for QT prolongation is the T-wave should be less than halfway between the preceding QRS complex and the next QRS complex in a patient who has a normal heart rate.

Incorrect Answers:
Answer 1: Orthostatic hypotension presents with lightheadedness when the patient stands up followed by syncope. This patient's symptoms occur randomly and suddenly at rest with no other symptoms suggestive of orthostatic hypotension.

Answer 2: Seizure would present with loss of consciousness, possibly tonic-clonic activity, and finally a post-ictal phase. This patient has a rapid loss of consciousness with a rapid return to baseline without a postictal phase.

Answer 3: Stroke could present with sudden-onset syncope. Specifically, a vertebrobasilar stroke would present with syncope, nausea, vomiting, and ataxia. This patient has no persistent neurological deficits to support a diagnosis of stroke.

Answer 5: Vasovagal syncope would present with a warm, flushed feeling followed by syncope with a rapid return to baseline. It is not typically a recurrent event with no preceding symptoms in the setting of a prolonged QT.

Bullet Summary:
Cardiac arrhythmias can cause syncope which presents with a rapid loss of consciousness followed by a rapid return to baseline without a postictal phase.